Cooperative Fish and Wildlife Research Units Program: Montana Wildlife
Education, Research and Technical Assistance for Managing Our Natural Resources

We studied the breeding biology of the south-temperate Cape Penduline Tit (Anthoscopus minutus) to enable a comparison of its life history with related, north-temperate members of the family Remizidae, namely Eurasian Penduline Tit (Remiz pendulinus) and Verdin (Auriparus flaviceps). We used this comparison to test key predictions of three hypotheses thought to explain latitudinal variation in life histories among bird species, the seasonality and food limitation hypothesis, nest predation hypothesis and adult mortality hypothesis. Contrary to the general pattern of smaller clutch size and lower adult mortality among south-temperate birds living in less seasonal environments, Cape Penduline Tit has a larger clutch size than Verdin, a clutch size similar to Eurasian Penduline Tit and higher adult mortality than both species. Cape Penduline Tit differs most notably in parental behavioural strategy, exhibiting bi-parental care at all stages of nesting together with facultative cooperative breeding, whereas Eurasian Penduline Tit has uni-parental care and Verdin has a combination of female-only incubation but bi-parental nestling care. Consequently, Cape Penduline Tit exhibits greater nest attentiveness during incubation, a greater per-nestling feeding rate and greater post-fledging survival. The relatively large clutch size, high nestling feeding rates and associated high adult mortality in Cape Penduline Tit in a less seasonal environment support key predictions of the adult mortality hypothesis and run counter to key predictions of the seasonality and food limitation hypothesis in explaining life history variation among Remizidae species. These results add to a growing body of evidence of the importance of age-specific mortality in shaping life history evolution.