Extreme microclimate conditions in artificial nests for Endangered African Penguins

Abstract

SummaryAfrican Penguins Spheniscus demersus naturally breed in guano burrows which provide shelter from predators and extreme weather conditions. Past guano harvesting has removed this habitat and artificial nests of different types have been deployed, with previous research identifying variable success of these different types. We investigated climatic conditions in two types of artificial nests, and compared them to natural burrows and surface nests for two weeks in the incubation and early chick-rearing phases of the 2012 summer breeding season on Bird Island, Algoa Bay, South Africa. We also compared breeding success since 2009 between some of these nest types. Natural burrows remained the best insulated from extremes of temperature and humidity, with temperatures consistently higher and humidity consistently lower than in exposed nests and the two types of artificial nests. Fibreglass nests retained temperatures > 30°C, when Spheniscus penguins start being heat-stressed, for the longest periods of time. Sustained high temperatures will induce increased energy expenditure associated with active thermoregulation for birds in these nests. The combination of high temperatures and low humidity could also have contributed to damaging water loss in the eggs and reduced egg survival, as suggested by the consistent lower hatching success in the fibreglass nests. Cement nests had more moderate temperatures than fibreglass nests and higher breeding success, possibly due to superior ventilation. Vegetation cover had no effect on the temperature regime inside fibreglass nests. To maximise conservation efforts for these endangered penguins, additional research should be conducted towards engineering artificial nests that better mimic the conditions of natural burrows.