Snake Skin as Protection Against Predators

August 13, 2013 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.

Significance of Egg Coloration to Embryo Development

October 18, 2011 by  
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Researchers continue to debate the purpose of bird egg pigmentation, with the most popular theory being that camouflage is the main reason for the variation in eggshell colors, with the speckles and splotches of color providing protection from predators. This was the theory put forward by renowned biologist Alfred Russel Wallace in the late 19th century, a position that was challenged by naturalist Alexander M’Aldowie who believed the pigmentation of eggshells served to shield developing embryos from harmful radiation.

Wallace’s theory was the more widely accepted argument, and later research studies on this topic would be based on the fight for survival aspect that supports the necessity for Alexander camouflage. Other accepted theories to arise in subsequent years included the role that pigmentation plays in retaining heat and continuing the incubation process when the eggs are unattended, as well as signaling unpalatability to would-be egg-eaters and serving as identification for host birds that have parasitic eggs laid in their nests.

Although all these theories have merit, in a recently published review of a series of studies in the Journal of Avian Biology of 14 September, biologists Phillip Cassey and Golo Maurer of the University of Adelaide in Australia take the embryo’s view of its protective covering in offering possible explanations for the purpose of eggshell coloration. One of these explanations validates the original theory put forward by Alexander M’Aldowie where the pigmentation of the eggshell helps to filter, but not block, ultraviolet light for the developing embryo. It is interesting to note that even the darkest eggs, using the emu as an example, allow some light to filter through. It was also noted that pigmentation differs at each end of the egg, most likely to provide directional cues to the embryo, as well as to assist cells and structures in their early alignment.

As in the case of gulls, which commonly lay a clutch of three eggs, with the second egg laid being noticeably and consistently darker than the other two, the variations in eggshell pigmentation could be a significant factor in facilitating staggered hatching. Moreover, it has been proposed that the variations in eggshell coloring could assist the embryo in learning to recognize the difference between light and dark, calibrating circadian rhythms, as well as encouraging DNA repair and shaping bacterial communities within the egg. Researchers have also noted that pigmentation is affected by rainfall and weather, possibly compensating for local and seasonal conditions. Certainly, there is much still to learn about the marvelous world of birds, and with advancing science, more of these mysteries will no doubt be solved.

American Oystercatcher (Haematopus palliates)

February 9, 2009 by  
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The American Oystercatcher (Haematopus palliates) is a coastal bird that can be found along the Gulf Coast and over most of the Atlantic Coast. This is a bird that is 16 inches in length and can be identified by is predominantly black body, grayish-brown back and wings, and a snowy white belly. This coastal bird has pink legs and a bright orange or blood red bill, with yellow eyes and an orange orbital ring. Juvenile birds have a dark tip at the end of their bills and their eyes are dark. Although its coloring does not make the best fashion statement, it does make them distinctive. Being a coastal bird, the American Oystercatcher relies on the ocean for its food that consists of mussels, oysters and clams, Unfortunately, coastal developments by humans are increasingly encroaching on the habitat and lifestyle of these birds.

American Oystercatchers are migratory birds, with the breeding populations located in the north often migrating to the southeastern areas of the United States during the winter months. Due to development and coastal activities, populations in the Massachusetts area have increased in numbers. In contrast to the northern populations, it seems that the birds that are found along the Atlantic and Gulf coasts, are more established and remain permanent residents of the area. Many IBA’s (Important Bird Areas) have been established to provide the American Oystercatchers with safe nesting grounds, and winter habitats for the migratory populations. There are approximately thirty breeding pairs that are protected by the Hatteras National Seashore IBA, in North Carolina, and the Altamaha River Delta IBA, in Georgia, is home to approximately 250 migratory American Oystercatchers. Many of these IBA’s, including the Big Bend Ecosystem IBA, Cedar Keys National Wildlife Refuge and Hillsborough Bay IBA in Florida, play an important role in the conservation of these beautiful birds. These areas are also motivated by the fact that in the 1850’s, American Oystercatchers had become extremely scarce in the mid-Atlantic areas, and only began increasing in population numbers during 20th century.

Not only does human development threaten these coastal birds, but they also fall victim to hurricanes and oil-spills. All these factors make nesting very difficult for the birds. American Oystercatchers nest on the ground, which enables them to blend in with their surroundings as a form of camouflage. Their eggs are gray in color and are speckled, having a pointed shape which prevents the eggs from rolling away. But no matter how many preventative measures the American Oystercatcher has, it remains up to humans to protect these birds, and the land they live on.

Perfect Winter Camouflage

January 29, 2007 by  
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The Ptarmigan is a type of grouse living in the far north, in Alaska, northern Canada, Greenland, Scandinavia and Siberia. In summer, its feathers are brown and mottled like the tundra it lives in. Like many other bird species, it uses brownish camouflage to hide from predators.

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Bird Watching: What’s with the Camouflage

September 18, 2006 by  
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There are hard-core birders that feel they need to dress up like a supporting player in a Rambo movie in order to get deep in to the bird’s environment. As a result, you see quite a few bird enthusiasts dressed up in camouflage pants and shirts, their faces smeared with green grease paint. It’s no wonder they aren’t scaring away the very birds they are hoping to see in the first place.

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