How to live in colonies: spatial foraging strategies of the black-headed gull.

This paper describes some spatial foraging strategies observed in the course of the breeding season in five adult radio-tagged black-headed gulss (Larus ridibundus). 1. Individual foraging distances increased continuously during the nesting period. 2. The maximum foraging distance observed was 18.5 km. 3. All birds showed nearly constant flight directions over the whole breeding period. 4. It is suggested that the continuous increase in foraging distances reduces intraspecific competition around the colony. 5. Because of long foraging distances it seems to be advantageous to use only a small constant foraging sector. This behaviour can probably optimize spatial memory and enhance energetic and temporal efficiency.