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Application of Avian Repellents to Eastern White Pine Seed

1958; Wiley; Volume: 22; Issue: 3 Linguagem: Inglês

10.2307/3796464

1937-2817

Herschel G. Abbott,

Ecology and Vegetation Dynamics Studies

Birds are one of the most damaging biological factors with which a forest nurseryman must at times contend. A survey conducted in 1955 (Abbott, 1956) indicated that 85 per cent of the forest nurseries in the United States experienced sufficient damage to seedbeds by birds to necessitate the adoption of control measures. These measures, which were in use in 1954, consisted primarily of screening the seedbeds, shooting the birds, and using firecrackers and other noise makers as deterrents. Less popular methods of controlling bird damage included the use of flashing devices, poisoning, and even the presence of a captive redtailed hawk (Buteo jamaicensis) in the vicinity of the seedbeds. Certain of these controls have proven to be adequately effective, such as screening of seedbeds, particularly at small nurseries. Shooting, although effective, is not necessarily economical and is scarcely a desirable means of control. It may not only present legal difficulties, but it also eliminates birds that are highly beneficial to nursery culture except during brief periods of the year. Extreme measures, such as shooting, although undesirable, may be justified by the fact that one acre of nursery land often supports several thousand dollars' worth of future planting stock. However, some means of successfully repelling birds, rather than exterminating them, is to be preferred. The Denver Wildlife Research Laboratory of the U.S. Fish and Wildlife Service has been working since 1951 on the development of a suitable repellent that can be applied to tree seed prior to sowing directly in the field or in seedbeds at a nursery. Such a material should be nontoxic to birds as well as repellent to them, if it is to meet the requirements of a true repellent. It must also be safe for man to use, nondetrimental to soil and seed, reasonable in cost, and capable of withstanding the effects of weather elements (Neff and Meanley, 1956). The most basic of all these requirements is, however, that the material actually repel birds. In the spring of 1956, arrangements were made with the Denver Wildlife Research Laboratory to test four materials at the Amherst State Nursery, Amherst, Massachusetts, for their comparative effectiveness as bird repellents. The repellents tested were anthraquinone, Morkit, quinizarine, and Arasan Seed Disinfectant and Protectant (50 per cent tetramethyl thirum disulfide). These materials, in powder form, were applied to the seed at a 15 per cent concentration, using a 25 per cent asphalt emulsion as an adhesive in the manner described by Mann and Derr (1955) and Mann, Derr, and Meanley (1956). Early in June, eight out of a total of 117 seedbeds established at the nursery were selected for this test. On June 5, the test beds were broadcast seeded with eastern white pine (Pinus strobus) seed, each of four beds being sown with seed treated with a different one of the four repellents to be tested, the remaining four with untreated seed. The number of seeds per pound was determined for each lot of seed, and the weight of the seed sown was varied, causing each seedbed to contain a comparable number of viable seed. Each bed contained approximately 5,600 viable seed or 140 per square foot. The usual practice of mulching seedbeds with burlap was not followed in the case of the eight test beds, which were left fully exposed except for the presence of seedbed frames (without covers). Bird activities were observed at the nursery for one to two hours during both morning and evening feeding periods when the birds were most active. These observations were continued for 14 days after seeding. The following 16 species of birds were identified within the limits of the nursery; grackles (Quiscalus quiscula), chipping sparrows (Spizella passerina), house sparrows (Passer domesticus), song sparrows (Melospiza melodia), robins ( Turdus migratorius), starlings (Sturnus vulgaris), flickers ( Colaptes auratus), blue jays (Cyanocitta cristata), kingbirds (Tyrannus tyrannus), catbirds (Dumetella carolinensis), crows (Corvus brachyrhynchos), mourning doves (Zenaidura macroura), goldfinches (Spinus tristis), pheasants (Phasianus colchicus), yellow warblers (Dendroica petechia), and Baltimore orioles (Icterus galbula). However, only the first four of these species-grackles, chipping sparrows, house sparrows, and song sparrows-were attracted by the seed in the nursery beds. Grackles greatly outnumbered all other species and were so aggressive in their activities in the test seedbeds that the results of their feeding were quick to overshadow the actions of all other species. The exposed seedbeds were first visited by actively feeding birds five days after seeding, when nine visitations by grackles were made during a period of 30 minutes, all in beds containing untreated seeds. At the end of two weeks, germination was largely completed and nearly all the untreated seeds had been destroyed by birds. Visitations noted totaled 99 during the morning feeding period as compared to 93 in the evening. Although Table 1 shows that only 62 per cent of the visitations observed were made by grackles, it is estimated that over 95 per cent of the seed destruction should be attributed to this species. 1 Contribution No. 1119 of the Experiment Station, College of Agriculture, University of Massachusetts, Amherst, Massachusetts.