CONTRASTING PHENOTYPIC CORRELATIONS IN FOOD PROVISION OF MALE TENGMALM OWLS (AEGOLIUS-FUNEREUS) IN A TEMPORALLY HETEROGENOUS ENVIRONMENT

We examined the food provision rate of male Tengmalm's owls, Aegolius funereus, during one 3 year vole cycle consisting of consecutive low, increase and peake vole years. The data were collected in the mid-nest ling period when males provisioned the whole family. In the low vole y ear, males with a low loading index (g/cm(2)) of flying area fed their offspring more often than did males with a high loading index, wherea s in the peak vole year the opposite trend was evident. Similar relati onships were found in the food mass provisioned to the nest. In the in crease vole year, male body size had no effect on feeding efficiency. In the peak vole year, when large voles are abundant, heavy males prey ed on larger voles than were generally available in their territories, indicating that largeness may increase strike power in hunting attemp ts. In the low vole year, when breeding is costly due to food scarcity and extensive hunting area, small males are more economical fliers an d efficient hunters than large males. The contrasting trends in correl ations between male size and feeding efficiency in years of vole abund ance versus scarcity suggest that no fixed phenotype may most efficien tly cope with variable food supply.