Timing of nesting and breeding behaviour of red-throated ant-tanagers (Habia fuscicauda), a resident bird of lowland Panama

Birds have been invaluable in testing models in ecology but there is a geographical bias because most models are based on temperate species, whereas the majority of birds live in the tropics.;I also examined seasonal variation in male song output to determine if song functions in 1) territory defence 2) pair coordination of nesting and 3) as part of the extra-pair mating system. Male song was infrequent during the non-breeding season and increased dramatically particularly at the onset of nesting. Social interactions at territory borders were most frequent during the fertile period of the female, however no territory take-overs by males took place, suggesting these may play a role in the extra-pair mating system. Paternity analysis revealed high rates of extra-pair fertilizations (41% of the nestlings) suggesting that an important function of male song may be to influence female choice of extra-pair mates.;Finally, I examined seasonal variation in male testosterone levels to determine whether males show high levels of testosterone during breeding, consistent with the hypothesis that high competition for mates is associated with high testosterone concentration and aggressive behaviour (Stutchbury and Morton 2001). I collected blood samples for hormone analysis and during the breeding season I observed aggressive behaviour. Testosterone levels showed a significant increase with breeding, however testosterone concentration was not related to aggressive behaviour during playback experiments. Further study is needed to determine whether male testosterone levels in ant-tanagers influence extra-pair mating success.;I studied breeding seasonality and mating behaviour of red-throated ant-tanagers, Habia fuscicauda, a species with a mixed diet of insects and fruit. I examined whether timing of breeding is influenced by variation in food quality and if early nests have higher survival than later nests. Nesting started following the first rains of the season and females with a higher proportion of insects in the diet initiated nests significantly earlier, suggesting that insect food is important in influencing the timing of nesting. Nest predation was high (> 90% nests) and early nesting was not associated with higher nest survival.