Climate change link to decline in seabirds' food source
Scientists have blamed climate change for a massive drop in the availability of one of the North Sea's major sources of food for Scotland's seabirds.
The Centre for Ecology and Hydrology said the number of sand eels in their diet fell by 48% between 1985 and 2014.
The small fish is the meal of choice for many species, including the European shag and the puffin.
The decline coincides with an increase in the North Sea's temperature by 0.037 degrees Celsius per year since 1982.
Scientists have been studying the European shag colony on the Isle of May, in the Firth of Forth, for more than three decades.
The team, which also included researchers from the University of Liverpool, found that while the number of sand eels had declined, the number of other fish prey appearing in the bird's diet had increased.
Data from 1985 showed that the birds were consuming on average one new type of prey a year. By 2014, this had increased to 10 new species of prey a year.
The diversity in the shag's diet is being linked with the increase in temperature of the North Sea, considered by researchers to be one of the most rapidly-warming marine ecosystems on the planet.
Richard Howells, a scientist at the CEH in Edinburgh, said: "Our study ties in with many observations of changes in the abundance, distribution and phenology of many species in the North Sea, and a decline in the availability and size of sand eels.
"Climate models predict further increases in sea surface temperature and weather variability in the region, with generalisation in shag diet, one way in which this species appears to be responding to this change."
Short-term weather conditions also impacted on the bird's ability to feed, with windier conditions on a daily basis linked to fewer sand eel in the diet, which the team said could affect the ability of parents to successfully feed their chicks.
"Changes in the prey types consumed by this population suggest that adults may now be hunting across a broader range of habitats than they did in the past, such as rocky habitats where they can find the Rock Butterfish", Mr Howells said.
The team hopes that by identifying the effects of both long-term temperature trends and short-term weather variability, the study will improve understanding of how seabirds are affected by climate change and how future conservation efforts can be directed.
The results of the study, presented in the Marine Ecology Progress Series, were produced in collaboration with researchers from the University of Liverpool, the Sir Alister Hardy Foundation for Ocean Science and Biomathematics and Statistics Scotland.