Two-barred crossbill

The two-barred crossbill or white-winged crossbill (Loxia leucoptera) is a small passerine bird in the finch family Fringillidae. It breeds in the coniferous forests of North America and the Palearctic.

Taxonomy
The two-barred crossbill was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the crossbills in the genus Loxia and coined the binomial name Loxia leucoptera. Gmelin specified the locality as Hudson Bay and New York. The specific epithet leucoptera is from Ancient Greek leukopteros meaning "white-winged" (leukos means "white" and pteron means "wing"). Gmelin based his account on the "white winged crossbill" that had been described in 1783 by the English ornithologist John Latham in his multi-volume work A General Synopsis of Birds. Latham had examined a specimen in the Leverian Museum in London.

Two subspecies are recognised:
 * L. l. bifasciata (Brehm, CL, 1827) – north Europe to east Siberia and northeast China
 * L. l. leucoptera Gmelin, JF, 1789 – Alaska, Canada and north USA

Description
The two-barred crossbill is 14.5 - 17 cm in length and weighs 25 - 40 g. It has short legs, a forked tail, a crossed bill and two prominent white wing-bars. The male of the nominate subspecies has forehead, crown, nape and upper-parts bright raspberry-red. The are black or blackish brown with pink edges. The upper tail coverts are black with white fringes. The female lacks the pink and instead has greenish-yellow head and upperparts.

The two-barred is easier to identify than other crossbills, especially in North America, where only the red crossbill (Loxia curvirostra) and this species occur. Within its Palearctic range, this species is smaller-headed and smaller-billed than the parrot crossbill and Scottish crossbill, so the main confusion between species both there and in North America is with the red or common crossbill.

The main plumage distinction from the red crossbill is the white wingbars which give this species its English and scientific names. There are also white tips to the tertials. The adult male is also a somewhat brighter (pinker) red than other male crossbills. Some red crossbills occasionally show weak white wingbars, so care is needed with the correct identification of this species. The chip call is weaker and higher than that of the red crossbill.

Another crossbill species on Hispaniola in the Caribbean was previously treated as a subspecies (Loxia leucoptera megaplaga), but is now treated as a distinct species: the Hispaniolan crossbill (Loxia megaplaga). It is associated with the Hispaniolan pine tree (Pinus occidentalis), and differs from the two-barred crossbill in darker plumage, a stouter bill, and its geographic isolation compared to other crossbill species.

Distribution and habitat
This bird breeds in the coniferous forests of Alaska, Canada, the northernmost United States and across the Palearctic extending into northeast Europe. It nests in conifers, laying 3–5 eggs.

This crossbill is mainly resident, but will irregularly irrupt south if its food source fails. The American race seems to wander more frequently than the Eurosiberian subspecies. This species will form flocks outside the breeding season, often mixed with other crossbills. It is a rare visitor to western Europe, usually arriving with an irruption of red crossbills.

Food and feeding
They are specialist feeders on conifer cones, and the unusual bill shape is an adaptation to assist the extraction of the seeds from the cone. The two-barred crossbill has a strong preference for larch (Larix), in Eurosiberia using Siberian larch (Larix sibirica) and Dahurian larch (L. gmelinii), and in North America Tamarack larch (L. laricina). It will also take rowan (Sorbus) berries, and in North America, also eastern hemlock (Tsuga canadensis) and white spruce (Picea glauca) cones.

Breeding
The nest is placed 2 - 20 m above the ground, usually against the trunk of a conifer. The nest is built by the female and mainly consists of conifer twigs. The clutch of 3-4 eggs is incubated by the female for 14-15 days. The chicks are fed by both parents. They fledge after 22-24 days but then remain with their parents for up to 6 weeks.

Books

 * Benkman C. W. 1992. White-winged Crossbill (Loxia leucoptera). In The Birds of North America, No. 27. (A. Poole, P. Stettenheim, and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, DC: The American Ornithologists’ Union.

Thesis

 * Benkman CW. Ph.D. (1985). THE FORAGING ECOLOGY OF CROSSBILLS IN EASTERN NORTH AMERICA (AVES, BREEDING BEHAVIOR, MORPHOLOGY, CONIFERS). State University of New York at Albany, United States, New York.

Articles
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 * Benkman CW. (1987). Crossbill Foraging Behavior Bill Structure and Patterns of Food Profitability. Wilson Bulletin. vol 99, no 3. p. 351-368.
 * Benkman CW. (1987). Food Profitability and the Foraging Ecology of Crossbills. Ecological Monographs. vol 57, no 3. p. 251-267.
 * Benkman CW. (1989). Intake Rate Maximization and the Foraging Behavior of Crossbills. Ornis Scandinavica. vol 20, no 1. p. 65-68.
 * Benkman CW. (1990). Intake Rates and the Timing of Crossbill Reproduction. Auk. vol 107, no 2. p. 376-386.
 * Benkman CW. (1994). Comments on the ecology and status of the hispaniolan crossbill (Loxia leucoptera megaplaga), with recommendations for its conservation. Caribbean Journal of Science. vol 30, no 3-4. p. 250-254.
 * Benkman CW. (1997). Feeding behavior, flock-size dynamics, and variation in sexual selection in crossbills. Auk. vol 114, no 2. p. 163-178.
 * Coady G. (2001). First nest record of white-winged crossbill in the greater Toronto area. Ontario Birds. vol 19, no 3. p. 101-111.
 * Deviche P. (1997). Seasonal reproductive pattern of white-winged Crossbills in interior Alaska. Journal of Field Ornithology. vol 68, no 4. p. 613-621.
 * Deviche P. (2000). Timing, pattern, and extent of first prebasic molt of White-winged Crossbills in Alaska. Journal of Field Ornithology. vol 71, no 2. p. 217-226.
 * Deviche P & Hahn TP. (1995). SEasonal reproductive pattern of interior Alaska white-winged crossbills (Loxia leucoptera). American Association for the Advancement of Science, Arctic Division. p. Landscapes Human ecology, landscape ecology, earth system science.
 * Deviche P & Sharp PJ. (2001). Reproductive endocrinology of a free-living, opportunistically breeding passerine (White-winged Crossbill, Loxia leucoptera). General and Comparative Endocrinology. vol 123, no 3. p. 268-279.
 * Elmberg J. (1993). Song differences between North American and European White-winged Crossbills (Loxia leucoptera). The Auk. vol 110, no 2. p. 385.
 * Eykhler V & Vasyukova TT. (1981). A New Species of the Genus Docophorulus Mallophaga Philopteridae from the White-Winged Crossbill Loxia-Leucoptera-Bifasciata. Entomological Review. vol 60, no 3. p. 99-101.
 * Fischer S, Mauersberger G, Schielzeth H & Witt K. (1992). 1ST BREEDING RECORD OF 2-BARRED CROSSBILL (LOXIA-LEUCOPTERA) IN CENTRAL-EUROPE. Journal Fur Ornithologie. vol 133, no 2. p. 197-202.
 * Gallant D. (2004). White-winged crossbills obtain forage from river otter Feces. Wilson Bulletin. vol 116, no 2. p. 181-184.
 * Gordon P, Morlan J & Roberson D. (1989). First Record of the White-Winged Crossbill in California USA. Western Birds. vol 20, no 2. p. 81-88.
 * Groth JG. (1992). Further Information on the Genetics of Bill Crossing in Crossbills. The Auk. vol 109, no 2. p. 383.
 * Groth JG. (1992). White-Winged Crossbill Breeding in Southern Colorado with Notes on Juveniles Calls. Western Birds. vol 23, no 1. p. 35-38.
 * Hahn TP, Pereyra ME & Sharbaugh SM. (2003). Effects of photoperiod on brain GnRH plasticity and peripheral reproductive physiology in three species of cardueline finches. Society for Neuroscience Abstract Viewer & Itinerary Planner. p. 611.
 * Hahn TP, Pereyra ME, Sharbaugh SM & Bentley GE. (2004). Physiological responses to photoperiod in three cardueline finch species. General and Comparative Endocrinology. vol 137, no 1. p. 99-108.
 * Hahn TP, Wingfield JC, Mullen R & Deviche PJ. (1995). ENDOCRINE BASES OF SPATIAL AND TEMPORAL OPPORTUNISM IN ARCTIC-BREEDING BIRDS. American Zoologist. vol 35, no 3. p. 259-273.
 * Hobson KA & Bayne E. (2000). Breeding bird communities in boreal forest of western Canada: Consequences of "unmixing" the mixedwoods. Condor. vol 102, no 4. p. 759-769.
 * Kepler AK, Kepler CB & Dod A. (1975). FIRST NEST RECORD OF WHITE-WINGED CROSSBILL IN HISPANIOLA. Condor. vol 77, no 2. p. 220-221.
 * Koenig WD & Knops JMH. (2001). Seed-crop size and eruptions of North American boreal seed-eating birds. Journal of Animal Ecology. vol 70, no 4. p. 609-620.
 * Latta SC, Sondreal ML & Brown CR. (2000). A hierarchical analysis of nesting and foraging habitat for the conservation of the Hispaniolan White-winged crossbill (Loxia leucoptera megaplaga). Biological Conservation. vol 96, no 2. p. 139-150.
 * Latta SC, Sondreal ML & Mejia DA. (2002). Breeding behavior of the endangered Hispaniolan Crossbill (Loxia megaplaga). Ornitologia Neotropical. vol 13, no 3. p. 225-234.
 * MacDougall-Shackleton SA, Deviche PJ, Crain RD, Ball GF & Hahn TP. (2001). Seasonal changes in brain GnRH immunoreactivity and song-control nuclei volumes in an opportunistically breeding songbird. Brain Behavior and Evolution. vol 58, no 1. p. 38-48.
 * McNair DB. (1990). First Modern Record of White-Winged Crossbill in Georgia USA a Commentary. Oriole. vol 53, no 4. p. 49-50.
 * Mundinger PC. (1979). Call Learning in the Carduelinae Ethological and Systematic Considerations. Systematic Zoology. vol 28, no 3. p. 270-283.
 * Nankinov DN, Ilkov PG & Stoychev KS. (1999). White-winged crossbill (Loxia leucoptera bifasciata C. L. Brehm, 1827) in Bulgaria. Acta Zoologica Bulgarica. vol 51, no 1. p. 49-51.
 * Oberle MW. (1986). First Modern Record of White-Winged Crossbill in Georgia USA. Oriole. vol 51, no 2-3. p. 25-27.
 * Oberle MW & Hahn T. (1994). More on the White-winged crossbill in Georgia. Oriole. vol 59, no 1. p. 26-27.
 * Parchman TL & Benkman CW. (2002). Diversifying coevolution between crossbills and black spruce on Newfoundland. Evolution. vol 56, no 8. p. 1663-1672.
 * Parchman TL, Benkman CW & Britch SC. (2006). Patterns of genetic variation in the adaptive radiation of New World crossbills (Aves : Loxia). Molecular Ecology. vol 15, no 7. p. 1873-1887.
 * Pereyra ME, Sharbaugh SM & Hahn TP. (2005). Interspecific variation in photo-induced GnRH plasticity among nomadic cardueline finches. Brain Behavior and Evolution. vol 66, no 1. p. 35-49.
 * Pulliainen E. (2002). Chemical composition of the seed food of late-summer-breeding two-barred crossbills Loxia leucoptera. Aquilo Ser Zoologica. vol 30, p. 79-81.
 * Sealy SG, Sexton DA & Collins KM. (1980). Observations of a White-Winged Crossbill Loxia-Leucoptera Invasion of Southeastern Manitoba Canada. Wilson Bulletin. vol 92, no 1. p. 114-116.
 * Steinberg B & Tozer R. (2003). White-winged Crossbill predation by Blue Jay. Ontario Birds. vol 21, no 1. p. 34-37.
 * Stradi R, Rossi E, Celentano G & Bellardi B. (1996). Carotenoids in bird plumage: The pattern in three Loxia species and in Pinicola enucleator. Comparative Biochemistry and Physiology B-Biochemistry & Molecular Biology. vol 113, no 2. p. 427-432.
 * West GC. (1974). ABNORMAL BILL OF A WHITE-WINGED CROSSBILL. Auk. vol 91, no 3. p. 624-626.