Abstract
The importance of nest characteristics for birds breeding in the extreme climate conditions of polar regions, has been greatly understudied. Nest parameters, like nest orientation, exposure and insulation, could strongly influence microclimate and protection against precipitation of the nest, thereby affecting breeding success. A burrow nesting seabird, the Wilson’s storm-petrel (Oceanites oceanicus) is an excellent model species to investigate the importance of nest characteristics, as it is the smallest endotherm breeding in the Antarctic. Here, we investigated the effects of nest parameters such as internal nest dimensions, nest micro-topography and thermal properties of the nest burrow and the influence of weather conditions on breeding output, measured as hatching success, chick survival, and chick growth. We collected data during the austral summers of 2017 and 2018, on King George Island, maritime Antarctica. Our results showed that the thermal microclimate of the nest burrow was significantly improved by a small entrance size, a low nest height, and insulation and tended to be enhanced by a low wind exposition index and an eastern nest site orientation. In addition, an eastern nest site orientation significantly reduced the chance of snow blocking. However, the relationships between nest characteristics and breeding output were complex and might be affected by other parameters like food availability and parental quality. The relation between chick growth and nest air temperature remained especially indistinct. Nevertheless, our results indicate that nest characteristics that enhance the thermal microclimate and reduce the risk of snow blocking favoured both hatching success and chick survival. Due to climate change in the Antarctic, snowfall is expected to increase in the future, which will likely enhance the importance of nest characteristics that determine snow blocking. Additionally, despite global warming, thermally favourable nest burrows will likely still be advantageous in the highly variable and challenging Antarctic climate.
Highlights
Avian breeding success is determined by many variables such as parental effort, food availability, parasites, predation and nest characteristics [1,2,3,4,5,6,7,8]
We initially modelled each breeding output parameter with the nest parameters that were associated with the thermal microclimate and snow blocking as obtained in step 3, and breeding season to account for inter-annual differences (S6 and S7 Tables for the model selection of hatching success and chick survival, respectively)
We found that nest air temperature was significantly related to weather conditions; higher nest air temperature was associated with higher air temperature and northern winds with low speeds (Table 3)
Summary
Avian breeding success is determined by many variables such as parental effort, food availability, parasites, predation and nest characteristics [1,2,3,4,5,6,7,8]. A suboptimal nest microclimate can be caused by various factors, such as extreme nest temperatures and exposure to wind or precipitation [17,18,19,20,21]. Suboptimal nest temperatures during incubation have been shown to have a negative impact on embryonic development [22,23]. Suboptimal thermal nest conditions caused by a high nest temperature have been shown to retard chick growth in blue tits (Cyanistes caeruleus) and eastern kingbirds (Tyrannus tyrannus) [31,32]. This highlights the importance of the thermal microclimate of the nest on breeding success
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