Red Crossbill
Loxia curvirostra
Summary 7
The red crossbill (Loxia curvirostra) is a small passerine bird in the finch family Fringillidae, also known as the common crossbill in Eurasia. Crossbills have distinctive mandibles, crossed at the tips, which enable them to extract seeds from conifer cones and other fruits.
Distribution 8
Red crossbills are found throughout the northern hemisphere. They are not migratory, but wander widely outside of the breeding season. Occasional irruptions may involve thousands of birds traveling to areas outside of their normal range. In the Americas, red crossbills are found in northern boreal and high altitude coniferous forests from coastal Alaska throughout much of Canada to the maritime provinces and south to northern Minnesota, Wisconsin, Michigan, New York, New Hampshire, Vermont, and Maine. They are found in appropriate habitat throughout the Sierra, Rocky Mountain, and Sierra Madre mountain ranges, as well as smaller mountain ranges in Baja California, Honduras, Nicaragua, Belize, and the Mexican volcanic belt. Small, disjunct breeding populations are found in the Appalachian Mountains and occasional breeding populations are found in appropriate habitat outside of their typical range. In the Palearctic, red crossbills are found from the British Isles across northern Europe, Russia, and Asia to the Kamchatka Peninsula and Japan. They are also found in appropriate habitat in mountain ranges, including the Alps, Pyrenees, Himalayas, Vietnam, the Philippines, and into the Atlas Mountains of northern Africa. They co-occur with other Loxia species in Scotland (Loxia scotica), Scandinavia and western Russia (Loxia pytyopsittacus), and North America (Loxia leucoptera).
Biogeographic Regions: nearctic (Native ); palearctic (Native )
Other Geographic Terms: holarctic
Morphology 9
Red crossbills are medium-sized finches with distinctive, curved mandibles that are crossed at their tips. Males are slightly larger than females (males: 23.8 to 45.4 g, females: 23.7 to 42.4 g). Males are a deep red color, sometimes reddish yellow, with dark brown flight and tail feathers. Females are olive to gray or greenish yellow on the breast and rump with dark brown flight and tail feathers. Immature birds are overall streaked with brown on a lighter background. The tail is notched. Red crossbills don't undergo any seasonal changes in plumage. They are easily distinguished from other species by their crossed bills, except for other Loxia species. In North America, white-winged crossbills (Loxia leucoptera) are distinguished by their white wing bars.
Red crossbills show a striking amount of geographic variation in body size and bill size and shape, despite the fact that populations regularly co-occur and that all populations range widely outside of the breeding season. Morphologies are also associated with distinctive call types. Some researchers have proposed up to 8 North American cryptic species based on call type and associated morphology. Similar levels of variation and tight association of call types and foraging morphology is observed in the Palearctic. Some evidence of reproductive isolation has been reported in the Palearctic, but mitochondrial DNA sequence data does not support the notion of reproductive isolation, instead finding that mitochondrial haplotypes mixed at continental scales.
Basal metabolic rate of captive red crossbills was estimated at 19% higher than expected for their body size.
Range mass: 23.7 to 45.4 g.
Range length: 14 to 20 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful
Habitat 10
Red crossbills are found almost exclusively in mature, coniferous forests, including spruce (Picea), fir (Abies), hemlock (Tsuga), and pine (Pinus) forests. They can also be found in mixed decidous-coniferous forests, provided there are ample supplies of conifer seeds to eat. Specific "call types" of red crossbills are associated with 1 or more conifer species. For example, two large-billed types of red crossbills in western North America are found closely associated with the large cones of Engelmann's spruce (Picea engelmanni), ponderosa pine (Pinus ponderosa), and table mountain pine (Pinus pungens). Another, eastern type associates mainly with Newfoundland black spruce (Picea mariana). Small-billed red crossbills associate with conifers with smaller cones, such as hemlocks (Tsuga) and Douglas-fir (Pseudotsuga). This close association between call types and conifer species has led to the description of many subspecies and speculation about strong selection of food types on bill-shape and subsequent reproductive isolation through vocalizations (call types). However, a study of mitochondrial DNA showed no evidence of reproductive isolation among subspecies or call types. Morphological differences among populations specialized to particular conifer species may be the result of rapid local adaptations.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
Migration 11
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Wanders irregularly when population high and or food supply low (Terres 1980).
Sources and Credits
- (c) Sergey Yeliseev, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/13861029@N00/2043886667
- Creator:Dave Menke, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/thumb/0/07/Loxia_curvirostra2.jpg/460px-Loxia_curvirostra2.jpg
- (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/JOM-Loxia-curvirostra-00011.jpg
- (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/JOM-Loxia-curvirostra-00007.jpg
- (c) Scott Bowers, some rights reserved (CC BY-NC), http://www.planetscott.com/speciesdetail/8831/red-crossbill-(loxia-curvirostra)
- (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/JOM-Loxia-curvirostra-00012.jpg
- (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Loxia_curvirostra
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31403330
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31403332
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31403331
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28945387
