Associating with kin affects the trade-off between energy intake and exposure to predators in a social bird species

Individuals have to trade- off energy intake against the risk of predation when foraging. However, in group-living species, social interference will limit the range of choices for subordinate individuals. The trade- off between foraging and predation risk may be even more complex in species that associate in family groups because relatives can provide benefits to each other that are withheld from nonrelatives. As a consequence, nonrelatives may be forced to take greater risks to gain similar amounts of energy as relatives. Here, I investigate how the energy-risk trade- off varies among individuals in a social, group- living species, the Siberian jay, Perisoreus infaustus. Groups in this species consist of a breeding pair, together with retained offspring and/ or nonrelated immigrants. I manipulated food quality at feeding sites that differed in their visibility to predators and observed the differences in foraging patterns between different group members. Adults and their offspring fed more often at the protected feeding site when it contained high- quality food, but switched to the more exposed site when this site offered higher quality food than the protected site. In contrast, immigrants spent a similar amount of time at each feeding site, independent of food quality. Birds generally spent more time waiting for access to the high- quality food source and protected feeding site, and family members generally harassed immigrants that tried to access these sites. None the less, all birds had a similar overall food intake, suggesting that immigrants pay substantially higher costs than other members to attain the equivalent level of energy intake. (C) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.