Birds eavesdrop on chipmunks to protect nests

Ovenbirds and veeries both build their nests on the ground, risking the loss of their eggs or chicks to neighbouring chipmunks, which resemble squirrels.

But Quinn Emmering and Kenneth Schmidt from Texas Tech University wondered whether the 'chips', 'chucks' and 'trills' which chipmunks use, to communicate to one another, were being eavesdropped on by the birds.

Emmering and Schmidt tested their theory that ovenbirds and veeries might be eavesdropping on chipmunks' calls before deciding where to nest by setting up a playback experiment.

"Chipmunks are vociferous, calling often during the day and sometimes joining in large choruses. We thought this might be a conspicuous cue that nesting birds could exploit," said Emmering, according to a Texas Tech statement.

At 28 plots, a triangular arrangement of three speakers played either chipmunk or grey tree frog calls, while at 16 'silent' control sites no recordings were played.

They found that veeries and ovenbirds nested much further away from plots where chipmunk calls were played.

Interestingly the size of the response was twice as high in ovenbirds, which nested 20 metres further away from chipmunk-playback sites than silent control sites, while veeries nested only 10 metres further away.

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