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PLEASE VISIT SCRUB JAYS
Jerry P. Clark
Scott E. Hygnstrom
The scrub (or California) jay (Aphelocoma coerulescens, Fig. 1) is distinguished by its crestless head, olive-gray back, and white throat, outlined in blue. Its head, tail, and wings are blue. Calls are harsh, raspy, and varied, often in series of ones or twos. It belongs to the same family (Corvidae) as the other jays, magpies, and crows.
Scrub jays are found in the western United States, parts of Mexico, and in central Florida. Although they do not migrate long distances, they do move to lower elevations in winter.
Scrub jays commonly inhabit the oak and brush-covered foothills of the mountains, timbered canyons, river bottoms, oak-lined sloughs and creeks, as well as the shade trees and dense shrubbery of residential areas.
Beal (1910) reported that the diet of the scrub jay consisted of 73% plant and 27% animal matter. The plant matter was about one-third fruits and berries, and two-thirds acorns, nuts, and grain. Nuts and acorns are often stored or hidden for later use, though it is debatable how many hiding places jays remember. The animal matter varied greatly, and included insects, spiders, snails, and small vertebrates, including bird’s eggs and nestlings.
Nests are usually found on brush-covered hillsides or in creek bottoms in low bushes, shrubs, and trees. Most nests are located near water, but sometimes they may be found up to a mile (1.6 km) away. Egg laying occurs from early March through June, with the peak occurring in April. Usually 4 to 6 eggs are laid. Incubation lasts about 16 days and the young are able to leave the nest in about 18 days. Scrub jays do not flock to the degree that crows or starlings do. Jays usually feed alone, but where populations are high, they may form nearly continuous lines when flying to and from a food source.
Jays are omnivorous and therefore may damage several agricultural crops such as nuts, fruits, grains, peas, corn, and berries. They also take insects, small mammals, reptiles, and eggs and young of gamebirds and songbirds. Jays have a pronounced preference for fruits. Cherries, plums, prunes, pears, figs, grapes, and other fruits are often pecked and eaten. Depredations on almonds, pecans, and pistachios can be severe.
Scrub jays are classified as migratory nongame birds in the Code of Federal Regulations. They may be controlled only under a permit from the US Fish and Wildlife Service.
Place bird netting over fruit trees, vines, and gardens to exclude jays from the immediate area.
Frightening devices are only moderately effective in protecting crops from scrub jays. Almond and pistachio growers commonly use gas cannons, Av-Alarm® devices, and shooting to frighten or disperse jays.
None are registered.
|Fig. 2. Scrub jays can be taken by the use of a rat snap trap. Bait the trap with a nut or nut meat and set as illustrated.|
Jays can be taken by using conventional rat traps baited with a shelled or unshelled almond or the meat of half an English walnut (Fig. 2). The best location for the rat trap is on a vertical limb of a tree. Nail it high enough in the tree to be out of reach of small children. Beneath the vertical limb there should be a horizontal limb that is frequented by jays. Fasten the trap, trigger down, with the bait about 7 inches (18 cm) above the horizontal limb. The trap will still work if it is placed on a horizontal limb, but other species of birds might accidentally step on the trigger. Other baits may be used. An unshelled almond is probably less likely to attract other birds than are the exposed almond or nut meats. Acceptance of nut baits is not as good when there is an abundant supply of ripe fruit or nuts available.
Trapping efficiency has been increased by enlarging the wire bail with a 7-x 9-inch (17.8- x 22.9-cm) piece of 1-inch (2.5-cm) mesh welded wire. Cut a 1-x 4-inch (2.5- x 10.2-cm) slot out of the middle of the welded wire to provide clearance for the trigger release wire and wire it onto the bail. Also consider using a 4-x 6-inch (10.2- x 15.2-cm) piece of sheet metal. Cut a “V” out of the sheet metal (for clearance of the trigger release wire) and fold over 1/2 inch (1.3 cm) of each edge to hold the metal on the bail. The trigger mechanism can also be enlarged by attaching a thin round piece (half-dollar size) of wood. This trap improvement was developed by Bill Clark and Rocky Loop, of the Tulare County, California, Department of Agriculture.
Little success has been obtained in trapping jays with modified Australian crow traps.
Shooting will reduce the number of jays present but it is costly and rather futile as a method of complete crop protection.
A 1984 survey of 92 California pistachio growers estimated losses from scrub jays to be slightly less than $50,000 on 14,263 acres. This average crop loss to jays amounted to $3.41 per acre ($8.53/ha). In 1985, an assessment of jay damage in pistachio orchards in Tulare County, California, revealed average losses of $150 per acre ($375/ ha). Pistachio growers may underestimate their losses from scrub jays because the damage is distributed at low levels over most of the bearing trees in the orchard.
Figures 1 and 3 were reproduced from Clark (1986).
Figure 2 was adapted from Robbins et al (1983) by Clint Chapman, University of Nebraska-Lincoln.
Beal, F. E. L. 1910. Birds of California in relation to the fruit industry. Biol. Survey Bull. No. 34. USDep. Agric.
Clark, J. P. 1986. Depredating birds. Pages 701-1 - 726-1 in J. P. Clark, ed. Vertebrate pest control handbook. Calif. Dep. Food Agric. Sacramento.
Crabb, C. A., T. P. Salmon, and R. E. Marsh. 1986. Bird problems in California pistachio production. Proc. Vertebr. Pest Conf. 12:295-298.
Peterson, R. T. 1961. A field guide to western birds. Houghton Mifflin Co. Boston. 309 pp.
Robbins, C. S., B. Brunn, and H. S. Zim. 1983. Birds of North America. Golden Press. New York. 360 pp.
Scott E. Hygnstrom; Robert M. Timm; Gary E. Larson
PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994
Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska -Lincoln
United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control
Great Plains Agricultural Council Wildlife Committee
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