THERMOREGULATION OF AMBIENT TEMPERATURE BY NESTS OF FURNARIIDAE (AVES)

Many works refer to thermoregulation in bird nests with emphasis on thermal insulation - the reduction of heat loss - and the influence of wind when the nests are occupied by birds while they are sleeping or in the reproductive stage. As numerous arthropods take refuge in bird’s nests in winter and also during summer, the question arises as to how the interior of the nest vacated by the bird behaves with respect to the ambient temperature. Internal and external temperatures in sunny and/or cloudy days during winter and summer were measured in Furnariidae nests built with sticks. During the summer, it is observed that the inside of the nest is somewhat warmer than the outside between 7-8 pm and 9-10 am, and cooler during the day. On a cloudy day, the temperature curve inside the nest was always above the external temperature curve. This pattern is found also in winter when, in addition, nest temperature at night is higher than ambient temperature; during the day, nest temperature is slightly lower than ambient temperature and exhibits imperceptible fluctuations. With external temperatures below 0ºC at night, nest temperature was always above 0ºC. This would explain why the stick nests of Furnariidae are preferred by more than 100 species of arthropods when choosing a refuge, either in winter or in summer.