Removal and Repopulation of Breeding Birds in a Spruce-Fir Forest Community

Robert E. Stewart, John W. Aldrich
1951 The AUK: A Quarterly Journal of Ornithology  
IN 1949, while engaged in population studies of birds in northern Maine, the authors accumulated considerable information concerning population dynamics of birds inhabiting the Spruce-Fir forest community. This information was obtained in connection with investigations of the effective control by breeding birds of an infestation of the spruce budworm, Choristoneura fumiferana Clem. Field studies were conducted during June and July on two separate areas; a square 40-acre tract which was used as
more » ... which was used as an experimental area, and a rectangular 30-acre tract that served as a control area. The two areas were 1.25 miles apart and were both within one-half mile of the shore of Cross Lake, located about 14 miles southeast of Fort Kent, Aroostook County, Maine. In the experimental area an attempt was made to eliminate or to reduce drastically the bird population by use of firearms, while in the control area the natural bird population was allowed to remain unmolested. Both skins and stomachs of the birds killed were preserved for the Fish and Wildlife Service collections. The spruce budworm populations were studied in both areas before, during, and after the removal of the birds in order to see if any differential developed between the two areas in their total populations. The entomological portion of the field study was conducted by Philip B. Dowden and V. M. Carolin of the Bureau of Entomology and Plant Quarantine of the U.S. Department of Agriculture. Stomach contents of the birds collected were analyzed by Robert T. Mitchell of the Fish and Wildlife Service. The results of the various phases of this work concerning the effective control by birds of spruce budworms will appear in a separate report. The present paper includes an analysis only of the data on removal and repopulation of birds in the experimental area. The Spruce-Fir forest in the experimental area was somewhat varied. The canopy in certain sections of the forest had been partially opened by selective lumbering, resulting in a fairly dense understory growth of conifers. The other portions of the forest with a closed canopy contained little or no understory. Balsam fir, Abies balsamea, and black spruce, Picea mariana, were the primary dominant trees throughout the forest. The majority of the trees ranged between 40 and 60 feet in height. Small sections of mixed coniferous-deciduous [Auk 472 STewArT x•D Ar,v•ma, Removal and Repopulation of Birds [Oct. groups of fledglings, of the Golden-crowned Kinglet and Red-breasted Nuthatch were observed, but they were practically all removed from the area soon after they were first encountered during the first few days of collecting. The constant pressure of collecting and the resultant turn-over in adult birds completely prevented the development of other nestling populations in the study area during the collecting period. Small, roving groups of adult non-breeding birds were found in the area from time to time. The most common of these were the American Robin and Cedar Waxwing, both species being occasionally represented by from one to nine individuals. These birds were noted with increasing frequency during the latter part of the collecting period, Vol. 68]
doi:10.2307/4080843 fatcat:pqm33jlcqndzvlj7v5nnj7z2me