Since 1979, the Denver Wildlife Research Center, U.S. Fish and Wildlife Service, has conducted an accelerated research program on the blackbird-sunflower problem which occurs annually in the Dakotas and Minnesota. The objective is to develop effective, cost beneficial, and environmentally safe methods for reducing blackbird damage to ripening sunflower. A multidisciplinary approach involving interrelated studies of problem definition, ecology, and control methods development is being used. Preliminary results are presented from several studies involving: state- and county-wide estimates of damage; frequency distribution and timing of damage; compensatory growth in early damaged sunflower heads; breeding male blackbird censuses; mass-marking migratory red-winged blackbirds (Agelaius phoeniceus) in spring roosts; food habits of red-wings; the chemical frightening agent, 4-aminopyridine; the avian repellent, methiocarb; decoy crops for blackbirds; frightening devices; and bird-resistant varieties of sunflower. Management strategies suggested from these studies are provided.

Since 1964, when the effectiveness of methiocarb for preventing pheasants (Phasianus colchicus) from damaging sprouting corn was proven in South Dakota, an aggressive program has been carried out by personnel of the Denver Wildlife Research Center and many cooperators to develop methiocarb as a broad-spectrum avian repellent. The successful use of methiocarb for preventing damage caused by several species of birds to sprouting corn in several states and to sprouting soybeans in South America is reviewed. Recent results obtained from spraying methiocarb on ripening rice in California, ripening sorghum in Colorado and Oklahoma, cherries in Michigan, and grapes in New Hampshire are summarized.

Field trials involving two chemical bird frightening agents are described. DRC-736-treated cracked corn was tested in feedlots in Colorado to reduce damage by redwinged blackbirds, and it was considered to be very effective. Sharp reductions in bird numbers occurred immediately after each baiting, and populations at feedlots remained very low for several weeks after treatment. 4-aminopyridine (DRC-1327) was evaluated in reducing blackbird damage to ripening corn using two different methods, either spraying ears or using broadcast baits, and in both trials was successful. Only a few frightened birds were needed in a field to frighten away others in the flock.

A combination Purivox® Double-John carousel propane exploder and CO2 pop-up scarecrow operated in synchrony was evaluated in five ripening sunflower fields in 1981 and 1982, respectively, near Devils Lake and Westhope, North Dakota. In each field, this treatment was evaluated in an alternating off-on sequence of 5-day intervals for a period of 20 days. In 1981, devices were deployed at one unit per 8 to 10 acres and in 1982 at one unit per 4 to 6 acres. The degree of effectiveness for reducing bird damage in three of five fields that met selection criteria ranged from 71 to 87% with a mean of 78%. During the first 10-day cycle, damage on these three fields was reduced 70, 89, and 95% or a mean of 84%, while in the second cycle damage was reduced an average of 59%. In the remaining two fields in which blackbirds were well established, damage was only reduced 8 and 31% during the entire test period. This was attributed to well-established feeding patterns in the fields by large flocks of blackbirds from a nearby roost. The cost to operate one unit on 6 acres of sunflower was $14 per acre if prorated over a 10-year period (the expected unit life). Bird damage must be 18% or higher before a grower could expect a return on money invested with this device. The cost-benefit ratio in this study was 1:2.3 because damage exceeded the 18% level. Although the cost-benefits of the combination scare device indicated that for most growers in North Dakota the cost of control would exceed the dollars saved, it would be most useful in about 1.2% of the fields which annually get more than 18% damage.

Seed rice was treated with 0.25% methiocarb to test its effectiveness as a blackbird repellent in Vermilion Parish, Louisiana in the spring of 1975. Two replications of 3 treated and 3 untreated plots showed 68% more seedlings in treated plots (2,393) than in untreated plots (1,429). Half as many birds (chiefly redwing blackbirds, Agelaius phoeniceus, were recorded in treated (1.18/min) as in untreated plots (2.39/min).

Red-winged blackbirds (Agelaius phoeniceus) have been discouraged from using cattle feedlots near Denver, Colorado, by baiting alleys with cracked corn treated with an aversion-producing immobilizing agent, DRC-736 [4-(methylthio)-3,S-xylyl N-methylcarbamate]. In three studies, large populations of redwings were reduced 70% - 98% within a few days and protection lasted about a month. In a fourth study, simultaneous baiting of three heavily used feedlots reduced redwing use by more than 90% within hours and was apparently responsible for these birds abandoning their roost and relocating in areas where they caused little trouble. Mortality was low (less than 5% of affected redwings in the fourth study), and few birds of nontarget species were affected.