Ground cavity nest temperatures and their relevance to Blue Swallow Hirundo atrocaerulea conservation
AbstractBlue Swallows Hirundo atrocaerulea are 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 cavity Tn was significantly different to mean Ta. Tn ranged from 17.0 ± 0.1 ºC to 28.5 ± 0.3 ºC and varied less than Ta (14.0 ± 0.2 to 47.7 ± 0.4 ºC). Mean ground cavity Tn averaged 3.3 ± 0.9 ºC warmer than mean Ta for 58% of nests, and mean Ta averaged 2.6 ± 0.5 ºC warmer than mean ground cavity Tn for 42% of nests. There was no significant difference in mean ground cavity Tn for the aardvark-excavated holes (22.7 ± 1.6 ºC) and sinkholes (21.5 ± 1.2 ºC). Blue Swallows also nest in man-made holes, potentially a way to increase nesting sites. Mean aardvark-excavated Tn (19.2 ± 0.1 ºC) was significantly warmer than mean artificial cavity Tn (18.5 ± 0.2 ºC). Further investigation of breeding success of Blue Swallows in relation to Tn, incubation strategies and predation risk needs to be addressed in future studies for a better understanding of their reproductive ecology.
Keywords: artificial nest, Blue Swallows, critically endangered, microclimate, natural nest
OSTRICH 2013, 84(3): 221–226