Data from: Breeding site departure and post-departure movement strategy in Vireo olivaceus (Red-eyed Vireo)

Few studies have been able to assess the decision-making process behind
migratory departures from the breeding site and the extent to which
extrinsic cues that favor departure from fall stopover sites also apply to
initial departure from breeding sites. Factors influencing departure may
vary between species that first make short-distance regional movements vs.
those that immediately begin long-distance migration, but for most
migratory songbirds, it is unknown which post-departure movement strategy
they use or why. We used an automated radio telemetry network to track
adult male Vireo olivaceus (Red-eyed Vireo) as they departed their
northwest Pennsylvania breeding site on fall migration to determine their
post-departure movement strategy. We also assessed how local weather
conditions, including surface pressure, humidity, precipitation, and wind,
influenced the probability of departing the breeding site on fall
migration. For the individuals for whom we could confidently ascertain
departure day and time, 86% departed during the first 2 hr after sunset.
Net displacement was positive, and birds headed directly south towards
Florida. Birds were more likely to depart on nights with rising surface
pressure and high humidity, and frequently departed in unsupportive wind
conditions (headwinds). Our results suggest that V. olivaceus initiates
true long-distance migratory flights after departing from its breeding
sites. Birds may have departed under unsupportive wind conditions due to
the scarcity of tailwinds at the breeding site. Alternatively, birds
leaving their breeding areas in the fall may be less selective of optimal
weather conditions for departure than birds departing stopover habitats,
as they have higher fuel loads and ample time to compensate during the
rest of their migratory journey.