The goshawk, a swifter and more persistent hunter, will press its attack on birds such as Ruffed Grouse, ptarmigan, and pheasant for as much as 1 km, particularly if the flight course is across open ground. The accipitrine hawks, long considered by many people to be destructive to songbird populations, are actually of great service to their prey species. Goshawks, especially through their infrequent invasions of the mid-continent, were once believed a serious menace to introduced game birds such as Gray Partridge and pheasant. Although they do sharply reduce the populations of these species, they do so far more selectively than hunters with shotguns. Loss of habitat for breeding hawks and for their prey has accelerated in recent years as people cleared more forested areas for agriculture, suburban developments, and industrial uses.
Hawks require large undisturbed areas for successful nesting.
Researchers believe that a decline in the number of hawks and other birdeating raptors in North America began and still persists in the agricultural areas of the middle latitudes. Although this population decline is probably due in part to habitat loss, it is also a result of indirect poisoning by insecticides. Small birds that feed on sprayed insects retain the tiny concentrations of chemicals in the insects' bodies and pass these residues on to the hawks. In a food chain, insecticides that do not decompose much, such as DDT and dieldrin, accumulate at higher levels in each succeeding link, so that the hawks build up significantly more insecticide residues than do their prey. These residues can reach levels poisonous enough to interfere with reproduction.