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Island scrub jay

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The island scrub jay (Aphelocoma insularis), also known as the island jay or Santa Cruz jay, is a bird in the genus, Aphelocoma, which is endemic to Santa Cruz Island off the coast of Southern California. Of the over 500 breeding bird species in the continental U.S. and Canada, it is the only insular endemic landbird species.[3]

Island scrub jay
On Santa Cruz Island, California

Critically Imperiled  (NatureServe)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Aphelocoma
Species:
A. insularis
Binomial name
Aphelocoma insularis
Henshaw, 1886
   Year-round resident range on Santa Cruz Island

Description

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The island scrub jay is closely related to the California scrub jay (the coastal population found on the adjacent mainland), but differs in being larger, more brightly colored, and having a markedly stouter bill. They will bury, or cache, the acorns in the fall and may eat them months later. They also eat insects, spiders, snakes, lizards, mice and other birds' eggs and nestlings.

Taxonomy

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The island scrub jay was first described by American ornithologist Henry Wetherbee Henshaw in 1886[4] and an archaeological specimen at site SCRI-192 dating from the 1780s-1812 on Santa Cruz Island is the earliest evidence of the bird in the historic period.[5] This bird is a member of the crow family, and is one of a group of closely related North American species named as scrub jays. These were formerly treated as a single species, the scrub jay (as Aphelocoma coerulesens), with five subspecies,[6] but are now considered four species: the Florida scrub jay (A. coerulescens), the island scrub jay, the California scrub jay (A. californica), and Woodhouse's scrub jay (A. woodhouseii). DNA studies indicate that the island and coastal forms have long been isolated from their relatives inland.[7] The relationships within the genus have been studied in several papers (e.g.[8])

Island scrub jays seem to be incapable of crossing to the mainland. However they were once present on three of California's northern Channel Islands, San Miguel Island, Santa Rosa Island, and Santa Cruz Island where they persist today.[9] Reliable historical observer records for island scrub jays in addition to Santa Cruz Island include only a single 1892 account on neighboring Santa Rosa Island, only about 10 km (6 mi) away.[5] The historic observation on Santa Rosa Island is supported by a Pleistocene archaeological record of a single island scrub jay femur from a Late Pleistocene-Holocene site (SRI-V-3) found by Paul Collins of the Santa Barbara Museum of Natural History.[5] There are also two Late Holocene archaeological remains found in San Miguel Island cave sites.[9] There are no definite occurrences of a scrub-jay on any other of the Channel Islands, or on the Coronado Islands, only 13 km (8 mi) from the mainland.

Early studies suggested that the ancestor of the present population was storm-borne or carried on driftwood to Santa Cruz, or that the colonization occurred during a period of glaciation 70,000 to 10,000 years ago, when sea levels were much lower and the channel between the coast and the islands was correspondingly narrower.[10] More recent DNA studies show that, although other island endemics such as the island fox and the Santa Cruz mouse may have diverged from their mainland relatives around 10,000 years ago, the scrub jays separated in a period of glaciation around 151,000 years ago. The most recent analysis indicates that the island scrub jay has been evolving in isolation for approximately one million years,[8] i.e. over multiple glacial cycles. Up to about 11,000 years ago, the four northern Channel Islands were one large island, so island scrub jays must have been present on all four islands initially, but became extinct on Santa Rosa, San Miguel and Anacapa after they were separated by rising sea levels.[11]

Distribution and habitat

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The island scrub jay is found today only on Santa Cruz Island, the largest of California's Channel Islands with an area of 250 km2 (96 mi2).[12] The island is a nature reserve, the eastern 24% being administered by National Park Service as the part of the Channel Islands National Park and the rest of the island by the Nature Conservancy.[13] Fossil remains for island scrub jays have been found on Santa Rosa and San Miguel Islands.[14]

Island scrub jays occur in oak chaparral and bishop pine (Pinus muricata) woodland on Santa Cruz Island. Island scrub jays in pine habitat have longer, shallower bills than individuals in oak habitat; variation in bill shape is heritable, and individuals mate nonrandomly with respect to bill morphology.[15]

Breeding

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Females lay 3 to 5 eggs. Incubation lasts approximately 20 days. These jays are generally monogamous and, unlike some other jays, are not cooperative breeders. Both sexes build a nest 1 m (3 ft) to 8 m (26 ft) above the ground. Further details in.[16]

Etymology

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The genus name, Aphelocoma, comes from the Latinized Ancient Greek apheles- (from ἀφελής-) "simple" + Latin coma (from Greek kome κόμη) "hair", in reference to the lack of striped or banded feathers in this genus, compared to other jays. The species name, insularis, comes from the Latin for "from an island".

Conservation status

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The island scrub jay is classed as vulnerable on the IUCN Red List because its small range makes it potentially vulnerable to a catastrophic incident such as disease or a large fire that destroys their habitat.[1] Population size in 2008 and 2009 was estimated to be 1700 - 2300, making this one of the rarest songbird species in the United States.[17] The entire range of island scrub jays is currently protected in Channel Islands National Park and the species is not at imminent risk of extinction. However, the establishment of West Nile virus (WNV) in southern California in 2003 may pose a threat if it crosses to Santa Cruz Island from the mainland. Corvids are especially vulnerable to WNV. In addition, the increased occurrence of wildfires in southern California may portend a catastrophic fire there.[3] Shrub cover has increased since the removal of sheep (1980–91) and feral pigs (2005–07) from Santa Cruz Island, which may increase the fire risk.[3] Overgrazing by non-native ungulates may have caused extirpation of island scrub jays on Santa Rosa Island. Re-establishing a second population of island scrub jays on Santa Rosa Island and San Miguel Island may accelerate the restoration of native plant and tree species because of the scatter-hoarding seed caching behavior of Aphelocoma species.[3]

Human interaction and uses

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The Chumash people who were the original inhabitants of the northern Channel Islands may have eaten the local scrub jay, or used its feathers for decoration, since they are known to have made feather bands including jay feathers on the Californian mainland. Human activities may have contributed to the presumed extinction of the island scrub-jay from the smaller islands.[11]

References

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  1. ^ a b BirdLife International (2012). "Aphelocoma insularis". IUCN Red List of Threatened Species. 2012. Retrieved 26 November 2013.[dead link]
  2. ^ "NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 19 April 2022.
  3. ^ a b c d S. A. Morrisson; et al. (December 2011). "Proactive conservation management of an island-endemic bird species in the face of global change" (PDF). BioScience. 61 (12): 1013–1021. doi:10.1525/bio.2011.61.12.11. S2CID 85961132. Retrieved 2014-04-04.
  4. ^ Henshaw, H W (1886). "Description of a new jay from California". Auk. 3 (4): 452–453. doi:10.2307/4625442. JSTOR 4625442.
  5. ^ a b c Collins, P. W. (2009). "Historic and Prehistoric Record for the Occurrence of Island Scrub-Jays (Aphelocoma insularis) on the Northern Channel Islands, Santa Barbara County, California". Santa Barbara Museum of Natural History Technical Reports – No. 5: 1–83.
  6. ^ Madge, Steve; Burn, Hilary (1994). Crows and jays: a guide to the crows, jays and magpies of the world. London: A & C Black. pp. 70–71. ISBN 0-7136-3999-7.
  7. ^ Delaney, Kathleen Semple; Zafar, Saba; Wayne, Robert K (2008). "Genetic Divergence and Differentiation within the Western Scrub-Jay (Aphelocoma californica)". Auk. 125 (4): 839–849. doi:10.1525/auk.2008.07088. S2CID 85393011.
  8. ^ a b McCormack, John E.; Heled, Joseph; Delaney, Kathleen S.; Peterson, A. Townsend; Knowles, L. Lacey (2011). "Calibrating Divergence Times on Species Trees Versus Gene Trees: Implications for Speciation History of Aphelocoma Jays". Evolution. 65 (1): 184–202. doi:10.1111/j.1558-5646.2010.01097.x. hdl:2027.42/79292. PMID 20681982. S2CID 8672729.
  9. ^ a b Paul W. Collins; Daniel A. Guthrie; Emily L. Whistler; René L.Vellanoweth; Jon M. Erlandson (2018). "Terminal Pleistocene–Holocene Avifauna of San Miguel and Santa Rosa Islands: Identifications of Previously Unidentified Avian Remains Recovered from Fossil Sites and Prehistoric Cave Deposits". Western North American Naturalist. 78 (3): 370–403. doi:10.3398/064.078.0311. S2CID 91383468. Retrieved October 20, 2023.
  10. ^ Atwood, Jonathan L (1980) Breeding biology of the Santa Cruz Island Scrub Jay, pp. 675–688 in Power, D M (1980). The California Islands: Proceedings of a multidisciplinary symposium. Santa Barbara, California: Santa Barbara Museum of Natural History. ISBN 0-936494-01-8.
  11. ^ a b Delaney, Kathleen Semple; Wayne, Robert K (2005). "Adaptive units for conservation: Population distinction and historic extinctions in the Island Scrub-Jay" (PDF). Conservation Biology. 19 (2): 523–533. Bibcode:2005ConBi..19..523D. doi:10.1111/j.1523-1739.2005.00424.x. S2CID 56305274. Retrieved July 24, 2015.
  12. ^ "BirdLife International Species factsheet: Island Scrub-jay Aphelocoma insularis". BirdLife International. Retrieved 20 May 2012.
  13. ^ "Santa Cruz Island". National Park Service. Retrieved 20 May 2012.
  14. ^ Collins, Paul W.; Guthrie, Daniel A.; Whistler, Emily L.; Vellanoweth, René L.; Erlandson, Jon M. (2018). "Terminal Pleistocene–Holocene Avifauna of San Miguel and Santa Rosa Islands: Identifications of Previously Unidentified Avian Remains Recovered from Fossil Sites and Prehistoric Cave Deposits". Western North American Naturalist. 78 (3): 370–403. doi:10.3398/064.078.0311. ISSN 1527-0904. S2CID 91383468.
  15. ^ Langin, Kathryn M.; Sillett, T. Scott; Funk, W. Chris; Morrison, Scott A.; Desrosiers, Michelle A.; Ghalambor, Cameron K. (2015). "Islands within an island: Repeated adaptive divergence in a single population: REPEATED ADAPTIVE DIVERGENCE WITHIN A POPULATION". Evolution. 69 (3): 653–665. doi:10.1111/evo.12610. PMID 25645813. S2CID 10916622.
  16. ^ Caldwell, Luke; Bakker, Victoria J.; Sillett, T. Scott; Desrosiers, Michelle A.; Morrison, Scott A.; Angeloni, Lisa M. (2013). "Reproductive Ecology of the Island Scrub-Jay". Condor. 115 (3): 603–613. doi:10.1525/cond.2013.120028. ISSN 1938-5129. S2CID 45886719.
  17. ^ Sillett, T. Scott; Chandler, Richard B.; Royle, J. Andrew; Kéry, Marc; Morrison, Scott A. (2012). "Hierarchical distance-sampling models to estimate population size and habitat-specific abundance of an island endemic". Ecological Applications. 22 (7): 1997–2006. Bibcode:2012EcoAp..22.1997S. doi:10.1890/11-1400.1. ISSN 1051-0761. PMID 23210315. S2CID 12163232.

Further reading

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