Population-level body condition correlates with productivity in an arctic wader, the dunlin Calidris alpina, during post-breeding migration

Abstract

Weather and predation constitute the two main factors affecting the breeding success of those Arctic waders whose productivity is highly variable over the years. We tested whether reproductive success is associated with the post-breeding condition of adults, in which in ‘good’ years (with warm weather, plentiful food and low predation pressure) the condition of breeders and their productivity is high. To verify this hypothesis, we used a 10-year dataset comprising 20,792 dunlins Calidris alpina, trapped during migration at a stopover site on the southern Baltic Sea shore. Males were consistently in a slightly worse condition than females, likely due to male-biased parental investment in brood rearing. Annual productivity indices were positively correlated with the respective condition indices of breeders from the Eurasian Arctic, indicating that in ‘good’ years, despite great effort spent on reproduction, breeders leave the breeding grounds in better condition. The pattern did not hold for 1992: productivity was low, but the average condition of adults during migration was the highest noted over the decade. We suggest that the delayed effect of the Mount Pinatubo eruption in the Philippines in 1991, could be responsible for the unexpected high condition of Arctic breeders in 1992. High population-level average condition, coupled with the low productivity could stem from severe weather caused by the volcano eruption a year before and strong predation pressure, which in turn lead to a reduced investment in reproduction. The importance of large-scale episodic phenomena, like this volcano eruption, may blur the statistical associations of wildlife with local environmental drivers.

The interplay between moult of flight feathers and fuelling conducted on the breeding grounds of the Great SnipeGallinago mediafrom the eastern European, lowland population

“…Stable body condition may be caused by less intense displaying in the late breeding season combined with resource allocation toward the moulting of primary feathers. In females, we also did not find a decrease in those parameters, although chick rearing is considered energetically demanding (Tulp et al 2009, Neubauer et al 2017. We think that suitable conditions on the studied site, ensuring rich feeding sites in a wide range of environmental conditions, create environmental allowing females to maintain the body condition, while delaying the onset of their moult (Williams 2018).…”

“…In females, we also did not find a decrease in those parameters, although chick rearing is considered energetically demanding (Tulp et al . 2009, Neubauer et al . 2017).…”