Tundra-breeding birds face diverse conservation challenges, from accelerated rates of Arctic climate change to threats associated with highly migratory life histories. Here we summarise the status and trends of Arctic terrestrial birds (88 species, 228 subspecies or distinct flyway populations) across guilds/regions, derived from published sources, raw data or, in rare cases, expert opinion. We report long-term trends in vital rates (survival, reproduction) for the handful of species and regions for which these are available. Over half of all circumpolar Arctic wader taxa are declining (51% of 91 taxa with known trends) and almost half of all waterfowl are increasing (49% of 61 taxa); these opposing trends have fostered a shift in community composition in some locations. Declines were least prevalent in the African-Eurasian Flyway (29%), but similarly prevalent in the remaining three global flyways (44–54%). Widespread, and in some cases accelerating, declines underscore the urgent conservation needs faced by many Arctic terrestrial bird species.

How species interact modulate their dynamics, their response to environmental change, and ultimately the functioning and stability of entire communities. Work conducted at Zackenberg, Northeast Greenland, has changed our view on how networks of arctic biotic interactions are structured, how they vary in time, and how they are changing with current environmental change: firstly, the high arctic interaction webs are much more complex than previously envisaged, and with a structure mainly dictated by its arthropod component. Secondly, the dynamics of species within these webs reflect changes in environmental conditions. Thirdly, biotic interactions within a trophic level may affect other trophic levels, in some cases ultimately affecting land–atmosphere feedbacks. Finally, differential responses to environmental change may decouple interacting species. These insights form Zackenberg emphasize that the combination of long-term, ecosystem-based monitoring, and targeted research projects offers the most fruitful basis for understanding and predicting the future of arctic ecosystems.

Capsule: During 1928–2016, initiation of egg-laying advanced in two wader species, remained unchanged in one, and was delayed in one species. The changes across years and variation among species can be explained by climatic variables and differences in migratory strategies. Aims: To document possible changes in initiation of egg-laying in common Danish wader species since the early part of the 20th century and seek possible correlations between egg-laying, timing of arrival and environmental factors. Methods: Annual records of the first eggs and chicks found on the scientific reserve of Tipperne in western Denmark 1928–2016 were analysed using linear regression to determine patterns in timing of egg-laying, pre-breeding length and influence of climate factors. Results: Two short/medium-distance migrant wader species, Northern Lapwing Vanellus vanellus and Common Redshank Tringa totanus advanced breeding initiation by about one week, with winter North Atlantic oscillation Index and spring temperature as important predictors. By contrast, two long-distance migrants, Black-tailed Godwit Limosa limosa and Ruff Calidris pugnax, did not advance egg-laying, and Ruff actually delaying it. As a result, the pre-laying period was significantly prolonged in both Black-tailed Godwit (21 days) and Ruff (52 days), while there was no significant change for Common Redshank. Conclusion: Long-distance migrants are able to adjust spring arrival but unlike short/medium-distance migrants, do not necessarily adjust breeding initiation.