Annual Winter Bird Count 1990-1999, Archbold Biological Station, Biennial Report 1999-2000

Archbold Biological Station Annual Winter Bird Count, 1990-1999

Project Director: John W. Fitzpatrick, Cornell University
Database Manager: Fred E. Lohrer

[ WBC Summary & Data | Biennial Contents | Lake Placid Christmas Bird Count ]

During 1990-1999, 10 annual Winter Bird Counts (WBC) were conducted in mid-January, on 4800 acres of Archbold’s main property (but excluding the southeastern-most Hicoria Tract), using National Audubon Society Christmas Bird Count (CBC) methods. The effort was to count all birds at the Station. The count area was divided into 15 units following property tract boundaries (see Conservation article, map [b]). For all years counts were conducted on days with normal seasonal temperatures and, but for one year (1994), on days with little wind. Biases from observer variability were minimized by using, as much as possible, the same observers year after year in the same property unit, and usually units the observers were familiar with from their field research. Two observers participated in all 10 counts, one in 9 counts, and several in 6 counts. Overall 55 ornithologists and field ecologists participated. [see WBC summary] The WBCs gave us a good assessment of Archbold’s winter bird community and a better understanding of species population trends and relative abundance. The Archbold data can be compared with the adjacent and overlapping Lake Placid CBC, conducted during the same years in late December, and with many other Florida CBCs.

Results. Over the count decade, 113 bird species were observed, with 55 species (48.6%) seen every year [see WBC summary]. Of these 55, all but 2 (anhinga, belted kingfisher) are land birds. This reflects the predominance of upland (forest and shrub land) habitats at Archbold and scarcity of fresh-water habitats (Lake Annie notwithstanding). Conversely, of the 12 species seen in one year only, 7 are water birds. Thus, this brief review concentrates on land birds recorded in all 10 years with examples of patterns of relative abundance and of annual variation. The values given in the following discussion are 10-year means.

Relative abundance of species. Of four diurnal raptors, the American kestrel (10.9 birds) and the red-tailed hawk (9.1) were several times more abundant than the two accipiters, the sharp-shinned (4.0) and the Cooper’s hawk (2.6). The relative abundance of six woodpecker species varied greatly (see Fig. 1, below). The red-bellied woodpecker was the most abundant (116), followed by the downy and northern flicker (both 54), and then the relatively uncommon hairy (11.2) and pileated (7.8). The abundance of red-headed woodpeckers (22.0) varied greatly between years (see below). Of the non-warbler winter insectivorous passerines, the ruby-crowned kinglet and the house wren were similar in abundance (39.0 and 40.1, respectively), and the larger eastern phoebe was less abundant (25.0). Of the three mimids, the northern mockingbird was twice as abundant (188) as the gray catbird (91.6) and three times as abundant as the brown thrasher (63.8). Of the four most abundant wood-warblers, the yellow-rumped (646) was twice as abundant as the pine (281), three times the palm (210), and six times the common yellowthroat (110). Inexplicably, the 1999 count for the apparently sedentary northern cardinal (144) was double the 9-year average of 65.

Annual variation in abundance. Some examples highlight variation in annual abundance. The acorn-specialist red-headed woodpecker varied from rare to abundant, perhaps on a 3-year cycle (see Fig. 2, below). Although the three mimids occurred at different levels of abundance (see above), they all showed similar trends in annual variation (see Fig. 3, below). Two insectivorous passerines with similar abundance, the ruby-crowned kinglet and the house wren, showed opposite trends in abundance for six years (1990-95) and similar trends for four years (1996-99).

And finally, to close this brief review, the WBCs definitely established the great crested flycatcher (5.6), a common breeder, as a regular, although inconspicuous, winter resident.

Abundance of selected bird species at Archbold Biological Station during annual winter bird counts, 1990-1999: Fig. 1 (top). Six woodpecker species; Fig. 2 (middle). Red-headed woodpecker; Fig. 3 (bottom). Three mimids. Figs. by Reed Bowman.

Fig. 2. Red-headed woodpecker.
Fig. 3. Three mimids.

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Archbold Biological Station, P.O. Box 2057, Lake Placid, Florida 33862 USA
Phone: 863-465-2571, FAX: 863-699-1927, Email: archbold@archbold-station.org