Energetics and body temperature regulation in two convergent dove species from extreme habitats

Abstrakti

The small Australian Diamond Dove Geopelia cuneata (38 g) and African Namaqua Dove Oena capensis (36 g) live in desert and semi-desert habitats . They can be regarded as ecological counterparts on the two continents . They are both diurnal and active even throughout the hottest part of the day. Therefore, they regularly encounter extremely high temperatures (up to 60-70°C), especially when feeding on the hot ground . Metabolic rates (MR) of both species are 20-50% below expected values . This has been described for other desert pigeons before, while species from temperate regions have MR in the expected range of all birds . Both species tolerate elevated body temperatures (Tb ; up to 44.8 °C) under high external heat load . Additionally, they show effective heat loss mechanisms (panting, gular flutter) so that metabolic heat is dissipated as fast as it is produced by the organism without a further rise in body temperature . These physiological characteristics enable them to be active and forage on the ground throughout the day even when temperatures are highest. The two dove species are opportunistic breeders in adaptation to the unpredictable climatic conditions in their habitat. This can be seen from their fast pre- and postnatal development: The nestling time and total energy investment per juvenile are only 50% of the values expected for tropical birds . Thus, several broods can be raised under favourable conditions, especially when rainfall occurs .