Early bird doesn't always get worm, UNC resear...(ettle down and start incubating the eggs...),Health

Sockman believes this contributes to the lower probability that first-laid eggs will hatch at all but also helps to ensure that overall, a greater number of reasonably healthy, strong and feisty chicks hatch and go on to develop into young birds.

At these elevations, conditions can be fairly harsh even during the summer when Lincoln's sparrows breed, said Sockman. Its often freezing at night, which is hard on an un-incubated egg, while daytime temperatures are warm enough to foster the growth of harmful microbes. As a result, since the mother sparrow isnt keeping them at the most optimal incubating temperature from day one, first-laid eggs can be exposed to environmental conditions that lower the chance those embryos will ever see the world outside their shell.

If the female did start incubating all her eggs as soon as she laid them, it would increase the probability theyd all hatch. But it would also give a huge head start to those first-laid eggs and the chicks that emerge from them, putting their younger siblings at even more of a competitive disadvantage once they begin battling for food and their mothers attention, said Sockman. It may also reduce the number of eggs she is capable of laying.

The mothers careful balancing of this trade-off enables her to end up with three or four relatively equally robust offspring, instead of one or two strong hatchlings and several runts of the litter, said Sockman.

Sockman now intends to examine what, if any repercussions laying order has once young birds reach adulthood. The severely competitive environment in the nest may have consequences on the individual's ability to compete for resources and mates the following year when it is reproductively mature, said Sockman.

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