Fat shortage makes birds dumber, less numerous

Young seabirds that do not eat enough fat are slow learners and are less likely to grow into smart adult birds, a new research study says.

This finding could explain some of the declines seen in seabird colonies during the past 30 years, where climate change or overfishing have reduced the number of fatty fish for the birds to feed on.

Alexander Kitaysky, from the University of Alaska, Fairbanks, and his team monitored the development of 20 red-legged kittiwakes, born in captivity. The chicks were divided into four groups, with each group being fed a different diet. Five chicks were fed silverside, a fatty fish. Another five were given rainbow smelt, a low-fat fish. The remaining chicks were given restricted diets of either silverside or rainbow smelt.

In the wild, kittiwakes have to learn to look for particular colours and patterns in the ocean to find the best places to fish. The scientists tried to recreate this for the captive chicks by making them search for their food among a checkerboard of different coloured bowls. Chicks on the unrestricted fatty diet quickly learned which bowls contained the food, but chicks on the restricted or lean diets were very slow learners and had trouble learning the colours and patterns associated with their food.

Scientists say their study may explain the decline in seabirds seen on the Pribilof Islands, in the south-east Bering Sea, over the last 30 years.

A climate change in the north Pacific and Bering Sea in the mid-1970s resulted in fewer fatty fish around the islands. By the early 1980s, red-legged kittiwake populations on the islands plummeted by 50 per cent.