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Why Are Birds' Eggs Speckled?

Date:
September 7, 2005
Source:
Blackwell Publishing Ltd.
Summary:
Most perching birds lay eggs speckled with reddish protoporphyrin spots toward the egg's blunt end. Evidence in a paper by Gosler, Higham & Reynolds soon to appear in Ecology Letters suggests 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, and females nesting on low-calcium soils, laid thinner-shelled, more-spotted eggs.
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FULL STORY

Birds' eggs are unique in their diverse pigmentation. This diversity isgreatest amongst perching birds (order Passeriformes: 60% of all birdspecies), which include many familiar species including tits andwarblers. Despite intense interest, the purpose, in most species, ofthese patterns was unknown.

Most passerines lay eggs speckled with reddish protoporphyrin spotsforming a ring around the egg's blunt end, on an otherwise unpigmentedshell. Evidence in a paper by Gosler, Higham & Reynolds soon toappear in Ecology Letters now suggests that rather than giving a visualsignal, protoporphyrins strengthen the eggshell by compensating forreduced eggshell-thickness caused by calcium deficiency.

Pigmentspots on great tit eggs specifically marked thinner areas of shell,with darker spots marking yet thinner shell than paler spots, andfemales nesting on low-calcium soils, laid thinner-shelled,more-spotted eggs than those on high-calcium soils nearby. Pigmentationmay offer a way to assess eggshell quality.


Story Source:

The above story is based on materials provided by Blackwell Publishing Ltd.. Note: Materials may be edited for content and length.


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Blackwell Publishing Ltd.. "Why Are Birds' Eggs Speckled?." ScienceDaily. ScienceDaily, 7 September 2005. <www.sciencedaily.com/releases/2005/09/050907095627.htm>.
Blackwell Publishing Ltd.. (2005, September 7). Why Are Birds' Eggs Speckled?. ScienceDaily. Retrieved May 3, 2015 from www.sciencedaily.com/releases/2005/09/050907095627.htm
Blackwell Publishing Ltd.. "Why Are Birds' Eggs Speckled?." ScienceDaily. www.sciencedaily.com/releases/2005/09/050907095627.htm (accessed May 3, 2015).

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