Ground cavity nest temperatures and their relevance to Blue Swallow Hirundo atrocaerulea conservation.

Blue SwallowsHirundo atrocaeruleaare Critically Endangered within South Africa. They nest in natural underground holes in mist-belt grasslands. Temperature dataloggers were used to record ground cavity nest (Tn) and ambient temperature (Ta) for one artificial and 11 natural Blue Swallow nests. Mean ground cavityTnwas significantly different to meanTa.Tnranged from 17.0 ± 0.1 °C to 28.5 ± 0.3 °C and varied less thanTa(14.0 ± 0.2 to 47.7 ± 0.4 °C). Mean ground cavityTnaveraged 3.3 ± 0.9 °C warmer than meanTafor 58% of nests, and meanTaaveraged 2.6 ± 0.5 °C warmer than mean ground cavityTnfor 42% of nests. There was no significant difference in mean ground cavityTnfor the aardvark-excavated holes (22.7 ± 1.6 °C) and sinkholes (21.5 ± 1.2 °C). Blue Swallows also nest in man-made holes, potentially a way to increase nesting sites. Mean aardvark-excavatedTn(19.2 ± 0.1 °C) was significantly warmer than mean artificial cavityTn(18.5 ± 0.2 °C). Further investigation of breeding success of Blue Swallows in relation toTn, incubation strategies and predation risk needs to be addressed in future studies for a better understanding of their reproductive ecology. [ABSTRACT FROM PUBLISHER]