Geographical trends in breeding parameters of swallows Hirundo rustica and house martins Delichon urbica

摘要: Geographical trends in demographic traits were studied Swallow Hirundo rustica and House Martin Delichon urbica from populations the western Palaearctic. Clutch size increased with latitude second clutches longitude clutches. The number of broods per season decreased latitudinally for longitudinally as well. eggs pair breeding thus both species Martin. It is suggested that difference longitudinal response between two due to higher more weatherinfluenced foraging niche Hatchability latitude. Between year population variations Swallow. Ashmole's (1961) hypothesis did not account geographical clutch size. variation nest predation could explain variance Royama's (1969) model on taking food availability, time available feeding temperature-dependent energy requirements young into consideration explained a large fraction among species. absolute metabolic level nestlings north south.