Data from: Differences in speed and duration of bird migration between spring and autumn

It has been suggested that birds migrate faster in spring than in autumn
because of competition for arrival order at breeding grounds and
environmental factors such as increased daylight. Investigating spring and
autumn migration performances is important for understanding ecological
and evolutionary constraints in the timing and speed of migration. We
compiled measurements from tracking studies and found a consistent
predominance of cases showing higher speeds and shorter durations during
spring compared to autumn, in terms of flight speeds (airspeed, ground
speed, daily travel speed), stopover duration, and total speed and
duration of migration. Seasonal differences in flight speeds were
generally smaller than those in stopover durations and total
speed/duration of migration, indicating that rates of foraging and fuel
deposition were more important than flight speed in accounting for
differences in overall migration performance. Still, the seasonal
differences in flight speeds provide important support for time selection
in spring migration.