Use of Artificial Brown-Headed Cowbirds Eggs As a Potential Management Tool in Detering Parasitism
Ortega CP, Ortega JC, Cruz A. 1994. Use of Artificial Brown-Headed Cowbirds Eggs As a Potential Management Tool in Detering Parasitism. The Journal of Wildlife Management. 58(3):488 - 492
We added artificial and real brown-headed cowbird (Molothrus ater) eggs to red-winged blackbird (Agelaius phoeniceus) nests in 1985 and 1991 to determine the effect of egg addition on subsequent nest parasitism. We added large artificial eggs measuring 26.1 × 17.2 mm, similar in size to red-winged blackbird eggs, and small artificial eggs measuring 20.1 × 16.1 mm, similar in size to brown-headed cowbird eggs. Brown-headed cowbirds avoided parasitizing nests to which we added real or artificial cowbird eggs. In 1985, only 5.3% (3 of 57) of experimental nests were parasitized by cowbirds, compared with 31.5% parasitism of control nests (P = 0.001, n = 54). Although not statistically significant, in 1991, only 6.0% (2 of 40) experimental nests suffered cowbird parasitism, compared with 16.0% parasitism of control nests (P = 0.294, n = 25). Artificial egg size did not affect parasitism rates (P = 0.823). Addition of real or artificial eggs did not affect clutch size (P = 0.234) or hatching success (P = 0.656) of red-winged blackbirds. Addition of brown-headed cowbird eggs (real or artificial) to red-winged blackbird nests may deter future parasitism. For endangered host species, the addition of artificial or real inviable cowbird eggs should be evaluated as a management tool.
- Type
- Journal Article
- Authors
- Ortega, Catherine; Ortega, Joseph; Cruz, Alexander
- Units
- ORPI
- Keywords
- Agelarius phoeniceus, Birds, brownheaded cowbird, Clutch Size, Colorado, Cowbird, Ecosystem Management, Eggs, Molothrus ater, Parasitism, red-winged blackbird