Proceedings of the Vertebrate Pest Conference

Bird damage was assessed weekly from soon after anthesis until harvest in two sunflower fields in the Sacramento Valley, California, during 1982. Damage chronology was similar at both sites, with damage concentrated in the second to fourth weeks after anthesis when the seeds were in the doughy stage of development. Less than 10% of the total losses caused by birds occurred during the final month before harvest. Overall bird damage was quite low (0.20 and 0.26%) in each field and in one, damage by wind was 2.4 times greater than that caused by birds. Brewer's blackbirds (Euphagus cyanocephalus) and house finches (Carpodacus mexicanus) both occurred in low-to-moderate numbers in one field, while high numbers of blackbirds, mostly red-winged blackbirds (Agelaius phoeniceus) occurred at the other field. At both fields, the numbers of blackbirds recorded peaked during the dough stage of sunflower development, whereas finches were most numerous somewhat later in the damage season. Analysis of the esophagi of 15 red-winged blackbirds collected at one field showed that in addition to sunflowers, various wild grass seeds and insects were consumed.