As if having kids isn't hard enough. An apparently confused common loon (Gavia immer) spent 43 days incubating and trying to hatch two rocks, wildlife biologists report. Although other birds have been known to incubate inanimate objects, including pine cones and pebbles, "as far as we know this is the first time the behavior has been documented in loons," says biologist Stephen DeStefano of the U.S. Geological Survey in Amherst, Massachusetts. In the summer of 2011, two of DeStefano's colleagues, Kiana Koenen and Jillian Pereira of the Massachusetts Department of Conservation and Recreation, were monitoring the roughly 10 pairs of loons that nest each year on the Quabbin Reservoir in southern New England. The striking black-and-white waterbirds, known for their mournful calls, like to lay their eggs on floating piles of rotting plants. To aid the Quabbin loons, local conservationists have built floating platforms piled high with dirt and vegetation. But the biologists noticed that one platform-nester was taking an awfully long time to produce chicks, which usually hatch in just 28 days. Investigating the nest (inset, lower left), the researchers discovered the loon was sitting on two roughly egg-sized rocks (inset, upper right), "which were still warm from the loon's body heat ," they report this month in Northeastern Naturalist. The stones were probably mixed in with the material that had been dumped on the platform, they speculate. And the loon, which appeared to be a young bird, may have been engaged in "mock" nesting, which can help novice parents develop nesting skills. Whatever the scientific explanation, the bird is certainly off to a rocky start.
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