CHAPEL HILL Competing against older brothers and sisters can be tough work, as any youngest child will tell you.
But new research from a biologist at the University of North Carolina at Chapel Hill shows that when it comes to some birds, you should reserve any underdog sympathies for the first born or rather, first laid siblings as well.
The finding, published in the March 12 issue of PLoS ONE, runs somewhat counter to common wisdom, which holds that baby birds that are laid before their brood mates have a better chance of surviving long enough to leave the nest.
But after studying a population of Lincolns sparrows in a remote stretch of Colorados San Juan Mountains, Keith Sockman, an assistant biology professor in UNCs College of Arts and Sciences, has discovered that first-laid eggs are, in fact, the least likely to hatch at all.
I believe this is the first study to follow siblings from laying through fledging and demonstrate that the effect of laying order on hatching is very different from its effect post-hatching, said Sockman.
It is a well-documented fact that being born just a day or so later often sets the stage for a situation whereby youngest hatchlings die. Thats because theyre too small to compete against their feistier brood-mates for the limited resources provided by their parents. Such competitive disparities caused by hatching or birth order can be found in other animals from beetles to marsupials to humans which sometimes produce their young in series, then rear the resulting offspring simultaneously.
But Sockman says up until now, such observations have usually failed to take account of what happens to eggs before they hatch.
Female Lincolns sparrows lay one egg per day, usually producing three to five eggs in total. While carefully observing and tracking the tiny birds for three breeding seasons, Sockman and his team of researchers noticed that typically, mothers do not s
|Contact: Patric Lane|
University of North Carolina at Chapel Hill