The Introduction Article is just the first of 11 articles in each species account that provide life history information for the species. The remaining articles provide detailed information regarding distribution, migration, habitat, diet, sounds, behavior, breeding, current population status and conservation. Each species account also includes a multimedia section that displays the latest photos, audio selections and videos from Macaulay Library’s extensive galleries. Written and continually updated by acknowledged experts on each species, Birds of North America accounts include a comprehensive bibliography of published research on the species.
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California Scrub-Jay becomes scarce on the coastal-desert transition in southern California. In California, coloration varies from relatively dark individuals on the central coast (e.g., San Francisco Bay) to paler birds in the Central Valley, where the crown, hindneck, sides of neck, and breast are less purplish, and in the northeast, where birds are grayer.
The California Scrub-Jay is a familiar jay occurring in coastal states of the western United States, from Washington to California and south to the southern tip of Baja California. This species is the result of a recent taxonomic split of the Western Scrub-Jay (Aphelocoma californica) complex, leading to recognition of both the California Scrub-Jay (A. californica) and Woodhouse’s Scrub-Jay (A. woodhouseii) (
Gowen, F. C., J. M. Maley, C. Cicero, A. T. Peterson, B. C. Faircloth, T. C. Warr and J. E. McCormack. (2014). Speciation in Western Scrub-Jays, Haldane's rule, and genetic clines in secondary contact. BMC Evolutionary Biology no. 14:135.
Gowen et al. 2014,
Chesser, R. T., K. J. Burns, C. Cicero, J. L. Dunn, A. W. Kratter, I. J. Lovette, P. C. Rasmussen, Jr. Remsen, J. V., J. D. Rising, D. F. Stotz and K. Winker. (2016). Fifty-seventh supplement to the American Ornithologists' Union Check-list of North American Birds. Auk no. 133 (3):544-560.
Chesser et al. 2016), the latter species occupying inland areas of the southwestern United States, extending into southern Mexico.
Beyond differences in their geographic ranges, California Scrub-Jays generally occupy dry scrub and oak woodland, often in residential areas, whereas Woodhouse’s Scrub-Jays occur in dry scrub and woodland, especially pinyon–juniper (Pinus–Juniperus). The California Scrub-Jay differs outwardly from the Woodhouse’s Scrub-Jay by having brighter blue upperparts, paler underparts, and a darker, more distinct breast-band. Relative to the latter species, the California Scrub-Jay has a heavier and more hooked bill (
Pitelka, F. A. (1951d). Speciation and ecologic distribution in American jays of the genus Aphelocoma. Univ. Calif. Publ. Zool. no. 50:195-464.
Pitelka 1951d), which is believed to be an adaptation for consuming acorns (
Peterson, A. T. (1993). Adaptive geographical variation in bill shape of Scrub Jays (Aphelocoma coerulescens). Am. Nat. no. 142:508-527.
Peterson 1993,
Bardwell, E., C. W. Benkman and W. R. Gould. (2001). Adaptive geographic variation in Western Scrub-Jays. Ecology no. 82:2617-2627.
Bardwell et al. 2001). Further, the two species exhibit differences in behavior and vocalizations (
Dunn, J. L. and K. L. Garrett. (2001). Parapatry in Woodhouse's and California Scrub-Jays revisited. West. Birds no. 32:186-187.
Dunn and Garrett 2001,
Curry, R. L., A. T. Peterson and T. A. Langen. (2002). "Western Scrub-Jay (Aphelocoma californica)." In The birds of North America, no. 712., edited by A. Poole and F. Gill. Philadelphia, PA: The Birds of North America, Inc.
Curry et al. 2002). Calls of the California Scrub-Jay are typically harsher, 1-syllabled and lower-pitched than the 2-syllabled calls of Woodhouse’s Scrub-Jay (
Dunn, J. L. and K. L. Garrett. (2001). Parapatry in Woodhouse's and California Scrub-Jays revisited. West. Birds no. 32:186-187.
Dunn and Garrett 2001).
The California Scrub-Jay is sister to the Island Scrub-Jay (A. insularis), endemic to Santa Cruz Island, California (
Peterson, A. T. (1990a). Birds of Eagle Mountain, Joshua Tree National Monument, California. West. Birds no. 21:127-135.
Peterson 1990a,
Peterson, A. T. (1992a). Phylogeny and rates of molecular evolution in the Aphelocoma jays (Corvidae). Auk no. 109:133-147.
Peterson 1992a), and is closely related to Woodhouse’s Scrub-Jay (
Gowen, F. C., J. M. Maley, C. Cicero, A. T. Peterson, B. C. Faircloth, T. C. Warr and J. E. McCormack. (2014). Speciation in Western Scrub-Jays, Haldane's rule, and genetic clines in secondary contact. BMC Evolutionary Biology no. 14:135.
Gowen et al. 2014). Species limits among the scrub-jays are not clear. Geographically isolated populations on Santa Cruz Island have fixed allelic differences from other populations. However, California and Woodhouse’s scrub-jays have few or no fixed differences in alleles and interbreed where their geographic ranges contact in western Nevada and east-central California, and in desert ranges of eastern California (
Peterson, A. T. (1990a). Birds of Eagle Mountain, Joshua Tree National Monument, California. West. Birds no. 21:127-135.
Peterson 1990a,
Peterson, A. T. (1990b). Evolutionary relationships of the Aphelocoma jays. Chicago, IL: Univ. of Chicago.
Peterson 1990b,
Peterson, A. T. (1992a). Phylogeny and rates of molecular evolution in the Aphelocoma jays (Corvidae). Auk no. 109:133-147.
Peterson 1992a). Despite ongoing gene flow, the hybrid zone is narrow, and there is evidence for selection against hybrids (
Gowen, F. C., J. M. Maley, C. Cicero, A. T. Peterson, B. C. Faircloth, T. C. Warr and J. E. McCormack. (2014). Speciation in Western Scrub-Jays, Haldane's rule, and genetic clines in secondary contact. BMC Evolutionary Biology no. 14:135.
Gowen et al. 2014).
Evidence from studies of breeding biology and demography of the California Scrub-Jay has presented a general picture of a less social, non-cooperative species (
Ritter, L. V. (1972). The breeding biology of scrub jays. Master's Thesis, California State Univ., Chico.
Ritter 1972,
Ritter, L. V. (1983b). Nesting ecology of scrub jays in Chico, California. West. Birds no. 14:147-158.
Ritter 1983b,
Ritter, L. V. (1984). Growth of nestling scrub jays in California. J. Field Ornithol. no. 55:48-53.
Ritter 1984,
Carmen, W. J. (1988). Behavioral ecology of the California Scrub Jay (Aphelocoma coerulescens californica): a non-cooperative breeder with close cooperative relatives. Phd Thesis, Univ. of California, Berkeley.
Carmen 1988,
Carmen, W. J. (2004). Non-cooperative breeding in the California Scrub Jay: Stud. Avian Biol. Cooper Ornithological Society.
Carmen 2004). Along with being a model species for studies on behavioral evolution, the California Scrub-Jay is a model in studies of foraging behavior and cognitive abilities, including spatial memory (
Clayton, N. S., D. P. Griffiths and A. Dickinson. (2000). "Declarative and episodic-like memory in animals: personal musings of a scrub jay." In The evolution of cognition., edited by C. Heyes and L. Huber, 273-288. Cambridge, MA: MIT Press.
Clayton et al. 2000,
Clayton, N. S., K. Yu and A. D. Dickinson. (2001). Scrub jays (Aphelocoma coerulescens) can form integrated memory for multiple features of caching episodes. J. Exper. Psychol.: Anim. Behav. Proc. no. 27:17-29.
Clayton et al. 2001,
Emery, N. J. and N. S. Clayton. (2001a). Correction: effects of experience and social context on prospective caching strategies by scrub jays. Nature no. 447:349.
Emery and Clayton 2001a,
Emery, N. J. and N. S. Clayton. (2001b). Effects of experience and social context on prospective caching strategies by scrub jays. Nature no. 414:443-446.
Emery and Clayton 2001b). The California Scrub-Jay is adept at locating and selecting food and in dealing adaptively with social competition from other jays (
Langen, T. A. (1999). How Western Scrub-Jays, Aphelocoma californica, select a nut: effects of the number of options, variation in nut size, and social competition among foragers. Anim. Cognit. no. 2:223-233.
Langen 1999,
Clayton, N. S., D. P. Griffiths and A. Dickinson. (2000). "Declarative and episodic-like memory in animals: personal musings of a scrub jay." In The evolution of cognition., edited by C. Heyes and L. Huber, 273-288. Cambridge, MA: MIT Press.
Clayton et al. 2000,
Clayton, N. S., K. Yu and A. D. Dickinson. (2001). Scrub jays (Aphelocoma coerulescens) can form integrated memory for multiple features of caching episodes. J. Exper. Psychol.: Anim. Behav. Proc. no. 27:17-29.
Clayton et al. 2001,
Emery, N. J. and N. S. Clayton. (2001a). Correction: effects of experience and social context on prospective caching strategies by scrub jays. Nature no. 447:349.
Emery and Clayton 2001a,
Emery, N. J. and N. S. Clayton. (2001b). Effects of experience and social context on prospective caching strategies by scrub jays. Nature no. 414:443-446.
Emery and Clayton 2001b).
The complexity of behavioral patterns within this species continues to pose challenging questions for ornithologists. Along with its close relatives, the California Scrub-Jay is expected to play an ongoing role in research that investigates the ecological and evolutionary factors affecting corvids, as well as other birds.
Recommended Citation
Curry, R. L., A. T. Peterson, T. A. Langen, P. Pyle, and M. A. Patten (2017). California Scrub-Jay (Aphelocoma californica), version 3.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.cowscj1.03