Seasonal changes in the altitudinal distribution of nocturnally migrating birds during autumn migration.

ABSTRACT: Wind plays a significant role in the flight altitudes selected by nocturnally migrating birds. At mid-latitudes in the Northern Hemisphere, atmospheric conditions are dictated by the polar-front jet stream, whose amplitude increases in the autumn. One consequence for migratory birds is that the region's prevailing westerly winds become progressively stronger at higher migration altitudes. We expect this seasonality in wind speed to result in migrants occupying progressively lower flight altitudes, which we test using density estimates of nocturnal migrants at 100 m altitudinal intervals from 12 weather surveillance radar stations located in the northeastern USA. Contrary to our expectations, median migration altitudes deviated little across the season, and the variance was lower during the

SUBMITTER: La Sorte FA 

PROVIDER: S-EPMC4807445 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature