Florida Scrub-jay

Aphelocoma coerulescens coerulescens

Description

The Florida scrub-jay is about 10-12 in (25-30 cm) long and weighs about 2.7 oz (77 g). It is similar in size and shape to the blue jay (Cyanocitta cristata ), but it differs in coloration and lacks a crest. Its head, nape, wings, and tail are colored pale blue, and the back and belly are pale grey. Its throat and upper breast are lightly striped and bordered by a pale blue-gray bib. The sexes are not distinguishable by plumage, but males average slightly larger than females, and the female makes a distinct "hiccup" vocalization. Juvenile birds less than about five months of age are distinguished by their plumage, which is smoky gray on the head and back and lacks the blue crown and nape of adults. Molting occurs between early June and late November, and peaks between mid-July and late September. During late summer and early fall, when the first basic molt is nearly complete, fledgling scrub-jays may be indistinguishable from adults.

Behavior

The Florida scrub-jay is extremely habitat-specific, sedentary, and territorial. It has a social structure that involves cooperative breeding, a trait that western North American populations of scrub-jays do not exhibit. Florida scrub-jays live in groups ranging from two (a single mated pair) up to extended families of eight adults and one to four juveniles. Fledgling birds remain with the breeding pair in their natal territory as "helpers," forming a closely-knit, cooperative family group. Pre-breeding numbers are generally reduced to either a pair with no helpers or families of three or four individuals (a pair plus one or two helpers). The family group has a dominance hierarchy, with breeder males being most dominant, followed by helper males, breeder females, and then female helpers. Helpers participate in sentinel duties, territorial defense, predator mobbing, and the feeding of nestlings and fledglings.

Florida scrub-jay pairs occupy a year-round, multi-purpose territory. The territory size averages 22-25 acres (9-10 hectares), with a minimum of about 2 acres (5 hectares). The availability of suitable territories is a limiting factor for scrub-jay populations. Because of this limitation, non-breeding adult males may remain on their natal territory as helpers for up to five years, waiting for a territory (or sometimes a mate) to become available.

The nest of the Florida scrub-jay is an open cup, with an outside diameter of about 8 in (18-20 cm), and inside diameter of 3.5 in (8-9 cm). The basket is bulky and constructed of coarse twigs, while the inside is lined with tightly wound palm fibers. Nesting normally occurs from the beginning of March through June. Nesting failures are almost always caused by predation, most frequently by ground-based predators such as climbing snakes, raccoons, and domestic cats. Clutch size ranges from one to five eggs, but is typically three or four eggs. Eggs are incubated for 17-18 days, and fledging occurs 16-21 days after hatching. Only the breeding female incubates and broods the eggs and nestlings, but both parents and juvenile helpers feed the young. The average annual production of young is two fledglings per pair, and the presence of helpers improves fledging success. Annual productivity must average at least two young fledged per pair for a population of scrub-jays to maintain long-term stability.

Florida scrub-jays forage mostly on or near the ground, often along habitat edges. They visually search for food by hopping or running along the ground beneath the scrub, or by jumping from shrub to shrub. Insects, particularly orthopterans and lepidopteran larvae, comprise the majority of the animal diet throughout most of the year. Acorns are by far the most important plant food. They sometimes eat small vertebrate animals.

Habitat

The Florida scrub-jay is endemic to ancient dune ecosystems or scrubs, which occur on well-drained to excessively well-drained, nutrient-poor, sandy soils. Its oak-dominated scrub habitat is adapted to nutrient-poor soil, periodic drought, high seasonal rainfall, and frequent wildfire. The dominant oaks are stunted, low-growing species, such as sand live oak (Quercus geminata ), Chapman oak (Q. chap-manii ), myrtle oak (Q. myrtifolia ), and scrub oak (Q. inopina ). In optimal habitat, the oaks are 3-10 ft (1-3 m) high, interspersed with 10-50% unvegetated, sandy openings, and with a sand pine (Pinus clausa ) canopy of less than 20%. Larger trees and dense herbaceous vegetation are uncommon.

Distribution

The Florida scrub-jay was historically distributed throughout the Florida peninsula in suitable scrub habitat. It occurred in 39 of the 40 counties south of (and including) Levy, Gilchrist, Alachua, Clay, and Duval Counties. The current range is smaller, and the population much less. On the Atlantic Coast, Florida scrub-jays extend from Flagler to Palm Beach Counties. On the Gulf Coast, they occur patchily from Levy, Citrus, western Marion, and northwestern Sumter Counties south to Sarasota, western DeSoto, Charlotte, Lee, and northwestern Collier Counties. In central Florida, they range from southwestern Clay through Putnam and Marion Counties, south through Polk, Highlands, and Glades Counties. The Florida scrub-jay has been extirpated from Broward, Dade, Duval, Gilchrist, Hendry, Pinellas, and St. Johns Counties.

The distribution and status of the Florida scrub-jay across its range was updated during 1992-1993. Based upon that survey, the overall population was divided into five subregions, corresponding to the major areas of sand deposits located on the Florida peninsula. Three of the subregions are considered "core populations" because they contain most of the remaining Florida scrub-jays. These core populations occur at Merritt Island/Cape Canaveral Complex, Ocala National Forest, and on the southern Lake Wales Ridge. Scrub-jay populations outside of the three core subregions consist of smaller sub-populations that are isolated to varying degrees.

Threats

The Florida scrub-jay is threatened because of the loss, fragmentation, and degradation of its scrub habitat throughout Florida. This damage is due primarily to the conversion of its habitat to urbanized and agricultural land-uses, as well as the suppression of wildfires. Scrub habitats of Florida are some of the most imperiled natural communities in the United States, with estimates of habitat loss since presettlement times ranging from 70 to more than 80%. Historically, this community type occurred as large, contiguous patches, some of them over hundreds of miles in extent. Today, only relict patches of dry oak scrub remain.

Throughout the northern part of their range, population declines of Florida scrub-jays are attributed to scrub fragmentation and degradation, due primarily to widespread fire suppression. Citrus conversion and residential development continue to be the most important factors causing the decline of scrub-jay populations in the southern parts of their range. Since about 1985, their total population has declined by about 25-50%, and the species has become extirpated from seven counties. The most recent estimate of the population of the Florida scrub-jay (in 1993) was 11,000 birds, or about 4,000 pairs. This population is no more than about 15% of the estimated pre-settlement population, and corresponds to a similar reduction in the distribution of scrub habitat. As of 1993, half of the remaining Florida scrub-jays occurred in Brevard and Highlands Counties. A total of 19 occupied counties contained 30 or fewer groups of scrub-jays.

Conservation and Recovery

Overall conservation measures for the Florida scrub-jay must be based on an understanding of the demography and behavior of the species, as well as the long-term management needs of its oak scrub habitat. All Florida scrub-jays reside within a territory, which must contain sufficient habitat to sustain a family group throughout the year. It is critical to know the density of territories supported by the habitat, the total area of suitable habitat available, and the long-term management required to maintain its suitability for scrub-jays.

The fate of the Florida scrub-jay depends on the effective protection and management of the remaining oak scrub habitat, both on public and private lands. Management to maintain or increase the numbers of scrub-jays is directly correlated with the amount of habitat available to support territorial pairs. Florida scrub-jays will not persist in scrub that is not burned regularly. Natural wildfires, which typically occur from lightening strikes during May to September, are a frequent influence on scrub habitat succession. These fires probably occurred at intervals of 5-40 years during presettlement times. Oak scrub revegetates to its pre-burn structure and species composition about four to five years after a burn. A fire frequency of about once every 10-20 years is considered optimal for scrub-jays. In the absence of natural fires, the oak scrub community requires management prescriptions, including controlled burns or, less preferably, mechanical treatment to maintain habitat suitability. Studies at Archbold Biological Station concluded that small, isolated populations of Florida scrub-jays are more likely to become extirpated by demographic fluctuations if their habitat is not maintained by periodic burning. Habitat management for scrub-jays should include rotations of prescribed burns, each covering a relatively small portion of a preserved tract of scrub. Patches in the tract should be burned every 10-20 years; shorter intervals are applicable to faster growing coastal scrubs, while longer intervals are suitable in slow-growing central-ridge scrubs. Small patches left unburned provide cover and foraging sites as the scrub regenerates. No more than 25% of an area should be burned at any time. It is critical to maintain connections among patches of suitable habitat to facilitate the dispersal of scrub-jays, and also to include buffer habitat around scrub patches. Effective reserve design to support a protected population of Florida scrub-jays in average habitat is thought to require at least 750 acres (304 hectares) of periodically burned oak scrub. This assumes that a sustainable population of scrub-jays consists of 15-30 territories located within 2.4 mi (4 km) of at least one other population containing more than 30 territories, and the need for 25 acres (10 hectares) per territory. Florida scrub-jay populations with fewer than 30 territories cannot be considered safe from extirpation over the long term. Although most of the population of Florida scrub-jays resides on conserved public lands, the overall numbers are in decline. Management practices on public lands should focus on enhancing and creating scrub habitat to assist with scrub-jay recovery. Conservation on private lands requires acquisition programs for scrub habitat, through state efforts such as the Conservation and Recreation Lands program, and the implementation of habitat conservation plans to protect large tracts of private scrub habitat (including the negotiation of conservation easements). The U.S. Fish and Wildlife Service is using digital data analyzed using a geographic information system to evaluate the amount of occupied scrub habitat and unoccupied but restorable scrub throughout Florida. These methods are also being used to identify areas suitable for creating habitat reserves on both public and private lands, including establishing connections among existing areas of protected habitat. In addition, spatially explicit models are being used to predict the results of alternative reserve designs and to help with implementing the optimal conservation measures for long-term protection and enhancement of the Florida scrub-jay. Consideration is also being made of population enhancement and establishment by the translocation of birds.

Contact

U.S. Fish and Wildlife Service
Jacksonville Ecological Services
Field Office
6620 Southpoint Drive, South. Suite 310
Jacksonville, Florida, 32216-0958
Telephone: (904) 232-2580
Fax: (904) 232-2404
http://www/fws.gov/r4jafl/

References

Breininger, D.R., M.J. Provancha, and R.B. Smith.1991. "Mapping Florida Scrub Jay Habitat for Purposes of Land Use Management." Photogram-metric Engineering and Remote Sensing 57: 1467-1474.

U.S. Fish and Wildlife Service. 1999. "South Florida Multi-Species Recovery Plan." U.S. Fish and Wildlife Service, Southeast Region, Atlanta, GA.