Island scrub jay

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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

The island scrub jay (Aphelocoma insularis), also known as the island jay or Santa Cruz jay, is a bird in the genus,

endemic landbird species.[3]

Description

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

The island scrub jay was first described by American

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,

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

The island scrub jay is found today only on

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

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

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

The island scrub jay is classed as vulnerable on the

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

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

  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. ^
    S2CID 85961132
    . Retrieved 2014-04-04.
  4. 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. ISBN 0-7136-3999-7
    .
  7. S2CID 85393011
    .
  8. ^
    S2CID 8672729
    .
  9. ^
    S2CID 91383468
    . Retrieved October 20, 2023.
  10. ISBN 0-936494-01-8
    .
  11. ^
    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. S2CID 91383468
    .
  15. S2CID 10916622
    .
  16. S2CID 45886719
    .
  17. S2CID 12163232
    .

Further reading

External links

Wikimedia Commons has media related to Aphelocoma insularis.
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