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At least 181 records · Page 10Linked to original sources
USGS1999

A taxonomic study of crested caracaras (Falconidae)

The taxonomic status of the crested caracaras (Caracara spp., Falconidae) has been unsettled for many years. Current sources such as the AOU Check-list recognize a single species that includes three taxa formerly considered distinct, citing observations by Hellmayr and Conover (1949) on two specimens considered to be intermediate. We studied plumage characters and measurements of over 392 museum specimens and found no evidence of clinal change between the northern and southern continental populations. Sixteen specimens from localities near the Amazon River where these two populations sporadically meet exhibit a mosaic of plumage elements from both forms. Measurements of wing chord, bill length, and bill depth indicate that size is positively correlated with latitude north and south of the equator and that females are larger than males in the northern population. These populations do not meet in western South America. We conclude that three biological species can be identified in the crested caracaras: the insular Guadalupe Caracara (Caracara lutosus); and two continental species, Northern (C. cheriway) and Southern caracara (C. plancus), neither of which shows subspecific variation.

The Wilson Bulletin↗
USGS2001

Kirtland's warbler diet as determined through fecal analysis

The endangered Kirtland's Warbler (Dendroica kirtlandii) nests primarily in large (>32 ha) stands of young (5- to 25-yr-old) jack pine (Pinus banksiana) which grow on Grayling sand soil. These specific habitat requirements restrict the Kirtland's Warbler breeding range to only 13-16 counties in the northern lower peninsula of Michigan. Although the nature of the species' affinity for this habitat is poorly understood, one theory suggests that higher prey abundance in young jack pine may play a role. To explore further the hypothesis that Kirtland's Warblers choose nesting habitat due to prey abundance, a more thorough knowledge of the warblers' diet is needed. To better understand the diet, we identified arthropod and plant fragments found in 202 Kirtland's Warbler fecal samples, collected from June to September, 1995-1997. The major food items recorded were spittlebugs and aphids (Homoptera; found in 61% of all samples), ants and wasps (Hymenoptera; 45%), blueberry (Vaccinium augustifolium; 42%), beetles (Coleoptera; 25%), and moth larvae (Lepidoptera; 22%).

The Wilson Bulletin↗
USGS1996

Radio telemetry documents 24-hour feeding activity of wintering lesser scaup

We used radio telemetry to record 198 h of feeding behavior of five Lesser Scaup (Aythya affinis) on the Indiana Harbor Canal in northwestern Indiana during January and February 1994. Lesser Scaup fed for short periods of time intermittently during each 24-h period. Lesser Scaup fed a total of 96 min during the day and 226 min during the night. They fed more between sunset and midnight (31.9% of the period, P = 0.003) than between sunrise and noon (11.6%) or noon and sunset (19.5%); time spent feeding between midnight and sunrise (26.3%) did not differ from other times of day. Mean dive duration (22.9 ± 0.64 sec) did not vary by time of day ( P = 0.186-0.744). These results are the first 24-h feeding activity reported for individually marked Lesser Scaup.

The Wilson Bulletin↗
USGS1983

Nesting biology of laughing gulls in relation to agricultural chemicals in south Texas USA 1978-1981

Various aspects of the breeding biology of Laughing Gulls ( Larus atricilla ) have been studied extensively in Florida (Dinsmore and Schreiber 1974, Schreiber et al. 1979, Schreiber and Schreiber 1980), New Jersey (Bongiorno 1970, Burger and Beer 1976, Burger 1976, Montevecchi 1978), and Massachusetts (Noble and Wurm 1943), but little is known of their yearly fledging success in Texas or elsewhere. The Laughing Gull is a common colonial nester along most of the Texas coast, second only to the Cattle Egret ( Bubulcus ibis ) in breeding abundance; however, the Laughing Gull may be threatened in Texas because of suspected declines at certain traditional nesting locales (Blacklock et al. 1979). Since Laughing Gulls often nest in proximity to agricultural and industrial areas, we were concerned that environmental pollutants might be adversely affecting productivity. In 1978-1981 we conducted studies along the south Texas coast to learn more about the nesting ecology of Laughing Gulls and to evaluate the effects of environmental contaminants on reproduction.

Texas↗
USGS1998

The effects of mesquite invasion on a southeastern Arizona grassland bird community

We determined which vegetal features influenced the distribution and abundance of grassland birds at the Buenos Aires National Wildlife Refuge, Arizona. The density and distribution of mesquite (Prosopis velutina) exerted the strongest influence on the grassland bird community. Abundances of Pyrrhuloxia (Cardinalis sinuatus; r2 = 0.363, P = 0.025) and Lucy's Warbler (Vermivora luciae; r2 = 0.348, P = 0.04), and total abundance of birds (r2 = 0.358, P = 0.04) were positively correlated with increasing density of mesquite (Prosopis velutina), whereas abundance of Cactus Wren (Campylorhynchus brunneicapillus; r2 = 0.452, P = 0.02) was negatively correlated with increasing mesquite density. Abundance of Loggerhead Shrike (Lanius ludovicianus; r2 = 0.693, P < 0.001) was positively correlated with an increasing patchiness of mesquite. Shrub-dependent bird species dominated the community, accounting for 12 of the 18 species and 557 of the 815 individuals detected. Species relying on extensive areas of open grassland were largely absent from the study area, perhaps a result of the recent invasion of mesquite into this semi-desert grassland.

The Wilson Bulletin↗
USGS1998

Landscape and fine scale habitat associations of the Loggerhead Shrike

This study was conducted to determine landscape and fine-scale vegetative variables associated with breeding Loggerhead Shrikes (Lanius ludovicianus) on Fort Riley Military Reservation, Kansas. Because Fort Riley is an Army training site, the influences of training disturbance to the vegetation, and range management practices on bird habitat patterns were also investigated. Breeding birds were surveyed in 1995 and 1996 using point counts. Survey plots were identified, a priori, at the landscape scale as either grassland, savannah, or woodland edge according to cover by woody vegetation. In 1996, fine-scale habitat at survey points and at bird use sites was measured and a principal components analysis used to characterize the fine-scale herbaceous vegetation structure. A military disturbance index was developed to quantify the severity of vehicle disturbance to the vegetation at survey and bird use sites. Shrikes were associated with savannah habitat at the landscape scale. Sites used by Loggerhead Shrikes were characterized at the fine-scale by tall, sparse, structurally heterogeneous herbaceous vegetation with high standing dead plant cover and low litter cover. At the fine-scale, tree and shrub density did not differ between sites used and not used by shrikes. Used sites did not differ from survey sites with respect to military training disturbance, hay harvest, or the number of years since a site was last burned. Our results in this study suggest that the shifting mosaic of vegetation on Fort Riley resulting from training and range management practices maintains adequate habitat for breeding shrikes.

The Wilson Bulletin↗
USGS1998

A description of the first live Poouli captured

The Poouli (Melamprosops phaeosoma) is an endangered Hawaiian honeycreeper found only on Maui, Hawaii. It was rare at the time of its discovery in 1973, but by 1997 was on the brink of extinction with fewer than six individuals left. Two specimens were collected for the description of the species, but both proved to be immature by comparison with a pair of adults at a nest. Until 1997 no Poouli had ever been captured alive, and consequently descriptions of adult Poouli were produced from field observations. In 1997, I captured an adult male Poouli which is described here for the first time. Detailed comparisons of the plumage of this adult with that of an immature specimen and previous descriptions of the species are discussed in this paper, as are differences in plumage between adult and immature males and females that may aid the sexing and ageing of birds in the field.

The Wilson Bulletin↗
USGS1998

Observations of geese foraging for clam shells during spring on the Yukon-Kuskokwim Delta, Alaska

We studied the behavior of geese on exposed river ice during spring on the Yukon-Kuskokwim Delta. The predominant behavior while on the ice for both sexes was foraging; however, females foraged more than males. Visual inspection of the ice revealed no potential plant or animal food items. However, numerous small (<20 mm) clam shells ( Macoma balthica ) and pieces of shell were noted. It appeared that geese were foraging on empty clam shells. This potential source of calcium was available to breeding geese just prior to egg formation and geese likely stored this calcium in the form of medullary bone for use during egg formation.

Alaska↗
USGS1999

Patterns of variation in size and composition of Greater Scaup eggs: Are they related?

We studied egg size variation of Greater Scaup ( Aythya marila ) nesting on the Yukon-Kuskokwim Delta, Alaska from 1991-1996. Mean egg size was 64.36±0.03 (SE) ml. Egg size did not vary with clutch size or serve as an index of body size. There was less than 2% overlap in total clutch volumes for clutches of different sizes indicating that phenotypic clutch size-egg size trade-offs are not occurring among individuals. At the population level, Greater Scaup have less variation in egg size than other species of waterfowl. The proportion of variation in egg size caused by differences among females was 0.20, caused by differences within females among years was 0.25, and caused by differences within females and years (i.e., clutches) was 0.56. The proportion of egg lipid decreased with increasing egg size while the proportion of egg protein increased with egg size. Thus, Greater Scaup appear to trade-off lipid for protein as egg size increases. The proportion of variation that was due to differences among females in total egg protein was 0.79 and in total egg lipid was 0.49. We conclude that in the absence of a fitness trade-off between clutch size and egg size, selection has reduced among-individual variation in egg size.

Alaska↗
USGS1999

Do mammalian nest predators follow human scent trails in the shortgrass prairie?

Nest predation, the major cause of nest failure in passerines, has exerted a strong influence on the evolution of life history traits of birds. Because human disturbance during nest monitoring may alter predation rates, we investigated whether human scent affected the survival of artificial ground nests in shortgrass prairie. Our experiment consisted of two treatments, one in which there was no attempt to mask human scent along travel routes between artificial nests, and one in which we masked human scent with cow manure, a scent familiar to mammalian predators in the study area. We found no evidence that human scent influenced predation rates, nor that mammalian predators followed human trails between nests. We conclude that scent trails made by investigators do not result in lower nesting success of passerines of the shortgrass prairie where vegetation trampling is minimal, mammalian predators predominate, and avian predators are rare.

The Wilson Bulletin↗
USGS1999

The response of a Kansas winter bird community to weather, photoperiod, and year

We conducted a bird census along the same route nearly each week for 14 winters (194 censuses), and compared the mean number of species per station and the total number of species recorded on the census with the length of photoperiod and weather variables. We found significant differences among winters for both indicators of species richness. This result is consistent with previous studies in which abundance of food was measured in the same general area. Both indicators of species richness were negatively associated with the number of days after 1 November. This result is consistent with the hypothesis that wintering species dependent on nonrenewed food resources lose individuals to mortality or emigration. Further, there was a positive relationship between photoperiod and both indicators of species richness. This result is consistent with the hypothesis that the detection of individuals in the early morning hours increases with the amount of daylight they have available for foraging and social behaviors. Wind speed and temperature had negative and positive relationships, respectively, to species richness. The number of species per station was greatest on days when the ground was covered with dew and least on days when snow depth was more than 15 cm. When the 'winters' were divided into four 30-day 'quarters', most of the 61 species were recorded with equal frequency in each quarter. Eight species were detected less frequently at the end of winter than in the beginning. Four species exhibited the reverse pattern. Two species were recorded more frequently at the beginning and at the end of the winter than during the middle. Temperature, wind, photoperiod, successive winter day, year, and species-specific evolutionary history all affect winter bird species richness.

The Wilson Bulletin↗
USGS1999

Effects of wind turbines on upland nesting birds in Conservation Reserve Program grasslands

Grassland passerines were surveyed during summer 1995 on the Buffalo Ridge Wind Resource Area in southwestern Minnesota to determine the relative influence of wind turbines on overall densities of upland nesting birds in Conservation Reserve Program (CRP) grasslands. Birds were surveyed along 40 m fixed width transects that were placed along wind turbine strings within three CRP fields and in three CRP fields without turbines. Conservation Reserve Program grasslands without turbines and areas located 180 m from turbines supported higher densities (261.0-312.5 males/100 ha) of grassland birds than areas within 80 m of turbines (58.2-128.0 males/100 ha). Human disturbance, turbine noise, and physical movements of turbines during operation may have disturbed nesting birds. We recommend that wind turbines be placed within cropland habitats that support lower densities of grassland passerines than those found in CRP grasslands.

The Wilson Bulletin↗
USGS2003

Survival and habitat of Ruffed Grouse nests in northern Michigan

Effective management of Ruffed Grouse (Bonasa umbellus) populations requires a full understanding of chick production. Previous reports of nest survival for Ruffed Grouse are biased because they did not account for successful nests being more likely to be found, and the role of habitat quality in determining nest survival is unknown. We determined survival rates of Ruffed Grouse nests in northern lower Michigan using the less biased Mayfield estimator, defined differences between first and second nests, and compared the local habitat characteristics of successful and unsuccessful nests. Median hatching dates were 10 June for first nests (n = 34) and 1 July for second nests (n = 6). First nests had a lower survival rate (0.442, 95% CI = 0.270-0.716), a higher mean clutch size (12.7 eggs ?? 0.3 SE), and higher egg hatching rate (0.960, 95% CI = 0.900-0.997) than did second nests (nest survival = 0.788, 95% CI = 0.491-1.00; clutch size = 7.3 eggs ?? 0.3 SE; and hatching rate = 0.826, 95% CI = 0.718-0.925). Nest survival, annual production (3.4 hatchling females/adult female, 95% CI = 2.3-5.0), and fall recruitment (1.0 juvenile females/adult female, 95% CI = 0.3-2.4) were less than previously reported estimates. Habitat characteristics at nest sites varied widely and did not differ appreciably between successful and unsuccessful nests.

The Wilson Bulletin↗
USGS1983

Vegetation characteristics important to common songbirds in east Texas

Multivariate studies of breeding bird communities have used principal component analysis (PCA) or several-group (three or more groups) discriminant function analysis (DFA) to ordinate bird species on vegetational continua (Cody 1968, James 1971, Whitmore 1975). In community studies, high resolution of habitat requirements for individual species is not always possible with either PCA or several-group DFA. When habitat characteristics of several species are examined with a DFA the resultant axes optimally discriminate among all species simultaneously. Hence, the characteristics assigned to a particular species reflect in part the presence of other species in the analyses. A better resolution of each species' habitat requirements may be obtained from a two-group DFA, wherein habitats selected by a species are discriminated from all other available habitats. Analyses using two-group DFAs to compare habitat used by a species with habitat unused by the same species have the potential to provide an optimal frame of reference from which to examine habitat variables (Martinka 1972, Conner and Adkisson 1976, Whitmore 1981). Mathematically (DFA) it is possible to maximally separate two groups of multivariate observations with a single axis (Harner and whitmore 1977). A line drawn in three or n-dimensional space can easily be positioned to intersect two multivariate means (centroids). If three or more centroids for species are analyzed simultaneously, a single line can no longer intersect all centroids unless a perfectly linear relationship exists for the species being examined. The probability of such an occurrence is extremely low. Thus, a high degree of resolution can be realized when a two-group DFA is used to determine habitat parameters important to individual species. We have used two-group DFA to identify vegetation variable important to 12 common species of songbirds in East Texas.

Texas↗
USGS1985

Interspecific relationships between American coots and waterfowl during fall migration

Interactions between American Coots ( Fulica americana ) and water-fowl during the breeding season are well-documented (Ryder 1959, Nudds 1981). Ducks and coots use similar nesting, feeding, brooding, and loafing sites during the breeding season (Munro 1939, Sooter 1945, Ryder 1959). Coots create potential nest sites, repulse predators, provide predation buffers for ducks (Sooter 1945; Ryder 1958, 1959), and may also destroy eggs and young of other marsh-nesting birds (Munro 1937, Burger 1973, McNicholl 1975). Coots, ducks, and swans often feed cooperatively (Ryder 1959, Anderson 1974, Ryan 1981); and American Wigeon ( Anas americana ) and Gadwell ( ) may rob feeding coots (Knapton and Knudsen 1978, Ryan 1981). Interspecies aggression between coots and waterfowl usually occurs when ducks approach coot nests or broods (Ryan and Dinsmore 1979). Despite these interactions, the numbers of duck broods produced in areas in Utah with nesting coots and in areas where coots have been removed were similar (Ryder 1958, 1961). Densities of coots and ducks, and brood counts of coots and ducks for a 26-year period in Saskatchewan also indicated no significant relationship between numbers of coots and waterfowl (Nudds 1981). Coots and waterfowl from large areas of breeding habitat concentrate on smaller areas during the nonbreeding season (Weller 1975:102). These species may also change diets and habitats during migration and while wintering (Weller 1975). This study documents associations between waterfowl and coots during fall migration and examines feeding and behavioral interactions between coots and waterfowl in mixed flocks. Specifically, we (1) describe temporal and spatial overlap among migrations of coots and waterfowl, (2) present behavioral interactions among species, and (3) document food habits of birds feeding sympatrically during fall migration in Oklahoma.

The Wilson Bulletin↗
USGS1985

Influence of various land uses on windbreak selection by nesting Mississippi kites

Contemporary land-use practices have dramatically altered breeding habitats of birds of prey (Cramp, pp. 9-11 in World Conf. Birds of Prey, R. D. Chancellor, ed., ICPB, London, England, 1977). Some land uses appear to influence strongly both the nesting activity (White, Trans. North Am. Wild. Nat. Resour. Conf. 39:301-312, 1974) and abundance (Olendorff and Stoddart, pp. 44-48 in Management of Raptors, F. N. Jamerstrom, B. E. Harrel, and R. R. Olendorff, eds., Proc. Conf. Raptor Conserv. Tech., Raptor Rep. 2, Fort Collins, Colorado, 1974) of raptors. The Mississippi Kite ( Ictinia mississippiensis ) is a locally common raptor of the south-central plains of North America. In the prairie grasslands of western Oklahoma and south-western Kansas, kites commonly nest in tree plantings designed as windbreaks, irrespective of windbreak width, age, or tree species compositions (Parker, Ph.D. Diss., Univ. Kansas, Lawrence, Kansas, 1974; Love and Knopf, Proc. Ann. Meet. For. Comm. Great Plains Agric. Counc. 30:69-77, 1978). Much of the potential nesting habitat within this region, however, is not used by kits (Parker and Ogden, Am. Birds 33:119-129, 1979). In this paper, we assess the potential influence of various land-use practices on windbreak selection by nesting Mississippi Kites.

The Wilson Bulletin↗