Bird Damage to Sunflower in North Dakota, South Dakota and Minnesota, 1979-1981 (and Influence of Environmental Factors on Blackbird Damage to Sunflower)

摘要

Sunflower growing areas in North Dakota, South Dakota, and Minnesota were surveyed for bird damage from 1979 through 1981. Individual fields were sampled each year, and bird damage on sample sunflower heads was estimated using a gridded, plastic template. The average bird loss estimates in 1979 and 1980, respectively, were 0.8 percent (n=933 fields) and 2.0 percent (n=555 fields). As part of a 3-year survey designed to estimate the extent of sunflower weed losses to blackbirds in North Dakota, South Dakota, and Minnesota, several habitat variables were recorded at each survey field in an effort to identify potential predictors of among-field and within-field variations in damage. Variables included the presence or absence of certain habitat types near the survey field, the size of the survey field, the distance between rows, and the average head size and plant height.