![]() ![]() “While hypotheses such as these might be true for some birds, no broad study had yet been conducted to see if these ideas would hold up at a large scale - across all birds generally,” said evolutionary biologist and behavioral ecologist, Mary Caswell Stoddard, an assistant professor at Princeton University who was determined to find the answer. Unfortunately, it's difficult to point to any one hypothesis as being more correct than any other for explaining avian egg shapes because previous studies have been small and limited to only a few of the more than ten thousand species of birds. GrrlScientist via a Creative Commons license a larger image by Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden / CC BY-SA 3.0) maleo (Macrocephalon maleo) (Credit: Arisdp / CC BY-SA 3.0) common murre (Uria aalge) (Credit: derived from a larger image by Didier Descouens / CC BY-SA 4.0). Left to right: brown hawk-owl (Ninox scutulata) (Credit: derived from. Although this idea seems most "squishy", it holds promise as a sort of "Grand Unified Hypothesis" that explains the evolutionary reasons underlying egg shapes for all bird species. And conical eggs are more resistant to breaking if they're being knocked around, as happens in crowded nesting colonies.Īnother hypothesis proposed that flight adaptations that have changed the morphology of the pelvis, abdomen, or oviduct indirectly influence egg shape ( ref). Conical eggs may best accommodate the increased number pores on the blunt end that enhance respiration necessary to support accelerated neural development essential to precocial birds. On the other hand, both elliptical and asymmetrically conical eggs pack closely together to allow for the most efficient distribution of heat amongst eggs within a multi-egg clutch. Spherical eggs are most economical to create, requiring the smallest amount of precious calcium to create the eggshell for any given volume. For example, spherical eggs are less likely to break under the weight of an incubating parent due to the shell's uniform strength. ![]() Other hypotheses focus on the mechanical properties of the eggshell, the physiological aspects involved in incubation, or the variety of economies associated with a particular egg shape. Well, that explanation certainly seemed plausible - so much so that British broadcaster and naturalist David Attenborough even repeated it in one of his TV programs - but that idea was also just plain wrong: investigations by several researchers recently disproved the rolling hypothesis ( ref).
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