Relationships between scan and interscan durations in three avian species

Abstract

Foraging birds interrupt a feeding bout to scan the environment for potential predators; their behaviour can therefore be described as an alternating sequence of scans (S) and interscan intervals (I). The ratio of I to S oscillates rhythmically during a foraging period; this is consistent across three avian species (Barbary dove, Streptopelia risoria; chough, Pyrrhocorax pyrrhocorax; and goldfinch, Carduelis tristis) and in a variety of social and foraging contexts. Thus, although there are differences in the mean ratio (possibly related to differences in food-handling time), all samples show the same pattern of cycling in the ratio of I to S. In addition to these oscillations, the length of an interscan interval tends to vary in direct proportion to the length of the preceding scan in solitary individuals (Barbary doves); however, in flock foragers (choughs and goldfinches) there is an inverse relationship between I and S.