Ambient Temperature And Nest Temperature Variation In Enclosed Nests (Spanish Sparrow) And Open-Cup Nests (Iberian Azure-Winged Magpie)

Abstract Temperature plays a central role in the life of birds, especially during egg incubation and nestling thermal brooding. I investigated nest temperature variation relative to ambient temperature during incubation in an enclosed nest-builder species (Spanish sparrow Passer hispaniolensis) and an open-cup nest-builder species (Iberian azure-winged magpie Cyanopica cooki). The data for empty enclosed nests showed that the nest structure acted as a temperature buffer which reduced the impact of night-time temperature variation within the nest. The buffer effect was reduced as ambient temperature increased at dawn. The presence of an adult increased the difference between nest temperature and ambient temperature, and dissociated its variation from the ambient temperature variation. The enclosed nest also retained the body heat released by an adult in the nest. Both effects had a positive effect on the temperature balance in the nest. By contrast, open-cup nest temperature was more affected by the ambient temperature, although it did not affect the egg temperature directly. Thus the absence of an incubating parent would endanger the hatchability in open-cup nests more rapidly than in enclosed nests. The life histories of the investigated species correspond to these findings, i.e. a more pronounced presence of the female in the Iberian azure-winged magpie nests.