Birds migrating earlier as global temperatures rise

Desdemona Despair

29 December 2016 (BBC News) – Migrating birds are arriving at their breeding grounds earlier as global temperatures rise, a study has found.

Birds have reached their summer breeding grounds on average about one day earlier per degree of increasing global temperatures, according to the research by Edinburgh University.

The study looked at hundreds of species across five continents.

It is hoped it will help scientists predict how different species may respond to future environmental change.

Reaching their summer breeding grounds at the wrong time – even by a few days – may cause birds to miss out on maximum availability of vital resources such as food and nesting places.

Late arrival to breeding grounds may, in turn, affect the timing of offspring hatching and their chances of survival. [more]

Birds migrating earlier as temperatures rise

ABSTRACT: There are wide reports of advances in the timing of spring migration of birds over time and in relation to rising temperatures, though phenological responses vary substantially within and among species. An understanding of the ecological, life-history and geographic variables that predict this intra- and interspecific variation can guide our projections of how populations and species are likely to respond to future climate change.

Here, we conduct phylogenetic meta-analyses addressing slope estimates of the timing of avian spring migration regressed on (i) year and (ii) temperature, representing a total of 413 species across five continents. We take into account slope estimation error and examine phylogenetic, ecological and geographic predictors of intra- and interspecific variation.

We confirm earlier findings that on average birds have significantly advanced their spring migration time by 2·1 days per decade and 1·2 days °C⁻¹. We find that over time and in response to warmer spring conditions, short-distance migrants have advanced spring migratory phenology by more than long-distance migrants. We also find that larger bodied species show greater advance over time compared to smaller bodied species. Our results did not reveal any evidence that interspecific variation in migration response is predictable on the basis of species’ habitat or diet.

We detected a substantial phylogenetic signal in migration time in response to both year and temperature, suggesting that some of the shifts in migratory phenological response to climate are predictable on the basis of phylogeny. However, we estimate high levels of species and spatial variance relative to phylogenetic variance, which is consistent with plasticity in response to climate evolving fairly rapidly and being more influenced by adaptation to current local climate than by common descent.

On average, avian spring migration times have advanced over time and as spring has become warmer. While we are able to identify predictors that explain some of the true among-species variation in response, substantial intra- and interspecific variation in migratory response remains to be explained.

Temporal shifts and temperature sensitivity of avian spring migratory phenology: a phylogenetic meta-analysis