Breeding Birds in a Florida Suburb

Abstract

A study of bird populations in the residential suburbs of St. Petersburg and Gulfport, Pinellas County, Florida based on observations made in three study plots totaling 100.5 acres during portions of two years, 1968 and 1964. The dominant vegetation is described in detail. Part I includes our estimates of the total number of breeding pairs for each plot, which varied from 200 pairs per 100 acres in new residential suburbs to 500 and 600 pairs per 100 acres in mature suburbs. Of the 11 species that breed in the three plots, four, the House Sparrow, Mourning Dove, Blue Jay, and Mockingbird, were the most abundant and accounted for more than 90 per cent of the total. House Sparrows alone comprised about 50 per cent of all breeding birds. Only four species not found in the quadrats, two of which are introduced, breed in similar habitats in the county. When natural areas are replaced by suburbs a marked change in avian species composition occurs, and, with the eventual maturing of the suburbs, breeding populations increase in pairs per hundred acres from an estimated maximum of 200 pairs to 500 or 600 pairs. Part I also discusses the birds breeding in peripheral habitats, total breeding populations for the two cities, non-breeding birds, and predators. Part II deals with the breeding biology of several of the more common breeders, excluding the House Sparrow, based on almost 900 nest records. A discussion of currently existing methods for measuring nesting success is followed by an explanation of a new method which may prove useful in certain other studies. By this method a calculated number of hypothetical unfound failures are added to the sample of known nests to compensate for nests found after incubation or egg laying has begun. Using our method we found that nest success was approximately 40 per cent for Mourning Doves breeding in pine-dominated suburbs and 20 per cent for those breeding in oak-dominated suburbs. Based on the same method nest success for Mockingbirds was about 52 per cent in the two habitats combined. A method of expressing nest-site preference based on the relative abundance of plants and the distribution of nests is proposed also. Additional information on phenology of nesting, clutch size, and nest location is given in the species accounts. Information is especially extensive for the Mourning Dove where 625 nestings were analyzed.