Trends in breeding performance in wader populations at Zackenberg, high Arctic Greenland, in relation to environmental drivers 1996–2018

Despite the availability of ever more data on population trends in Arctic waders, we still have limited insight into the factors influencing reproductive success and its resulting contribution to population trajectories. Here, we present data from Zackenberg in high Arctic Greenland that show no changes in timing of egg laying nor clutch size over more than two decades. With variation among species, we found earlier egg laying in seasons with earlier snowmelt, more invertebrates during the pre-laying period, earlier appearance of invertebrates and higher June temperatures. In addition, we found larger clutch sizes with earlier snowmelt, and lower clutch sizes with later nest initiation dates, together with increasing variability in clutch size during the study years in one species. Nest success was lower in late breeding seasons but seemed to increase with season progress, while nest success was much lower during the lasts 18 years of the study period than during the first part of the period. The reason for this could be both increased Arctic fox activity on the tundra and increased researcher activity at nests, which leaves olfactory clues for the foxes. Numbers of juvenile Dunlins produced seem to be negatively correlated with our index of fox activity on the tundra during nesting and fledging, whereas we found no correlations between fox activity and lemming abundance. The effects of severe events in a number of years are described, including a next to non-breeding year in 2018. Our study adds to our understanding that the Arctic is not a homogeneous biome but may show quite different regional patterns of climate change effects.