Generalist predators using small mammals as their primary prey are suggested to shift hunting alternative prey such as bird nests, when small mammals are in short supply (the alternative prey hypothesis, APH). Nest survival and survival of young individuals should be positively linked to small mammal abundance and negatively linked to predator abundance, but little information exists from survival of chicks, especially until recruitment. We test these predictions of the APH using 13 years (2002-2014) of life history data from a ground nesting shorebird breeding on coastal meadows. We use small mammal abundance in the previous autumn as a proxy for spring predator abundance, mainly of mammalian predators. We examine whether small mammal abundance in the spring and previous autumn explain annual variation in nest survival from depredation and local recruitment of the southern dunlin Calidris alpina schinzii. As predicted by the APH, survival from nest predation was positively linked to spring small mammal abundance and negatively linked to autumn small mammal abundance. Importantly, local recruitment showed opposite responses. This counterintuitive result may be explained by density dependent survival. When nest depredation rates are low, predators may show stronger numerical and functional responses to high shorebird chick abundance on coastal meadows, whereas in years of high nest depredation, few hatching chicks lure fewer predators. The opposite effects on nest and local recruitment demonstrate the diverse mechanisms by which population size variation in primary prey can affect dynamics of alternative prey populations.

The nest survival data have been gathered by following the fate of nests. See published paper (Pakanen et al. 2011; 2014, 2022) for more details. The dataset is ready for analysis in program MARK. Sea reame file for info.

The local recruitment data is a capture-recapture dataset. It has been collected by ringing chicks at hatching and following their subsequent recruitment to the population as adults. See published paper (Pakanen et al. 2016, 2017, 2022) for more details.The dataset is ready for analysis in program MARK. Sea reame file for info.

Pakanen V-M, Luukkonen A, Koivula K (2011) Nest predation and trampling as management risks in grazed coastal meadows. Biodivers Conserv 20: 2057–2073 https://doi.org/10.1007/s10531-011-0075-3

Pakanen VM, Rönkä N, Thomson R, Koivula K (2014) Informed renesting decisions: the effect of nest predation risk. Oecologia 174:1159–1167 https://doi.org/10.1007/s00442-013-2847-9

Pakanen V-M, Aikio S, Luukkonen A, Koivula K (2016) Grazed wet meadows are sink habitats for the southern dunlin (Calidris alpina schinzii) due to nest trampling by cattle. Ecol Evol 6: 7176–7187 https://doi.org/10.1002/ece3.2369

Pakanen VM, Koivula K, Flodin L-Å, Grissot A, Hagstedt R, Larsson M, Pauliny A, Rönkä N, Blomqvist D (2017) Between-patch natal dispersal propensity declines with increasing natal patch size and distance to other patches in two endangered Southern Dunlin Calidris alpina schinzii metapopulations. Ibis 159: 611–622 https://doi.org/10.1111/ibi.12463

Pakanen VM, Tornberg T, Airaksinen E, Rönkä N, Koivula K (2022) The abundance of small mammals is positively linked to survival from nest depredation but negatively linked to local recruitment of a ground nesting precocial bird. Ecology and Evolution.

The data files can be opened in Program MARK.