Effects of site fidelity, group size and age on food-caching behaviour of common ravens, Corvus corax

Abstract

The storage of food is widespread among mammals and birds and can be flexibly adjusted to various contexts such as competition, food availability or energetic demands. In bird species, nonbreeders often move through large areas whereby periods of long-term settlement can alternate with short-term visits. In food-caching species these differences in the degree of local settlement might change the benefits gained from storing food, and caching may only be advantageous during periods of prolonged settlement. We examined whether differences in local settlement influence food-caching behaviour of wild common ravens at a local anthropogenic food source with high interspecific and intraspecific competition. We found that individuals with a higher degree of site fidelity (i.e. prolonged periods of local settlement) engaged in food caching more than individuals with less site fidelity (i.e. short periods of local settlement); this effect was even stronger in the presence of potential predators representing a high-risk foraging situation. Further, juvenile ravens were less likely to cache than subadults and adults, and an increasing number of conspecifics present at the feeding site decreased the likelihood of caching. We found considerable individual variation in respect to the area used for caching. We suggest that individuals with higher site fidelity may gain more benefits from caching food and/or that they are more successful in obtaining food potentially due to more experience with the local foraging situation. Research is needed to examine the exact causes of the observed link between food-caching behaviour and the different degrees of site fidelity. Our findings show that differences in movement and settlement decisions can influence ecological aspects such as food acquisition and thus may have important consequences for individual fitness and population dynamics. • We studied how differences in site fidelity affect food-caching behaviour of ravens. • Individuals with a high site fidelity cached food more frequently. • This effect was even stronger in the presence of predators. • Young ravens cached food less often compared to older individuals. • Caching behaviour decreased with an increasing number of conspecifics.