Christmas Bird Count Research Articles

Decline of the Rufous-Sided Towhee in the Eastern United States

ABSTRAcr.-The Rufous-sided Towhee (Pipilo erythrophthalmus) is a forest-generalist species that migrates short distances, with most of its range confined to the contiguous United States. Using migration count data from the northeastern United States, national Breeding Bird Survey data, and regional Christmas Bird Count data, I show that the towhee is making one of the most dramatic declines of a non-endangered species yet reported in the United States. Breeding Bird Survey data from New England states show that the towhee has been declining monotonically at about 8 to 10% per year. Populations in the Northeast are now at levels only about 13% of what they were when the Breeding Bird Survey began in 1966. Christmas Bird Count data from the southeastern United States also showed a decline in towhees, whereas Breeding Bird Survey data from the same region showed smaller declines, or no declines. This suggests that declines in wintering migratory towhees from the Northeast might explain most of the declines found in the Southeast using Christmas Bird Count data. The most likely explanation for this long-term, chronic decline in New England towhees is a gradual reversion of southern New England from a landscape with much early-successional habitat to a more forested landscape. Natural forest succession, following human-induced forest changes earlier in this century, may explain the current declines in towhees. Received 2 March 1992, accepted 25 November 1992.

51st Annual Saskatchewan Christmas Bird Count – 1992

51st Annual Saskatchewan Christmas Bird Count – 1992

50th Annual Saskatchewan Christmas Bird Count – 1991

50th Annual Saskatchewan Christmas Bird Count – 1991

Temperature and The Northern Distributions of Wintering Birds

Root (1988b) proposed that a physiological limit on metabolic rate constrains the northern distributions of wintering birds. Thermoregulation requires that metabolic rate increase as temperature declines, and hence a ceiling on metabolism that is reached before food or other factors become limiting would set the northern extent of a species distribution. I compared data with two predictions stemming from the proposal. First, there should be close correspondence between the northern range boundaries of species and temperature isotherms. To test this, I re—evaluated the data and found that only 8—42% of the species that Root classified as limited by temperature had northern range boundaries that corresponded to particular temperature isotherms. The second prediction examined was new: Species' northern limits should scale to body mass, because the ceiling on metabolism is stated as a multiple of basal metabolic rate, which itself scales to body mass. Large species should extend farther north than small species. A test of the prediction using Root's data showed little evidence that a constraint strongly affects the distributions of birds. In a second test, I analyzed additional recent Christmas Bird Counts that include areas farther north than were available to Root. I found that species of all sizes occur at the lowest temperatures, indicating that a ceiling on metabolism does not generally constrain the distributions of birds wintering in North America. My analysis turned up one other unexpected result: Few large passerines in North America have northern distribution boundaries that occur in warm, southerly areas, whereas small species have northern distribution boundaries in southern as well as in northern areas. The pattern might reflect the relationship between body size and the size of a species' geographic range coupled with the geography of North America. Large species tend to have only large geographic ranges, whereas small species are not so restricted. The avifauna of North America north of Mexico is bounded by a barrier formed by the Gulf of Mexico and a turnover in avifauna between the United States and Mexico. To the north of such a barrier, the northern distribution boundaries of large species should be well away from the barrier because of their large size.

Christmas Bird Count Update – Val Marie, Saskatchewan

Christmas Bird Count Update – Val Marie, Saskatchewan

49th Annual Saskatchewan Christmas Bird Count – 1990

49th Annual Saskatchewan Christmas Bird Count – 1990

Long-Term Trends of Chickadee Populations in Western North America

We evaluated population trends of Black-capped (Parus atricapillus), Chestnut-backed (P. rufescens) and Mountain (P. gambeli) chickadees in the Pacific Northwest of North America using 41 years (1944-1985) of data from Christmas Bird Counts. Most (76-83%) locations showed no significant trends (long-term increases or decreases in numbers of chickadees detected per observer hours) for any of the three species. Five to 14% of the locations had significant declines and 10 to 13% had significant increases. The recent range expansion by Chestnut-backed Chickadees in the Sierra Nevada of California was not accompanied by declines in Mountain Chickadee numbers. Chestnut-backed Chickadee populations no longer appear to be increasing in the Sierra Nevada; however, some populations in the San Francisco Bay region of California are apparently still increasing.

Monitoring Butterfly Populations Using the Fourth of July Butterfly Count

-The Xerces Society's Fourth of July Butterfly Count (4J), patterned after the popular Christmas Bird Count (CBC), is a nationwide, volunteer, annual 1-day census of butterflies and skippers at selected sites. The ornithological literature is reviewed, although not exhaustively, to summarize the methods for analyzing CBC data and to list the types of studies using these data. Applications of ornithologists' experiences with, concerns about, and uses for, CBC data to 4J studies are discussed, as well as issues, problems and opportunities specific to the Lepidoptera and 4J. This discussion is augmented by the results of a survey of midwestern 4J compilers. Two prototype studies using 4J data are offered: a nationwide analysis of monarch data 1979-1988 and an analysis restricted to the Midwest 1986-1989 on the fluctuations of immigrant species. DESCRIPTION AND PURPOSES OF BUTTERFLY COUNT The Xerces Society started the Fourth of July Butterfly Count (4J) in 1975 and has sponsored it annually since. The methods of the butterfly count are patterned after the highly successful Christmas Bird Count (CBC), founded in 1900 and sponsored by the National Audubon Society, except for the time of year. The 4J count period informally extends several weeks before and after this holiday, although counts outside this time period are also accepted. People initiating a count establish a 15-mile diam count area, which is to remain the same each year the count is conducted. In a 1-day period, participants keep track of the number of each species of butterfly (i.e., butterfly and skipper) seen, method of identification, time in the field, weather, number of observers in how many field parties, and distances traveled and how (car, foot, etc.). Results are published annually by the Xerces Society (10 Southwest Ash Street, Portland, Oregon 97204). Like the CBC counts, the 4J counts are diverse. Some counts census city parks, campuses, arboretums or nature centers, while others census more natural areas. Amateur lepidopterists conduct some counts, while professional lepidopterists conduct others. Some counts are held for fun, while others are part of research or monitoring projects. Nature centers also conduct counts as educational ventures for their members or the general public. Many counts census both developed and wild areas and mix amateur and professional lepidopterists as counters. The butterfly count was started for various reasons. Most important, it was meant to be a pleasant and educational experience both for people interested in butterflies and the general public, who often help out. The program presents butterflies, and by association invertebrates in general, in a positive and appealing way to the public. A secondary purpose of the 4J count was as an informal tool for studying and monitoring butterfly populations, especially to learn more about the ranges and sizes of butterfly populations and how weather and other variables affect butterflies. I surveyed the 16 count compilers active any year(s) from 1986 to 1988 inclusive in the Midwest (Ohio to Iowa and Michigan to Minnesota, hereafter Midwest). They filled out a separate survey for each of the 19 count circles counted in one or several of those three years. Responses from 14 compilers representing 17 counts were received. As for how midwestern counts got started, word of mouth from someone familiar with 4J was the most frequent method of recruiting a count's compiler (n = 7), although membership drives for the Xerces Society were nearly as effective (n = 5). R. M. Pyle's

Review: Atlas of Wintering North American Birds: An Analysis of Christmas Bird Count Data, by Terry Root

Review: <i>Atlas of Wintering North American Birds: An Analysis of Christmas Bird Count Data</i>, by Terry Root

Scale of Investigation and the Detection of Competition: An Example from the House Sparrow and House Finch Introductions in North America

I present an example that illustrates an evaluation of interspecific competition by combining investigations conducted on different scales. Results from investigations on different scales are interpreted with an assessment of the scales on which the competitors perceive habitat and each other. Interference competition between the introduced house sparrow (Passer domesticus) and native house finch (Carpodacus mexicanus) observed at backyard nest boxes for 4 yr in the western United States may have resulted in habitat segregation on a larger scale along a rural-urban habitat gradient. Competition may be occurring in the eastern states since the introduction of C. mexicanus in 1940. Christmas Bird Count data were examined for patterns in species abundance predicted by competition theory, using three scales of investigation: local (area 24 km in diameter), regional (area 250 km in diameter), and continental (between areas of sympatry and allopatry). The major findings suggest that competition has not influenced patterns of changes in the abundances of the competitors on a local scale in urban and rural habitats in the eastern United States or on a regional scale in the eastern and western United States. On a continental scale, the presence of C. mexicanus may have accelerated widespread declines in the density of P. domesticus in areas of sympatry across the United States, possibly because of the energetic demands of interference competition. The dissimilar behavior and foraging strategies of the competitors may permit coexistence in all habitats, such that the niche of P. domesticus is included in the niche of C. mexicanus. Differences in the perception of habitat by the competitors may preclude the development of habitat segregation along a rural-urban habitat gradient. A multi-scale approach to evaluating interspecific competition suggests that investigations on any single scale (e.g., a field experiment) may overemphasize or miss the importance of competition.

48th Annual Saskatchewan Christmas Bird Count – 1989

48th Annual Saskatchewan Christmas Bird Count – 1989

Reviews

Abstract Atlas of Wintering North American Birds—an Analysis of Christmas Bird Count Data. By Terry Root, 1988. University of Chicago Press, Chicago and London. 336 pp. Price hb £59.95, pb £33.95., by Les Underhill Handbook of North American Birds. Volumes 4 and 5: Diurnal Raptors Parts 1 and 2. Edited by R.S. Palmer, 1988. Yale University Press, New Haven and London. 433 and 465 pp. Price $30 and $50., by David C. Houston Ecological Change in the Uplands. Edited by M.B. Usher and D.B.A. Thompson, 1988. Special publications series of the British Ecological Society No 7. Blackwell Scientific Publications, Oxford. 449 pp., 3 colour, 1 b & w photographs. Price £35.00., by Roderick Leslie Oxford Surveys in Evolutionary Biology. V Edited by Paul H. Harvey and Linda Partridge, 1989. University Press, Oxford. 259 pp. Price £35.00., by Jeremy Greenwood Ecology and our Endangered Life Support Systems. By Eugene P. Odum, 1989. W.H. Freeman, Oxford and Sinauer Associates Inc., Sunderland, Mass. 283 pp., b/w photographs. Price £10.95., Tim Birkhead Raptors in the Modern World. Edited by B.-U. Meyburg & R.D. Chancellor, 1989. Proceedings of the III World Conference on Birds of Prey and Owls. WWGBP, Berlin, London and Paris. 612 pp. Price pb. £25.00., by Humphrey Crick Also received, full reviews of which appeared in BTO News. The Birds of Cambridgeshire. By P.M.M. Bircham, 1989. University Press, Cambridge. 280 pp., line drawings. Price £19.50. The Birds of Egypt. Edited by S.M. Goodman and P.L. Meininger, 1989. University Press, Oxford. 551 pp., 6 colour plates by Sherif M. Baha el Din. Price £70.00. Birds in Ireland. By C.D. Hutchinson, 1989. T & A.D. Poyser, Calton. 215 pp., b/w photographs, line drawings by J. Busby. Price £19.00. Rare Birds in Britain and Ireland. J.N. Dymond, P.A. Fraser & S.J.M. Gantlett, 1989. T & A.D. Poyser, Calton. 366 pp., many line drawings and maps. Price £19.00.

Stomach Contents of Dunlins Collected in Western Washington

The dunlin (Calidris alpina) is the most common sandpiper (Family Scolopacidae) that winters on the Pacific coast of North America (Bent 1927; Jewett et al. 1953; and Christmas Bird Count data published in American Birds during the last two decades). The food eaten by dunlins has been described from many locations throughout their distribution (see review in Cramp and Simmons 1983). In North America, food eaten by dunlins has been described from the Arctic (Holmes 1966; Baker 1977), at migratory stop-overs in the midwest (Brooks 1962) and British Columbia (Munro 1936), and at wintering areas in British Columbia (Fry 1980) and California (Recher 1964; Holmes 1966; Holmberg 1971). In addition, the food eaten by dunlins has been described from populations wintering in Grays Harbor (Smith and Mudd 1976; Kalinowski et al. 1982) and the San Juan Islands (Couch 1966) in Washington state. In this note, we describe the amounts and kinds of food eaten by dunlins at four estuaries in western Washington state; three in Puget Sound (Kennedy Creek delta, Nisqually River delta and Samish Bay) and one in Grays Harbor on the coast (Bowerman Basin). A description of these areas is provided by Brennan et al. (1985). We have previously summarized the food eaten by dunlins in western Washington in relation to the availability of prey and patterns of over-winter weight changes in dunlins (Buchanan et al. 1985). Our purpose here is to provide a complete listing of all food items obtained from our collections of dunlins.

Atlas of wintering North American birds: an analysis of Christmas bird count data

The of Wintering North American Birds represents the effects of thousands of people who have participated in the Christmas Bird Counts, an annual event sponsored since 1900 by the National Audubon Society. Unlike a conventional field guide, the Atlas doesn't show what birds look like, but rather tells where to find them in the winter months. Terry Root has used the data from the 1963-72 counts to provide the first large-scale biogeographical account of birds wintering in North America. Using sophisticated computer techniques, Root has translated the data into both traditional contour maps and innovative new maps that stimulate three dimensions. The maps show at a glance that, for example, the Baltimore Oriole winters primarily along the eastern seaboard, with the densest populations in Florida between Tallahassee and Gainesville and in North Carolina from Rocky Mount to the Croatan National Forest.

47th Annual Saskatchewan Christmas Bird Count – 1988

47th Annual Saskatchewan Christmas Bird Count – 1988

Audubon Christmas Bird Counts: Saskatchewan Tops in High Individual Numbers

Audubon Christmas Bird Counts: Saskatchewan Tops in High Individual Numbers

Atlas of the Wintering North American Birds: An Analysis of Christmas Bird Count Data, by Terry Root [Review

Atlas of the Wintering North American Birds: An Analysis of Christmas Bird Count Data, by Terry Root [Review

Population Ecology of Snowy Owls during Winter on the Great Plains of North America

We used data from Christmas Bird Counts (1961-1984) and road counts (1983-1985) to study the winter population ecology of Snowy Owls (Nyctea scandiaca) on the Great Plains of North America. Numbers of owls wintering between 45°N and 53°N increased with latitude. Owl abundance fluctuated from year to year, but fluctuations were not synchronous among count localities across the Great Plains. Owls first appeared on our study sites in southwestern Alberta in early November and individuals continued to arrive until late December or early January. Spring departure occurred during late February and early March, with a few owls remaining until late March. During midwinter, the mean number of owls censused on four study sites ranged from 1.3 to 5.8 owls/100 km in 1983-1984 and from 1.7 to 10.2 owls/100 km in 1984-1985. Although all age-sex classes were represented on the Alberta study areas in both winters, adult birds predominated. Both the Christmas Bird Count data and our fieldwork indicate that owl dispersion is patchy, and that the abundance of owls within patches may vary markedly from year to year. We recommend that future studies of winter raptor populations select multiple study sites to permit detection of patterns that occur over areas larger than a single study site.

46th Annual Saskatchewan Christmas Bird Count – 1987

46th Annual Saskatchewan Christmas Bird Count – 1987

A Summary of Saskatchewan Christmas Bird Counts: 1942–1986

A Summary of Saskatchewan Christmas Bird Counts: 1942–1986