High-altitude flights of Pallid Swifts in the breeding range revealed by GPS trackers

During the breeding period parents must move between foraging and nesting sites to collect food and nourish their offspring. Foraging in distant areas is expected to accrue high travel costs and should be balanced by food intake. Swifts can fly continuously at considerably high altitudes in the African wintering quarters, but little data are available on flight activity during the breeding season. Between 2018 and 2022, we equipped 19 Pallid Swifts Apus pallidus with GPS trackers (n = 34) to measure flight altitude, home ranges, and to assess how flight patterns are influenced by habitat type and weather variables, including wind speed and direction. Swifts flew on average 6 km from the nest and displayed a home-range size of 481 km2. The flight altitude was on average 920 m a.s.l., 700 m above the colony site. Habitat type and ground wind speed and direction did not influence flight patterns. The continuous high-altitude flights of swifts in the breeding range appear to be an extraordinary adaptation of these aerial insectivores and suggests that aerial arthropods can be abundant at high altitudes in breeding quarters too.