Birds
Red Crossbill
Loxia curvirostra · also called red crossbills
High in a conifer heavy with unopened cones, a red crossbill wedges its oddly crossed bill between the scales, prying one open to reach a seed that a straight-billed bird could never extract.
Overview
The red crossbill, Loxia curvirostra, is a nomadic songbird native to coniferous forest across a broad range of North America, with its specific distribution shifting from year to year depending on where cone crops are most abundant. Its uniquely crossed bill, flexible year-round breeding schedule, and distinct populations specialised on different conifer species make it one of the more anatomically and behaviourally unusual songbirds in North America.
A bill shaped by its food supply
The red crossbill’s oddly overlapping bill tips look almost like a deformity at first glance, but they are in fact a precise tool built specifically for prying open the one food source this species depends on almost entirely.
Status
Least Concern — widespread across suitable coniferous forest throughout North America, with numbers and locations fluctuating year to year with cone crop availability.
Red Crossbill: common questions
Why does the red crossbill have a crossed bill?
This species has a distinctively crossed bill, with the upper and lower tips overlapping rather than meeting, an adaptation that lets it pry apart the tightly closed scales of unopened conifer cones, giving it access to seeds that most straight-billed birds are simply unable to reach.
Why does the red crossbill move around so much?
This species moves nomadically across large distances from year to year, tracking the irregular and unpredictable conifer cone crops it depends on for food, meaning the specific areas where the species is common can shift considerably depending on which forests are producing abundant cones in a given year.
When does the red crossbill breed?
Unlike most birds, which breed on a fixed seasonal schedule, this species can breed during almost any month of the year, timing its reproduction to whenever a sufficiently large local conifer cone crop becomes available, an unusually flexible breeding strategy tied directly to its specialised food source.
Are all red crossbills the same?
Not quite; this species includes several distinct populations, sometimes called call types, each associated with a particular conifer species and showing a subtly different bill size suited to prying open that specific tree's cone structure, differences that researchers can distinguish even though the populations look very similar overall.