Environmental conditions e g winds and weather are hypothesized to

We tested these predictions by analysing the prevailing environmental conditions (wind direction, wind speed, cloudiness, visibility, time of season) during departure. We also compared critical individual characteristics (species, age, fuel reserves) and differences in the behaviour (departure timing and directions, stopover duration) between JNJ 303 that did not pass FINO 2 and those that did, hence taking a longer flight than necessary over the Baltic Sea.
Based on the general hypothesis that resulting flight duration over a given distance is determined by a combination of internal and external factors affecting the speed and straightness of the flight, we predicted that: (1) the duration of the flight between Falsterbo and FINO 2 would primarily be affected by winds (assistance by tail winds or hindrance by head winds); (2) cloudy weather and weather with low visibility would prolong the duration by entailing orientation difficulties resulting in less straight flight paths; (3) the flight duration would be longer in young migrants and migrants with smaller fuel reserves because of less precise orientation and more tortuous flight paths; (4) the flight duration would be longer in birds departing from Falsterbo in a direction deviating from the direction towards the offshore receiver station.