Boreal

Habitat

Breeding bird survey

Ecology

Biology

Climate change

Taiga

Reproduction

Geography

Seasonal breeder

Phenology

Proceedings of the National Academy of Sciences

Significance The changing climate is causing shifts in the timing of species activity. We use data on over 820,000 nesting records to quantify changes in the beginning, end, and duration of breeding among boreal birds. In addition to a general advance of breeding, we find an overall contraction of the breeding period. This pattern was most common among resident and short-distance migrating species. Overall, we detect a shift in the community-level distribution of bird reproduction, involving the start and end of reproduction and how concentrated the breeding period is. From a methodological perspective, our study illustrates that a focus on quantifying phenological advances alone may mask important patterns of phenology change across the season.

Shifts in timing and duration of breeding for 73 boreal bird species over four decades