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Loxia curvirostra Linnaeus, 1758
Red Crossbill
Family: Fringillidae

Species account author: Jamie Fenneman
Introduction to the Birds

Photograph

© Tim Zurowski     (Photo ID #7976)

Map


Distribution of Loxia curvirostra in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Adult male
Although all red colouration is described here as brick-red, some individuals are more orange-red. The back, scapulars, and rump coverts are brick-red, often with darker feather centres on the back and scapulars producing a mottled effect (especially on the scapulars); uppertail coverts dark brown with brick-red feather edges. The wings (wing coverts, flight feathers) are brownish-black with very fine reddish-brown edges on the feathers; wing coverts and tertials sometimes with paler, broader buffy or whitish edges forming two narrow wing bars. The deeply-notched tailed is brownish-black with narrow reddish-brown feather edges. The underparts are extensively brick-red, gradually becoming more grayish or whitish on the lower belly and undertail coverts; undertail coverts with brownish feather centres. The head is wholly brick-red, with dusky-grey lores and upper and rear portions of the ear coverts. The iris is dark, the unusual bill is blackish or dark grey with distinctively crossed tips to the mandibles, and the legs and feet are blackish.

Adult female
The plumage pattern is similar to the male, but the female is variably yellow or olive to grey where the male is brick-red or orange-red. Some females are particularly dull and greyish, while others are brighter yellowish or greenish. The back and scapulars are greenish-yellow or olive to olive-grey, with paler feather edges on the scapulars and dark feather centres on the back (producing a mottled effect). The lower back and rump are relatively bright olive to yellowish-green and the uppertail coverts are dark olive-grey with paler feather edges. Tail and wings dark brownish-black with very narrow olive or yellowish-green feather edges. The underparts are olive-yellow to yellowish, with a paler belly, a grayish or brownish wash on the flanks, and whitish undertail coverts with dark brown feather centres. The head is yellowish-green to olive-grey with a pale whitish throat and dusky grey-brown lores and upper and rear areas of the ear coverts. Bare part colouration is similar to that of the male.

Immature male
This plumage is acquired at ~3 months of age and is retained throughout much of the first year of age. This is an extremely variable plumage, with individuals ranging from yellowish or greenish (similar to females) to reddish or orangey-red like adult males, although they are never as intensely red as adult males. Younger individuals are always yellowish or greenish, while older individuals acquire varying amounts of reddish feathering. The upperwing coverts are narrowly tipped and edged with buff, forming two narrow wing bars (infrequently shown in adult males). Some immature males retain streaking on the underparts from juvenal plumage.

Immature female
This plumage is acquired at ~3 months of age and is held throughout much of the first year. It is very similar to the plumage of the adult female, but some individuals retain dark streaking on the underparts from juvenal plumage.

Juvenile
The back and scapulars are grey-brown with a greenish tinge to the feathers and olive-green feather edges. The rump is yellowish to yellowish-green with dark brown feather centres creating streaks; the uppertail coverts are dark brown with olive feather edges. The tail and wings are dark brownish-black, with pale buff tips and narrow feather edges on the tertials and greater and median upperwing coverts, creating two narrow pale wing bars. The underparts are dull buffy-grey to pale yellowish, washed with brown on the sides and flanks, with heavy, narrow blackish-brown streaks throughout (less extensive on the belly). The head is dark olive, with the crown and nape grey-brown and often tinged with olive-green and edged with paler buff; the ear coverts are finely streaked with buff and the feathers of the lower throat are finely edged with yellow or olive-green. Bare part colouration is similar to that of the adults, but very young juveniles do not have fully crossed mandibles until several weeks after fledging.

Measurements
Total Length: 15-16 cm
Mass: 26-35 g

Source: Adkisson (1996); Sibley (2000) .


Biology

Identification

The Red Crossbill is most similar to the White-winged Crossbill, but is generally easily distinguished in all plumages by its lack of bold white wing bars. Although some individuals may have thin pale edges to the wing coverts that form narrow wing bars, these never approach the thickness and brightness of the wing bars of the White-winged Crossbill. Male White-winged Crossbill is further distinguished by its rose-red or even pinkish head and body, which is very different from the brick-red to orangey-red head and body of the Red Crossbill. Female and immature male Red Crossbills are wholly unstreaked yellowish-green to orangey-yellow and are very different from the duller, streaked female White-winged Crossbill. Some orangey-yellow immature male Red Crossbills approach the colouration of immature male White-winged Crossbill, but are nonetheless easily distinguished by the differences in wing pattern. Juveniles of both species, which are both heavily streaked, are similarly identifiable by wing pattern.
Vocalizations

The song and various call notes vary among different populations; see ‘Taxonomy’ for information on variation in call types. The song of the Red Crossbill (which is given by both sexes, although louder and more frequently by the male) is a somewhat choppy series of short, hard or clicking phrases with some buzzy notes and many call notes interspersed, often beginning with several two-note phrases: tikit tikit tikuti ti chupity chupity chupity tokit kyip kyip kyip jree-jree-jree. The most commonly-heard call, which is usually given in flight, is a series of hard, sharp notes: kip-kip-kip-kip; these calls are also given singly, especially when perched.

Source: Adkisson (1996); Sibley (2000).

Bird calls (and videos) from Cornell's Lab of Ornithology
Breeding Ecology

Courtship
The breeding season of this species extends throughout 9-10 months of the year, with courtship and even nesting behaviours often occurring as early as mid-winter. The Red Crossbill is apparently monogamous, and appears to maintain pair bonds throughout the year (although it is unknown if these birds remain paired for more than one year). Pair formation occurs between birds within the same flock, beginning with the male singing either from the top of a tall tree or from flight. These display flights involve the male flying with slow wingbeats above the canopy while singing loudly. Additional courtship behaviours include ‘billing’ and courtship feeding.

Nest
The timing of nest building is extremely variable and corresponds more to the local abundance of conifer seeds than to the time of year. In British Columbia, nest building can begin as early as December in some years, and regularly between February and July. The nest is built solely by the female, although the male remains nearby and often sings throughout the process. It is placed within dense foliage on a side branch in the canopy of a coniferous tree, often quite far out from the trunk, at a height of 2-20 m (usually 6-11 m in height). Most nests are well-concealed by the foliage of the canopy. The nest itself is a bulky cup (10-13 cm across, ~5 cm deep) of small conifer twigs, grasses, moss, and conifer needles that is lined with plant down, fine grasses, hair, lichens, feathers, and fine shreds of bark. Winter nests are larger and bulkier than those constructed during the summer months.

Eggs
The timing of egg-laying is extremely variable. Although most birds lay a single clutch each year, there is evidence that during years of peak seed production in conifers this species may be able to produce 2-4 broods in a season. The clutch of (1) 3-4 (5) eggs is laid any time between mid-February and late July (rarely as early as early January), with most egg-laying occurring in March and April; eggs are found in B.C. between early January and mid-August. The smooth, glossy eggs are white to pale green or even pale rose-pink, with cinnamon, reddish-brown, and purplish splotches and streaks that are concentrated at the larger end. The female alone incubates the eggs for a period of 12-16 days. This species is an extremely rare host for Brown-headed Cowbird parasitism.

Young
The young are altricial and naked at hatching, except for small amounts of soft, dark grey down on the head and back; the skin is pink, the mouth is deep red, the bill is pinkish-red, and the gape flanges are yellow or yellowish-pink. The young are brooded by the female alone, although both parents contribute to feeding them, and fledge at 15-25 days of age. After fledging, the young remain with the parents, traveling as a family group, and are fed by the parents for up to a month before beginning to forage on their own. If female lays a second clutch, the fledglings are tended by the male alone. Nestlings and dependent fledglings occur in B.C. between late January and mid-September.

Source: Adkisson (1996); Baicich and Harrison (1997); Campbell et al. (2001).
Foraging Ecology

This species feeds primarily on the seeds of coniferous trees, particularly pines, spruces, hemlocks, and Douglas-fir. Different populations are adapted to feed on a particular species of tree (or sometimes several different species), which has led to slight morphological variations in the size and structure of the bill to accommodate these different seeds (see ‘Taxonomy’). Occasionally, this species will feed on the seeds of deciduous trees and shrubs, and rarely even herbaceous vegetation, but this is very infrequent. It consumes moderate amounts of insects during the summer, as well as buds, catkins, and galls. This species sometimes visits bird feeders, but does so much less frequently than most other finches. Seed production of coniferous trees is typically extremely variable from year to year and as a result this species is almost always nomadic, with flocks wandering very large areas of the continent in search of regions with high productivity of their preferred coniferous tree. Massive numbers of Red Crossbills sometimes occur over vast areas of the province where there is high seed productivity, but can be nearly absent within a short period once the region’s conifer seeds have been depleted. These nomadic flocks are almost always composed only of Red Crossbills, and it is even rare for different ‘call types’ (see ‘Taxonomy’) of Red Crossbill to intermingle in the same flock.

The Red Crossbill acquires the seeds of coniferous trees by using its extremely unusual bill, with its crossed mandibles, to separate the tight-fitting cone scales and then uses its very muscular and manipulative tongue to extract the seed within. Flocks typically land in the crown of a conifer, assess the seed productivity of that individual tree, and either leave immediately (if there are few seeds) or remain and quietly extract seeds from the cones. Birds are generally very quiet when foraging, and often the first clue to their presence in a tree are the cracking sounds that they create when opening the cones and consuming the seeds. They generally consume only the largest seeds in the cones and do not waste energy on extracting small or difficult-to-access seeds. Because of the nutritional limitations of their diet, Red Crossbills are regularly attracted to areas where they can consume salt, such as along the sides of mountain roads during the winter; occasionally eats small bones to extract calcium. Regularly consumes grit to aid with digestion.

Source: Adkisson (1996)

Habitat


The various ‘call types’ of Red Crossbill typically occur in association with particular species of trees, but all types are closely associated with mature coniferous forests throughout their distribution. This includes forests that are dominated by Western and Mountain Hemlocks (Types 1 & 3), Sitka Spruce (Type 1), Engelmann Spruce (Types 5 & 7), White Spruce (Type 1), Douglas-fir (Type 4), Lodgepole Pine (Types 2, 5 & 7), or Ponderosa Pine (Type 2) in B.C. Most call types are closely tied to the particular tree species or several species that are mentioned here, but almost all call types will occasionally venture into forests dominated by other trees in times of poor seed production of the preferred tree species. It occasionally ventures into riparian mixed woodlands or even deciduous stands, but is rarely far from coniferous trees. In winter, this species sometimes congregates along roadsides (especially in the southern interior) where it consumes grit and salt.

Source: Adkisson (1996); Campbell et al. (2001).

Distribution

Global Range

In North America, the Red Crossbill occurs throughout the boreal forests of Canada and the northeastern U.S., ranging south along the Appalachians to Georgia. In western North America, it is widespread throughout both Canada and the U.S. from the Rocky Mountains to the Pacific coast, and even occurs south into northern Mexico along the Sierra Madre. It also occurs widely throughout northern Eurasia.
BC Distribution

Breeding
This species breeds throughout the entire province. Populations are characteristically highly irruptive, especially along the coast, and are closely tied to the seed production of various species of coniferous trees. It is generally uncommon across most of northern B.C. and in the central interior north of the Chilcotin, although it is rare in northeastern B.C. east of the Rocky Mountains. It is generally fairly common along the entire coast, including Vancouver Island and the Queen Charlotte Islands, although it is highly irruptive throughout this region and populations may range from nearly absent in some years to abundant in others at any given location. Common throughout the southern interior north to the Chilcotin region and east to the Rocky Mountains, with interannual population fluctuations at any given area ranging from uncommon or fairly common to abundant.

Non-breeding
This species is highly irruptive during the non-breeding season, as in the breeding season. It is generally fairly common along the coast, including Vancouver Island and the Queen Charlotte Islands, although its abundance in any particular area can range from nearly absent to very common between years. It is generally common across the southern interior north to the Chilcotin region, ranging from uncommon to abundant between years. Rare to uncommon (depending on the year) in the northern Fraser Plateau and Bulkley Valley of the central interior. Accidental in winter in the northern Rocky Mountains of northeastern B.C.

Migration
Populations across northern B.C. appear to vacate the area during the coldest months of the year, retreating to areas in southern and central B.C. in the late fall (October-November) and returning north early in the spring (March-April, occasionally as early as February). Elsewhere throughout the range of this species, flocks are characteristically nomadic and wander over very large areas in search of forests with high seed productivity. As a result of this wandering, entire populations often vacate large portions of the species’ range for prolonged periods (sometimes several years) if there is not sufficient seed production to support the population. This leads to a highly irregular pattern of abundance in many areas, with huge fluctuations in the population between years.

Source: Campbell et al. (2001).

Conservation

Population and Conservation Status

This is a highly irruptive species, and therefore its overall populations status is often difficult to assess. In some years it may be th most abundant species in its habitat, but in other years it may be entirely absent. At the national level, the form inhabiting the island of Newfoundland (Type 8, also known as L.c.percna) is endangered (COSEWIC [Committee on the Status of Endangered Wildlife in Canada]) and may be close to extinction. In British Columbia, however, populations appear to be stable and secure and the species is not recognized as a species of conservation concern provincially.

Source: Adkisson (1996).

Taxonomy


The taxonomy of the Red Crossbill ‘complex’ has been the topic of much discussion over the past 15+ years. Previous ornithologists attempted to grapple with the pronounced variation in size and bill structure in this species through the recognition of at least 8 different subspecies, but recent researchers studying this species have found its taxonomy to be far more complicated than what is represented by these somewhat arbitrarily-defined subspecies. In particular, Jeff Groth of the American Museum of Natural History published research in the early 1990s that showed the ‘Red Crossbill’ to consist of at least 8 discrete types (6 in B.C.) based on subtle differences in bill morphology and call notes. In many cases, these ‘call types’ broadly overlapped in distribution but rarely, if ever, interbred. They appeared to flock and mate based on call note, and recordings of their call notes could be used to differentiate among them (these differences are also often apparent to the human ear). These small differences, particularly those in bill structure, have evolved so that each ‘call type’ is able to exploit the seeds of a particular type of conifer, whether it be the small, soft seeds of hemlocks (small-billed types) or the large, hard seeds of pines (large-billed types). The situation appeared to suggest that the ‘Red Crossbill’ is actually a species complex involving multiple species with very similar plumage patterns and small (but apparently significant) differences in call notes and bill shape.

Other researchers over the past decade have followed up on this research and have found an additional call type (Type 9) in southern Idaho that was recently (March 2009) described as a completely new species, the ‘South Hills Crossbill’ (Loxia sinesciurus). It occurs alongside at least two other call types, but interbreeding between it and the other types occurs at a frequency of <1% of mated pairs. This assortative mating has led to a relatively high level of genetic divergence, and thus the description as a new species. A similar situation has occurred in Europe, which has led to the recognition of the Scottish Crossbill (Loxia scotica) and may lead to the recognition of additional species in the future.

Because of these recent advances, and the apparent dissolution of the previously-recognized subspecies, there is no currently-accepted system of intraspecific taxonomy within this species. The recognition of the ‘call type’ system, as outlined by Groth, has gained momentum over the past few years, however, and appears to be the dominant working taxonomy by ornithologists studying the species. As a result, this taxonomy will be followed for B.C., although the former subspecies that relate to the new ‘call types’ will be mentioned for historical context. In all likelihood, these call types represent distinct species.

The ‘call types’ recorded in British Columbia are as follows:

Type 1 (‘Spruce Crossbill’)
This call type corresponds with birds that were formerly classified as L.c.neogaea. It has been recorded in the Appalachian Mountains of eastern North America, as well as in southern B.C. and northwestern Washington, but likely also occurs along the southern border of the boreal forest in the intervening areas. It is one of the smallest and smallest-billed call types (only Type 3 is smaller). Its flight call is very similar to that given by Type 2, but averages slightly shorter, sharper, and dryer, without the descending quality to each note: chewt-chewt-chewt or kiip-kiip-kiip-kiip. It is also very similar to the calls of Types 3 and 5, and definitive identification of this call type may require the analysis of recordings and spectrographs. Type 1 birds in the Pacific Northwest have been found feeding on hemlock and Sitka Spruce, while birds in the Appalachians tend to focus on Eastern White Pine and White Spruce. White Spruce is abundant throughout the boreal forests of northern North America (including northern B.C.), and thus this call type may yet be found to be more widespread than the relatively few records indicate.

Type 2 (‘Ponderosa Pine Crossbill’)
This call type corresponds with birds formerly recognized as several different subspecies, including L.c.bendirei in B.C. This call type has been found widely throughout western North America, north to south-central B.C., as well as in various locations throughout the eastern United States and eastern Canada (especially in the Appalachians), and may occur throughout the intervening areas of central Canada. Type 2 may be the most widespread call type in North America. It is a relatively large, large-billed call type (only Type 6, which occurs in Mexico and southeastern Arizona, is larger). Its flight call is extremely similar to that of Type 1 birds, but averages slightly longer and more musical, with a distinctive descending quality to each note: cheewp-cheewp-cheewp-cheewp or kewp-kewp-kewp-kewp; sound recordings and spectrograph analysis are likely required for definitive identification. Type 2 birds are closely tied to ‘hard’ pines such as Lodgepole Pine and, especially, Ponderosa Pine, but will occasionally forage on the seeds of spruces and Douglas-fir and it may have the most varied diet of any of the call types.

Type 3 (‘Hemlock Crossbill’)
This call type includes birds that were formerly recognized as L.c.sitkensis. It has been found primarily along the Pacific coast of Canada and the United States (north to Alaska), as well as in the northeastern U.S. and eastern Canada (possibly also occurring in intervening areas of central Canada). This is the smallest and smallest-billed call type, and the males have a greater tendency to have extensively yellow or orange plumage than in other types. Its flight calls are weaker and squeakier than the flight calls of other call types, with a descending quality to each note: chep-chep-chep-chep or kyip-kyip-kyip-kyip. It is very closely associated with hemlocks (Western and Mountain Hemlocks in B.C.) and appears to feed on other conifers (spruce, larch, Douglas-fir) only during periods of poor seed production in hemlock stands.

Type 4 (‘Douglas-fir Crossbill’)
This call type includes birds that were previously attributed to L.c.neogaea. It has been found throughout much of western North America, north at least to the Queen Charlotte Islands and east to the Rocky Mountains, as well as sporadically in the northeastern United States and eastern Canada. It is almost identical to Type 1 in size and structure, but has distinctive musical, bouncy flight call with an upslurred quality to each note that is audibly different from any other call type: kwit-kwit-kwit-kwit or whit-whit-whit-whit (the whit sound is very similar to the call notes of some Empidonax flycatchers, particularly Least and Dusky Flycatchers). It is closely associated with Douglas-fir in the west, and is especially common in areas where the coastal variety of this tree species occurs (interior forms of this tree do not retain their seeds in the cones throughout the winter, thus these crossbills do not have a food resource of sufficient size and reliability to support a large population); it will also consume the seeds of Lodgepole Pine, although this is not the preferred food source.

Type 5 (‘Lodgepole Pine Crossbill’)
This call type includes some birds that were previously assigned to L.c.bendirei. It has been found primarily in the Rocky Mountains and in mountain ranges west to California and north into the southern and central interior of British Columbia. It is a mid-sized call type, averaging slightly larger and larger-billed than Type 4 and Type 7, but slightly smaller and smaller-billed than Type 2. The call is very similar to that of Type 3, but is higher-pitched and slightly drier: chit-chit-chit-chit. It is closely associated with the interior race of Lodgepole Pine as well as with high-elevation forests of Engelmann Spruce, although it occasionally feeds on other conifers.

Type 7 (‘Cordilleran Crossbill’)
This call type does not correspond with any previously-described subspecies of Red Crossbill. It has been found sporadically in the mountains of western North America from the Cascades east to the Rocky Mountains, north into south-central British Columbia. It is a mid-sized type that averages slightly smaller than Types 2 and 5, but slightly larger than Types 1 and 4. Its flight calls are similar to those of Type 3 but are slightly flatter (lacking a descending quality to each note), stronger, and lower-pitched and sound somewhat warbled: chip-chip-chip-chip. Like Type 5, it is associated with interior race of Lodgepole Pine as well as Engelmann Spruce, but likely feeds on other conifers as well when necessary.

Source: Adkisson (1996); Groth (1996); Sibley (2000); Benkman (2007); Young (2008); Benkman et al. (2009)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
NativeS5YellowNot Listed



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