An evaluation of DRC-2698 treated with baits for reducing blackbird populations associated with sunflower damage

From 30 August to 18 September 1985, sunflower and corn mixed baits (75% sunflower meats and 25% cracked corn) treated with 1.50% CAT, (N-(3-chloro-4-methylphenyl) acetamide) were evaluated for reducing blackbird populations near Churchs Ferry, North Dakota. Baits were applied on baiting lanes in sunflower fields with an electric seeder mounted on an all-terrain cycle. Three noncommercial (decoy) sunflower fields were baited with CAT-treated baits diluted 1:9 with similar mixture of untreated bait at a rate of 50 lbs/lane acre (9.3 total treated acres). Based on total bait consumption, the estimate of blackbirds killed by the CAT treatment ranged from 13,266 to 30,650. The total amount of CAT-treated mixed bait consumed was 62.1 pounds. The predominant species causing damage in the test fields was the red-winged blackbird (Agelaius phoeniceus). Overall, redwings constituted an average of 73% of all birds observed in test fields, yellow-headed blackbirds (Xanthocephalus xanthocephalus) 23%, and common grackles (Quiscalus quiscula) 4%. Peak number of blackbirds feeding in test fields during observation periods varied from 2,250 to 10,635. Peak roost counts for roosts near test fields ranged from 60,000 to 90,000 blackbirds. Baits treated with an acutely toxic pesticide were evaluated as part of the bait mix and singly on sunflower rows as a toxic-marker. Birds and small mammals did not become immobilized and die close to ingestion sites. These results precluded the use of this toxic marker baits for estimating the number of birds accepting CAT baits. This technique does not appear promising as a technique for reducing local populations and associated sunflower loss