The main threat to barn swallows is agriculture including farming practices, loss of foraging areas, livestock rearing, improved hygiene, land drainage, and the use of herbicides and pesticides.
The main threat to the barn swallow is the intensification of agriculture. Barn swallow populations are generally considered to be stable and sufficiently extensive. However, declines in the amount of acreage devoted to agriculture in recent years have resulted in reduced barn swallow numbers. This can be attributed to a reduction in habitat as the barns and outbuildings which once housed barn swallows, give way to more urban settings.
Changes in farming practices such as the abandonment of traditional milk and beef production have resulted in a loss of suitable foraging areas. In addition, there has been a reduction in food supply. Insects attracted by the presence of livestock and the ideal surrounding habitat are the primary food source for barn swallows living in agricultural areas. Locations where farming has ceased exhibit a 50% reduction in insect populations. Intensive livestock rearing, improved hygiene, land drainage, and the use of herbicides and pesticides all reduce the numbers of insect prey available.
Lastly, suitable nest sites are often scarcer on modern farms.