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/mediumdistance
migrants, do not necessarily adjust breeding initiation.