Passerine Populations Research Articles

Pattern and Process in Grassland Bird Communities

Variations in abundance and distribution of bird species and avifaunal and community organization at regional, local, and within—plot levels were studied during 1969 and 1970 at a shortgrass prairie in Colorado and during 1970 at six additional International Biological Program (IBP) grassland sites. Patterns were generally not distinct at the regional level, although low rainfall sites tended to support fewer individuals and less biomass than more mesic sites. The dominant bird species were widely distributed, but 70% of all species recorded were present at only one of the seven sites. Local plot—to—plot differences, associated with grazing intensity, were considerably more important than the regional differences. Vegetational and avifaunal relationships of plots were determined by similarity—cluster analysis and by examination of vegetation structure. Variations in the number of breeding bird species, bird—species diversity, or equitability, were unrelated to the gradient of plots from tallgrass through shortgrass to desert, but standing crop biomass generally decreased along this gradient. The plots differed in the proportions of small, medium, and large—sized species. Shortgrass sites were generally dominated by omnivorous species; plots with a greater vegetation structure supported more carnivorous forms. Only carnivorous species occurred at the desert site. The effect of grazing on bird populations varied among the treatment plots at the various sites. In the Colorado shortgrass prairie, grazing season had a greater effect on community organization than grazing intensity. Patterns of variation were much more pronounced when single species rather than breeding faunas were considered. Grasshoppers, Lepidoptera larvae, beetles (especially curculionids, carabids, cerambycids, and scarabaeids), ants, and various seeds were the most important prey of the dominant bird species. Small sparrows and larks had generally similar diets. The diets of the larger meadowlarks and shorebirds differed from those of the former group and also differed from each other. The proportion of seeds and arthropods in the diets of Lark Buntings and Horned Larks varied considerably with time. Diurnal raptors, studied at only one site, were widely dispersed, occurring at densities and standing crops substantially less than those of small passerine populations. Owls preyed chiefly upon small mammals and insects, but the proportions of these food items in the diet differed significantly among the four species studied. The estimated energy intake of the breeding bird populations from April through August ranged from 1.01 to 2.33 kcal/m2; thus the energy flux through avian consumers in grasslands is apparently very small. In general, seeds decreased in importance as energy sources and arthropods increased in importance along a gradient from shortgrass through mixed grass to tallgrass plots. Secondary production estimated for six grazing—treatment plots ranged from 3.9 to 6.9 x 10—3 g/m2. The role of birds as consumers in the dynamics of grassland ecosystems is considered. It is suggested that birds may act as controllers of other elements of system function or may not be closely evolved into the functional framework of the ecosystem at all, existing on "excesses" in production.

Annual Testicular Cycle and Bill Color Change in the Eastern American Goldfinch

THE avian testicular cycle of seasonally-breeding birds consists of three phases: a regeneration phase when the tissues of the regressed gonad are reorganized, an acceleration phase characterized by development and growth of the testis, and a culmination phase in which the birds are responsive to certain environmental end stimuli that result in their nest building and gamete deposition (Marshall, 1961). Among wild populations of north-temperate passerines such a cycle has been demonstrated by histological examination of the testis in only a few early nesting species (e.g. Blanchard, 1941; Bullough, 1942; Blanchard and Erickson, 1949; Threadgold, 1956a, 1956b; Marshall and Coombs, 1957). Comparative study of the cycles of more species, particularly late nesters, is desirable. An analysis of seasonal changes in external characters that reflect seasonal changes in the gonad may provide an indirect method of determining the testis cycle in other species quickly. Bill color and postnuptial molt are well-suited for such an analysis as, in certain species, they are readily measurable from museum skins. Both characters have been correlated with changes in the titer of one or more of the gonadal hormones (Witschi and Fugo, 1940; Kobayashi, 1954a, 1954b, 1954c, 1958; Witschi, 1961; Engels, 1962), and Marshall (1961) associates the onset of the postnuptial molt with early regeneration phase and the termination of postnuptial molt with the onset of acceleration phase. The Eastern American Goldfinch, Spinus t. tristis, exhibits both a seasonal change in bill color and a late breeding season, and is principally single-brooded. Throughout the northern part of its range this goldfinch generally does not nest until July and later (Walkinshaw, 1938; Stokes, 1950; Nickell, 1951; Berger, 1968), and breeding behavior occurs seasonally later in this species than in other passerines nesting in northeastern North America. Field experiments conducted in Ithaca, New York revealed that not until late June or early July do female goldfinches begin gathering cotton artificially supplied them in their nesting habitat since early June, and they do not begin collecting thistle papus, a major natural nesting material, until July or, more rarely, in the last week of June (Mundinger, 1968). This correlates temporally with the onset of nest construction. In a study field in Ithaca only about 6 percent (2 of 35 nests) of all nests were initiated as early as the period mid-June to 1 July in 1963-65. Likewise the males do not engage in the defense of a geographically fixed area with flight song display and other territorial behaviors until nest construction begins or, in some cases, only a few days

Territorial Behavior: The Main Controlling Factor of a Local Song Sparrow Population

IT has been shown frequently that territories are compressible. It is also known that the average territory size for a species in a given area may be significantly influenced by local conditions. However, it has been doubted whether territories can ever shrink to a point beyond which they can become no smaller and thus set an upper limit to the numbers of that local population. This paper describes a situation in which a local passerine population, affected by favorable environmental conditions, could reach high densities for several consecutive years, and in which the upper limit was set by territorial behavior. It throws some light on how territorial behavior, combined with other factors, may regulate a given population. Conclusions are based in part on data already available; nevertheless, references are made to factors-food and nestling mortality-that have not yet been fully investigated. Song Sparrows (Melospiza melodia), the subjects of this study, defend a territory that normally includes mating, nesting, and feeding grounds, and thus falls into the territory category A of Nice (1941). This study, undertaken in order to find out the regulatory mechanism in a local Song Sparrow population, was started in the spring of 1960 and is still in progress. Some data concerning this population were also available for the period between 1957 and 1960 (R. Drent and G. van Tets, pers. comm.).

Notes on the Gapeworms (Nematoda: Syngamidae) of Galliform and Passeriform Birds in New York State

The importance of the gapeworm (Syngamus trachea) as a parasite of young gallinaceous birds is common knowledge. Since Klee (1903) first associated an outbreak of gapeworms in pheasants with the high incidence of the parasites in a nearby rookery, considerable interest in the possibility of cross-infection between the gapeworms of poultry and those of perching birds has been evidenced. A number of British investigators have surveyed passerine populations for gapeworms (Lewis, 1925, 1926; Elton & Buckland, 1928; Morgan, 1931; Campbell, 1935), and artificial transmission of syngami from starlings, rooks, blackbirds (Turdus merula) to chickens has been accomplished (Leiper, 1926; Taylor, 1928; Rice, 1929; Clapham, 1934, 1935; Morgan & Clapham, 1934). In this hemisphere Cram (1930) has reported S. trachea from some passeriforms in Alaska; Walker (1886), Manter & Pinto (1928), and Webster (1943) have recorded observations on gapeworms in robins; Cuvillier (1932) artificially transmitted gapeworms of pheasant origin to the house sparrow, and Ripple (1941) infected chickens with gapeworms of robin origin. No extensive surveys of passeriform birds for information on the occurrence of gapeworms have been made in this country to our knowledge. Almost every morphological character proposed for the division of the genus into species (Leiper, 1913; Chapin, 1925) has been questioned (Chapin, 1925; Lewis, 1928). There has been nt treatment of all the avian parasites of the genus since Cram's (1927) which could not consider the status of S. merulae Baylis, 1926, or the taxonomic problems indicated by the work of Lewis (1928). It is the purpose of this article to record observations on the gapeworms we have encountered in galliform and passeriform birds and to discuss the identity of the parasites.

Avian Hosts for Malaria Research

Previous articleNext article No AccessAvian Hosts for Malaria ResearchFruma WolfsonFruma Wolfson Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 16, Number 4Dec., 1941 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/394639 Views: 3Total views on this site Citations: 3Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:K. L. Durrant, P. P. Marra, S. M. Fallon, G. J. Colbeck, H. L. Gibbs, K. A. Hobson, D. R. Norris, B. Bernik, V. L. Lloyd, R. C. Fleischer Parasite assemblages distinguish populations of a migratory passerine on its breeding grounds, Journal of Zoology 274, no.44 (Jan 2008): 318–326.https://doi.org/10.1111/j.1469-7998.2007.00387.xGeoffrey Lapage A list of the parasitic Protozoa, Helminths and Arthropoda recorded from species of the Family Anatidae (Ducks, Geese and Swans), Parasitology 51, no.1-21-2 (Apr 2009): 1.https://doi.org/10.1017/S0031182000068517Warner W. Carlson Recent Advances in the Search for Synthetic Antimalarials**From the Department of Research in Pure Chemistry, Mellon Institute of Industrial Research, Pittsburgh, Pa.**This is the seventh of a series of review articles. Part of the cost of publication of this series of review articles is paid from the treasury of the National Conference on Pharmaceutical Research., Journal of the American Pharmaceutical Association (Scientific ed.) 33, no.44 (Apr 1944): 97–106.https://doi.org/10.1002/jps.3030330401