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Which animal dug this 5 cm diameter hole deep into mud and build a large mound around it?

Which animal dug this 5 cm diameter hole deep into mud and build a large mound around it?


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I noticed the large structure below today at the edge of a very small pond in northern Taiwan lowlands. It is June and it has rained a bit the past few days, and this 15 cm mud dome with a 5 cm diameter hole going straight down looked fresh and wet and glistening.

It is hard to tell for sure but it looks like the borough went deep enough to reach the water line of the pond next to it, but I could not tell because it's dark inside and I did not have a flashlight.

The mound is large, perhaps 15 cm tall and wide, which suggests that a lot of material has been removed and the tunnel could be quite deep.

The pond is only about 3 x 5 meters in diameter.

Question: Snake? Crab? Mole? What further information can I collect about it that would help to identify what produced this?

click images for full size view


A crustacean (land crayfish). There are a lot to choose from.

http://web.nchu.edu.tw/~htshih/crab_fw/fw-crabe.htm


Garden Animal Poo Identification: Your Complete Guide on Critter Faeces

Your delightful garden is bound to attract some critters like hedgehogs, rabbits, and many others. Based on any potential damage, it’s important to find out who’s been sleeping in your garden – hence this garden animal poo identification guide.

We’ll discuss the size, colour, and texture below. You’ll find out how to distinguish between similar faeces and which animal droppings are nature’s true ironic hipsters.


Rats Digging Holes in Backyard

Finding rat holes can be challenging which emphasizes the need to hire a licensed pest control technician. They appear as gaps created by crumbling mortar, cracks in a foundation, and so on. Rats prefer to access their nests through quiet areas which explains why you rarely find a rat hole in a doorway

If not for the strict pesticide regulations in Ontario, for instance, lots of homeowners may resort to the use of strong chemicals in their bid to get rid of these pests. While you may find over the counter products in Toronto they contain smaller concentrations of active ingredients.

Rats are a difficult pest to deal with and you need to be on the lookout for the following signs of an invasion. Remember they are good climbers. It means they can gain access into your home from various points such as access spaces for HVAC systems and electrical wiring. Signs of a rat problem include:

1. Droppings:If you notice rat droppings in your home as you clean it, that means this pest has gained access to your home. The droppings which resemble seeds are a bit shiny when they are fresh and become dark over time.

2. Bits Of Hair:It is also typical for rats to shed from time to time. So, be alert to bits of hair that may look black, gray, or tan following their squeezing through gaps or brushing up against a wall.

3. Tracks and Paths:Rats have the habit of using the same routes as they move around a home. This means that they leave tracks which may be evident through the dust that shows frequent tail drag marks or forefingers.

4. Strong Smell:Rats leave strong smells in the areas where they travel. So, if there is the smell of urine that you are not sure of, it means your home has been infested by rats.

5. Debris:Discovery of debris such as rubbish or wood chips reveal the presence of rats.

As you uncover rat holes, do not hesitate to block them without trapping the rat first. Blocking the holes may cause them to chew their way out but if they do not find a way out and die in your home, they decompose and emit a very terrible smell. A decomposed body may attract bacteria and other pests which would lead to a disaster.


Bowers: Architecture But Not Nests

Firstly, there are structures built by birds which do not really fit into any of the above categories because they are not nests. These are the bowers of the various species of Bowerbird.

Male Bowerbirds build structures – which though often involving great effort – are not actually nests.

These bowers, built by 14 of the 18 known species of Bowerbird, are stages or advertisements. They are built to attract females, which presumably are attracted to larger more ornate structures and which judge a male on his collection of treasures.

Great bowerbird displays objects to another bird at its bower

The real nest is built by the female after she has been mated by her chosen male. She incubates the eggs and raises the young on her own, while the male stays with his bower to try and attract more females.

Bowerbirds build different sorts of bowers even within one species. Different populations build different designs and collect different ‘treasures’.

Some simple bowers consist of an avenue of twigs – in which the male bird walks up and down to display himself to the female. Some of these may have the sticks painted with yellow, brown or purple plant juices.

More complicated bowers involve towers of sticks and display arenas on which the male arranges his collection of treasures and around which he displays himself. Treasures include feathers, particularly blue ones, snail shells, beetle wings and heads, bones, flowers and anything else which takes the bird’s fancy.

This may include man-made objects such as silver spoons, car keys, gun cartridges, tin mugs, buttons and other colourful scraps of material.

The most impressive bower is built by the Vogelkop Gardener Bowerbird (Amblyornis inornatus) from New Guinea, which in some areas builds a huge open-fronted roofed hut up to 2.2 m tall and 2 or more metres across. This structure is built by a bird the size of a Song Thrush!

Australasian Bowerbirds are not the only birds to build structures that are not ever destined to be nests.

Others include the Tooth-billed Cat Bird (Scenopoeetes dentirostris), also from Australia, and Jackson’s Whydah (Euplectes jacksoni) from Kenya and Tanzania. Both of these make structures which are quite simple in comparison with some of the bowers described above.

Cat birds line a 1-2 m arena with upside down fresh leaves, which they cut from vegetation with their toothed bill.

Jackson’s Whydah is a leking species in which each male has a personal arena about 1 m across with a pseudo-nest. Mating normally takes place during inspection of the pseudo-nest by the female. Like all leking species, the female builds the true nest later, incubates the eggs and raises the young on her own.


American Robin Nest

American robin eggs are among the easiest to recognize with their pale or medium blue color that typically lacks markings. On occasion, robin eggs, which are just over 1 inch long, can also be white or lightly speckled. An American robin’s deep cup nest is constructed from grass and mud and lined with finer grass. Robins build their nests in the crook of a tree, on a nesting shelf, or in nearly any sheltered location.


Which Bird Made That Nest?

The diversity of behavior among bird species is nowhere so dramatic as in their nest construction. Each species builds a specifically precise nest that differs in functional ways from those of almost all others. The variations are as endlessly diverse as the color patterns on a feather. Chimney swifts use their saliva to glue dry twigs onto vertical walls in a chimney cavity or hollow tree. A masked weaver bird&rsquos nest is a finely woven bag with a long, vertical entrance tunnel that is hung from the tip of a thin branch, whereas a sociable weaver builds a communal structure that may weigh a ton. An eagle&rsquos massive structure of branches can support a large man, while a plover merely scratches a few pebbles together on a sandbar. Owls never build anything at all but use others&rsquo nests or nest holes. A murre lays its single egg on a sea ledge, and a fairy tern &ldquonest&rdquo is a bare fork on a tree limb.

While some northern woodland birds build their nests on the ground, many nest in trees. One of the pleasures to be had in the winter months is seeing these nests that had been hidden by summer foliage. When leaves drop, nests are revealed full of snow, they seem to glow against stark tree limbs. The nest owners are no longer around, making positive identification difficult, but many of these nests can be identified if you match them to geographical area, habitat, and other aspects of nest location.

Below are descriptions of some of the more common nests likely to be found and identified in the winter woods. You may not find them all in one winter, but this &ldquofield guide&rdquo should provide you with the basis for a continuing adventure.

Robin, Turdus migratorius: A robin&rsquos nest is both universally familiar and frequently misidentified. Nests are built at any height but generally in a protected place, such as inside a barn or where a thick limb forks. The giveaway clue is a mud cup about 3 inches across that in the summer is lined with a thin layer of fine grass. The exterior of the nest is a rough jumble of twigs, leaves, and pieces of bark. Nests exposed to the weather will usually dissolve and collapse by spring nests under cover can persist for years.

Red-eyed vireo, Vireo olivaceus: Red-eyed vireos build their nests at any height, but always in a deciduous tree. Their nests can be found in both forest and edge habitat. The nest is always a hanging cup suspended along its edges from a thin, horizontal, forked branch. It is a neat, tidy, compact structure that will have bits of birch bark, and usually also wasp paper, decorating the outside. The inside cup diameter of a vireo nest is 2 inches.

Baltimore oriole, Icterus galbula: Oriole nests are baglike nests woven out of fibers, most commonly those stripped from old, decaying milkweed plants. Nests are almost always high in deciduous trees and at the tips of branches, not in deep forest.

Chectnut-sided warbler, Dendroica pensylvanica: Chestnut-sided warblers nest in open, edge habitat and also close to the ground, in small shrubs and bushes. This nest, with its very light and flimsy appearance, is made almost entirely of very fine grasses.

Cedar waxwing, Bombycilla cedrorum:Cedar waxwings nest in small evergreens or deciduous trees in edge habitat. The nest cup is untidy on the outside like a robin&rsquos and of similar size, but it lacks the mud cup and is typically garnished on the outside with lichens and/or moss.

American goldfinch, Carduelis tristis: American goldfinches make solid and tidy cup nests out of plant fibers and line them with thistle down. Nests are usually found out on a branch of a deciduous tree in fairly open habitat, such as a bog, edge of field, or suburban area. The nest is built with its base on the branch, not suspended like that of the vireo. Droppings are a dead giveaway (although they may be washed off by late winter), since goldfinches are the only local open-nesting songbird that allows feces to accumulate on the nest edge.

Least flycatcher, Empidonax minimus: A narrow (1.5 inches across) but deep nest cup placed into a thick, vertical fork so as to be almost hidden by it. Nests are found in deep edge habitat.

Red-winged blackbird, Agelaius phoeniceus: Red-winged blackbird nests could be confused with catbird nests, except that they&rsquore found in relatively open marshland. Nests are often built into a tuft of grass, or in a bush, or in cattails within a foot of the ground or water. Common grackles may nest in the same sites (but also in many others). Grackle nests can be distinguished from those of red-winged blackbirds by their larger (inside diameter about 3.5 inches), more compacted nest cup.

Scarlet tanager, Piranga olivacea: Unlike the other nests in this story, scarlet tanager nests are composed almost entirely of twigs. Nests have an interior nest cup 3 inches across and feature a thin lining of rootlets. They are almost see-through in the winter. They can be distinguished from the similar-looking nest of the rose-breasted grosbeak by their location: tanagers nest high in forest trees, whereas grosbeaks tend to nest in young bushy trees. Mourning dove nests have a similarly flimsy structure but no visible cup. Most mourning dove nests are blown away before winter arrives.

Red-breasted nuthatch, Sitta canadensis: Chickadees, nuthatches, and woodpeckers nest in holes in trees, and the nests of these species can be differentiated, to some extent, by the size of the hole. A pileated woodpecker nest hole is 4 inches in diameter, a hairy woodpecker&rsquos is 2 inches, a sapsucker&rsquos is 1.5 inches, a chickadee&rsquos is 1 inch (in those cases where it makes its own nest hole), and a red-breasted nuthatch&rsquos, like the one pictured here, is also 1 inch. The holes are almost perfectly round.

Red-breasted nuthatches build substantial nests of moss, down, and fibers in their nest cavities, whereas woodpeckers never put in any nest material. When abandoned, tree-hole nests can be recycled by any of a variety of birds or by other tenants. Note the diagnostic globs of pitch brought to the nest to plaster at and below the entrance to the hole this pitch probably functions to restrict predator access. The tree in this photograph is a dead red maple.

Winter wren, Troglodytes troglodytes: All wren nests are domed, with a small entrance hole at the side. Those of the winter wren are most commonly garnished on the outside with green moss and small spruce or fir twigs. Although the wrens may place their nest under a stream bank, in hanging moss close to the ground, or in a small, densely branched tree, they are most commonly found in root tip-ups of wind-blown trees.

Ruby-throated hummingbird, Archilochus colubris: Ruby-throated hummingbirds garnish their walnut-sized nests with lichens to &ldquomimic&rdquo bumps on limbs. Nests are lined with soft white plant down. The only nest that is similar in habitat, placement, and appearance, though it is substantially larger, is that of the wood peewee.

Bernd Heinrich is professor emeritus of biology at the University of Vermont. His book Nesting Season is scheduled for publication in March 2010.

Bird Nest Photos & Illustrations Photo Gallery

© 2009 by the author this article may not be copied or reproduced without the author's consent.

Discussion

This is a very well thought-out article. I’m doing some research on birds for a Cub Scout project. I found some info in here that will help as I work up an outdoor adventure for the boys! :-)

Thanks, and good luck with your book.

When cleaning out my Purple Martin gourds I found a straw nest that was completely round with an opening in one side. What bird makes a nest like this?

I found a nest like a robin’s, however it was mud lined. What bird makes such a nest?

I saw a couple of huge nests here in upstate NY and would love to know what kind of bird built them. They were on top of a powerline and they look to be about 3 feet wide. One of the nests had babies in it, that were not really babies at all, cause they were huge. The bird looks to be mostly black, or dark in color, with a white breast. Can anyone help me identify these amazing birds.

I believe you saw an osprey’s nest. Osprey often nest on powerline platforms. They are large, fish-eating raptors, so their nests are usually not too far from water (sometimes they build their large nests on piers or bridges in/over water)—and they have large babies! See this site for more information on osprey, and photos of their powerline nesting sites: http://www.ospreynest.info/index.php?pagecontent=Power+line+nests&user=9&adcode=134

Thanks for writing!
Meghan

Yesterday in Lindsborg, KS I saw a shallow-cupped nest. The whole nest was on the flattish side. It was made entirely of cedar bark and was underneath a large red cedar. Any ideas on the bird who made that nest?

We have lived in our house for 10 years. This year (in April) we noticed a very large nest about half way up a tall pine tree. It appears to be about three feet across, and made out of sticks. We don’t have any large body of water in the immediate area. We do feed birds, but the biggest one we’ve seen is an occasional crow. We do live out of town, in a semi-rural setting. What type of bird would build such a large nest? Someone suggested it may be a squirrel’s nest, but it is not made of leaves.

I have two small birds that came last year and are back this year. I have a hanging bird house on my porch and they took up in it last year. They are small and really make a loud sound, like they are calling or talking to each other. They make their out of sticks. Any idea what kind of bird this is

Do blackbirds nest in cedar trees?

My birdhouse is filled with small dead twigs about 4” to 6” long. Does anyone know who would have put them in? A chickadee nested in it first and most of her nest was taken out and all these sticks put in.

I’ve noticed a small triangle/beehive looking bird nest in several places around DC. The nest is gray in color, appears to be made of paper/mud about the size of a melon with a small opening on the side. It hangs from a single branch with the pointy end toward the ground. Any ideals? I thought it was a wasp nest or beehive, but there are so many of them and I haven’t seen any insects flying around.

My birdhouse is filled with small dead twigs about 4” to 6” long. Does anyone know who would have put them in? We see swallows around the area, these birdhouses are specific for blue birds.

Evelyn, that sounds like a house sparrow nest. These non-native invasives are vicious predators that kill native birds like bluebirds. They pecked a phoebe to death in one of my boxes. They will sometimes create dummy nests of sticks to keep other birds from using nest boxes that they themselves are not using.

In our yard beneath a small maple I found a small nest (less than 4” across, shallow, less than 2” from top to bottom) made entirely of thistle down. What made this nest?

I found a fairly good sized nest under the hood of my propane tank with 5 blue eggs in it today. The nest is made of straw and feathers. Do you have any idea what it might be?

A nest the size of a regular orange with the hole the size of nickel in the side. There is a bird flying in and out but too small to see. The pictures here are too big . This nest is all enclosed. Thank you

I saw a few nests on a mango tree in Bhopal India.The leaves of a branch were almost moulded together with cobwebs & they were big & oblong.Which birds nest could that be?

The 3 foot nest is probably Osprey. I’ve seen them nesting in Colorado. My question is what bird lays white speckled eggs smaller than a dime in an enclosed nest shaped like a football with no hole. I found one dropped at a park with 5 eggs.

Anyone know what bird uses cedar bark to build a nest other then the Golden-cheeked warbler? I found an old bird nest in my yard made of cedar bark.

I don’t know a lot about birds, but I found a lovely straw cup shaped nest in a thorny bush 4 or 5 feet up. It had 5 blue speckled/mottled eggs in it. I was pruning the bush back, and I got to one or two feet from the nest before I saw it. A bird nearby had been squawking away, and stopped as soon as I left. Am I a home wrecker? Will the mama bird go back?

This is a very informative article. Makes it simpler to find out the bird from its nest. Check out these amazing bird nests made in the strangest places.

Is there a bird other than a Robin that makes a rounded nest with blue eggs? A bird nearby resembled a lark.

I put pieces of yarn out last spring, and was not sure if it had been used in any bird nests, but this spring when pruning my gardenia shrub, I found a nest made of coir strands (probably pulled out from my hanging baskets), with pieces of the yarn interwoven, and some of it actually “glued” on. What species of bird builds a nest like this?

We have a bird house that something has made a mud nest inside with only a small passage to get in or out unless it can sweeze in under the bird house eves. Any ideas what this is?

I see a mud nest about six inches high near a creek water flow area near a grass field in country type setting. Is that a red winged blackbird nest or robin or walking type bird nest? Or is it for snakes because it is dug in ground about 1 1/2 inches wide?

My friend found a neatly made nest of fine roots in a blue bird box. It is not a bluebird nest, nor a chickadee or titmouse. Any ideas who would make a nest of roots in a bird box?

January 2017, I have a nest about the size of a small soccer ball, but the shape of a hot air balloon, high in a tree at the at the tip end of a thin branch. Our home is on a lake in a forested area. The outside seems somewhat smooth, no sticks poking out. I have not seen a bird near it yet.

Kerri that birdhouse with the mud and small opening is probably bees or wasps. I had one two years ago on my porch and I couldn’t paint my porch because they kept chasing me away. So be careful. They got me more than once.

This nest was beautifully constructed in the middle of a hanging flower arrangement outside of our porch. The nest is tight. I swear if it fell in a pond it would float for days. The eggs (6) are a half inch in length, colour is light to medium shade of blue with a few tiny black spots on the ends. Nobody has seen the mother yet though she scared me one night after dark when I went to water the plant. This was before I knew the nest was there. Anyway the chicks are beginning to hatch this morning I’d like to know what species of bird we are raising.

I have found a tree with three or four nesting cavities only 3 or 4 feet off the ground. They are similar in size it pileated woodpecker cavities. Would the make cavities so close to the ground?

Remember not to take nests from the wild it is always best to leave them where they are, even if you think they re not being used.

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19 Grasscutter [ править | править код ]

The grasscutter (Thryonomys swinderianus and Thryonomys gregorianus) is found in many forests and savannas of Africa. Its meat, said to resemble suckling pig, often sells for more per kilogram than chicken, beef, pork, or lamb. It is the preferred, and perhaps most expensive meat in West Africa. Indeed. in Ivory

Coast it sells for about $9 per kg. With prices like that, grasscutter is a culinary luxury that only the wealthy can afford.

If domestication of this wild species were successful in providing meat at a price similar to that of poultry (the second most popular meat), markets would be unlimited.2 However, as production costs are high, long-term research will be required before grasscutter production can be profitable to the small farmer. This research should now be undertaken.

In an effort to capitalize on the markets for this delicacy, agricultural extension services of Cameroon, Ghana, Ivory Coast, Nigeria, Togo, and particularly Benin are already encouraging farmers to rear grasscutters as backyard livestock. They furnish breeding stock and information, and maintain central offices for records. In addition, a bilateral cooperation project in Benin has started experimental work on improved breeding methods combined with the study of animal responses under domestication.3

In future, this vegetarian animal might become the African equivalent of South America's guinea pig, playing an important role in reducing Africa's chronic protein shortage.

Humid and subhumid Africa south of the Sahara.

Grasscutters are robust animals with short tails, small ears, and stocky bodies. Taxonomically, they are more closely related to porcupines than to common rats or mice.

Although many varieties have been described, there are probably only two species. The larger (Thryonomys swinderianus) weighs 9 kg or more and has a head-and-body length of up to 60 cm. The smaller species (Thryonomys gregorianus) may occasionally reach 8 kg and a body length of 50 cm.

Both species have yellow-brown to gray-brown bodies, with whitish bellies. The fur is extremely coarse, firm, and bristly - reflecting the animal's kinship to the porcupine. The tail is scaly and has short, sparse hairs.

Both species have thick, heavy claws and enormous orange incisors that can chew through even the toughest vegetation. (Grasscutters have been known to tear holes in corrugated iron fences.) Nevertheless, they do not bite when handled, although their claws sometimes cause injuries.4

Grasscutters occur in grassland or in wooded savanna throughout the humid and subhumid areas of Africa south of the Sahara. They often live in forest-savanna habitats where grass is present. They do not inhabit rainforest, dry scrub, or desert, but they have colonized the road borders in forest regions. Distribution is determined by availability of adequate or preferred grass species for food. Specifically, Thryonomys swinderianus occurs in virtually all countries of west, east, and southern Africa. Thryonomys gregorianus occurs in savannas in Cameroon, Central African Republic, Zaire, Sudan, Ethiopia, Kenya, Uganda, Tanzania, Malawi, Zambia, Zimbabwe, and Mozambique.

Despite heavy hunting, these animals are not threatened with extinction. Nonetheless, many individual populations are well below carrying capacity, or are extinct because of local overexploitation.

The larger grasscutter (T. swinderianus) generally lives in swampy, low-lying areas, especially along river banks and the borders of lakes and streams. Occasionally, it is found on higher ground among bushes and rocks, living where savanna grasses are dense and tangled enough to afford good cover. In Ivory Coast and southern Guinea, for instance, grasscutters are found (and hunted) throughout the savanna zones. And they can occur in close proximity to farmlands and people (for example, in southwest Nigeria).

Although the precise diet in the wild has not been determined, grasscutters are vegetarian. They consume nuts, bark, and the soft parts of grasses and shrubs. They particularly favor elephant grass and sweet potatoes. They commonly "raid" cassava and yam plantations, and are considered local pests.

Grasscutters reproduce year-round, although the births seem to peak at certain times of the year, correlated with weather conditions.5 Probably one male takes several females, and the family group possibly has more than one generation of young. The gestation is about 152 days. Apparently, litters normally contain between 2 and 4 young, but in Benin and Togo some litters of up to 11 or 12 are reported.6 Newborns are fully developed, their eyes are open, they weigh approximately 80 g, have thick fur, and quickly become accomplished runners.

Although they commonly forage in groups, grasscutters are generally solitary. They are nocturnal, and they travel at night through trails in reeds and grass, often to water. Most specimens seen in markets are males, possibly because males lead the groups and are thus most prone to being trapped.

When alarmed, these animals stamp their hind feet and give a strange booming grunt. When fleeing, they can run very fast and, given a chance, will take to water. They swim with ease.

For shelter, grasscutters usually weave nests of matted vegetation or scoop out shallow burrows.

In a broad geographic band across sub-Saharan Africa, cattle raising is severely limited by trypanosomiasis. There, other sources of animal protein, including rodents, are traditionally used. Thus, grasscutter meat constitutes an important food for many Africans. The animals are mostly caught and eaten by families for their own use, but some are sold in markets and especially in roadside stalls. Many families depend exclusively on selling bushmeat, particularly that of grasscutters. In Accra, Ghana, during one year, 73 tons of grasscutter meat were sold in the local market. This represented more than 15,000 animals. In southern Africa, too, people find that these rodents make tasty food, although they may cut off the tail to make the carcass look less ratlike.

The meat is usually eaten smoked, and is so much in demand that grasscutters are hunted in organized drives with spears, dogs, and sometimes fire. It is considered excellent, especially when cooked in soups and stews or barbecued.7 It has been described as resembling venison in flavor, but it is dark like the meat of wild duck.

In the savanna area of West Africa, people have traditionally captured wild grasscutters and raised them at home. As an extension of this, organized grasscutter husbandry has been initiated in West Africa. The animals are provided with marshy, tightly fenced areas with plenty of plant cover. The young are harvested from these areas and raised separately.

Ghanaian researcher Emanuel Asibey, a pioneer of this research, reports success at getting such captive stocks to reproduce. To this end, farmers are provided with breeding boxes and foundation grass cutter colonies. They are taught how to rear and feed the animals for home consumption or for cash income. Basically, the farmers make available large sheds where the animals can move freely. To prevent escape, the walls may be reinforced with cement plaster. The farmers also provide piles of grass, sugarcane, and other foods. A grasscutter reportedly takes about a month to adjust to such confinement. High mortality can occur in this period. The average weight of a mature, home-raised grasscutter is 4-7 kg. The average killing-out (dressed carcass) is 64 percent.8

The Wildlife Domestication Unit of Ibadan University in Nigeria, another pioneer of rodent domestication, has also reported the potential of domesticated grasscutter colonies.9

Research on grasscutter breeding, husbandry, and feeding is similarly being implemented by the Ministry for Rural Development in Benin and at the Lacena in Ivory Coast (see Research Contacts).

The demand for grasscutter meat is so large that it is not being met. Markets for it already exist over much of Africa,

Grasscutters can devastate such crops as rice, sugarcane, soybeans, peanuts, yams, cassava, sweet potatoes, oil-palm seedlings, maize, young rubber, sorghum, and wheat. Therefore, as with most rodents, they should be reared only in areas where they already exist.

In past years, captive animals in Benin have suffered fatal Clostridium infections during September and October. In 1986, a broad-spectrum antibiotic was given with outstanding results. During this season, the animals also suffered from ascarid worms, which were also successfully treated with standard drugs.10

RESEARCH AND CONSERVATION NEEDS

Research is needed in the following areas:

- Digestive physiology, feeding habits, feed preferences, feed conversion and growth rate

- Captive breeding and management (growth rates, space requirements, feed needs, etc)

- Performance under different environments

- Basic biology (for example, chromosome type, reproductive physiology, and social behavior both in its wild state and under controlled conditions).

Moreover, specimens should be gathered from different regions for comparative evaluation. A particular need is to select and breed docile specimens because today, even after several generations in captivity, the animal must still be handled with caution.

Although domestication of the grasscutter is encouraged, wild populations might also be managed to maximize and sustain production through habitat manipulation.


Contents

C. serpentina has a rugged, muscular build with a ridged carapace (upper shell), although ridges tend to be more pronounced in younger individuals. The carapace length in adulthood may be nearly 50 cm (20 in), though 25–47 cm (9.8–18.5 in) is more common. [4] C. serpentina usually weighs 4.5–16 kg (9.9–35.3 lb). Per one study, breeding common snapping turtles were found to average 28.5 cm (11.2 in) in carapace length, 22.5 cm (8.9 in) in plastron length and weigh about 6 kg (13 lb). [5]

Males are larger than females, with almost all weighing in excess of 10 kg (22 lb) being male and quite old, as the species continues to grow throughout life. [6] Any specimen above the aforementioned weights is exceptional, but the heaviest wild specimen caught reportedly weighed 34 kg (75 lb). Snapping turtles kept in captivity can be quite overweight due to overfeeding and have weighed as much as 39 kg (86 lb). In the northern part of its range, the common snapping turtle is often the heaviest native freshwater turtle. [7]

Common habitats are shallow ponds or streams. Some may inhabit brackish environments, such as estuaries. Common snapping turtles sometimes bask—though rarely observed—by floating on the surface with only their carapaces exposed, though in the northern parts of their range, they also readily bask on fallen logs in early spring. In shallow waters, common snapping turtles may lie beneath a muddy bottom with only their heads exposed, stretching their long necks to the surface for an occasional breath. Their nostrils are positioned on the very tip of the snout, effectively functioning as snorkels. [8]

Snapping turtles consume both plant and animal matter, and are important aquatic scavengers, but they are also active hunters that prey on anything they can swallow, including many invertebrates, fish, frogs, reptiles (including snakes and smaller turtles), unwary birds, and small mammals. In some areas adult snapping turtles can be incidentally detrimental to breeding waterfowl, as they will occasionally take ducklings and goslings, but their effect on such prey is frequently exaggerated. [9]

Common snapping turtles have few predators when older, but eggs are subject to predation by crows, American mink, skunks, foxes, and raccoons. As hatchlings and juveniles, most of the same predators will attack them as well as herons (mostly great blue herons), bitterns, hawks, owls, fishers, American bullfrogs, large fish, and snakes. [7] There are records during winter in Canada of hibernating adult common snapping turtles being ambushed and preyed on by northern river otters. [6] Other natural predators which have reportedly preyed on adults include coyotes, American black bears, American alligators and their larger cousins, alligator snapping turtles. [10] Large, old male snapping turtles have very few natural threats due to their formidable size and defenses, and tend to have a very low annual mortality rate. [6]

These turtles travel extensively over land to reach new habitats or to lay eggs. Pollution, habitat destruction, food scarcity, overcrowding, and other factors drive snappers to move it is quite common to find them traveling far from the nearest water source. Experimental data supports the idea that snapping turtles can sense the Earth's magnetic field, which could also be used for such movements (together with a variety of other possible orientation cues). [11] [12]

This species mates from April through November, with their peak laying season in June and July. The female can hold sperm for several seasons, using it as necessary. Females travel over land to find sandy soil in which to lay their eggs, often some distance from the water. After digging a hole, the female typically deposits 25 to 80 eggs each year, guiding them into the nest with her hind feet and covering them with sand for incubation and protection. [13]

Incubation time is temperature-dependent, ranging from 9 to 18 weeks. In cooler climates, hatchlings overwinter in the nest. The common snapping turtle is remarkably cold-tolerant radiotelemetry studies have shown some individuals do not hibernate, but remain active under the ice during the winter. [14]

Hibernating snapping turtles do not breathe for, in the northern part of their range, more than six months since ice covers their hibernating site. These turtles can get oxygen by pushing their head out of the mud and allowing gas exchange to take place through the membranes of their mouth and throat. This is known as extrapulmonary respiration. [15]

If they cannot get enough oxygen through this method they start to utilize anaerobic pathways, burning sugars and fats without the use of oxygen. The metabolic by-products from this process are acidic and create very undesirable side effects by spring, which are known as oxygen debt. [16] Although designated as "least concern" on the IUCN redlist, the species has been designated in the Canadian part of its range as "Special Concern" due to its life history being sensitive to disruption by anthropogenic activity. [17]

Currently, no subspecies of the common snapping turtle are recognized. [18] The former Florida subspecies osceola is currently considered a synonym of serpentina, while the other former subspecies Chelydra rossignonii [19] and Chelydra acutirostris are both recognized as full species. [18] [20]

In their environment, they are at the top of the food chain, causing them to feel less fear or aggression in some cases. When they encounter a species unfamiliar to them such as humans, in rare instances, they will become curious and survey the situation and even more rarely may bump their nose on a leg of the person standing in the water. Although snapping turtles have fierce dispositions, [21] when they are encountered in the water or a swimmer approaches, they will slip quietly away from any disturbance or may seek shelter under mud or grass nearby. [22]

As food Edit

The common snapping turtle is a traditional ingredient in turtle soup consumption in large quantities, however, can become a health concern due to potential concentration of toxic environmental pollutants in the turtle's flesh. [23]

Captivity Edit

The common snapping turtle is not an ideal pet. Its neck is very flexible, and a wild turtle can bite its handler even if picked up by the sides of its shell. The claws are about as sharp as those of dogs, but cannot be trimmed as can dog claws. Despite this, a snapping turtle cannot use its claws for either attacking (its legs have no speed or strength in "swiping" motions) or eating (no opposable thumbs), but only as aids for digging and gripping. Veterinary care is best left to a reptile specialist. A wild common snapping turtle will make a hissing sound when it is threatened or encountered, but they prefer not to invoke confrontations. [24]

It is a common misconception that common snapping turtles may be safely picked up by the tail with no harm to the animal in fact, this has a high chance of injuring the turtle, especially the tail itself and the vertebral column. [25] Lifting the turtle with the hands is difficult and dangerous. Snappers can stretch their necks back across their own carapace and to their hind feet on either side to bite. When they feel stressed, they release a musky odor from behind their legs.

It may be tempting to rescue a snapping turtle found on a road by getting it to bite a stick and then dragging it out of immediate danger. This action can, however, severely scrape the legs and underside of the turtle and lead to deadly infections in the wounds. The safest way to pick up a common snapping turtle is by grasping the carapace above the back legs. There is a large gap above the back legs that allows for easy grasping of the carapace and keeps hands safe from both the beak and claws of the turtle. It can also be picked up with a shovel, from the back, making sure the shovel is square across the bottom of the shell. The easiest way, though, is with a blanket or tarp, picking up the corners with the turtle in the middle.

Snapping turtles are raised on some turtle farms in China. [26]

In politics Edit

The common snapping turtle was the central feature of a famous American political cartoon. Published in 1808 in protest at the Jeffersonian Embargo Act of 1807, the cartoon depicted a snapping turtle, jaws locked fiercely to an American trader who was attempting to carry a barrel of goods onto a British ship. The trader was seen whimsically uttering the words "Oh! this cursed Ograbme" ("embargo" spelled backwards, and also "O, grab me" as the turtle is doing). This piece is widely considered a pioneering work within the genre of the modern political cartoon. [ citation needed ]

In 2006, the common snapping turtle was declared the state reptile of New York by vote of the New York Legislature after being chosen by the state's public elementary school children. [27]

Reputation Edit

While it is widely rumored that common snapping turtles can bite off human fingers or toes, and their powerful jaws are more than capable of doing so, no proven cases have ever been presented for this species, as they use their overall size and strength to deter would-be predators. [28] Common snapping turtles are "quite docile" animals underwater that prefer to avoid confrontations rather than provoke them. [28]

In 2002, a study done in the Journal of Evolutionary Biology found that the common snapping turtle (Chelydra serpentina) registered between 208 and 226 Newtons of force when it came to jaw strength. In comparison, the average bite force of a human (molars area) is between 300 and 700 Newtons. [29] [30] Another non-closely related species known as the alligator snapping turtle has been known to bite off fingers, and at least three documented cases are known. [31]

In recent years in Italy, large mature adult C. serpentina turtles have been taken from bodies of water throughout the country. They were most probably introduced by the release of unwanted pets. In March 2011, an individual weighing 20 kg (44 lb) was captured in a canal near Rome [32] another individual was captured near Rome in September 2012. [33]

In Japan, the species was introduced as an exotic pet in the 1960s it has been recorded as the source of serious bite injuries. In 2004 and 2005, some 1,000 individuals were found in Chiba Prefecture, making up the majority of individuals believed to have been introduced. [34]


Bird Nest Designs

Birds can create many different types of nests. While the same species will always create the same sort of nest structure—birds can't change their minds and invent new nest styles—there is great variety among nests types.

  • Cup: A simple cup-shaped nest is the most familiar, common nest type. The overall size, dimensions, and depth of the cup may differ, and some birds build distinct inner and outer cup layers. Cups are often positioned along tree branches or in tree forks or may be nestled on ledges or in any number of unique places.
    Birds That Build Cup Nests: Barn swallows, ruby-throated hummingbirds, yellow warblers, American robins, and many different passerines.
  • Scrape: A basic scrape is a shallow depression on the ground without much nesting material, though it may have a light lining of down, grass, pebbles, weeds, or other debris. Scrapes are popular nest types for terrestrial birds or birds that prefer open habitats that lack abundant trees, such as shorebirds or tundra species.
    Birds That Build Scrape Nests: Common ostrich, killdeer, American avocet, Arctic tern, and many shorebirds.
  • Burrow: A nesting burrow is dug into the ground and may be a shallow cave or could have a long tunnel leading to a nesting chamber. These nests are often excavated in soft material such as loose dirt banks or guano accumulation. The inner nesting chamber may be lined with some material or could be bare. Birds may excavate their burrows or may usurp suitable burrows from other animals.
    Birds That Nest in Burrows:Atlantic puffin, burrowing owl, great hornbill, barbets, kiwis, and many kingfishers.
  • Mound: A mound nest is built on the ground but is a relatively large accumulation of nesting material in a tall cone or bell-shaped structure. The eggs may be nearly buried in the nest, which helps provide additional protection and insulation, or they can rest on top of the mound. The height and diameter of the nest mound will vary.
    Birds That Build Mound Nests: Horned coot, Adelie penguin, malleefowl, and most flamingo species.
  • Cavity:Cavity-nesting birds are common and will either excavate their nesting cavities or use natural cavities in trees, snags, or cacti. Holes in telephone poles or even nestled in gaps in houses as well as birdhouses are also great options for cavity-nesting species. The interior cavity may be bare or could be lined with a variety of materials, and some birds may even build loose cups inside the cavity.
    Birds That Use Nest Cavities:Eastern bluebird, house sparrow, most woodpeckers, many parrots, tits, and chickadees.
  • Platform: A platform nest is a relatively large, bulky structure often built of larger twigs or sticks. The surface is typically flat or may have a very shallow depression, but not enough to be considered a deliberate cup. Many birds reuse platform nests for many years, often adding material to the nest each year.
    Birds That Build Platform Nests:Bald eagle, osprey, great blue heron, white stork, and many other raptors and large wading birds.
  • Pendant: Pendant nests are elaborately woven sacks that dangle from branches, giving birds in the nest great protection from predators. Some are not suspended very far from the branches while others may hang several feet below their attachment point. Birds enter the nest through an entrance on the side.
    Birds That Build Pendant Nests:Baltimore orioles, caciques, oropendolas, and most weaver bird species.
  • Sphere: A sphere or dome nest is almost completely enclosed and provides great protection and camouflage. The trade-off, however, is that these nests are often on the ground or in low areas and may be more susceptible to predators. The nest entrance is typically on the side so it still protects from the rain.
    Birds That Build Sphere Nests: American dipper, marsh wren, winter wren, ovenbird, and different meadowlarks.

Contents

Not every bird species builds or uses a nest. Some auks, for instance—including common murre, thick-billed murre and razorbill—lay their eggs directly onto the narrow rocky ledges they use as breeding sites. [7] The eggs of these species are dramatically pointed at one end, so that they roll in a circle when disturbed. This is critical for the survival of the developing eggs, as there are no nests to keep them from rolling off the side of the cliff. Presumably because of the vulnerability of their unprotected eggs, parent birds of these auk species rarely leave them unattended. [8] Nest location and architecture is strongly influenced by local topography and other abiotic factors. [9]

King penguins and emperor penguins also do not build nests instead, they tuck their eggs and chicks between their feet and folds of skin on their lower bellies. They are thus able to move about while incubating, though in practice only the emperor penguin regularly does so. Emperor penguins breed during the harshest months of the Antarctic winter, and their mobility allows them to form huge huddled masses which help them to withstand the extremely high winds and low temperatures of the season. Without the ability to share body heat (temperatures in the centre of tight groups can be as much as 10C above the ambient air temperature), the penguins would expend far more energy trying to stay warm, and breeding attempts would probably fail. [10]

Some crevice-nesting species, including ashy storm-petrel, pigeon guillemot, Eurasian eagle-owl and Hume's tawny owl, lay their eggs in the relative shelter of a crevice in the rocks or a gap between boulders, but provide no additional nest material. [11] [12] Potoos lay their single egg directly atop a broken stump, or into a shallow depression on a branch—typically where an upward-pointing branch died and fell off, leaving a small scar or knot-hole. [13] Brood parasites, such as the New World cowbirds, the honeyguides, and many of the Old World and Australasian cuckoos, lay their eggs in the active nests of other species. [14] [15] [16]

Scrape Edit

The simplest nest construction is the scrape, which is merely a shallow depression in soil or vegetation. [17] This nest type, which typically has a rim deep enough to keep the eggs from rolling away, is sometimes lined with bits of vegetation, small stones, shell fragments or feathers. [18] These materials may help to camouflage the eggs or may provide some level of insulation they may also help to keep the eggs in place, and prevent them from sinking into muddy or sandy soil if the nest is accidentally flooded. [19] Ostriches, most tinamous, many ducks, most shorebirds, most terns, some falcons, pheasants, quail, partridges, bustards and sandgrouse are among the species that build scrape nests.

Eggs and young in scrape nests, and the adults that brood them, are more exposed to predators and the elements than those in more sheltered nests they are on the ground and typically in the open, with little to hide them. The eggs of most ground-nesting birds (including those that use scrape nests) are cryptically coloured to help camouflage them when the adult is not covering them the actual colour generally corresponds to the substrate on which they are laid. [20] Brooding adults also tend to be well camouflaged, and may be difficult to flush from the nest. Most ground-nesting species have well-developed distraction displays, which are used to draw (or drive) potential predators from the area around the nest. [21] Most species with this type of nest have precocial young, which quickly leave the nest upon hatching. [22]

In cool climates (such as in the high Arctic or at high elevations), the depth of a scrape nest can be critical to both the survival of developing eggs and the fitness of the parent bird incubating them. The scrape must be deep enough that eggs are protected from the convective cooling caused by cold winds, but shallow enough that they and the parent bird are not too exposed to the cooling influences of ground temperatures, particularly where the permafrost layer rises to mere centimeters below the nest. Studies have shown that an egg within a scrape nest loses heat 9% more slowly than an egg placed on the ground beside the nest in such a nest lined with natural vegetation, heat loss is reduced by an additional 25%. [23] The insulating factor of nest lining is apparently so critical to egg survival that some species, including Kentish plovers, will restore experimentally altered levels of insulation to their pre-adjustment levels (adding or subtracting material as necessary) within 24 hours. [24]

In warm climates, such as deserts and salt flats, heat rather than cold can kill the developing embryos. In such places, scrapes are shallower and tend to be lined with non-vegetative material (including shells, feathers, sticks and soil), [25] which allows convective cooling to occur as air moves over the eggs. Some species, such as the lesser nighthawk and the red-tailed tropicbird, help reduce the nest's temperature by placing it in partial or full shade. [26] [27] Others, including some shorebirds, cast shade with their bodies as they stand over their eggs. Some shorebirds also soak their breast feathers with water and then sit on the eggs, providing moisture to enable evaporative cooling. [28] Parent birds keep from overheating themselves by gular panting while they are incubating, frequently exchanging incubation duties, and standing in water when they are not incubating. [29]

The technique used to construct a scrape nest varies slightly depending on the species. Beach-nesting terns, for instance, fashion their nests by rocking their bodies on the sand in the place they have chosen to site their nest, [30] while skimmers build their scrapes with their feet, kicking sand backwards while resting on their bellies and turning slowly in circles. [31] The ostrich also scratches out its scrape with its feet, though it stands while doing so. [32] Many tinamous lay their eggs on a shallow mat of dead leaves they have collected and placed under bushes or between the root buttresses of trees, [33] and kagus lay theirs on a pile of dead leaves against a log, tree trunk or vegetation. [34] Marbled godwits stomp a grassy area flat with their feet, then lay their eggs, while other grass-nesting waders bend vegetation over their nests so as to avoid detection from above. [35] Many female ducks, particularly in the northern latitudes, line their shallow scrape nests with down feathers plucked from their own breasts, as well as with small amounts of vegetation. [36] Among scrape-nesting birds, the three-banded courser and Egyptian plover are unique in their habit of partially burying their eggs in the sand of their scrapes. [37]

Mound Edit

Burying eggs as a form of incubation reaches its zenith with the Australasian megapodes. Several megapode species construct enormous mound nests made of soil, branches, sticks, twigs and leaves, and lay their eggs within the rotting mass. The heat generated by these mounds, which are in effect giant compost heaps, warms and incubates the eggs. [1] The nest heat results from the respiration of thermophilic fungi and other microorganisms. [38] The size of some of these mounds can be truly staggering several of the largest—which contain more than 100 cubic metres (130 cu yd) of material, and probably weigh more than 50 tons (45,000 kg) [38] —were initially thought to be Aboriginal middens. [39]

In most mound-building species, males do most or all of the nest construction and maintenance. Using his strong legs and feet, the male scrapes together material from the area around his chosen nest site, gradually building a conical or bell-shaped pile. This process can take five to seven hours a day for more than a month. While mounds are typically reused for multiple breeding seasons, new material must be added each year in order to generate the appropriate amount of heat. A female will begin to lay eggs in the nest only when the mound's temperature has reached an optimal level. [40]

Both the temperature and the moisture content of the mound are critical to the survival and development of the eggs, so both are carefully regulated for the entire length of the breeding season (which may last for as long as eight months), principally by the male. [38] Ornithologists believe that megapodes may use sensitive areas in their mouths to assess mound temperatures each day during the breeding season, the male digs a pit into his mound and sticks his head in. [41] If the mound's core temperature is a bit low, he adds fresh moist material to the mound, and stirs it in if it is too high, he opens the top of the mound to allow some of the excess heat to escape. This regular monitoring also keeps the mound's material from becoming compacted, which would inhibit oxygen diffusion to the eggs and make it more difficult for the chicks to emerge after hatching. [40] The malleefowl, which lives in more open forest than do other megapodes, uses the sun to help warm its nest as well—opening the mound at midday during the cool spring and autumn months to expose the plentiful sand incorporated into the nest to the sun's warming rays, then using that warm sand to insulate the eggs during the cold nights. During hot summer months, the malleefowl opens its nest mound only in the cool early morning hours, allowing excess heat to escape before recovering the mound completely. [42] One recent study showed that the sex ratio of Australian brushturkey hatchlings correlated strongly with mound temperatures females hatched from eggs incubated at higher mean temperatures. [43]

Flamingos make a different type of mound nest. Using their beaks to pull material towards them, [44] they fashion a cone-shaped pile of mud between 15–46 cm (6–18 in) tall, with a small depression in the top to house their single egg. [45] The height of the nest varies with the substrate upon which it is built those on clay sites are taller on average than those on dry or sandy sites. [44] The height of the nest and the circular, often water-filled trench which surrounds it (the result of the removal of material for the nest) help to protect the egg from fluctuating water levels and excessive heat at ground level. In East Africa, for example, temperatures at the top of the nest mound average some 20 °C (40 °F) cooler than those of the surrounding ground. [44]

The base of the horned coot's enormous nest is a mound built of stones, gathered one at a time by the pair, using their beaks. These stones, which may weigh as much as 450 g (about a pound) each, are dropped into the shallow water of a lake, making a cone-shaped pile which can measure as much as 4 m 2 (43 sq ft) at the bottom and 1 m 2 (11 sq ft) at the top, and 0.6 m (2.0 ft) in height. The total combined weight of the mound's stones may approach 1.5 tons (1,400 kg). Once the mound has been completed, a sizable platform of aquatic vegetation is constructed on top. The entire structure is typically reused for many years. [46]

Burrow Edit

Soil plays a different role in the burrow nest here, the eggs and young—and in most cases the incubating parent bird—are sheltered under the earth. Most burrow-nesting birds excavate their own burrows, but some use those excavated by other species and are known as secondary nesters burrowing owls, for example, sometimes use the burrows of prairie dogs, ground squirrels, badgers or tortoises, [47] China's endemic white-browed tits use the holes of ground-nesting rodents [48] and common kingfishers occasionally nest in rabbit burrows. [49] Burrow nests are particularly common among seabirds at high latitudes, as they provide protection against both cold temperatures and predators. [50] Puffins, shearwaters, some megapodes, motmots, todies, most kingfishers, the crab plover, miners and leaftossers are among the species which use burrow nests.

Most burrow nesting species dig a horizontal tunnel into a vertical (or nearly vertical) dirt cliff, with a chamber at the tunnel's end to house the eggs. [51] The length of the tunnel varies depending on the substrate and the species sand martins make relatively short tunnels ranging from 50–90 cm (20–35 in), [52] for example, while those of the burrowing parakeet can extend for more than three meters (nearly 10 ft). [53] Some species, including the ground-nesting puffbirds, prefer flat or gently sloping land, digging their entrance tunnels into the ground at an angle. [54] In a more extreme example, the D'Arnaud's barbet digs a vertical tunnel shaft more than a meter (39 in) deep, with its nest chamber excavated off to the side at some height above the shaft's bottom this arrangement helps to keep the nest from being flooded during heavy rain. [55] Buff-breasted paradise-kingfishers dig their nests into the compacted mud of active termite mounds, either on the ground or in trees. [49] Specific soil types may favour certain species and it is speculated that several species of bee-eater favor loess soils which are easy to penetrate. [56] [57]

Birds use a combination of their beaks and feet to excavate burrow nests. The tunnel is started with the beak the bird either probes at the ground to create a depression, or flies toward its chosen nest site on a cliff wall and hits it with its bill. The latter method is not without its dangers there are reports of kingfishers being fatally injured in such attempts. [49] Some birds remove tunnel material with their bills, while others use their bodies or shovel the dirt out with one or both feet. Female paradise-kingfishers are known to use their long tails to clear the loose soil. [49]

Some crepuscular petrels and prions are able to identify their own burrows within dense colonies by smell. [58] Sand martins learn the location of their nest within a colony, and will accept any chick put into that nest until right before the young fledge. [59]

Not all burrow-nesting species incubate their young directly. Some megapode species bury their eggs in sandy pits dug where sunlight, subterranean volcanic activity, or decaying tree roots will warm the eggs. [1] [38] The crab plover also uses a burrow nest, the warmth of which allows it to leave the eggs unattended for as long as 58 hours. [60]

Predation levels on some burrow-nesting species can be quite high on Alaska's Wooded Islands, for example, river otters munched their way through some 23 percent of the island's fork-tailed storm-petrel population during a single breeding season in 1977. [61] There is some evidence that increased vulnerability may lead some burrow-nesting species to form colonies, or to nest closer to rival pairs in areas of high predation than they might otherwise do. [62]

Cavity Edit

The cavity nest is a chamber, typically in living or dead wood, but sometimes in the trunks of tree ferns [63] or large cacti, including saguaro. [63] [64] In tropical areas, cavities are sometimes excavated in arboreal insect nests. [65] [66] A relatively small number of species, including woodpeckers, trogons, some nuthatches and many barbets, can excavate their own cavities. Far more species—including parrots, tits, bluebirds, most hornbills, some kingfishers, some owls, some ducks and some flycatchers—use natural cavities, or those abandoned by species able to excavate them they also sometimes usurp cavity nests from their excavating owners. Those species that excavate their own cavities are known as "primary cavity nesters", while those that use natural cavities or those excavated by other species are called "secondary cavity nesters". Both primary and secondary cavity nesters can be enticed to use nest boxes (also known as bird houses) these mimic natural cavities, and can be critical to the survival of species in areas where natural cavities are lacking. [67]

Woodpeckers use their chisel-like bills to excavate their cavity nests, a process which takes, on average, about two weeks. [64] Cavities are normally excavated on the downward-facing side of a branch, presumably to make it more difficult for predators to access the nest, and to reduce the chance that rain floods the nest. [68] There is also some evidence that fungal rot may make the wood on the underside of leaning trunks and branches easier to excavate. [68] Most woodpeckers use a cavity for only a single year. The endangered red-cockaded woodpecker is an exception it takes far longer—up to two years—to excavate its nest cavity, and may reuse it for more than two decades. [64] The typical woodpecker nest has a short horizontal tunnel which leads to a vertical chamber within the trunk. The size and shape of the chamber depends on species, and the entrance hole is typically only as large as is needed to allow access for the adult birds. While wood chips are removed during the excavation process, most species line the floor of the cavity with a fresh bed of them before laying their eggs.

Trogons excavate their nests by chewing cavities into very soft dead wood some species make completely enclosed chambers (accessed by upward-slanting entrance tunnels), while others—like the extravagantly plumed resplendent quetzal—construct more open niches. [66] In most trogon species, both sexes help with nest construction. The process may take several months, and a single pair may start several excavations before finding a tree or stump with wood of the right consistency.

Species which use natural cavities or old woodpecker nests sometimes line the cavity with soft material such as grass, moss, lichen, feathers or fur. Though a number of studies have attempted to determine whether secondary cavity nesters preferentially choose cavities with entrance holes facing certain directions, the results remain inconclusive. [69] While some species appear to preferentially choose holes with certain orientations, studies (to date) have not shown consistent differences in fledging rates between nests oriented in different directions. [69]

Cavity-dwelling species have to contend with the danger of predators accessing their nest, catching them and their young inside and unable to get out. [70] They have a variety of methods for decreasing the likelihood of this happening. Red-cockaded woodpeckers peel bark around the entrance, and drill wells above and below the hole since they nest in live trees, the resulting flow of resin forms a barrier that prevents snakes from reaching the nests. [71] Red-breasted nuthatches smear sap around the entrance holes to their nests, while white-breasted nuthatches rub foul-smelling insects around theirs. [72] Eurasian nuthatches wall up part of their entrance holes with mud, decreasing the size and sometimes extending the tunnel part of the chamber. Most female hornbills seal themselves into their cavity nests, using a combination of mud (in some species brought by their mates), food remains and their own droppings to reduce the entrance hole to a narrow slit. [73]

A few birds are known to use the nests of insects within which they create a cavity in which they lay their eggs. These include the rufous woodpecker which nests in the arboreal nests of Crematogaster ants and the collared kingfisher which uses termite nests. [74]

Cup Edit

The cup nest is smoothly hemispherical inside, with a deep depression to house the eggs. Most are made of pliable materials—including grasses—though a small number are made of mud or saliva. [75] Many passerines and a few non-passerines, including some hummingbirds and some swifts, build this type of nest.

Small bird species in more than 20 passerine families, and a few non-passerines—including most hummingbirds, kinglets and crests in the genus Regulus, some tyrant flycatchers and several New World warblers—use considerable amounts of spider silk in the construction of their nests. [76] [77] The lightweight material is strong and extremely flexible, allowing the nest to mold to the adult during incubation (reducing heat loss), then to stretch to accommodate the growing nestlings as it is sticky, it also helps to bind the nest to the branch or leaf to which it is attached. [77]


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