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Wednesday, December 5, 2007

Bird Egg Identification

3-d oval shaped may or may not be white, with or without spots, varying in their external appearance - there are so many types of eggs. Here, we talk of only birds’ eggs. All birds lay eggs. These exhibit a great diversity of shape, colour and patterns. Despite their fragility, the calcium carbonate shells provide protection and a self-enclosed environment for the developing chicks. Bird egg identification is complicated because there are so many species of birds and they lay eggs that are externally different. It has taken scientists years to learn the art of and formulising methods on how to recognise and identify the eggs of different birds. It is quite an art, and because it is done through scientific means it’s a scientific art. Therefore, bird egg identification is by all means a scientific art.

Most eggs that are laid in sheltered nests or holes in the ground are white and those laid in uncovered nests have protective colouring. Birds’ eggs differ greatly in size making bird egg identification quite scientific. Hummingbirds lay the smallest eggs and ostriches the largest, making identification of these birds’ eggs easier. The eggs of most birds are shaped like domestic chicken eggs. However, the eggs of cliff-nesting species are sharply pointed at one end. The shape of these eggs prevents them from rolling off the cliff. Many birds have plain-coloured eggs. The eggs of ground nesters are heavily camouflaged with speckles and other markings. Birds' eggs are unique in their diverse pigmentation.

This diversity is greatest amongst perching birds, also called passerines, which make up almost 60% of all bird species. This category includes many familiar species including tits and warblers. Most passerines lay eggs speckled with reddish protoporphyrin spots forming a ring around the egg's blunt end, on an otherwise un-pigmented shell. Scientists and ecologists suggest that rather than giving a visual signal, protoporphyrins strengthen the eggshell by compensating for reduced eggshell-thickness caused by calcium deficiency. Pigment spots on great tit eggs specifically marked thinner areas of shell, with darker spots marking yet thinner shell than paler spots, and females nesting on low-calcium soils, laid thinner-shelled, more-spotted eggs than those on high-calcium soils nearby. Pigmentation may offer a way to assess eggshell quality and aids in bird egg identification.

Bird egg identification of South American game birds is the most intriguing because they have solid metallic colors and a finish like that of a new automobile. Most birds that nest in dark holes, like the kingfisher and the woodpeckers, lay plain white eggs; whereas those of the kill deer and terns laid in exposed places with no protecting nest are colored like the soil or gravel and are very difficult to find. The majority of birds that build protective nests lay eggs having a ground color of some delicate tint with spots, streaks or scrawls of darker pigment such as purple, brown or black and, often, this forms a kind of wreathe around the larger end. Robins and bluebirds have blue eggs but those of some other thrushes are spotted with darker color. These formulae and methods formulated by scientists have made the whole process of bird egg identification, so much simpler.

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