Posted: 22 Jun 2017 11:30 AM PDT see full article here
The evolution of the amniotic egg — complete with membrane and shell — was key to vertebrates leaving the oceans and colonizing the land and air but how bird eggs evolved into so many different shapes and sizes has long been a mystery. Now, an international team of scientists took a quantitative approach to that question and found that adaptations for flight may have been critical drivers of egg-shape variation in birds….
…”To maintain sleek and streamlined bodies for flight, birds appear to lay eggs that are more asymmetric or elliptical. With these egg shapes, birds can maximize egg volume without increasing the egg’s width — this is an advantage in narrow oviducts.”
So an albatross and a hummingbird, while two very different birds, may have evolved similarly shaped eggs because both are high-powered fliers.
“It’s clear from our study that variation in the size and shape of bird eggs is not simply random but is instead related to differences in ecology, including the amount of calcium in the diet, and particularly the extent to which each species is designed for powerful flight” says coauthor Dr. Joseph Tobias from Imperial College, UK.
Mary Caswell Stoddard, Ee Hou Yong, Derya Akkaynak, Catherine Sheard, Joseph A. Tobias, L. Mahadevan. Avian egg shape: Form, function, and evolution. Science, 2017 DOI: 10.1126/science.aaj1945