Snake Skin as Protection Against Predators

February 17, 2015 by  
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Birds use all sorts of materials to build and pad their nests with, and are very good in general at adapting whatever is at hand to suit their needs. Some birds even use the shed skins of snakes in their nest building, raising the question as to whether the snake skin is merely a handy and comfortable material to line a nest with, or whether it is actually intended to scare predators off. A study carried out by Arkansas State University ornithologists concluded that some bird species clearly use the snake skin to deter predators by incorporating it into their nests in some way, or by prominently displaying a snake skin near the nest, or both.

The Tufted Titmouse (Baeolophus bicolor) and Blue Grosbeak (Passerina caerulea) are among the bird species that include pieces of snake skin in their nests, while Great Crested Flycatchers (Myiarchus crinitus) are known to display a snake skin outside their nesting cavity, as well as using an entire coiled snake skin in the nest. These will remain there throughout the incubation and fledgling stage of breeding. The study noted that the main predators of the eggs of Great Crested Flycatchers are rat snakes and flying squirrels – the latter being fond of bird’s eggs and the former preying on both birds and their eggs, as well as on flying squirrels. It was also noted that flying squirrels and Great Crested Flycatchers have a very similar geographical spread, and as all three species favor cavities as habitats, it is likely they will encounter one another. As the flying squirrel does its best to avoid the rat snake, it has been suggested that the shed skin of the snake acts as a deterrent to the squirrel.

A test carried out by the researchers confirmed that to be so. Using 60 nest boxes in which quail eggs were placed, researchers added snake skins into 40 of the boxes, with 20 boxes having no snake skin in them. All of the 40 boxes with snake skins were left untouched, while up to 20 percent of the nests without snake skins were raided by flying squirrels – evidence that some birds use snake skins specifically to ward off predators, and it appears to work.

Killdeer (Charadrius vociferus)

February 9, 2009 by  
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The Killdeer (Charadrius vociferus) is probably one of the best known plover species in America. Commonly seen in parking lots, fields and farms, the Killdeer is renowned for its clever predator evasion tactics. A farmer’s friend, the Killdeer is certainly well-worth getting to know. Join us as we learn more about this fascinating bird.

America’s Killdeer is a stunning bird and quickly identified. Its length measures in at between 20 and 28 cm and its wingspan at 46 to 48 cm. It is much the same size as a typical robin, but its legs are much longer. Most notable are the two thick black bands running across the Killdeer’s white chest. The rump, tail and lower back are also a distinctive orange color. The Killdeer’s throat and short neck are white and a white band marks the forehead, with a black band just above. to the side of each eye is a striking white eyestripe. The Killdeer’s wings and upperback are brown and the wings are boldly striped with white, typically seen when flying. This beautiful bird is very vocal and emits a loud kill-deeah sound.

The Killdeer has been classified as a shorebird, but it is frequently seen far off from water in pastures, on golf courses and at airfields. They are quick runners and fantastic fliers. During the summer the Killdeers nest in southern Canada, their range stretching from Newfoundland all the way to British Columbia and up to Alaska. They also nest through the United States and into Mexico. Winters are spent in Long Island and the coasts of British Columbia and the north of South America. Migration is slow and flight takes place in the day and night. Killdeers are keen insect eaters, dining on beetles, worms, grasshoppers, bugs, dragon flies, caterpillars and other creatures which cause damage to farmers’ crops. They also feed on other types of invertebrates including spiders, snails, crustacea, centipedes and so forth.

Nests are simple scrapes in the ground which may be lined. A clutch of 4 to 6 eggs is laid and incubation lasts 22 to 30 days. The hatching chicks are precocial and hop out of the nest as soon as their soft down feathers have dried. As mentioned already, the Killdeer has remarkable skills when it comes to guarding its nest and young. Should a grazing animal accidentally wander too close, the adult Killdeer will run toward the animal with its wings outstretched. If the intruder is a predator the parents will fly about, calling loudly. This is followed by a distraction display of feigning injury. This “injured” bird keeps just out of reach of the threatening individual so as to draw it away from the nest. As the predator moves far enough away from the nest and the young have had time to take cover, the Killdeer parent flies off.

American Avocets (Recurvirostra americana)

February 9, 2009 by  
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American Avocets (Recurvirostra americana) are beautiful, elegant birds which are found in water-filled areas such as marshes, coastal bays, mudflats and saline lakes. During the summer months the American Avocet makes its way to the western Great Plains of America and are dotted through Saskatchewan, Alberta, Montana, North and South Dakota, New Mexico and Texas. In the winter months they migrate to California and Mexico as well as along the coast that runs from North Carolina to Texas. American Avocet’s are listed with the Federal Migratory Bird Treaty Act as being a threatened species due to habitat destruction.

The American Avocet is a shorebird with a distinctive long, upward curving black bill. Its long legs are grey-blue in color and thus it has received the nickname “blue shanks”. Its back and sides are clearly marked with white and black stripes. It measures about 43-47 cm, with a wingspan of 72 cm. Its eyes are dark brown. When it is breeding season, the head and neck turn a pink-tan color, but are usually gray-white. Female American Avocets are a bit smaller than the males and the bill is more curved and shorter. When bird watching along the shoreline, listen out for the call of the avocet, a high-pitched “kleek” sound.

American Avocets feed on aquatic invertebrates found in their habitat. They will forage in shallow water, whilst wading or swimming. The avocet will swing its unusual bill along the ground under the water so as to disturb the aquatic prey, grabbing it for a tasty meal.

American Avocets engage in complex courtship displays when breeding season arrives. This display involves the male avocet preening himself with water. The intensity increases into a massive splashing and then he mounts the female to mate. Following copulation the avocet pair run along with their necks intertwined. American Avocet nests are simply a scrape in the ground that is carefully lined with vegetation, feathers and so forth. Between 3 and 4 little green-brown eggs with dark spots are laid in the nest. Whilst in the nesting phase the avocets become very aggressive, even attacking intruders. They will use a number of methods, such as dive-bombing, to distract predators from the nest. Incubation lasts 22 – 24 days and is carried out by both the male and female. The young hatchlings are able to fend for themselves immediately after making their way out into the world.

American Avocets had a major drop in numbers during the 1960s and 70s due to wetland destruction and contamination. In 1995 special provision was made to protect the wetland habitats of California. The avocets are battling to get their numbers up, but it is hoped that they will flourish in the future.

Andean Condors (Vultur gryphus)

February 9, 2009 by  
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Oftentimes when people think of vultures they think of an ugly, onimous bird, gloomily waiting around for the death of other creatures, a nightmarish bird. However, vultures play a vital role in our ecosystems and are certainly nothing to fear as they clean-up the landscape.

Andean Condors (Vultur gryphus), part of the vulture family, are the largest flying birds on the Earth. Originally they could be seen in the skies of Tierra del Fuego right along the South American Andes mountain range. Sadly, hunting led to a reduction in numbers and Andean Condors teetered on the brink of extinction. In 1973 the Andean Condor bird species was marked on the Endangered Species list. For many years South American’s have seen the powerful, huge Andean Condor as a symbol of health and strength. Villagers have sought the bones and organs of this fine creature for medicinal purposes and thus they were, and continue to be, subject to hunting. Habitat loss as well as air, water and food pollution have also led to a drastic reduction in the numbers of Andean Condors. Fortunately, though, various organizations have been involved in the conservation of this remarkable bird species, resulting in improved numbers of Andean Condors in certain localities.

As the world’s largest flying bird, the Andean Condor weighs between 9 and 12 kgs, or 20 to 30 pounds as an adult. Their impressive wingspan extends 10 feet or 3 meters assisting them to stay aloft for hours on rising air currents. Andean Condors are black, their wings are patched with white and they have a white ruff around the area of the neck. They have bare heads and the males are recognized by their fleshy comb. Wild Andean Condors can live to the age of 50 years, whilst captive birds have been known to live to about 75 years.

Condors mate for life, and their nests are carefully constructed on cliff ledges, with eggs are often being laid on bare rock. In fact, this is a great locality for a nest as it affords a measure of protection from potential predators. Andean Condors are slow breeders and mating typically takes place every second year in July depending on food availability. The courtship display involves unusual hissing and clucking noises accompanied by the male strutting with his wings out. Incubation of the single egg lasts 54 to 58 days. Both of the condors will care for the young one until its second year.

Andean Condors spend much of their day soaring on the updrafts of warm air currents. They forage over a vast area relying on their outstanding vision to spot their main food source – carrion. Once a meal has been spotted they will descend to feed with other carrion eaters such as the Turkey Vulture, Black Vulture and King Vulture. Interestingly Andean Condors have an eating hierarchy with males of all ages dominating. Their bald head is perfectly adapted for dining on carrion as the bird is able to reach right into the carcass without feathers becoming soiled. Andean Condors will also feed on bird eggs and newborn animals should it be necessary.

Andean Condors are a truly remarkable bird species worthy of conservation efforts and very important for the continued functioning of South American ecosystems.

Black Swift (Cypseloides niger)

February 9, 2009 by  
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The Black Swift (Cypseloides niger), like other swifts, spends most of its time in the air. A nearctic-neotropical migrant bird species, the Black Swift breeds in areas ranging from Alaska to California, Montana and Colorado. During the winter months you will spot them in the tropics. If you are traveling through mountains or near coastal cliffs in the range of the Black Swift you are more likely to see them.

How can you identify the Black Swift? This bird species has the typical swift shape with a cigar-shaped body and crescent wings. The Black Swift is, however, a large and rather bulky swift measuring 7 inches in length. The tail is short with a deep notch. All the plumage is black except for its whitish forehead which is only seen at close quarters. Juvenile Black Swifts are marked by little white flecks. To clarify your identification of this quick moving bird, listen out for its harsh ci-chi-chi-chit call.

Black Swifts tend to be habitat specific, requiring particular conditions for nesting. Their prefered habitat is in forests near rivers. Typically they will nest behind waterfalls or even on wet cliffs and sometimes in limestone caves. These swifts enjoy a nesting environment that is damp, dark and difficult for predators to reach. Another important factor when choosing a nest site is that it must have an easy flyway for entering and leaving the nest. Because of their very particular nesting requirements, Black Swifts’ distribution is very patchy. The nests are constructed in a cup-like shape made of mud, algae and moss. Black Swifts will either nest on their own or may become part of a small colony. The female bird will lay just one egg in June or July which both parents take turns incubating. Incubation lasts about 4 weeks. The young swift will be able to fly at between 45 and 49 days old.

Black Swifts forage whilst flying either singly or in groups. They frequently forage in wide open areas or above the forest canopy in search of small airborne insects. These are certainly fascinating birds that you will want to watch out for.

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