Island scrub jay
|Island scrub jay|
Year-round resident range on Santa Cruz Island
The island scrub jay (Aphelocoma insularis) also 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. The island scrub jay (ISSJ) 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.
The island scrub jay was first described by American ornithologist Henry Wetherbee Henshaw in 1886 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. 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, Aphelocoma coerulesens, with five subspecies, but are now considered four species: the Florida scrub jay, A. coerulesens, 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. The relationships within the genus have been studied in several papers (e.g. )
Island scrub jays seem to be incapable of crossing significant bodies of water. Reliable historical observer records for ISSJ in addition to Santa Cruz Island include only a single 1892 account on neighboring Santa Rosa Island, only about 10 km (6 mi) away. 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. The historic observation on Santa Rosa Island is supported by an archaeological record of a single ISSJ femur from a Late Pleistocene-Holocene site (SRI-V-3).
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. 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 ISSJ has been evolving in isolation for approximately one million years , i.e. over multiple glacial cycles. Up to about 11,000 years ago, the four northern Channel Islands were one large island, so ISSJ 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.
Distribution and habitat
The island scrub jay is found only on Santa Cruz Island, the largest of California's Channel Islands with an area of 250 km2 (96 mi2). 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. Fossil remains for ISSJ have been found on Santa Rosa and San Miguel Islands.
ISSJ occur in oak chaparral and bishop pine (Pinus muricata) woodland on Santa Cruz Island. ISSJ 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. 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 .
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".
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. Population size in 2008 and 2009 estimated to be 1700 - 2300, making this one of the rarest songbird species in the United States. The entire range of ISSJ 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. Shrub cover has increased since the removal of Santa Cruz sheep (1980–91) and feral pigs (2005–07) from Santa Cruz Island, which may increase the fire risk. Overgrazing by non-native ungulates may have caused extirpation of ISSJ on Santa Rosa Island. Re-establishing a second population of ISSJ on Santa Rosa Island may accelerate the restoration of native plant and tree species because of the scatter-hoarding seed caching behavior of Aphelocoma species.
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.
- BirdLife International (2012). "Aphelocoma insularis". IUCN Red List of Threatened Species. 2012. Retrieved 26 November 2013.CS1 maint: ref=harv (link)old-form url
- 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.
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- 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.
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- 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 0936494018.
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- "BirdLife International Species factsheet: Island Scrub-jay Aphelocoma insularis". BirdLife International. Retrieved 20 May 2012.
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- 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. doi:10.1890/11-1400.1. ISSN 1051-0761. PMID 23210315. S2CID 12163232.
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