Female choice in the penduline tit Remiz pendulinus: the effects of nest size and male mask size

Why do females prefer some males over others? Females often use multiple cues, and to distinguish between these cues one needs to manipulate putative male traits. We carried out a test of multiple cues hypothesis in a polygamous bird, the penduline tit Remiz pendulinus. In this passerine both males and females mate with up to six mates within a breeding season, and a single parent (male or female) incubates the eggs and raises the chicks. Males build sophisticated nests, and previous studies suggested that females prefer males with large nest to small ones, since large nests provide direct benefit to females via reduced cost of incubation. Males sport wider eye-stripes ('masks') than females, and males with large masks find a mate faster than males with small masks. In a mate choice experiment using factorial design and two levels for each trait, we show that females prefer males with large masks, whereas they do not show preference for large nests. These results suggest that in penduline tits (i) females pay more attention to a trait that signals indirect benefit (mask size) than a trait that is related to direct benefits (nest size), and (ii) nest preference may be context-dependent.