Blue-winged Teal Research Articles

Timing of Nest Searches for Upland Nesting Waterfowl

Searches for duck nests should maximize the probability of locating nests, while minimizing the possibility of causing nest abandonment. Thus, we collected nest attendance data for 44 mallard (Anas platyrhynchos), 13 blue-winged teal (A. discors), 12 lesser scaup (Aythya affinis), 8 northern shoveler (Anas clypeata), 6 gadwall (A. strepera), and 4 green-winged teal (A. crecca) females to determine the optimal times of day to search for active nests. Females of most species attended nests from 0800 to 1400 central standard time (CST). The overall probability of nest attendance during this time was 91.4 ± 2.6 (SE) %. Consequently, nest searches for upland nesting waterfowl should be initiated after 0800 and should be terminated by 1400 CST

Factors affecting egg viability and incubation time in prairie dabbling ducks

I determined hatching success for 328 dabbling duck (Anas spp.) eggs that were experimentally subjected to varying lengths of preincubation delay and then artificially incubated. Hatchability declined as unincubated eggs were exposed to longer preincubation delays. This effect was more pronounced at higher ambient temperatures and later in the nesting season, but did not vary with egg size or among duck species. These results are largely consistent with observed patterns of clutch-size variation among prairie-nesting waterfowl. Clutch size may be smaller later in the year and at lower latitudes owing to the negative effects of date and temperature on the ability of eggs to withstand preincubation delay. The timing of embryo mortality was bimodal, with peaks occurring during early development (<6 d) and just before hatching (>22 d); however, only early mortality was affected by preincubation delay. Eggs lost up to 2.6% of their initial mass as water vapor during preincubation delay, but the amount of water loss did not affect hatching success. Eggs subjected to preincubation delay required about 1 additional day to hatch. Incubation time was related to egg size in northern shovelers (Anas clypeata) and in all species combined, but not in blue-winged teal (Anas discors) or mallards (Anasplatyrhynchos). These data provide only weak support for the hypothesis that large eggs are costly because they take longer to hatch.

Factors affecting waterfowl use of constructed wetlands in northwestern Minnesota

Waterfowl pair and brood use of constructed wetlands was evaluated during 1980–81 on 4 Wildlife Management Areas in northwestern Minnesota. Weekly ground counts of waterfowl were made at each of 109 wetlands during the April to mid-July nesting season and correlated with physical, vegetative, and limnological characteristics. The number of pairs of the 10 most common waterfowl species using the wetlands was 338 in 1980 and 239 in 1981, of which blue-winged teal (Anas discors) made up nearly half. Ducks used the constructed wetlands primarily during late May and early June. Eighteen habitat components were significantly correlated with pair numbers of 1 or more duck species. Wetlands with larger surface area and longer shoreline length had greater pair use, by every duck species except gadwall (Anas strepera). Other physical parameters correlated with duck use included distance to nearby large impoundments, wetland density, and distance to nearest constructed wetland.

Food Habits of Selected Dabbling Ducks Wintering in Yucatan, Mexico

In Mexico, even basic data on waterfowl feeding ecology are lacking. Consequently, we studied the food habits of blue-winged teal (Anas discors), northern shovelers (A. clypeata), and northern pintails (A. acuta) in coastal wetlands of Yucatan, Mexico from October 1987 to March 1988. Blue-winged teal and northern shovelers consumed primarily gastropods (≥98% aggregate volume) from October to 15 December. Teal and northern pintails consumed primarily tubercles of muskgrass (Chara sp.; >96%) after 15 December

A Modelling Strategy for Recovery Data from Birds Ringed as Nestlings

In this paper we propose a strategy for analysing recovery data from birds ringed as nestlings. The approach advocated starts with a global model, involving calendar year dependence of both reporting and first-year survival rates, and age-dependence of survival rates for older birds. Likelihood ratio tests are then used to choose between a range of submodels. The strategy is illustrated through application to three data sets, on mallards, herring gulls, and blue-winged teal. The effect of age-dependence operating also on reporting rates is examined through matched simulations, since a model with age-dependent reporting rates cannot be fitted directly. This reveals an underestimation of the first-year survival rates, when the probability of recovery for first-year birds is greater than that for older birds. It is argued that this bias may not be serious and indeed may be allowed for in practice. For mallards and teal, comparisons are drawn with the results from other models that additionally analyse recoveries of birds ringed as adults; the same general conclusions are reached.

The Significance of Body Mass to Female Dabbling Ducks during Late Incubation

Allocation of nutrients to eggs and to costs of incubation in waterfowl may be constrained by the need to maintain nutrient reserves to complete incubation. This hypothesis predicts that body mass of successfully nesting females is greater than that of unsuccessful females. This prediction was tested by comparing the body masses of successful and unsuccessful female dabbling ducks captured late in incubation. Successful Mallards (Anas platyrhynchos) and Northern Shovelers (A. clypeata) were significantly heavier than unsuccessful females, and this process constituted evidence of directional selection. Body masses of successful and unsuccessful Blue-winged Teal (A. discors) did not differ. We calculated residual (observed-predicted) body masses using published regression equations relating mass and stage of incubation in independent samples of shovelers and teal to test whether successful females in our study were relatively heavy. Residual body mass estimates of successful shovelers were significantly greater than those of unsuccessful ones; in teal, no relationship was found. Nutrient reserves may influence successful incubation in some prairie-nesting ducks and the relationship may be stronger in larger species that are most capable of storing nutrients.

Susceptibility of blue-winged teal, gadwall, and lesser scaup ducklings to experimental infection with Streptocara crassicauda

Blue-winged teal, gadwall, and lesser scaup ducklings were exposed experimentally to identical doses of Streptocara crassicauda larvae. The heaviest infections developed in the teal. Gadwall were also highly susceptible and infection levels were generally similar to those in teal. Lesser scaup developed comparatively light infections. Lesions were restricted to the gizzard and occurred in the softer areas of the lining under the tendinous surfaces. Nematodes were generally confined to the lesions in scaup, but not in teal or gadwall. In these two species, they were also found elsewhere under the softer portions of the lining and, to a lesser extent, under the grinding plates. Teal and gadwall developed more and larger lesions because of the greater number of nematodes that established. When corrected for worm number, no difference in lesion size was found among the three species.

Avian Paramyxoviruses from Migrating and Resident Ducks in Coastal Louisiana

Cloacal and tracheal swabs were collected from 1,409 hunter-killed ducks in Cameron Parish, Louisiana, during the 1986 and 1987 waterfowl seasons. Thirty avian paramyxoviruses (PMV's) were isolated from 605 blue-winged teal (Anas discors), 75 mottled ducks (A. fulvigula), 375 gadwalls (A. strepera), 334 green-winged teal (A. crecca), and 20 mallards (A. platyrhynchos). Prevalence of PMV decreased (P = 0.042) from September (4%) through November (2%) to December and January (1%). Juveniles had a higher prevalence of PMV (P less than 0.0001) than adults. An isolate from resident mottled ducks documents transmission of PMV's on the coastal wintering areas of Louisiana. The four serotypes isolated, PMV-1, PMV-4, PMV-6, and PMV-8, were typical of PMV's commonly associated with free-living waterfowl.

Trace elements in migrating blue-winged teal: Seasonal-, sex- and age-class variations

Migrating blue-winged teal (Anas discors) were collected in April (n = 48) and September (n = 53) 1983 on the Southern High Plains Region of Texas. Liver and breast muscle were analyzed for 14 trace elements, and tibias were analyzed for Pb content. Data were analyzed statistically to determine differences in concentrations between seasons, sexes and age classes. Concentrations of B, Cr, Mo, Pb, Zn, Hg, Cu and Se in livers, and of B, Cu, Mo, Pb and Se in muscle, were greater in autumn- than in spring-migrating blue-winged teal. Lead concentrations in livers, muscles and tibias reflected apparently low-level, chronic, oral exposure to this metal. Concentrations of Cr, Ni, Pb and Cu in livers, and of Cr and Zn in muscle, were greater in males than females. Greater Cd concentrations in livers of adults than in juveniles were attributed to the persistence of Cd in tissues. The trace metal concentrations we observed in our blue-winged teal samples generally were not sufficiently high to produce adverse physiological or reproductive effects.

Avian Influenza Viruses from Migratory and Resident Ducks of Coastal Louisiana

Cloacal and tracheal swabs were collected from 1389 hunter-killed ducks in Cameron Parish, Louisiana, during the 1986 and 1987 waterfowl seasons. Twenty-eight avian influenza viruses (AIVs) were isolated from 605 blue-winged teal (Anas discors), 75 mottled ducks (A. fulvigula), 375 gadwalls (A. stepera) and 334 green-winged teal (A. crecca). Prevalence estimates of AIV in ducks sampled during September, November, and December through January were 3.1%, 2.0%, and 0.4%, respectively. Differences in prevalence were detected by season (P = 0.044) and age class (P = 0.036). Two isolations from resident mottled ducks document transmission of AIV on these wintering areas. Much subtype diversity was present, with nine of 13 hemagglutinin (HA) and nine of nine neuraminidase (NA) subtypes recovered. Predominant HA and NA subtypes were typical of AIVs commonly associated with waterfowl. Results indicate that AIVs are transmitted in the wintering areas, and, although prevalence is low, these viruses continue to circulate within these duck populations during winter.

Levinseniella yucatanensis n. sp. (Digenea: Microphallidae) and Other Parasites from the Blue-Winged Teal, Anas discors, from Yucatan, Mexico

Levinseniella yucatanensis n. sp. from the ceca of the blue-winged teal (Anas discors L.) differs from Levinseniella byrdi Heard, 1968, in the transverse spination of the anterior third of the body, 4 very small pockets in a glandular copulatory pouch, and the minute size of the body (< 600 gtm long). Other parasites from the blue-winged teal from Yucatan were: Trichobilharzia physellae Talbot, 1936; Echinoparyphium aconiatium Dietz, 1901; echinostomes (immature); Cloacotaenia megalops Nietz, 1829; Epomidiostomum uncinatum Lundahl, 1848; and Trinoton querquedulae L., 1758. The purpose of this paper is to describe a new member of the trematode family Microphallidae and to give data for 6 other species of parasites found in 10 blue-winged teal (Anas discors) collected in 1977 near Sisal, Yucatan, Mexico. MATERIALS AND METHODS Ten birds were shot in a saltmarsh lagoon 17-19 February 1977 and examined within 6 hr. Trematodes and cestodes were fixed unflattened in AFA and nematodes were fixed in 70% ethanol. Trematodes and cestodes were stained with Harris' hematoxylin or Semichon's carmine, dehydrated, and mounted in permount. Nematodes were cleared in lactophenol, and ectoparasites were cleared and mounted in Hoyer's medium. Measurements are given in ,um with ranges followed by the mean in parentheses. Drawings were made with the aid of a camera lucida.

Use of Earthen Islands by Nesting Ducks in North Dakota

We studied duck nests on 1 natural island and 21 constructed islands on the J. Clark Salyer National Wildlife Refuge (NWR), North Dakota in 1982-83. We found 286 nests of 7 species; mallard (Anas platyrhynchos), gadwall (A. strepera), and blue-winged teal (A. discors) represented >90% of all nests. The mean annual nest density was 8.7/ha with a mean Mayfield-adjusted nest success of 24%. Islands on which the most ducks were produced were 335-1,085 m offshore, surrounded by 150-200 m of open water, and contained tall, dense, brush or forb cover. Three islands with these characteristics held 37% of the nests and produced 55% of total ducklings. Although gadwalls and mallards formed dense nesting concentrations, bluewinged teal showed little nest-clumping behavior or nest cover preferences. Other factors influencing production rates included a seasonal decline in nest success and between-year variability. To be cost effective, islands located in wetlands with large mink (Mustela vison) and raccoon (Procyon lotor) populations should have adequate spatial isolation and/or predator control. J. WILDL. MANAGE. 53(2):411-417 Recruitment rates of ducks in the intensively farmed portion of the prairie pothole region are low (Cowardin et al. 1983) because of declining habitat and concentration of nest and female duck predators (Sargeant and Arnold 1984). Recent efforts to improve waterfowl production have centered on restricting predator access (e.g., electric fencing) (Lokemoen et al. 1982), cover management (e.g., dense nesting cover [DNC], burning, mowing), and construction or improvement of nesting islands. Some island habitats attract large populations of nesting ducks (Drewien and Fredrickson 1970, Browne et al. 1983) and have high nest success due to the reduced impacts of predators (Duebbert 1966, Vermeer 1968). Artificial islands can potentially produce more ducks/unit area than other habitats, but they are expensive to construct and maintain, and in many areas may not improve nest success enough to justify costs (Lokemoen 1985). Several authors have made recommendations concerning island construction (Hammond and Mann 1956, Duebbert 1982), but only recently have they been tested quantitatively (Giroux 1981, Carlsen 1984). Our objectives were to quantitatively assess selected environmental variables that best explain duck nesting use and production for a group of earthen islands, and to recommend ways to improve waterfowl production on islands. We thank R. A. Stomstad and T. B. Brokke for field assistance. We are grateful to D. Walls for logistic support and personnel to assist with field work. Additional support was provided by the University of North Dakota Biology Department and the Institute for Ecological Studies. Special thanks are extended to R. D. Sayler who provided helpful advice and reviewed the manuscript. The final draft benefited from comments made by R. C. Drewein and H. F. Duebbert. This publication is Contribution 8 of the Institute for Ecological Studies, University of North Dakota.

Ecological studies on Cyathocotyle bushiensis (Digenea) and Sphaeridiotrema globulus (Digenea), possible pathogens of dabbling ducks in southern Québec.

Over the past 20 yr, recurrent late-summer mortality of dabbling ducks in southern Québec has been attributed to the digenean parasite Cyathocotyle bushiensis. This study attempted to determine whether this parasite was still implicated in the epizootics, and examined aspects of the ecology of the parasite in the definitive host. Comparison of prevalence and mean intensity of infection of all species of Digenea between salvaged carcasses and hunter-shot ducks revealed that C. bushiensis and a second digenean Sphaeridiotrema globulus were both significantly more prevalent in salvaged ducks. Mean intensity of infection was consistently higher for S. globulus in the salvaged carcasses than in hunter-shot ducks. These data provide strong circumstantial support for the hypothesis that C. bushiensis continues to contribute to the annual mortality, but also strongly suggest that S. globulus may be involved. Comparison of the relative numbers of each species of duck between the salvaged carcass sample and the hunter-shot sample revealed that blue-winged teal (Anas discors) occurred significantly more frequently in the salvaged carcass sample whereas wood ducks (Aix sponsa) were common in the hunter-shot sample but were never found in the salvaged carcass sample. A comparison of susceptibility to experimental infection with C. bushiensis revealed that mallards (Anas platyrhynchos), black ducks (Anas rubripes), blue-winged teal, pintail (Anas acuta) and lesser scaup (Aythya affinis) had similar susceptibilities but that wood ducks were significantly less susceptible to infection. Experimental infections also showed that age of mallards significantly influenced the number of parasites obtained 7 days postinfection; ducklings were most heavily infected. Significant differences were detected in the gross pathology caused by C. bushiensis among duck species. Data obtained from sentinel ducks placed in the field for 24 hr revealed that transmission of both C. bushiensis and S. globulus occurs at least between mid-May and mid-September and that large, potentially lethal, infections can be acquired in as little as 24 hr. Finally evidence is presented to suggest that ducks acquire resistance to challenge infections of C. bushiensis.

Duck Nest Success in the Prairie Pothole Region

We estimated nest success of mallard (Anas platyrhynchos), gadwall (A. strepera), blue-winged teal (A. discors), northern shoveler (A. clypeata), and northern pintail (A. acuta) for 5 regions in North Dakota, South Dakota, and Minnesota, for 1-3 periods between 1966 and 1984, and for 8 habitat classes. We obtained composite estimates of nest success for regions and periods by weighting each habitat proportional to the number of nest initiations. The distribution of nest initiations was derived from estimates of breeding populations, preferences of species for nesting habitats, and availability of habitats. Nest success rates ranged from 15,000 records of nests found in the United States portion of the Prairie Pothole Region (Fig. 1). Supplemental information on breeding population levels, nesting habitat availability, and habitat use by nesting 432 DUCK NEST SUCCESS * Klett et al.

Effects of methyl parathion in ducks and duck broods

AbstractNesting ducks (mallards, blue‐winged teal, cinnamon teal and wood ducks) were trapped, equipped with radio transmitters and released on two agricultural fields, both of which were bordered by waterways. One field was aerially treated with methyl parathion at the rate of 1.4 kg active ingredient (a.i.)/ha and the second field was an untreated control. Ducks were located with the aid of radiotelemetry after pesticide application and their activity monitored daily in both fields. Brood abandonment by hens and nesting hen mortality occurred only on the methyl‐parathion‐treated field postspray. Brain cholinesterase levels were significantly depressed in two of three nesting hens. Fifty‐eight percent of the 37 ducklings present in the control field on the day of spray survived to day 22 postspray. Sixteen percent of the 24 ducklings present in the treated field on the day of spray survived to day 22. The average daily rate of duckling loss was also greater in the treated field than in the control field. Nest abandonment rates could not be correlated with methyl parathion application.

La nidification de la sauvagine dans le marécage de la Rivière-du-Sud et la zone agricole environnante

Nesting of dabbling ducks was studied in 1983 and 1984 on a southern Quebec marsh. Nest locations were determined during the nesting period in all habitats of the marsh (926 ha) and in a sample representing 24.4% (284 ha) of the fields available for nesting in the neighbouring agricultural zone. A total of 115 nests were numbered, involving mainly Mallards (Anas platyrinchos) and Blue-winged Teals (Anas discors). In the agricultural zone, nesting grounds were used mainly by the teals. However, 62% of the nests were destroyed during the first haying. Although mallards usually nest on the ground in areas of dense grass, intense agricultural use of the land results in very few fields offering enough vegetation cover in the early spring for this early nesting bird. An important number of mallards are forced to nest in trees or on different substrates in the marsh. In that type of environment, flooded woodland is the most extensively used habitat, with a mean density of 5.5 nests/100 ha. Nesting success is higher in the marsh (44 and 34%, respectively, in 1983 and 1984) than in the agricultural zone (5%). In the marsh, the main cause of nest destruction is predation. Water level variation also influences nesting success.[Journal translation]

Niche Overlap and Habitat Use by Sympatric Duck Broods in Eastern Washington

We evaluated niche overlap and habitat use among duck broods on Turnbull National Wildlife Refuge (Turnbull NWR). During summer of 1983 and 1984, 485 observations were recorded in 46 days. Data were gathered on 320 feeding broods of 9 species along 12 niche dimensions. Mean niche overlap values ranged from 0.62 to 0.94 for 36 possible species pairs. The greatest niche separation occurred on hatching date and feeding depth dimensions. Gadwall (Anas strepera) and teal (A. discors and A. cyanoptera) broods were ecologically very similar. Both had sharp mid-season hatching peaks and fed over dense beds of submerged macrophytes. Five species of diving duck broods tended to feed in deeper water and over areas with sparse submerged macrophytes. Among diving ducks, bufflehead (Bucephala albeola) broods were ecologically distinct, feeding over sparse vegetation often far from land. Mallard (A. platyrhynchos) broods were ecologically isolated from other dabbling ducks. They fed in shallow water within stands of emergent vegetation. The niche for ring-necked duck (Aythya collaris) broods was most similar to dabbling ducks, but also showed similarities with other divers. J. WILDL. MANAGE. 52(1):95-103 Studies dealing with brood-rearing ecology often emphasize macrohabitat (Stoudt 1971, Mack and Flake 1980, Swanson et al. 1984). Multi-dimensional studies of niche and niche overlap by sympatric duck broods are lacking. However, several studies have reported temporal segregation for both adult ducks and broods. Nilsson (1970) observed species of diving ducks segregating their feeding activities by diurnal and nocturnal partitioning. Morning and evening feeding peaks have been documented for broods of various species (Hochbaum 1944, Chura 1963, Ringelman and Flake 1980). Ringelman and Flake (1980) reported some temporal differences in feeding activity between blue-winged teal and mallards in age classes I and II. Differences in hatching dates among sympatric duck species are well documented (Hochbaum 1944, Hines 1977, Toft et al. 1984). Koskimies and Lahti (1964) reported differences in low temperature tolerances for several species of ducklings. Dietary overlap has been reported for sympatric species of ducklings, especially neonates (Collias and Collias 1963, Bengtson 1971, Sugden 1973). Among older ducklings, overlap is reduced as species become morphologically (Nudds and Bowlby 1984, Nudds and Kaminski 1984) and behaviorally specialized (Collias and Collias 1963, Sugden 1973). Sugden (1973) suggested dietary overlap in ducklings may not represent competition because substantial overlap occurred only among very young broods. Collias and Collias (1963) reported that ducklings of different species tended to specialize on different invertebrates. Our study examined microhabitat use by duck broods. Our objectives were to describe quantitatively species-specific use for several spatial and temporal niche dimensions and measure niche overlap between and among species for these dimensions. We use the term brood to refer to ducklings within a accompanied by an adult hen. Thus, when we refer to habitat use we recognize that in some cases the brood-rearing hen may have selected the site. Our study was funded by the Turnbull Laboratory for Ecological Studies, Eastern Washi gton University. We are grateful to refuge personnel for their cooperation and use of equipment. Appreciation is extended to R. L. Carr and R. A. Soltero for advice and encouragement. We acknowledge J. R. Rees, R. B. Pharness, and J. R. Alldredge for their helpful suggestions. We thank D. C. Douglas, P. J. DuBowy, R. M. Kaminski, J. A. Mueth, L. W. Ratti, K. P. Reese, J. K. Ringelman, J. J. Rotella, M. W. Weller, and L. G. Sugden for careful review of the manuscript.

Experimental duck plague in blue-winged teal and Canada geese.

Ten adult blue-winged teal (Anas discors) and six Canada goose (Branta canadensis) goslings were inoculated with liver tissue from a natural case of duck plague in a wild mallard (Anas platyrhynchos). Four additional teal were placed in contact with the inoculated ducks. Inoculated teal died 63.5-68 hr after inoculation; two of the contact teal died 161-162 hr after exposure. Three of the goslings died 119-133 hr after inoculation, the others were killed when moribund 90-133 hr postinfection. The clinical course of disease was extremely rapid in both species. Signs were limited to sudden onset of profound weakness, ataxia, tremors and terminal convulsions. The only consistent gross lesion in the teal was a small dark spleen; half the teal also had inconspicuous foci of epithelial necrosis in the distal esophagus and in the cloaca. Goslings had more severe lesions, with focal hepatic necrosis visible in all, and mucosal necrosis over the intestinal lymphoid tissue, and intestinal hemorrhage in three birds each. Microscopic lesions in both species were similar to those reported in mallards. Duck plague might be overlooked at necropsy of blue-winged teal, because of the paucity of gross lesions.

Interspecific Aggression By Barrow's Goldeneye: a Descriptive and Functional Analysis

AbstractWe describe interspecific aggression and territoriality by a diving duck, the Barrow's goldeneye. Males of this species are strongly interspecifically territorial early during the breeding season, and in winter. Females are interspecifically territorial while tending broods of ducklings. Aggression was strongest against conspecifics, and against the con-generic bufflehead, which shares the same breeding habitat. Other diving ducks, which overlap in diet with goldeneyes, were frequently attacked, while dabbling ducks, with differing feeding habits, were generally tolerated, and were seldom attacked. One dabbling duck, the blue-winged teal, in which the drake resembles the Barrow's goldeneye drake in plumage, was attacked more strongly than other dabblers. We propose that the strong interspecific aggressiveness exhibited by the Barrow's goldeneye, and its congeners the bufflehead and common goldeneye, is a consequence of the strong intraspecific aggressiveness of these species. Selectivity in aggression towards victims of different species can be explained by two hypotheses. Species that have (1) similar diets, and (2) similar plumages to Barrow's goldeneye are selectively attacked.

Population dynamics of the helminth community from migrating blue-winged teal: loss of helminths without replacement on the wintering grounds

The main and interactive effects of host and seasonal factors on abundance of 22 common helminth species from fall and spring migratory blue-winged teal collected in the Texas Panhandle were examined. Although abundances of many common helminth species were greater in immature than adult birds just off the breeding grounds, fall-collected adults had higher abundances of most helminth species than did both juvenile and adult birds from the wintering grounds in Mexico. While total abundance of helminths declined on the wintering grounds to only 54% of that from fall-collected birds, overall species composition and abundances of some helminth species were equivalent in the host population throughout the year, regardless of changing geographic locality and migratory stress. The helminth fauna acquired in the northern latitude breeding grounds was not replaced by an ecologically equivalent fauna in the southern latitude wintering grounds. Only one species, Corynosoma constrictum, was lost without replacement during the wintering period. Schistorphus cucullatus, a parasite of the Raillidae, occurred in birds on the wintering grounds but was lost without replacement on the breeding grounds. Thus, most of these helminth species were capable of ubiquitous transmission across the range of this host and (or) infections of the respective species persisted through the migratory stress period. This study suggests that diversity in the helminth community of a migratory host species over its entire geographic range may largely result from differences between separate populations that have become isolated over time as a result of establishing specific migratory corridors, rather than from the short-term effects of environmental differences between regions representing the extremes of the overall migratory range (breeding and wintering grounds).