Short Note<br><br>Ground cavity nest temperatures and their relevance to Blue Swallow <i>Hirundo atrocaerulea</i> conservation

Abstract

Blue 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 (T_n) and ambient temperature (T_a) for one artificial and 11 natural Blue Swallow nests. Mean ground cavity T_n was significantly different to mean T_a. T_n ranged from 17.0 ± 0.1 ºC to 28.5 ± 0.3 ºC and varied less than T_a (14.0 ± 0.2 to 47.7 ± 0.4 ºC). Mean ground cavity T_n averaged 3.3 ± 0.9 ºC warmer than mean T_a for 58% of nests, and mean T_a averaged 2.6 ± 0.5 ºC warmer than mean ground cavity T_n for 42% of nests. There was no significant difference in mean ground cavity T_n 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 T_n (19.2 ± 0.1 ºC) was significantly warmer than mean artificial cavity T_n (18.5 ± 0.2 ºC). Further investigation of breeding success of Blue Swallows in relation to T_n, 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