Analyze This: Birds may decorate nests to scare off rivals

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Some birds are interior decorators, placing big, showy feathers in their nests. But rather than spiffing up their homes, these birds may be trying to spook nest-stealing neighbors.

Karen Wiebe is a behavioral ecologist. She studies animal behavior and ecosystems at the University of Saskatchewan in Saskatoon, Canada. Birds sometimes weave feathers into their nests to provide insulation. But Wiebe and her colleague, Tore Slagsvold of the University of Oslo in Norway, also saw birds placing large feathers on the surfaces of nests. Those feathers wouldn’t help with warmth. The researchers wondered whether the birds might be using the decorations to send a message.

For swallows and other birds that nest in holes and hollows, competition for nests can “be really ferocious,” Wiebe says. Birds scream, grapple and peck, sometimes killing an opponent. But these somewhat scarce holes can also hide danger. Owls, weasels or other predators may be lurking inside. If a nest contains feathers or other remains, it might be evidence that a predator had been there. Those holes might not be as desirable.

Wiebe and Slagsvold hypothesized that some birds may use feathers to create a mock kill site. Their goal: Scare competitors away.

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