There is increasing evidence that birds use chemical cues in different contexts, and this is changing the traditional view that placed birds alone as the only largely olfaction-free vertebrates. We performed a choice experiment to examine whether male house finches (C. mexicanus) exhibit any preferences for the sex of conspecifics when only their chemical cues are available. When exposed during the breeding season to the scent of a male or a female, males appeared to respond indiscriminately to both odours. However, when analysing a posteriori the choices of males in relation to their relative quality, males with worse quality than scent-donor males avoided the male-scented area, whereas males with better quality moved towards the male-scented area. Our results suggest that in the context of mate-choice/competition for mates, house finches may obtain information via olfaction to assess the quality of rival males.

During a 7‐year research project in a forested area of southeastern Spain, we studied territorial occupancy and reproductive success in a Booted Eagle Hieraaetus pennatus population. We monitored 65 territories, gathering information on 406 occupancy events and 229 breeding attempts, including those of two potential competitors, the Northern Goshawk Accipiter gentilis and the Common Buzzard Buteo buteo. Generalized linear mixed models were used to explain occupancy and productivity, by evaluating the relative contribution of three different types of variables (habitat, competition and past events) and considering territory as a random effect. We examined a set of a priori hypothesized models, together with a number of additional models, and selected the best models following an information‐theoretic approach. Our best models related territorial occupancy and productivity to previous breeding success (the fledging of one or two young), which appeared to be the most important factor determining the probability of reoccupation and the reproductive output in the subsequent year. The best occupation model revealed that the probabilities of occupancy were also conditioned by a competition variable (intraspecific nearest‐neighbour distance) and two habitat variables (the location of the nest on the valley slope and the distance to the nearest forest track). Unlike the best occupation model, however, the selected model for reproductive output did not incorporate any competition variable besides previous breeding success, but included another two habitat variables (the effects of trunk height and NNE orientation).

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