Dependence on climate-driven environmental cues in the initiation of life cycle stages is a critical attribute when assessing vulnerability of species to climate change impacts. This study focused on spring ice phenology as a cue to the settling of migratory waterbirds, asking whether there is an asynchrony between ice phenology and setting phenology that could affect breeding success of six species with divergent population trends. In the 37 study lakes in southeastern Finland, the ice-out date not only varied considerably between years, but became progressively earlier during the study period, 1991–2018. Settling phenology of all species tracked inter-annual variation in ice phenology. However, the degree of asynchrony between ice phenology and settling phenology varied between species, allowing discrimination between early and late settlers. Considerable inter-annual variation also occurred within species, but in only one species did the degree of asynchrony correlate with the ice-out date: for the horned grebe Podiceps auritus an earlier ice-out date meant greater asynchrony between settling phenology and ice phenology. The degree of asynchrony between settling phenology and ice phenology did not affect breeding success in any species. However, ice phenology per se affected breeding success of horned grebes: earlier ice-out was associated with lower annual breeding success. Breeding numbers of horned grebe showed a long-term decline. Results suggest that short-distance migratory birds are able to respond to climate change-driven phenological changes in their breeding environments, and that this ability may not depend on the relative timing of breeding.

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