In just 10 years, the number of diving ducks migrating to Lough Neagh in Northern Ireland for the winter months has dropped from 100,000 to less than 21,000, they said.
The ecosystem of the lake has dramatically changed in that time, leading to a huge decline in the numbers of insects and snails living at the bottom of the lake and serving as a food source for the birds, a university release said Wednesday.
"Historically the lake was heavily affected by organic pollution as a result of nutrients from agricultural run-off," Queen's researcher Irena Tomankova said. "This artificially boosted its productivity.
"Now that conservation schemes are beginning to have an effect and reduce levels of pollution, we are seeing increasing water quality and the unexpected consequence is fewer invertebrates and as a result less duck food."
In addition, the researcher said, winter temperatures in
Northern Europe have been increasing with climate change in the past 30 years, meaning that lakes that used to be frozen over in winter are now available for the birds to feed on.
Less food in Lough Neagh and more ice-free lakes closer to the bird's natural breeding grounds mean ducks no longer need to fly as far southwest and, as a result, Lough Neagh has lost some of its importance for overwintering water birds, they said.