Common Crossbill
Male Common Crossbill Female Common Crossbill
Conservation status
Least Concern
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Passeriformes Family: Fringillidae Genus: Loxia Species: L. curvirostra
Binomial name
Loxia curvirostra Linnaeus, 1758

The Common Crossbill (Loxia curvirostra) is a small passerine bird in the finch family Fringillidae. It breeds in the spruce forests of North America, where it is known as Red Crossbill, as well as Europe and Asia; some populations (different species?) breed in pine forests in certain areas of all three continents, and in North America, also in Douglas-fir. It nests in conifers, laying 3–5 eggs. Image File history File links Download high-resolution version (1440x960, 1310 KB) The Common Crossbill, or Red Crossbill (Loxia curvirostra) is a small passerine bird in the finch family Fringillidae. ... Image File history File links Red_Crossbill_(Female). ... The conservation status of a species is an indicator of the likelihood of that species continuing to survive either in the present day or the future. ... Image File history File links Status_iucn3. ... Least Concern (LC) is an IUCN category assigned to extant species or lower taxa which have been evaluated but do not qualify for any other category. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... Animalia redirects here. ... Typical Classes See below Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. ... “Aves” redirects here. ... Families Many, see text A passerine is a bird of the giant order Passeriformes. ... Genera Many, see text Finches are passerine birds, often seed-eating, found chiefly in the northern hemisphere and Africa. ... Species Loxia pytyopsittacus Loxia scotia Loxia curvirostra Loxia leucoptera Loxia megaplaga The crossbills are birds in the finch family Fringillidae. ... In biology, binomial nomenclature is the formal method of naming species. ... Carolus Linnaeus, also known after his ennoblement as  , (May 23, 1707[1] – January 10, 1778), was a Swedish botanist, physician and zoologist[2] who laid the foundations for the modern scheme of nomenclature. ... Families Many, see text A passerine is a bird of the giant order Passeriformes. ... “Aves” redirects here. ... Genera Many, see text Finches are passerine birds, often seed-eating, found chiefly in the northern hemisphere and Africa. ... Species About 35; see text. ... World map showing North America A satellite composite image of North America. ... World map showing the location of Europe. ... World map showing the location of Asia. ... Subgenera Subgenus Strobus Subgenus Ducampopinus Subgenus Pinus See Pinus classification for complete taxonomy to species level. ... Species See text. ... Orders & Families Cordaitales † Pinales   Pinaceae - Pine family   Araucariaceae - Araucaria family   Podocarpaceae - Yellow-wood family   Sciadopityaceae - Umbrella-pine family   Cupressaceae - Cypress family   Cephalotaxaceae - Plum-yew family   Taxaceae - Yew family Vojnovskyales † Voltziales † The conifers, division Pinophyta, also known as division Coniferae, are one of 13 or 14 division level taxa within the...

This crossbill is mainly resident, but will regularly erupt south if its food source fails. This species will form flocks outside the breeding season, often mixed with other crossbills. Species Loxia pytyopsittacus Loxia scotia Loxia curvirostra Loxia leucoptera Loxia megaplaga The crossbills are birds in the finch family Fringillidae. ... Flock of Barnacle Geese during autumn migration Many species of birds undertake seasonal journeys of various lengths, a phenomenon known as Bird migration. ...

The crossbills are characterised by the mandibles crossing at their tips, which gives the group its English name. They are specialist feeders on conifer cones, particularly the various spruce species but also some populations (different species?) in Douglas-fir and various pine species, and the unusual bill shape is an adaptation to assist the extraction of the seeds from the cone. The mandible (from Latin mandibÅ­la, jawbone) or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. ... The English language is a West Germanic language that originates in England. ... Mature female European Black Pine cone Male cones of a pine A cone (in formal botanical usage: strobilus, plural strobili) is an organ on plants in the division Pinophyta (conifers) that contains the reproductive structures. ...

Adult males tend to be red or orange in colour, and females green or yellow, but there is much variation.

This species is difficult to separate from Parrot Crossbill and Scottish Crossbill, both of which breed within its Eurasian range. The identification problem is less severe in North America, where only Red Crossbill and White-winged Crossbill occur. Binomial name Loxia pytyopsittacus Borkhausen,, 1793 The Parrot Crossbill (Loxia pytyopsittacus) is a small passerine bird in the finch family Fringillidae. ... Binomial name Loxia scotica Hartert,, 1904 The Scottish Crossbill (Loxia scotica) is a small passerine bird in the finch family Fringillidae. ... Binomial name Loxia leucoptera (Gmelin, 1789) The Two-barred Crossbill (Loxia leucoptera), known as the White-winged Crossbill in North America, is a small passerine bird in the finch family Fringillidae. ...

Plumage distinctions from Parrot and Scottish Crossbills are negligible. The head and bill are smaller than in either of the other species. Care is needed to identify this species. The glip or chup call is probably the best indicator. Closeup on a single white feather A feather is one of the epidermal growths that forms the distinctive outer covering, or plumage, on a bird. ...

Work on vocalisation in North America suggest that, in that continent alone, there are eight or nine populations of Red Crossbill with different calls, which rarely if ever interbreed. These forms also vary in terms of bill size and structure, and specialise on the seed cones of different species of conifer. Few ornithologists seem inclined to give these forms species status at present. Ornithology (from the Greek ornis = bird and logos = word/science) is the branch of zoology concerned with the scientific study of birds. ...

Some large-billed, pine-feeding populations currently assigned to this species in the Mediterranean area may possibly be better referred to either Parrot Crossbill or alternatively to new species in their own right, but as yet, research into them is still at a very early stage. These include Balearic Crossbill L. curvirostra balearica and North African Crossbill L. curvirostra poliogyna, feeding primarily on Aleppo Pine (Pinus halepensis); Cyprus Crossbill L. curvirostra guillemardi, feeding primarily on European black pine (Pinus nigra); and an as-yet unidentified crossbill with a Parrot Crossbill-size bill feeding primarily on Bosnian Pine (Pinus heldreichii) in the Balkans. These populations also differ on plumage, with the Balearic, North African and Cyprus races having yellower males, and the Balkan type having deep purple-pink males; this however merely reflects the differing anthocyanin content of the cones they feed on, as these pigments are transferred to the feathers. The Mediterranean Basin refers to the lands around and surrounded by the Mediterranean Sea. ... Binomial name Pinus halepensis Miller The Aleppo Pine (Pinus halepensis) is a pine native to the Mediterranean region. ... Binomial name Pinus nigra J.F.Arnold The European Black Pine Pinus nigra (generally called Black Pine in Europe), is a variable species of pine, occurring across southern Europe from Spain to the Crimea, and also in Asia Minor, Cyprus, and locally in the Atlas Mountains of northwest Africa. ... Binomial name Pinus heldreichii H. Christ The Bosnian Pine (Pinus heldreichii, synonym ; family Pinaceae) is a species of pine that occurs in the mountains of southeastern Europe, in southwestern Bulgaria, Bosnia, Albania, Macedonia, Greece (south to Italy, growing at 900-2,500 m altitude. ... This article or section does not adequately cite its references or sources. ... Plants with abnormally high anthocyanin quantities are popular as ornamental plants - here, a selected purple-leaf cultivar of European Beech Anthocyanins (from Greek: (anthos) = flower + (kyanos) = blue) are water-soluble vacuolar flavonoid pigments that appear red to blue, according to pH. They are synthesized exclusively by organisms of the plant...

Crossbill Diversity

Distinct Eurasian Common Crossbill populations:

• Balearic Crossbill, Loxia curvirostra balearica
  • Associated with Aleppo Pine Pinus halepensis
• North African Crossbill, Loxia c. poliogyna
  • Associated with Aleppo Pine Pinus halepensis
• Corsican Crossbill, Loxia c. corsicana
  • Associated with European Black Pine, Pinus nigra
• Cyprus Crossbill, Loxia c. guillemardi
  • Associated with European Black Pine, Pinus nigra
• Crimean Crossbill, Loxia c. mariae
  • Associated with European Black Pine, Pinus nigra?
• Luzon Crossbill, Loxia c. luzoniensis
  • Associated with Khasi Pine, Pinus kesiya
• Annam Crossbill, Loxia c. meridionalis
  • Associated with Khasi Pine, Pinus kesiya

As with Parrot and Scottish Crossbills all of the above are fairly sedentary forms associated with hard-coned Pinus species. The following are more associated with the softer cones of spruce and larch: Binomial name Pinus halepensis Miller The Aleppo Pine (Pinus halepensis) is a pine native to the Mediterranean region. ... Binomial name Pinus halepensis Miller The Aleppo Pine (Pinus halepensis) is a pine native to the Mediterranean region. ... Binomial name Pinus nigra J.F.Arnold The European Black Pine Pinus nigra (generally called Black Pine in Europe), is a variable species of pine, occurring across southern Europe from Spain to the Crimea, and also in Asia Minor, Cyprus, and locally in the Atlas Mountains of northwest Africa. ... Binomial name Pinus nigra J.F.Arnold The European Black Pine Pinus nigra (generally called Black Pine in Europe), is a variable species of pine, occurring across southern Europe from Spain to the Crimea, and also in Asia Minor, Cyprus, and locally in the Atlas Mountains of northwest Africa. ... Binomial name Pinus nigra J.F.Arnold The European Black Pine Pinus nigra (generally called Black Pine in Europe), is a variable species of pine, occurring across southern Europe from Spain to the Crimea, and also in Asia Minor, Cyprus, and locally in the Atlas Mountains of northwest Africa. ... Binomial name Pinus kesiya Royle ex Gordon The Khasi Pine (Pinus kesiya) is a pine native to the Khasi hills in the northeast Indian state of Meghalaya from where it got its name. ... Binomial name Pinus kesiya Royle ex Gordon The Khasi Pine (Pinus kesiya) is a pine native to the Khasi hills in the northeast Indian state of Meghalaya from where it got its name. ... This article deals with the tree; for the e-mail client see Pine email client Species About 115. ... Species About 35; see text. ... Species About 12; see text Siberian larch Male (above) and female (below right) cones of Japanese Larch emerging in spring Larches are conifers in the genus Larix, in the family Pinaceae. ...

• Altai Crossbill, Loxia c. altaiensis
  • Associated with Spruce sp.
• Tien Shan Crossbill, Loxia c. tianschanica
  • Associated with Schrenk's Spruce Picea shrenkiana
• Himalayan Crossbill, Loxia c. himalayensis
  • Associated with Himalayan Hemlock Tsuga dumosa
• Japanese Crossbill, Loxia c. japonica

North American Red Crossbill subspecies list based on biometrics: Species About 35; see text. ... Binomial name Picea schrenkiana Fisch. ... Binomial name Tsuga dumosa (D. Don) Eichler Tsuga dumosa, commonly called the Himalayan Hemlock or in Chinese, Yunnan Tieshan (Simplified Chinese: ; Traditional Chinese: ; Hanyu Pinyin: ), is a species of conifer native to the eastern Himalayas. ...

• Newfoundland Crossbill, Loxia c. percna Possibly extinct
• Lesser Crossbill, Loxia c. minor
• Sitka Crossbill, Loxia c. sitkensis
• Loxia c. neogaea
• Rocky Mountain Crossbill, Loxia c. benti
• Sierra Crossbill, Loxia c. grinnelli
• Bendire Crossbill, Loxia c. bendirei
• Mexican Crossbill, Loxia c. stricklandi
• Central American Crossbill, Loxia c. mesamericana
• South Hills Crossbill, Loxia c. ?

Jeff Groth's classification of North American Red Crossbill forms based on call-types: Trinomial name Loxia curvirostra pusilla Gloger, 1834 The Newfoundland Red Crossbill is a member of the common crossbill genus which has adapted its crossed bill for prying open the tightly closed spruce or pine cones in order to extract the seeds found abundantly on the island of Newfoundland. ...

• Type 1, corresponds with Loxia c. neogaea
  • Recorded on Tsuga species, Picea glauca, Pinus strobus
• Type 2, corresponds with Loxia c. benti/grinnelli/bendirei
  • Recorded on Pinus ponderosa scopulorum in the west and in various Pinus species in the east
• Type 3, corresponds with Loxia c. sitkensis and Loxia c. minor
  • Recorded on Western Hemlock Tsuga heterophylla
• Type 4, corresponds with Loxia c. neogaea
  • Recorded on Douglas Fir Pseudotsuga menziesii
• Type 5, corresponds with Loxia c. benti/grinnelli/bendirei
  • Recorded on Lodgepole Pine Pinus contorta latifolia
• Type 6, corresponds with Loxia c. stricklandi
  • Uses Pine species in Section Trifoliae
• Type 7, corresponds with Loxia c. benti/grinnelli/bendirei
  • In terms of diet this type is possibly a generalist
• Type 8, corresponds with Loxia c. percna
  • Uses Black Spruce Picea mariana
• Type 9, corresponds with South Hills Crossbill
  • Isolated population of Lodgepole Pine Pinus contorta latifolia

Summers' list of European Common Crossbill forms (with Parrot & Scottish) based on Flight/Excitement calls: This article deals with the tree; for the e-mail client see Pine email client Species About 115. ... Binomial name Tsuga heterophylla (Raf. ... Species See text Douglas-fir is the common name applied to coniferous trees of the genus Pseudotsuga in the family Pinaceae. ... Binomial name Pinus contorta Douglas Lodgepole Pine (Pinus contorta) is a common tree in western North America. ... Subgenera Subgenus Strobus Subgenus Ducampopinus Subgenus Pinus See Pinus classification for complete taxonomy to species level. ... Binomial name Picea mariana The Black Spruce (Picea mariana) is a common coniferous tree in North America. ... Binomial name Pinus contorta Douglas Lodgepole Pine (Pinus contorta) is a common tree in western North America. ...

• 1A, corresponds with "British" Crossbill
• 2B, corresponds with "Wandering" Crossbill
• 2D, corresponds with Parrot Crossbill Loxia pytyopsittacus
• 3C, corresponds with Scottish Crossbill Loxia scotica
• 3D, corresponds with Balearic Crossbill
• 3E, corresponds with North African Crossbill
• 4E, corresponds with "Glip" Crossbill
• 5D, corresponds with Cyprus Crossbill

"The Sound Approach's" classification of European Common Crossbill types based on call-types: Binomial name Loxia pytyopsittacus Borkhausen,, 1793 The Parrot Crossbill (Loxia pytyopsittacus) is a small passerine bird in the finch family Fringillidae. ... Binomial name Loxia scotica Hartert,, 1904 The Scottish Crossbill (Loxia scotica) is a small passerine bird in the finch family Fringillidae. ...

• "Wandering" Crossbill (Type A - flight call "Keep")
• "Bohemian" Crossbill (Type B - flight call "Weet")
• "Glip" Crossbill (Type C - flight call "Glip")
• "Phantom" Crossbill (Type D - flight call "Jip")
• "British" Crossbill (Type E - flight call "Chip")
• "Scarce" Crossbill (Type F - flight call "Trip")
• "Parakeet" Crossbill (Type X - flight call "Cheep")

References

• BirdLife International (2004). Loxia curvirostra. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern

The IUCN Red List of Threatened Species (also known as the IUCN Red List and Red Data List), created in 1963, is the worlds most comprehensive inventory of the global conservation status of plant and animal species and can be found here. ... The World Conservation Union or International Union for the Conservation of Nature and Natural Resources (IUCN) is an international organization dedicated to natural resource conservation. ...

External links

Wikimedia Commons has media related to:

Loxia curvirostra

• American Museum of Natural History - audiovisual guide
• Internet Bird Collection: Common Crossbill videos
• Cornell Lab of Ornithology - Red Crossbill
• USGS - Red Crossbill Information
• South Dakota Birds - Red Crossbill Information

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Wikicommons) is a repository of free content images, sound and other multimedia files. ...

Further reading

Book

Adkisson, C. S. 1996. Red Crossbill (Loxia curvirostra). In The Birds of North America, No. 256 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Union, Washington, D.C.

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.

• Coombs-Hahn TP. Ph.D. (1993). Integration of environmental cues to time reproduction in an opportunistic breeder, the red crossbill (Loxia curvirostra). University of Washington, United States -- Washington.

• Groth JG. Ph.D. (1990). Cryptic species of nomadic birds in the red crossbill (Loxia curvirostra) complex of North America. University of California, Berkeley, United States -- California.

• Simard JH. M.Sc. (2001). Habitat selection, ecological energetics, and the effects of changes in white pine forests on breeding red crossbills (Loxia curvirostra ) in Algonquin Provincial Park, Ontario. McGill University (Canada), Canada.

• Smith JW. Ph.D. (2005). The role of coevolution in promoting ecological speciation in red crossbills (Loxia curvirostra complex). New Mexico State University, United States -- New Mexico.

• Wren LS. M.Sc. (2001). Continental and regional distribution and abundance patterns of boreal cardueline finches: Influences of conifer seed availability. Memorial University of Newfoundland (Canada), Canada.

Articles

• Alonso D, Arizaga J, Miranda R & Campos F. (2003). Comparative biometrics of common crossbills (Loxia curvirostra) on the Iberian Peninsula and the Bealearic Islands. Vogelwarte. vol 42, no 1-2. p. 116-117.

• Alonso D, Arizaga J, Miranda R & Hernandez MA. (2006). Morphological diversification of common crossbill Loxia curvirostra populations within Iberia and the Balearics. Ardea. vol 94, no 1. p. 99-107.

• Arnaiz-Villena A, Guillen J, Ruiz-de-Valle V, Lowy E, Zamora J, Varela P, Stefani D & Allende LM. (2001). Phylogeography of crossbills, bullfinches, grosbeaks, and rosefinches. Cellular and Molecular Life Sciences. vol 58, no 8. p. 1159-1166.

• Barboza PS & Jorde DG. (2002). Intermittent fasting during winter and spring affects body composition and reproduction of a migratory duck. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. vol 172, no 5. p. 419-434.

• Benkman CW. (1987). Food Profitability and the Foraging Ecology of Crossbills. Ecological Monographs. vol 57, no 3. p. 251-267.

• Benkman CW. (1988). Flock Size Food Dispersion and the Feeding Behavior of Crossbills. Behavioral Ecology & Sociobiology. vol 23, no 3. p. 167-176.

• Benkman CW. (1988). On the Advantages of Crossed Mandibles an Experimental Approach. Ibis. vol 130, no 2. p. 288-293.

• Benkman CW. (1993). ADAPTATION TO SINGLE RESOURCES AND THE EVOLUTION OF CROSSBILL (LOXIA) DIVERSITY. Ecological Monographs. vol 63, no 3. p. 305-325.

• Benkman CW. (1993). The evolution, ecology, and decline of the red crossbill of Newfoundland. American Birds. vol 47, no 2. p. 225-229.

• Benkman CW. (1999). The selection mosaic and diversifying coevolution between crossbills and lodgepole pine. American Naturalist. vol 153, p. S75-S91.

• Benkman CW. (2003). Divergent selection drives the adaptive radiation of crossbills. Evolution. vol 57, no 5. p. 1176-1181.

• Benkman CW, Colquitt JS, Gould WR, Fetz T, Keenan PC & Santisteban L. (2005). Can selection by an ectoparasite drive a population of red crossbills from its adaptive peak?. Evolution. vol 59, no 9. p. 2025-2032.

• Benkman CW, Holimon WC & Smith JW. (2001). The influence of a competitor on the geographic mosaic of coevolution between crossbills and lodgepole pine. Evolution. vol 55, no 2. p. 282-294.

• Benkman CW & Lindholm AK. (1991). THE ADVANTAGES AND EVOLUTION OF A MORPHOLOGICAL NOVELTY. Nature. vol 349, no 6309. p. 519-520.

• Benkman CW & Miller RE. (1996). Morphological evolution in response to fluctuating selection. Evolution. vol 50, no 6. p. 2499-2504.

• Benkman CW, Parchman TL, Favis A & Siepielski AM. (2003). Reciprocal selection causes a coevolutionary arms race between crossbills and lodgepole pine. American Naturalist. vol 162, no 2. p. 182-194.

• Brauning DW, Brittingham MC, Gross DA, Leberman RC, Master TL & Mulvihill RS. (1994). Pennsylvania breeding birds of special concern: A listing rational and status update. Journal of the Pennsylvania Academy of Science. vol 68, no 1. p. 3-28.

• Brazier FH. (1996). A second breeding record of Red Crossbill in Regina. Blue Jay. vol 54, no 1.

• Clark WH. (1981). Highway Mortality of the Red Crossbill Loxia-Curvirostra. Journal of the Idaho Academy of Science. vol 17, no 1. p. 1-2.

• Clouet M. (2000). The breeding biology of the Common Crossbill Loxia Curvirostra in the Central Pyrenees. Bird Study. vol 47, p. 186-194.

• Clouet M. (2003). Bill size and breeding periode of pine forest crossbills. Revue D Ecologie-La Terre Et La Vie. vol 58, no 4. p. 419-433.

• Clouet M & Goar J-L. (2001). Note on the Philippine cross-bill Loxia curvirostra luzoniensis. Alauda. vol 69, no 2. p. 331-334.

• Coffey K, Benkman CW & Milligan BG. (1999). The adaptive significance of spines on pine cones. Ecology. vol 80, no 4. p. 1221-1229.

• Constantine M, & "The Sound Approach". (2006). The Sound Approach to Birding. A guide to understanding bird sound. ISBN-10: 9081093312

• Cornelius JM, Breuner CW & Hahn TP. (2004). Effects of food reduction on stress reactivity in an irruptive nomad, the red crossbill. Integrative and Comparative Biology. vol 44, no 6. p. 684-684.

• Dinsmore JJ. (1998). Iowa's avifauna: Recent changes and prospects for the future. Journal of the Iowa Academy of Science. vol 105, no 3. p. 115-122.

• Edelaar P. (2003). Are there morphological differences between the vocal types of the common crossbill?. Vogelwarte. vol 42, no 1-2. p. 115-116.

• Edelaar P. (2003). Is there assortative mating between the vocal types of the common crossbill?. Vogelwarte. vol 42, no 1-2.

• Edelaar P & Benkman CW. (2006). Replicated population divergence caused by localized coevolution? A test of three hypotheses in the red crossbill-lodgepole pine system. Journal of Evolutionary Biology. vol 19, no 5. p. 1651-1659.

• Edelaar P, Phillips RE & Knops P. (2005). Sexually dimorphic body plumage in juvenile Crossbills. Wilson Bulletin. vol 117, no 4. p. 390-393.

• Edelaar P & Terpstra K. (2004). The nominate subspecies of the Common Crossbill Loxia c. curvirostra polytypic? I. Morphological differences among years at a single site. Ardea. vol 92, no 1. p. 93-102.

• Förschler MI, Förschler L & Dorka U. (2006). Population fluctuations of siskins Carduelis spinus, common crossbills Loxia curvirostra, and citril finches Carduelis citrinella in relationship to flowering intensity of spruce Picea abies. Ornis Fennica. vol 83, no 2. p. 91-96. http://www.birdlife.fi/julkaisut/of/pdf/vol83-2/6F%F6rschler2524.pdf

• Frost MP. (1985). Citril Finches Serinus-Citrinella and Crossbills Loxia-Curvirostra Eating Minerals. British Birds. vol 78, no 1.

• Genard M & Lescourret F. (1987). The Common Crossbill Loxia-Curvirostra in the Pyrenees France Some Observations on Its Habitats and on Its Relations with Conifer Seeds. Bird Study. vol 34, no 1. p. 52-63.

• Gilbert FF & Allwine R. (1991). Spring Bird Communities in the Oregon Cascade Range USA. U S Forest Service General Technical Report PNW. vol 285, p. 145-159.

• Groth JG. (1988). Resolution of Cryptic Species in Appalachian Red Crossbills. Condor. vol 90, no 4. p. 745-760.

• Groth JG. (1993). Call matching and positive assortative mating in Red Crossbills. The Auk. vol 110, no 2. p. 398.

• Hahn T. (1990). PHYSIOLOGICAL CORRELATES OF OPPORTUNISTIC BREEDING IN THE RED CROSSBILL. American Zoologist. vol 30, no 4. p. A53-A53.

• Hahn T. (1992). Seasonal components of reproductive function in a reproductive opportunist, the red crossbill, Loxia curvirostra. American Zoologist. vol 32, no 5.

• Hahn TP. (1994). Crossbill diversity -- Evolutionary Differentiation in Morphology, Vocalizations, and Allozymes Among Nomadic Sibling Species in the North American Red Crossbill (Loxia curvirostra) Complex by J. G. Groth. The Condor. vol 96, no 3. p. 835.

• Hahn TP. (1995). Integration of Photoperiodic and Food Cues to Time Changes in Reproductive Physiology by an Opportunistic Breeder, the Red Crossbill, Loxia curvirostra (Aves: Carduelinae). Journal of Experimental Zoology. vol 272, no 3. p. 213-226.

• Hahn TP. (1996). Habitat preferences and biogeography of cryptic species in the North American red crossbill complex (Loxia curvirostra; Aves: Carduelinae). American Zoologist. vol 36, no 5.

• Hahn TP. (1998). Reproductive seasonality in an opportunistic breeder, the red crossbill, Loxia curvirostra. Ecology. vol 79, no 7. p. 2365-2375.

• Hau M. (2001). Timing of breeding in variable environments: Tropical birds as model systems. Hormones and Behavior. vol 40, no 2. p. 281-290.

• Hau M, Wikelski M & Wingfield JC. (2000). Visual and nutritional food cues fine-tune timing of reproduction in a neotropical rainforest bird. Journal of Experimental Zoology. vol 286, no 5. p. 494-504.

• Herbers JR, Serrouya R & Maxcy KA. (2004). Effects of elevation and forest cover on winter birds in mature forest ecosystems of southern British Columbia. Canadian Journal of Zoology-Revue Canadienne De Zoologie. vol 82, no 11. p. 1720-1730.

• Hernandez M, Alonso D, Arizaga J, Amezcoa A, Alda F, Murua A, Schroder P-C & Campos F. (2003). Comparative molecular study of populations of common crossbill (Loxia curvirostra) on the Iberian Peninsula and the Balearic Islands. Vogelwarte. vol 42, no 1-2.

• Hill GE & Benkman CW. (1995). Exceptional response by female red crossbills to dietary carotenoid supplementation. The Wilson Bulletin. vol 107, no 3. p. 555.

• Hogstad O. (1990). Winter Territoriality and the Advantages of Social Foraging in the Treecreeper Certhia-Familiaris. Fauna Norvegica Series C Cinclus. vol 13, no 2. p. 57-64.

• Holimon WC, Benkman CW & Willson MF. (1998). The importance of mature conifers to red crossbills in southeast Alaska. Forest Ecology and Management. vol 102, no 2-3. p. 167-172.

• Hubalek Z. (1984). Avifauna of the Island of Brac Yugoslavia. Larus. vol 37, p. 167-174.

• Iovchenko NP. (2003). Relationship of moult and breeding in the Tien Shan subspecies of the common crossbill Loxia curvirostra tianshanica. Vogelwarte. vol 42, no 1-2.

• Jacobs JD & Wingfield JC. (2000). Endocrine control of life-cycle stages: A constraint on response to the environment?. Condor. vol 102, no 1. p. 35-51.

• Jardine DC. (1994). Brood patch on a Common Crossbill Loxia curvirostra still in juvenile plumage. Bird Study. vol 41, no 2. p. 155-156.

• Jardine DC. (1994). Observations on the occurrence of red-orange female common crossbills Loxia curvirostra. Ringing & Migration. vol 15, no 2. p. 98-100.

• Jardine DC. (2000). Common Crossbill eating adelgids. Scottish Birds. vol 21, no 1. p. 52-53.

• Johnson NK, Marten JA & Ralph CJ. (1989). Genetic Evidence for the Origin and Relationships of Hawaiian Honeycreepers Aves Fringillidae. Condor. vol 91, no 2. p. 379-396.

• Kelsey R & Hahn TP. (2004). Distribution and abundance of a nomadic seed specialist, the red crossbill, in the western United States. Integrative and Comparative Biology. vol 44, no 6. p. 712-712.

• Knox AG. (1990). Identification of Crossbill and Scottish Crossbill. British Birds. vol 83, no 3. p. 89-94.

• Knox AG. (1990). THE SYMPATRIC BREEDING OF COMMON AND SCOTTISH CROSSBILLS LOXIA-CURVIROSTRA AND LOXIA-SCOTICA AND THE EVOLUTION OF CROSSBILLS. Ibis. vol 132, no 3. p. 454-466.

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