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Archive for March 26, 2015

White-winged Crossbills Nesting

White_winged crossbill by garth mcelroyrWhite-winged Crossbills inhabit the boreal forests of northern New England, the southern edge of their breeding grounds. This species, as well as Red Crossbills, are named for their bill which is supremely adapted to extracting seeds from conifer cones. Crossbills use their crossed bills to wedge open cone scales, after which they lift the seeds free with their tongues. Individuals can eat up to 3,000 conifer seeds per day.

White-winged Crossbills are erratic nesters that have been found breeding every month of the year. The birds nest whenever the available food supply is sufficient for egg formation and is likely to remain sufficient for at least three weeks, during the more energy demanding nestling stage.

Three nesting periods have been observed, each corresponding to the ripening of cones from different conifer species. The first season occurs in early July, when the cones of Tamarack, or American Larch, and White Spruce mature. The second nesting period begins in January and February, when they rely mainly on White and Red Spruce cone crops and the third season is starting now, as Black Spruce cones begin to open up. (Photo: public domain, male White-winged Crossbill)

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