EXPERIMENTAL TREE TRIMMING TO CONTROL AN URBAN WINTER BLACKBIRD ROOST

Every fall millions of blackbirds come down the Mississippi Flyway to return to their winter roosts in Arkansas, Louisiana, and East Texas. When these roosts are located in urban areas, public pressure makes the more common chemical means of control impractical. A less destructive and more permanent method of control was sought. At Rice University, in Houston, Texas, there has been a blackbird roost of various sizes and durations since 1956. For the past two years we have had the opportunity both to study roosting blackbird biology and experiment with habitat alteration as a control method. This particular report concentrates on the results and interpretation of the tree- trimming program initiated in August 1974. The birds involved are primarily Brown-headed Cowbirds (Molothrus ater), along with Starlings (sturnus vulgaris), Common and Great-tailed Grackles (Quiscalus quiscula and Cassidix mexicanus), Red-winged Blackbirds (Agelaius phoenicus) and Robins (Turdus migratorius). The campus comprises 121 ha and was planted with live oaks (Quercus virginiana) in 1912. These trees retain their foliage throughout the winter and now form a closed canopy over some 5-6 ha. In the 60s and early 70s most of the birds that came to Houston for the winter roosted in a 64-ha woodlot 10 km north of campus. In January 1970, the U.S. Fish and Wildlife Roosting Survey reported one million birds at this site we call the North Loop. Fifteen- thousand birds were estimated at Rice.

HIGHLIGHTS OF BIRD CONTROL RESEARCH IN ENGLAND, FRANCE, HOLLAND, AND GERMANY

The purpose of this paper is to present a brief review of the research being conducted in England, France, Germany, and The Netherlands on problems caused by nuisance and depredating birds. Much of the information presented has been obtained through correspondence with collaborators. In the fall of 1962, I discussed depredating bird and bird-airport problems with research workers in these countries, and also attended the meeting of the International Union of Applied Ornithology held in Frankfurt/Main. In November 1963, I attended an international symposium about the bird-airport problem, held in Nice, France. This paper will draw attention to the current research which I think will interest American investigators, but will not report every aspect of the foreign investigations. Details appear in the publications that are listed.