Natural selection causes early migration, shorter parental care for shorebirds

It turns out that some species simply avoid the periods when peregrines are around, by staying longer at breeding grounds, and migrate only when the coast is clear. Others appear to make a run for it before the peregrines start migrating themselves. And, according to the article -- those early-migrating species are capable of timing their breeding activities just spot-on, so that they can leave each year exactly when they need to.

The paper shows that in the years when peregrine migration begins early, the early-migrators appear to cut short their breeding activities, presumably to beat the onrush of raptors. Meanwhile, those species that migrate later do not need to shorten their nesting season. "This paper emphasizes the inherent conflict all migratory birds face between trying to produce as many offspring as possible while still maximizing their own survival" says Andy Davis, Editor-in-Chief of the journal.

According to Dr. Wesley Hochatchka, Assistant Director of Bird Population Studies at the Cornell Lab of Ornithology, "the behavior of one shorebird species, the Western Sandpiper, might appear counter-intuitive at first: why would parents end their care of offspring earlier in a year when weather was allowing for especially prolonged breeding season? This paper shows a complex decision process in which adult sandpipers are attempting to minimize their own risk of predation on migration, even if it means potentially limiting the amount of care to their own offspring."