Breeding birds and old field succession on fallow Long Island farmland. Bulletin of the AMNH ; v. 168, article 1

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New York : American Museum of Natural History
"A combination of both the horizontal and vertical approaches to the study of avian succession was applied over a 20-year period in research on the breeding birds of fallow farmland in Long Island, New York. Eight fields, representing stages in secondary plant succession from bare soil to a field 45 years old, varied in size from 0.41 to 1.88 hectares. Botanical data on average cover of herbaceous species and upright woody species, and on the density of trees by height class and by diameter characterize the vegetation of each study area. Breeding bird censuses were counts of all individuals, not indices to or estimates of population size. Particular attention was given to nest location and construction and to light readings taken at the nests to provide an index of relative nest cover. The sequence in which bird species became established in these fields was: red-winged blackbird, song sparrow, field sparrow, indigo bunting, common yellowthroat, blue-winged warbler, gray catbird, brown thrasher, and rufous-sided towhee. This is the same sequence of species derived by an arrangement in order of increasing cover at the nest. Likewise, this is the order in which these same species disappear from the continuum of communities that characterizes old field succession on Long Island. The concordance among these three sequences suggests that species-specific requirements with respect to cover at the nest plays an important role in determining which stages of old field succession a species finds attractive for nesting. There was a rapid increase in species diversity with an increase in age of the fields, and a leveling-off in numbers of territorial species from about 15 years (open shrubland) to 40 years (dense shrubby woodland) after cultivation. A more mature oak woodland in the same region (60 years after clear-cutting) had a greater species diversity than that of any earlier stage of old field succession. This progressive increase in species diversity with succession from herbaceous fields to mature forest is consistent with the findings of others. The density of breeding birds continued to increase beyond that age at which species diversity began to level off (about 15 years after cultivation) and did not reach peak density until another 15 years had elapsed. Density within the more mature oak woodland was significantly less than that of the 30- to 40-year old shrubby woodland. Whether or not there is a decline in density of breeding birds as succession approaches climax probably is determined by the relative availability of moisture. Other investigators have confirmed that in the more xeric successions, such as described in this study, a decline in density is the rule. In the more mesic successions, density is higher in the forest than in the intermediate shrubland stage. Species diversity and density were significantly lower in study areas where succession was arrested than in those permitted to revegetate naturally"--P. 5.
60 p. : ill., maps ; 26 cm.
Includes bibliographical references (p. 57-58).