Bourne Amanda R, Ridley Amanda R, Cunningham Susan J
FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
Australian Wildlife Conservancy, 322 Hay Street, Subiaco 6008, Western Australia.
Behav Ecol. 2023 Apr 15;34(4):562-570. doi: 10.1093/beheco/arad023. eCollection 2023 Jul-Aug.
Cooperative breeding, where more than two individuals invest in rearing a single brood, occurs in many bird species globally and often contributes to improved breeding outcomes. However, high temperatures are associated with poor breeding outcomes in many species, including cooperative species. We used data collected over three austral summer breeding seasons to investigate the contribution that helpers make to daytime incubation in a cooperatively breeding species, the Southern Pied Babbler , and the ways in which their contribution is influenced by temperature. Helpers spent a significantly higher percentage of their time foraging (41.8 ± 13.7%) and a significantly lower percentage of their time incubating (18.5 ± 18.8%) than members of the breeding pair (31.3 ± 11% foraging and 37.4 ± 15.7% incubating). In groups with only one helper, the helper's contribution to incubation was similar to that of breeders. However, helpers in larger groups contributed less to incubation, individually, with some individuals investing no time in incubation on a given observation day. Helpers significantly decrease their investment in incubation on hot days (>35.5°C), while breeders tend to maintain incubation effort as temperatures increase. Our results demonstrate that pied babblers share the workload of incubation unequally between breeders and helpers, and this inequity is more pronounced during hot weather. These results may help to explain why recent studies have found that larger group size does not buffer against the impacts of high temperatures in this and other cooperatively breeding species.
合作繁殖是指两个以上的个体共同投入养育一窝幼雏，这种现象在全球许多鸟类物种中都有发生，并且通常有助于提高繁殖成功率。然而，高温与许多物种（包括合作繁殖的物种）的不良繁殖结果有关。我们利用在三个澳大利亚夏季繁殖季节收集的数据，研究了帮手对合作繁殖物种——南方斑鸫白天孵化的贡献，以及温度对它们贡献的影响方式。与繁殖对的成员相比，帮手花费在觅食上的时间比例显著更高（41.8 ± 13.7%），而花费在孵化上的时间比例显著更低（18.5 ± 18.8%）（繁殖对成员觅食时间为31.3 ± 11%，孵化时间为37.4 ± 15.7%）。在只有一个帮手的群体中，帮手对孵化的贡献与繁殖者相似。然而，在较大群体中的帮手个体对孵化的贡献较少，在某些观察日，一些个体根本不参与孵化。在炎热的日子（>35.5°C），帮手会显著减少它们在孵化上的投入，而随着温度升高，繁殖者往往会保持孵化的努力程度。我们的结果表明，斑鸫在繁殖者和帮手之间不平等地分担孵化工作，而且这种不平等在炎热天气下更为明显。这些结果可能有助于解释为什么最近的研究发现，在这种以及其他合作繁殖物种中，较大的群体规模并不能缓冲高温的影响。
