Red Crossbill

Loxia curvirostra

Order:
Passeriformes
Family:
Fringillidae
Sections

Systematics

Welcome to the Birds of North America Online!

You are currently viewing one of the free species accounts available in our complimentary tour of BNA. In this courtesy review, you can access all the life history articles and the multimedia galleries associated with this species.

For complete access to all species accounts, a subscription is required. Subscriptions are available for as little as $5 for 30 days of complete access! If you would like to subscribe to BNA, please visit the Cornell Lab of Ornithology E-Store or call us at 877-873-2626 (M-F, 8:00-4:00 ET).

Enlarge
Figure 3. Variation in bill size and shape among North American Red Crossbills.

Drawings based on adult male specimens collected in Sheridan, Wyoming (A) and Beech Creek, Pennsylvania (B). North American populations show a diverse range of bill sizes and shapes which vary between the extremes illustrated here. Bill size and shape are even more variable among European and Asian populations. The mandibles may cross either to the left or the right. Drawing by Dan Otte.

Enlarge
Figure 4. Known Flight Call types of North American Red Crossbills.
Enlarge
Red Crossbill (L. c. percna; Newfoundland or Type 8).

Resident on Newfoundland. Second largest crossbill in New World. Male is deep red and female (pictured) is dark green.

© Chris Benesh, Newfoundland and Labrador, Canada, 4 July 2017
Enlarge
Red Crossbill (L. c. stricklandi; Sierra Madre or Type 6).

Resident in mountains from southeastern Arizona and southwestern New Mexico south to El Salvador. Largest billed and bodied crossbill in New World.

© Timothy Spahr, Arizona, United States, 8 January 2017
Enlarge
Red Crossbill (L. c. mesamericana; Central American or Type 11).

Resident in highlands from Guerrero (Mexico) and Belize south to northern Nicaragua. Smaller bill depth and wing length than Type 6.

© Moises Rodriguez, Sololá, Guatemala, 4 October 2017
Enlarge
Red Crossbill (L. c. minor; Western Hemlock or Type 3).

Resident in the Pacific Northwest from south-central Alaska south to Washington and Oregon, wanders irruptively regularly to the east. Smaller overall than L. c. japonica, with the bill sharply curved and “stumpy”; male redder (less orange) and undertail coverts grayish.

© Michael O'Brien, New Jersey, United States, 28 November 2012
Enlarge
Red Crossbill (L. c. corsicana).

Resident on Corsica. Similar to L. c. curvirostra, but bill deeper.

© Hugo Foxonet, Corse, France, 1 November 2017
Enlarge
Red Crossbill (L. c. poliogyna).

Resident in the Atlas Mountains in northwestern Africa. Bill shorter and deeper, wing shorter than in L. c. curvirostra; male more pinkish red, with head variably mottled gray in both sexes.

© Laura Keene, Meknès-Tafilalet, Morocco, 16 March 2014
Enlarge
Red Crossbill (L. c. guillemardi).

Resident in Cyprus, Turkey, the Caucasus, and Crimea. Similar to L. c. curvirostra, but larger overall with larger bill; male paler red and generally grayer and female dorsum dark gray (less olive).

© Chris Lamsdell, Lefkosia, Cyprus, 29 January 2018
Enlarge
Red Crossbill (L. c. meridionalis).

Resident in mountains of south-central Vietnam. Dorsum mottled with dark brown. Has the deepest bill of the Red Crossbills (only Parrot Crossbill is larger).

© Tom Wheatley, Lam Dong, Vietnam, 19 December 2014

Geographic Variation

In striking contrast to the White-winged Crossbill (52), North American Red Crossbills show much local and regional variation in bill and body size (Figure 3). This size variation was categorized into subspecies by numerous authors (1, 53, 54) on the assumption that each has a nonoverlapping breeding range (e.g., 53, 55, 56); see Groth (3) for a review of these taxonomic schemes. However, with a few exceptions on the periphery of the distribution (e.g., L. c. percna in Newfoundland, L. c. stricklandi in Mexico, and L. c. mesamericana in Middle America), the remaining subspecies have widely overlapping breeding distributions in the New World (2, 3), violating a basic tenet of subspecific designation, in which breeding ranges must not overlap geographically.

The key advance in classification was by Groth (2, 3) who demonstrated that the variation in bill and body size is best categorized not as subspecies but by the structure of their vocalizations, especially their contact calls (see Figure 4; see also Vocalizations: Vocal Array), with 8 distinctive “call types” numbered in sequence of their discovery. Each call type examined also differs in song (e.g., 12, 6), however, songs are not as easily categorized and song cannot be used to categorize females because they rarely sing. Although there is substantial variation in adult coloration (see Appearance: Plumage), it is not readily associated with call type (3). Subsequently, Benkman (57) discovered a ninth call type (Type 9) located in 2 isolated mountain ranges in southern Idaho. Irwin (6) distinguished an additional call type (Type 10) that had been categorized by Groth (3) within Type 4, and the subspecies confined mostly to Middle America, L. c. mesamericana, has been designated as Type 11 (13). Type 9 has been elevated to species status (Cassia Crossbill, L. sinesciuris); thus, there remain 10 call types.

Each call type has a range of morphological variation normally found within a songbird species (2, 3), which, combined with evidence of sympatric breeding and assortative pairing (58), led Groth (3) to propose that these call types are cryptic species. However, more recent genetic evidence (10) and the limited evidence of reproductive isolation outside of the Cassia Crossbill (11, 12) indicated that elevation to species status of the remaining call types is premature. For only the Cassia Crossbill is there strong support for monophyly (10) and strong evidence for reproductive isolation: 99.3% of 875 breeding pairs over 6 years were assortative (11, 12). Besides the Cassia Crossbill, Type 6 (L. c. stricklandi), found mostly in Mexico, is the most genetically distinct of the call types (10) and with further study might warrant species status. Neither Type 8 (L. c. percna) nor Type 11 (L. c. mesamericana) have been included in genetic analyses so their genetic distinctiveness remains unknown. However, based on the apparent similarity in ecology of Type 11 to that of the Cassia Crossbill (i.e., both call types rely on seeds in strongly serotinous pines year round), it could warrant species designation.

Call (vocal) types have also been described in Europe (59, 60, 61), and although Summers et al. (49) found ~95% assortative mating between call types, the extent to which vocal types are reproductively isolated and differ in morphology and ecology has received limited study (62, 63, 49). Most of the morphological variation in western Palearctic is between populations near the Mediterranean (especially Cyprus, Mallorca, northern Africa) and those to the north. Genetic studies (25) revealed no genetic differentiation among European vocal types, and stunningly little differentiation even between Parrot Crossbill (L. pytyopsittacus) and co-occurring Red Crossbills (see also Piertney et al. [64]). In contrast, the subspecies confined to areas of Aleppo pine (Pinus halepensis) in southeastern Spain (L. c. hispana), Mallorca (L. c. balearica) and the Atlas Mountains of northern Africa (L. c. poliogyna) are genetically distinct and the latter 2 subspecies are monophyletic (25). Size variation is greatest in central and eastern Asia (32) where additional research is needed.

Subspecies

Below are subspecies that can be distinguished by geographic distribution or bill size or both; many recognized subspecies in North America cannot be assigned with certainly (e.g., L. c. neogaea, L. c. bendirei [3]), however, subspecies L. c. neogaea is likely a match for an eastern call type, but definitive answers will require genetic assignment in the future.

  • L. c. percna Bent, 1912. Type 8 (3, 15). Formerly common, but now rare (65, 48) resident on Newfoundland, with recent evidence of breeding on Anticosti Island, Quebec (66) [type locality = Flatbay River, Newfoundland]. Second largest crossbill in New World. Male deep red and female dark green.
  • L. c. stricklandi Ridgway, 1885. Type 6 (3). Supercedes L. c. mexicana Strickland, 1851 (preoccupied). Resident in mountains from southeastern Arizona and southwestern New Mexico south to El Salvador [type locality = near Mexico City]. Largest billed and bodied crossbill in New World.
  • L. c. mesamericana Griscom, 1937. Type 11 (13). Resident in highlands from Guerrero (Mexico) and Belize south to northern Nicaragua [type locality = Rancho Quemado, Honduras]. The combination of smaller bill depth and wing length distinguish L. c. mesamericana from L. c. stricklandi (CWB). Although Howell (67) suggested that L. c. mesamericana might represent 2 taxa, measurements of 33 museum specimens with well occluded bills indicated there is seasonal variation in bill length (presumably because of seasonal variation in seed availability) and just one subspecies (coefficient of variation for bill depth, sexes combined = 3.50, which is similar to other call types in North America; CWB, unpublished data).
  • L. c. minor (Brehm, 1846). Type 3 (3). Includes L. c. sitkensis Grinnell, 1909, and L. c. reai Phillips, 1981 (see Payne [54]; cf. 68). Resident in the Pacific Northwest from south-central Alaska south to Washington and Oregon; more so than any of the other all types, wanders irruptively regularly to the east [e.g., type locality = Black River, Michigan; see 55]. Similar to L. c. japonica, but smaller overall with the bill sharply curved and “stumpy” (55); male redder (less orange) and undertail coverts grayish. Type 3 is among the most common call types in North America.
  • L. c. pusilla Gloger, 1833. Type 2 (2, 3). Occurs in the Appalachian Mountains [type locality = Georgia], but is widely distributed and most common in the southern Rocky Mountains of Intermountain West, and in the southern Cascades and Sierra Nevada south to the Transverse Ranges of southern California. Large billed and bodied, but smaller than Cassia Crossbill and L. c. stricklandi Type 6 found in western United States. Type 2 is very likely the most widespread and among the most common call types in North America.
  • L. c. curvirostra Linnaeus, 1758. Includes L. c. hispana Hartert, 1904, and L. c. anglica Hartert, 1904. Resident in southern Great Britain and continental Europe and east to Siberia and Amurland [type locality = Sweden]. Bill larger than all New World crossbills other than L. c. stricklandi. Recent genomic analyses of L. c. curvirostra in Europe did not reveal evidence for genetic differentiation between 2 vocal types or among geographically distinct samples with the exception of populations in southern Spain (putatively L. c. hispana) that were distinct and warrant further study (25); bills are relatively long and shallow in crossbills associated with Aleppo pine (Pinus halepensis) in southern Spain (69) that could represent L. c. hispana.
  • L. c. balearica Homeyer, 1862. Resident on Mallorca [type locality = Mallorca]. Like L. c. curvirostra, but smaller overall with shorter bill. Recent genomic studies found that L. c. balearica is genetically distinct and monophyletic (25), potentially warranting species designation.
  • L. c. bangsi Griscom, 1937. Usually combined with L. c. himalayensis but recent analyses by Edelaar (63) reveal a bimodal size distribution with L. c. bangsi representing the larger individuals as originally recognized by Griscom (1). Mountains of the Chinese provinces of Sichuan, Yunnan, and Gansu, and northern Myanmar and Sikkim [type locality = China, western Sichuan, Hadja-tungoo].
  • L. c. corsicana Tschusi, 1912. Resident on Corsica [type locality = Corsica]. Similar to L. c. curvirostra, but bill deeper.
  • L. c. poliogyna Whitaker, 1898. Resident in the Atlas Mountains in northwestern Africa (Algeria, Tunisia, and Morocco) [type locality = central Tunisia]. Bill shorter and deeper, wing shorter than in L. c. curvirostra; male more pinkish red, with head variably mottled gray in both sexes. Recent genomic studies found that L. c. poliogyna is genetically distinct and monophyletic (25), potentially warranting species designation.
  • L. c. guillemardi von Madarász, 1903. Includes L. c. caucasica Buturlin, 1907; L. nidificans Kleinschmidt, 1919; L. c. taurica Griscom, 1937; L. c. mariae Dement’ev, 1932; and L. c. vasvarii Keve, 1943. Resident in Cyprus, Turkey, the Caucasus, and Crimea [type locality = Troodos Mountain, Cyprus]. Similar to L. c. curvirostra, but larger overall with larger bill; male paler red and generally grayer and female dorsum dark gray (less olive).
  • L. c. himalayensis Blyth, 1845. Resident from northern India and Nepal east to south-central China (northern Yunnan) [type locality = Nepal]. The smallest-billed Red Crossbill.
  • L. c. altaiensis Sushkin, 1925. Includes L. c. minussensis Sushkin, 1925, and L. c. ermaki Kozlova, 1930. Resident in mountains in northern and western Mongolia [type locality = Ongudai, central Altai]; some birds move south in winter. Similar to L. c. himalayensis, but male deeper and darker blood red nearly throughout and female browner (less gray).
  • L. c. tianschanica Laubmann, 1927. Includes L. c. przewalskii Dement’ev, 1932, and L. c. turkestanensis Griscom, 1937. Resident around the Tien Shan Mountains in central Asia [type locality = Naryn, Kyrgyzstan]. Similar to L. c. himalayensis but paler overall, with male tending to be yellow (not red, but if so a rather pale hue) and female dull yellow (less olive or brown).
  • L. c. japonica Ridgway, 1884. Breeds in eastern Russia and northern and central Japan [type locality = Tateyama, Honshu]; winters south to southern Japan, the Korean Peninsula, and eastern China. Similar to L. c. tianschanica, but male generally orangish red.
  • L. c. meridionalis Robinson and Kloss, 1919. Resident in mountains of south-central Vietnam [type locality = Dalat]. Dorsum mottled with dark brown. Has the deepest bill of the Red Crossbills (only Parrot Crossbill is larger).
  • L. c. luzoniensis Ogilvie-Grant, 1894. Resident in the northern mountains on Luzon, Philippines [type locality = mountains of northern Luzon]. Among the smallest billed subspecies (only L. c. himalayensis and L. c. minor are smaller).

Related Species

The Fringillidae is among a handful of oscine passerine families with 9 primary feathers (cf. 70) and a recent evolutionary history; as a result, the family’s phylogenetic position has been unclear relative to other 9-primaried families, notably the Passeridae (Old World sparrows), Ploceidae (weavers), Estrildidae (waxbills, munias, and allies), and Viduidae (wydahs and indigobirds). Some taxonomists merged all of these families into a single, grand Fringillidae, whereas others have merged all 9-primaried oscines into a single family (named Emberizidae because of priority). Moreover, there remains dispute of whether the Hawaiian honeycreepers constitute a family, Drepanididae, or a subfamily of the Fringillidae. The latter treatment has prevailed in recent taxonomies, such that 4 major subdivisions (i.e., subfamilies) typically are recognized in the narrower Fringillidae (e.g., 71): the Fringillinae (chaffinches and snowfinches), Carduelinae (rosefinches, goldfinches, crossbills, siskins, and allies), Euphoniinae (euphonias and chlorophonias), and Drepanidinae (Hawaiian "honeycreepers"). Within the Carduelinae, the genus Loxia appears nearest Acanthis (redpolls) from which it diverged about 3.5 MYA (72).

The Loxia curvirostra complex diverged from the L. leucoptera complex less than 1 MYA (72). Beyond that, relationships within Loxia are muddy, chiefly because species limits within the L. curvirostra complex are controversial, perhaps in no small part because they do not conform well to expectations of standard models of geographic speciation. Current standard taxonomies recognize 4 species: L. curvirostra sensu stricto, the Red (or Common) Crossbill spanning much of the Holarctic; L. scotica, the Scottish Crossbill of Scotland; L. pytyopsittacus, the Parrot Crossbill of northern Europe; and L. sinesciuris, the Cassia Crossbill of southern Idaho. Three of these species have fairly small geographic ranges, and the validity of one species, L. scotica—which is intermediate in size between L. curvirostra of southern Great Britain and L. pytyopsittacus of Scandinavia—was dismissed for decades until assortative mating in sympatry was established (73, 49). Loxia sinesciuris, too, mates assortatively when its breeding season overlaps that of types 2 and 5 (11, 12). Call type-specific assortative mating has been found in both North America (58; C. Porter, unpublished data) and Europe (74). Nonetheless, the levels of assortative mating and the recency of divergence might not be sufficient for detecting strong genomic evidence of speciation. An analysis of 238,615 single nucleotide polymorphisms (SNPs) of L. curvirostra (7 call types), L. sinesciuris, and L. leucoptera (the White-winged Crossbill) found that the 3 species formed monophyletic groups, whereas populations of L. curvirostra exhibit either extensive gene flow or divergence only in the recent past (10). Further splits in the Loxia curvirostra complex should wait until high levels of assortative mating among birds of known call types are found.

Evidence for hybridization between L. curvirostra and other taxa is limited. In captivity, a male L. leucoptera caged with a female L. curvirostra produced 2 broods with 3 young each, and a resultant male hybrid, which had wing bars and bill size intermediate to its parents, was backcrossed with a female L. curvirostra, of which the offspring “appeared essentially like” L. curvirostra (H. B. Tordoff, personal communication). Tallman and Zusi (75) reported a putative natural hybrid between L. curvirostra and Spinus pinus, the Pine Siskin.

Recommended Citation

Benkman, C. W. and M. A. Young (2019). Red Crossbill (Loxia curvirostra), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.redcro.02