Merlin

White-winged Crossbill Life History

Habitat

Habitat Forests

Year-round, White-winged Crossbills inhabit coniferous forests, feeding primarily on spruce and tamarack seeds. Like Red Crossbills, they occur throughout forests of balsam fir and red, black, white, and Engelmann spruce. However, they are scarce or absent in most pine, hemlock, and Douglas-fir forests occupied by Red Crossbills. During periods of low food supply, many White-winged Crossbills wander far out of range. At such times, they frequent habitats that vary from weedy fields to ornamental plantings to pine forests. Their preference is for spruce species, and during irruption winters, they are attracted to small stands of spruce, as often found in older cemeteries, arboretums, or university campuses.

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Food

Food Seeds

White-winged Crossbills specialize in eating seeds from the cones of spruce and tamarack, the staples of their diet for most of the year. When spruce and tamarack seeds are scarce, they eat fir seeds. In summer, they eat insects, especially spruce budworm and coneworm, along with ants, spiders, and bugs. Less frequently, they eat buds of deciduous trees, and seeds of pine (red pine, eastern white pine), eastern hemlock, eastern redcedar, alder, birch, cottonwood, sweetgum, sunflower, goldenrod, ragweed, and various sedges and grasses. They take such alternative foods mostly during irruption years, in which large numbers leave the boreal forest because cone crops are low. To extract seeds from conifer cones, White-winged Crossbills usually grasp the cone with one foot and bite the cone where the scales meet, opening a gap between the scales, which can be widened with more action of the bill and by twisting the head. The seed can then be extracted using the tongue and longer upper mandible. They normally forage in trees but frequently feed on spruce cones that have fallen to the ground, which are more pliable than attached cones. The birds then husk the seed (remove the seed coat) and swallow the seed whole. To help grind their food, White-winged Crossbills consume small amounts of grit, often from roadsides or trails.

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Nesting

Nest Placement

Nest Tree

Female and male probably select the nest site together. The nest is usually in a spruce tree, near the trunk, often on the southeastern side of the tree.

Nest Description

Females build the nest, though males sometimes supply nesting material. Nests are cups made of conifer twigs, grasses, forbs, lichen, birch bark, and lined with roots, moss, lichen, hair, spider cocoons, and fine strips of bark. Nests average 4 inches across, 2.4 inches high, with interior cup 2.3 inches across and 1.5 inches deep.

Nesting Facts
Clutch Size:2-4 eggs
Egg Length:0.7-0.9 in (1.85-2.2 cm)
Egg Width:0.5-0.6 in (1.35-1.6 cm)
Incubation Period:14-16 days
Egg Description:

Bluish green to white with dark spots or blotches around large end.

Condition at Hatching:

Helpless and naked.

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Behavior

Behavior Foliage Gleaner

White-winged Crossbills usually begin nesting early in the year, often in late winter. They have been recorded nesting in all months, whenever food is plentiful. Displaying males perch high in spruces, sometimes in small groups, and begin singing. When females approach, males often pursue them in flight, and paired birds begin to bond by nibbling each other’s bills. Males also feed females in courtship, regurgitating a paste of spruce seeds into their bills. White-winged Crossbills appear to have a monogamous mating system, but no study has definitively confirmed this. Anatomical comparisons to Red Crossbills suggest White-winged males may be adapted to seek extra-pair copulations. Males do guard females closely after pairing, chasing away other males, and they defend the nest tree as well but do not establish a feeding territory, probably because food is so plentiful during the nesting season. Males alone care for the young after fledging, and it is possible that females then repartner to have a second brood (a system known as serial polyandry), as redpolls and goldfinches also do. White-winged Crossbills flock year-round, but in times of food scarcity, males tend to dominate females at food sources and older birds dominate younger ones. Their threat display involves leaning toward an intruder and opening the bill. Foraging in flocks allows crossbills to enjoy the benefits of having more eyes watching for predators. They may also communicate about cone crops, rapidly identifying and moving toward trees that provide superior seeds.

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Conservation

Conservation Low Concern

White-winged Crossbill populations are difficult to estimate, as these birds breed in the remote north and are nomadic, meaning they can be locally abundant in some years but absent the next. Overall, populations appear to have been stable between 1966 and 2015, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 79 million, with 21% spending part of the year in the United States and 42% in Canada. Partners In Flight rates the species a 6 out of 20 on the Continental Concern Score, indicating it is a species of low conservation concern. White-winged Crossbills may be affected by logging and fragmentation of their habitat, in particular by shorter rotation cycles for logging: spruce trees over 60 years old produce the most cones, but such trees are now scarce in managed forests. Crossbills may also succumb to poisoning in the winter if they ingest chemicals and salts used to clear roads.

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Credits

Benkman, C. W. (2012). White-winged Crossbill (Loxia leucoptera), version 2.0. In The Birds of North America (A. Poole, Editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Elmberg, J. (1993). Song differences between North American and European White-winged Crossbills (Loxia leucoptera). Auk 110 (2):385.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

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