Steven Ewing, RSPB Senior Conservation Scientist
At this time of year, most of our Slavonian grebes will be sitting on their nests, carefully concealed within emergent loch-side vegetation, patiently incubating their clutches of eggs. Slavonian grebes are without doubt one of the UK’s most enchanting waterbirds. Rather drab during the winter period, the birds take on a spectacular breeding plumage – chestnut flanks and neck, jet black back and head, finished off with golden ‘horns’ and a vivid red eye.
Photo: Wiki Commons
But all is not right with Slavonian grebes in the UK. Always a relatively rare breeding bird restricted to a small number of lochs in northern Scotland, long-term monitoring by a dedicated group of volunteers and RSPB staff has shown there are now only around 30 pairs, a 60% decline from around 80 pairs in the early 1990s.
RSPB scientists have made some key insights into the UK’s Slavonian grebes. We know that breeding success of birds in the UK is low in comparison to Scandinavian populations, with important causes of breeding failure including predation and loss of nests and clutches to flooding. Yet identifying the smoking gun – the key driver underlying the decline – remains elusive.
In the UK, climate change is having profound impacts on biodiversity – and perhaps those most at risk are the northern species, at the southern edge of their range in the UK. The Slavonian grebe is one of these potentially climate-sensitive species, having declined recently in line with the expectations of climate models. The possibility that climate change may be contributing to the decline of the Slavonian grebe in the UK has now been assessed and published this week in an RSPB study published in the Journal of Ornithology ( ).
Using data collected over 40 years, the study examines how annual changes in breeding success and population size are related to important weather variables throughout the year, and whether there have been any longer-term changes in these weather variables indicative of climate change. It appears that Slavonian grebes are particularly sensitive to weather conditions during the breeding season. Breeding success was lower during years with colder chick periods, suggesting high chick mortality during cold weather events. And drier breeding seasons led to higher population sizes. Crucially however, neither of these important weather variables showed longer-term changes, so there’s no clear link between climate change and the Slavonian grebe’s decline.
Nevertheless, we should be cautious about ruling climate change out as a factor affecting Slavonian grebe populations - it may operate via other routes than those considered here.
We have further exciting research in the pipeline for Slavonian grebes. A new RSPB research project, working with colleagues in Iceland and Norway, will examine regional scale population dynamics of Slavonian grebes in northern Europe. This will help us to find out how our grebes’ decline in Scotland might be understood in light of larger scale patterns – which might themselves be climate driven.