In recent decades, the number of Marbled Murrelets, a seabird of the Pacific coast, has declined.
Scientists in Canada and the US have analyzed the chemical composition of Murrelet feathers - some from birds carefully preserved since 1894 by the Burke Museum in Seattle.
The analysis shows that the diet of the Murrelets has changed dramatically in the last 40 years, to smaller and smaller prey items, which take longer to find.
This means that adult Murrelets are away from their nests longer, leaving the young birds unprotected.
Find out more here.