Red Crossbill

Loxia curvirostra



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Red Crossbill pair.

Strongly monogamous.

© Alex Wiebe, Ontario, Canada, 3 February 2018
Group of Red Crossbills.

Flocks year-round.

© Samuel Paul Galick, New Jersey, United States, 1 December 2012
Red Crossbills with Pine Siskins and White-winged Crossbills.

Pine Siskins and White-winged Crossbills will join Red Crossbill foraging flocks.

© Iain Fleming, Ontario, Canada, 5 March 2018


Walking, Hopping, Climbing, etc.

Hops on ground. Uses bill to grab branches, cones, and needles in parrot-like fashion when climbing in trees.


Flight is rapid and powerful; undulations are more pronounced in short flights than for flights over longer distances. Long-distance flights are usually high above canopy.


Preening, Head-Scratching, Stretching, Bathing, Anting, etc.

Scratches head by bringing foot over wing. Apparent comfort movements include a one-wing–one-leg stretch and a two-wing stretch. Aviary birds bathe avidly (43), as often as daily when given fresh water, even at low ambient temperatures (142). Bathing frequency is unknown for wild birds, but water bath aids in luring wild birds to live decoy (142). In aviary groups, bathing by one bird induces bathing by rest of group (43). Anting is unknown.

Sleeping, Roosting, Sunbathing

Roosts in dense foliage of conifers. Goes to roost early, stays in cover late, compared to most species (142, CWB). Captive individuals studied by Tordoff (43) roosted in thick clumps of needles at the ends of branches, 1 or 2 birds to a branch, creating a striking resemblance in the dark between birds and cones. On roost, wipes bill tips against each other; captive birds observed to extrude tongue to lubricate mandibles with saliva, then rub tips together by opening and closing, crossing bill tips opposite the crossing direction (43).

Sunbathing is highly ritualized; in direct sunlight, spreads primaries and tail, tilts head back so that sun shines in one eye, opens mouth so that tips are almost opposing, and maintains this posture for up to 5 min. This behavior, like bathing in water, is imitated by flockmates. Scratching and preening often precede and follow sunbathing (43).

Daily Time Budget

No details known. Foraging time should vary according to variations in seed accessibility and energetic demands of weather and annual cycle (17); may exceed 90% of daylight hours when days are shortest and coldest (14).

Agonistic Behavior

Physical Interactions

Conflicts over cones, roost, and perch sites, and mates lead to chases, and occasionally to fighting, including aerial, tumbling fighting (171). Ross (182) stated that males fight only males, females only females, but this is not true of White-winged Crossbill (CWB). Perhaps, since males are usually dominant to females (43), actual fighting between males and females is rare, and hence not readily observed; more careful observation of agonistic behavior is needed. More aggression occurs in large groups than in small groups for both White-winged Crossbill and Red Crossbill (135, CWB); degree of food dispersion seems to affect aggression (see Benkman [183]).

Communicative Interactions

Threat Display includes range of visual and vocal stimuli: looking and leaning toward competitor, opening bill, flicking wings, making harsh chatter, finally grabbing feathers (43, 149, CWB). Such conflicts can escalate to chases, grappling, and tumbling to ground together.



Little evidence for territories. Fighting between apparently breeding males has been interpreted as territoriality; 7 of 16 breeding males had a song perch located in top of tree about 60 m from nest (171, 184; see also 32). More careful study of banded individuals is needed. Like other cardueline finches, several pairs often nest semi-colonially in a small area, separated from other clusters of nests (171, 47).

Individual Distance

Captive individuals seldom roost or perch within a bill’s reach of each other, as in White-winged Crossbill (135); however, Tordoff (43) noted no fixed distance of tolerance, and as little as 6 cm, when birds were preening quietly).

In captive flocks, males are dominant over females; within each sex, there is a mostly linear hierarchy; within mated pairs, females are dominant over males (43, CWB). Dominance interactions are often observed in wild birds (43, CWB); see also 135.

Sexual Behavior

Mating System and Sex Ratio

Strongly monogamous (see Extra-pair Copulations, below). There is no evidence for polygyny in Red Crossbill, although it occurs rarely in Scottish Crossbill (182, 149). No data on serial polyandry or polygyny, but see Benkman (185) for White-winged Crossbill. Double-brooding is probable during large cone crops (186, 171, 149, 17). Birds in immature plumage have been found breeding (186, 187, CWB, MAY; T. Hahn, personal communication).

Probably regularly choose mates from within feeding flocks (47, 149, 32), thus mate choice is greatly influenced by flocking associations (21, 22). Males sing from treetops and chase females (149, 32). Males make slow-flapping display flights above forest, with loud singing and some gliding (171, 47, CWB, MAY; T. Hahn, personal communication). The extent to which mate choice is based on song is likely important, but has not been studied. Females induced into breeding condition using estradiol preferentially associated with males giving calls of their own call type (23) and with faster foragers (188). The former is critical for assortative pairing by call type, and the latter could act to accentuate natural selection on feeding performance and strengthen divergent selection between call types. May preferentially pair with individuals of their own call type who produce dissimilar contact calls perhaps to avoid inbreeding, because young birds imitate the contact calls of their parents (176, 24); then calls apparently converge if they remain paired.

Sex ratio is likely male-biased, but unbiased measures are not available.

Pair Bond

Courtship feeding and billing (touching or grabbing each other by the bill, “bill to bill”) are common. Courtship feeding is potentially an important source of food for female during nest-building and egg formation, although her own feeding rate remains high. Male constantly accompanies female after pairing. Paired birds often have matching calls (i.e., nearly identical contact calls; 58, 49), and Groth (58) found many such paired but nonbreeding birds implying that birds remain paired beyond one nesting attempt. Remaining paired between successive nesting attempts would be advantageous for rapid initiation of nesting upon locating suitable conditions.

Extra-Pair Copulations

Kleven et al. (189) found no evidence for extrapair paternity among 96 offspring from 34 broods in a Norwegian population of Red Crossbill. No to little extrapair paternity is consistent with the relatively small testes of Type 2 (11). Møller and Briskie (190) showed that extrapair paternity is generally uncommon in species when males have small testes relative to their body mass, and only 7 of 54 species in the dataset of Møller and Briskie (190) had smaller testes relative to body size than did Type 2 (11). Rare to little extrapair paternity in the Red Crossbill is also consistent with male mate guarding of females prior to egg laying, and the female’s reliance on male parental care.

Social and Interspecific Behavior

Degree of Sociality

Red Crossbill occurs in flocks year-round, like other crossbill species (47, 149, 135, CWB), with flock size being positively correlated with crossbill density (191). Flocking aids in food finding and assessment (see Diet and Foraging: Foraging Behavior: Food Habits), predator detection, and obtaining a mate (192). Benkman (183) showed that the probability of detecting a predator in sufficient time to reduce capture success by an avian predator increases with increasing flock sizes in the White-winged Crossbill. However, when crossbills are consuming seeds every few seconds the gain from increasing flock size beyond 5 is limited; in contrast, when feeding rates are low, larger flock sizes should aid predator detection. Where more than one call type is present, foraging birds usually only call back to passing individuals and flocks of the same call type (142). Passing individuals and flocks commonly join foraging birds of the same call type; heterotypics landed in response to playbacks of other call types (Type 2 landed in response to playback of Type 4 calls, and vice versa), but at only about half the frequency at which they landed to playbacks of their own call type (22). Most flock activities (feeding, bathing, preening) are highly coordinated (43). A flock that has been silently feeding gradually shows a crescendo in calling that peaks as the birds depart (see Diet and Foraging: Foraging Behavior: Food Habits). Predator alarm calls given by crossbills or other bird species tend to quiet a flock (CWB).


No evidence of obvious play.

Nonpredatory Interspecific Interactions

Pine Siskin frequently joins Red Crossbill foraging flocks in spruce forests; less frequently, flocks may be joined by Mountain Chickadee (Poecile gambeli) and Red-breasted Nuthatch (Sitta canadensis) (142). White-winged Crossbill and Red Crossbill join each other’s foraging flocks in spruce forests, but generally do not associate after departure (135), as is true when more than 2 call types forage simultaneously in the same tree (CWB).


Kinds of Predators

Potential predators living in same habitats with Red Crossbill include Sharp-shinned Hawk (Accipiter striatus), Cooper’s Hawk (A. cooperii), Merlin (Falco columbarius), Peregrine Falcon (F. peregrinus), and Northern Shrike (Lanius borealis, one report of predation by Austin [132]). Attacks seen on live decoys by Sharp-shinned Hawk, Northern Shrike, American Kestrel (Falco sparverius), and Northern Pygmy Owl (Glaucidium gnoma) (142; T. Hahn, personal communication). Sharp-shinned Hawk is probably the most important predator of free-flying crossbills in North America based on studies of predation of crossbills in England by Eurasian Sparrowhawk (Accipiter nisus) (193) and the few observations of predation in North America. Nest predators include red squirrel (see Nethersole-Thompson [149] for crossbill–squirrel interactions in Scotland), Steller’s Jay (Cyanocitta stelleri), and Canada Jay (Perisoreus canadensis).

Manner of Predation

Flying predators attempt to surprise Red Crossbill flocks in trees and when drinking or gathering grit on ground, and pursue them in the air (142).

Response to Predators

Red Crossbill gives Alarm Call to Clark’s Nutcracker (Nucifraga columbiana), Canada Jay (142), and even a Great Gray Owl (Strix nebulosa; J. Cornelius, personal communication). Flies away from trees when attacked by Sharp-shinned Hawk; power-dives into forest under attack from Merlin (T. Hahn, personal communication). See also Sounds and Vocal Behavior: Vocalizations.

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.