Crossbills

The Science of Birds

In this episode, which is number 111, Ivan Phillipsen explores the fascinating world of crossbills, a unique group of finches with an extraordinary beak adaptation. These birds, found across North America, Europe, and Asia, use their specialized crossed bills to extract seeds from conifer cones—a skill few other birds possess.

Ivan discusses the six recognized crossbill species, their distinct feeding strategies, and how their beaks evolved for this specialized diet.
The episode highlights the complex classification of crossbills, particularly the Red Crossbill, which has multiple "call types" that may represent different evolutionary paths. Ivan explains how these birds are nomadic, moving vast distances in search of conifer seed crops, and how some species, like the Cassia Crossbill, have adapted to specific tree species. The episode also covers the recent debate in the ornithological community about whether certain crossbill populations should be considered full species. Additionally, Ivan discusses how crossbills’ courtship behavior, nesting habits, and vocalizations vary among species.

Links of Interest

• Crossbills of North America: Species and Red Crossbill Call Types
• White-winged Crossbill feeding [VIDEO]

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Link to this episode on the Science of Birds website

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