Douglas Tallamy, an entomologist at the University of Delaware, makes a convincing case that one factor is the replacement of native plants with (often showier)

Douglas Tallamy, an entomologist at the University of Delaware, makes a convincing case that one factor is the replacement of native plants with (often showier) aliens which local insect populations can't eat. This then reduces the populations of birds which feed on those insects. Site for his books: http://www.bringingnaturehome.net/ http://www.bringingnaturehome.net/