By IANS
New York : Contrary to popular wisdom, the early bird is not the one that will survive the longest – in fact, a new study says the chances that the first-laid egg will hatch at all are remote.
The study, by researchers at the University of North Carolina, found that birds emerging from later eggs have a much better chance of surviving long enough to leave the nest, Sciencedaily reported.
“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 Keith Sockman, who led the study, which tracked a population of sparrows.
This is contrary to earlier studies, which showed that being born later is a disadvantage – the youngest hatchlings die because they are too small to compete for the limited resources provided by their parents.
But according to Sockman, these studies have usually failed to take account of what happens to eggs before they hatch.
The female sparrows that were studied lay one egg per day, usually producing three to five eggs in total.
Sockman noticed that, typically, mothers did not settle down and start incubating the eggs right away, since they still have other concerns during the laying cycle, such as foraging for food.
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 develop into young birds.
“If the female did start incubating all her eggs as soon as she laid them, it would increase the probability they’d 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 mother’s attention,” said Sockman.
“It may also reduce the number of eggs she is capable of laying.”
The mother’s 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.