More on our birds in a changing environment

Goldfinch. Photo by Mick DrydenRecently we saw how our partial migrant birds are changing their habits and no longer migrating down to the Mediterranean (here). Now, research by the BTO using detailed distribution maps of 122 species of bird further measures the ways that climate change could be affecting our local bird populations. Species distribution was found to be changing, but the range shifts detected could not be explained by any single climatic factor, indicating that the distribution changes for British birds are complex, multi-directional and species specific.

The BTO drew from breeding bird atlases developed two decades apart. Atlas data are collected in a standardised manner by thousands of volunteer bird surveyors, providing a unique barometer of the impacts of environmental change on this one component of British biodiversity.

Greylag geese. Photo by Mick DrydenFrom the early 1980s to the early 2000s, temperatures in spring and summer increased, which should have pushed some bird species to the northwest if this aspect of climate is key to their success, whilst higher temperatures in winter should have pushed them to the north and northeast. In contrast, if spring rainfall is critical to species, they should have been pushed to the west. Analyses looking at how bird distributions had actually changed over this period found that birds had indeed shifted to the north, on average by 13.5 km, which continued a trend seen in previous decades. However, more than a quarter of the species had also extended their ranges to the northwest and northeast, while almost half had retreated from southerly directions. The ranges of a few species such as greylag goose and great tit had extended in all directions while others like lesser spotted woodpecker and corn bunting had retreated from all directions. Overall the range shifts could not be explained by any single climatic factor, indicating that the distribution changes for British birds are complex, multi-directional and species specific.

Woodcock. Photo by Duncan WilsonAnother report published this month from Sweden shows that short distance migrants to this country had advanced their arrival to southern Sweden more over time than long-distance migrants. However, no such difference between long- and short-distance migrants could be seen in central Sweden suggesting that short distance migrants were either arriving in the south much earlier or even spending the winter there before moving further north. In long-distance migrants, the difference in first arrival between the historical and present-day dataset did not differ between southern and central Sweden. These results further establish that many short-distance migrants are becoming resident further north or shortening their migratory route, possibly due to climate change enabling more northerly wintering areas.According to annual first observation used in this study, this seems to be especially true for chaffinch, whooper swan, starling, and woodcock.

Cattle egret in Jersey. Photo by Mick Dryden

It is clear from this research that many of our birds are undergoing big changes in their patterns of migration and selection of wintering areas. A further change, the impact that the number of arriving species, like the egrets, new to particular areas will have on existing biodiversity is, however, not yet clear. As some of our bird species are not shifting their ranges as fast as others, or aren’t moving in the same direction, our bird communities of the future could be very different from those we know today. There is still much to learn if we are to manage the impacts of anthropogenic climate change on our wildlife, and studies such as these will help policymakers to adopt conservation and land management strategies that effectively assist species survival.

You can see the reports here:

Directionality of recent bird distribution shifts and climate change in Great Britain. Read abstract here

Change in spring arrival of migratory birds under an era of climate change, Swedish data from the last 140 years. Download paper here