Jerry R. Longcore

Chytridiomycosis Widespread in Anurans of Northeastern United States

Abstract An emerging disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis has been associated with morbidity, mortality, and extinction of species. Typically, researchers have detected B. dendrobatidis only when examining amphibians for causes of mortalities; few data exist on infection rates where mortalities are lacking. During May–September 2000–2002 we obtained amphibian specimens killed by vehicles and others collected at remote off-road sites throughout Maine, USA, and from federal lands in 5 states in the Northeast. We detected infected specimens, mostly green frogs (Rana clamitans), at 5 of 7 national wildlife refuges, a federal waterfowl production area, and Acadia National Park. Seven of 9 species, including all Ranidae species, were infected throughout Maine; rates ranged from 14.6% in American toads (Bufo americanus) to 25.7% in northern leopard frogs (Rana pipiens). We did not detect any infections in 50 eastern gray tree frogs (Hyla versicolor) or 21 spring peepers (Pseudacris crucifer). Species that hibernate in terrestrial habitats seem to have lower rates of infection than species that hibernate in aquatic habitats. Infections peaked in spring and autumn and were associated with air temperatures optimal for B. dendrobatidis growth. The relatively high infection rates among species without documented die-offs suggest that either losses have occurred undetected, that the fungus is endemic and species have attained a level of resistance to infections becoming lethal, or that climatic conditions of the Northeast have a role in preventing infections from being lethal. Data on prevalence and distribution of this chytrid fungus in the Northeast may be useful in modeling its origins and predicting long-term ecosystem effects involving anurans.

Movements and wetland selection by brood-rearing black ducks

Movements and wetland selection by brood-rearing black ducks (Anas rubripes) were studied in Maine during 1977-80. Eight radio-marked hens moved their broods an average of 1.2 km from the nest to rearing pond, but only 1 hen initiated secondary brood movements. Half of the 85 broods reared in the study area used only 3 wetlands, and most rearing ponds contained active beaver (Castor canadensis) colonies. Brood-rearing hens preferred Emergent ponds over lakes and Evergreen Scrub-Shrub wetlands, and did not occupy Dead Scrub-Shrub, Unconsolidated Bottom, or Aquatic Bed wetlands. Rearing ponds were large and possessed extensive areas of flooded mountain alder (Alnus incana), willow (Salix spp.), and herbaceous vegetation. Wetlands avoided by brood-rearing hens were those with large areas of open water, submergent aquatics, or ericaceous shrub vegetation. J. WILDL. MANAGE. 46(3):615-621 The ability of female black ducks to select brood-rearing ponds that will fulfill the changing food and habitat requirements of growing ducklings increases the prospects for brood survival. Many researchers (V. D. Stotts, unpubl. rep., Maryland Game and Inland Fish Comm., Fed. Aid Proj. W-30-R-7, 1959; Reed 1970; Hepp and Hair 1977) have recognized the importance of rearing areas and have identified the types of wetlands used by black duck broods. However, comparatively little is known about the wetland habitat components that serve as proximate factors (Hilden 1965) in the selection process. Studies of primary and secondary brood movements (Evans et al. 1952, Berg 1956, Stewart 1958, Beard 1964, Ball 1973) indicate that ducks actively select rearing areas. Wright (1954) observed a black duck hen leading her brood >3.2 km overland to a rearing area, and Young (1967) discussed the overland movements of 2 broods to a large pond >1.6 km away. Detailed data on brood movements of inland-nesting black ducks have been unavailable, but are necessary for an understanding of duckling survival and habitat selection. We investigated the selection of wetlands and habitat components by radio-marked and unmarked female black ducks, and the movements of marked, brood-rearing hens. We acknowledge the work of field assistants J. M. Connolly, J. D. Schoultz, J. Sease, and S. E. Staples. T. J. Dwyer, L. D. Flake, and G. M. Haramis provided comments on early drafts of the manuscript. Financial support for this study was provided in part by contract #14-160008-2125 from the Migratory Bird and Habitat Research Laboratory, U.S. Fish and Wildlife Service, and by the School of Forest Resources, University of Maine, Orono. STUDY AREA AND METHODS The 151-km2 study area was 30 km southwest of Bangor, Maine in the northern hardwoods-spruce ecoregion (Bailey 1978). Forty-four of the 118 study wetlands were created or modified by beaver. Most ponds were classified as EverI Present address: Colorado Division of Wildlife, Research Center, 317 W. Prospect, Fort Collins, CO 80526. J. Wildl. Manage. 46(3):1982 615 This content downloaded from 157.55.39.147 on Sun, 07 Aug 2016 07:03:12 UTC All use subject to http://about.jstor.org/terms 616 BROOD-REARING BLACK DUCKS* Ringelman and Longcore green or Deciduous Scrub-Shrub, Deciduous Forested, or Persistent Emergent wetland types (Cowardin et al. 1979), and ranged in size from 0.1 to 64.2 ha. A detailed description of the study area was presented by Ringelman (1980:3). Data on brood movements were attained by following radio-marked females which were captured before brood-rearing with nest traps (Coulter 1958) or rocket nets. Females were instrumented with 25-g, back-mounted transmitters and monitored 2-3 times per day with a mobile, null-peak tracking system using conventional telemetry techniques. Observations of unmarked broods, supplemented with telemetry records of radio-marked hens, provided data that were used in the analysis of habitat selection. Rearing ponds were defined as wetlands used by a brood for >24 hours. Brood surveys were conducted on all rearing ponds every 6-10 days from the last week in May through the end of July 1977-80. Most observations were made from tree stands 3-15 m above the waters surface. Black duck broods were characterized by number and age of ducklings (J. B. Gollop and W. H. Marshall, unpubl. rep., Miss. Flyway Tech. Sect., 1954), because a unique combination of these characteristics enabled us to re-identify individual broods during subsequent visits. Details of our brood survey methods are described elsewhere (Longcore and Ringelman 1980). The hypothesis that brood use differed significantly from the availability of each wetland class was tested with a z statistic (Neu et al. 1974). A stepwise forward discriminant analysis (Klecka 1975) was performed to identify individual habitat components characteristic of wetlands used vs. those avoided by broods. Twenty-eight habitat components (Table 1) were used as discriminating variables. Preliminary analyses indicated that variable means were proportional to standard deviations, so a logarithmic transformation (log[x + 1]) was applied to all data (Zar 1974:184) to avoid problems created by heteroscedasticity and non-normality (Box and Cox 1964, Eisenbeis and Avery 1972).

THE ROLE OF pH IN STRUCTURING COMMUNITIES OF MAINE WETLAND MACROPHYTES AND CHIRONOMID LARVAE (DIPTERA)

Aquatic vascular plants, or macrophytes, are an important habitat component for many wetland organisms, and larvae of chironomid midges are ubiquitous components of wetland fauna. Many chironomids are primary consumers of algae and detritus and form an essential energetic link between allochthonous and autochthonous primary production and higher trophic levels, while others are predators and feed on smaller invertebrates. Live macrophytes serve mostly as habitat, whereas plant detritus serves as both habitat and as a food source. Assemblages of macrophytes and chrinomid larvae were surveyed in ten Maine wetlands, five with low pH (<5.0) and five with high pH (>5.5), and explained in terms of physical and chemical habitat variables. Macrophyte richness was significantly greater, and richness of chironomid larvae was lower, in low pH wetlands. There was no difference in chironomid abundance related to pH. However, community structure was related to pH, suggesting that competitive dominance of a few taxa was responsible for lower richness in low pH wetlands, whereas competition was weaker in high pH wetlands, making coexistence of more chironomid taxa possible. An examination of individual chironomid taxa by stepwise multiple regression showed that distribution of most taxa was controlled by water chemistry variables and macrophyte habit (i.e., floating, submergent).

Survival of American Black Ducks radiomarked in Quebec, Nova Scotia and Vermont

We monitored survival of 397 radiomarked juvenile American black ducks (Anas rubripes) distributed among Les Escoumins (n = 75) and Kamouraska, Quebec (n = 84). Amherst Point, Nova Scotia (n = 89), and a site on the Vermont-Queber border (n = 149) during autumn 1990 and 1991. Eighty-six percent (215 of 250) of all confirmed mortalities during the study was from hunting: 72% of marked ducks were shot and retrieved and 14% were shot and unretrieved. We tested for differences in survival in relation to sex, body mass, year (1990-91, 1991-92), and among the 4 locations for each of 2 monitoring periods (early, EMP: late. LMP). With data from the EMP for Vermont-Quebec in 1990 and 1991, Les Escoumins in 1990, and Amherst Point in 1991, survival of hatching-year (HY) males and females did not differ (P = 0.357). For sexes combined for the EMP, survival of ducks was greater in 1991 than 1990 (P = 0.086), and differed among locations (P = 0.013). Survival (years combined was greater al Amherst Point than at Kamouraska (P = 0.003) and Vermont Quebec (P = 0.002) during the EMP. The highest survival rate at Amherst Point (0.545 ± 0.056 [SE]) was associated with the latest date (S Oct) of season opening: the lowest survival rate (0.395 ± 0.043) was at the Vermont-Quebec border, where hunter numbers and activity were greatest. For the LMP. no interaction between years and locations was detected (P = 0.942), and no differences in survival existed between vears (P = 0.102) and among locations (P = 0.349). No association was detected between body mass at capture and survival of combined males and females during the EMP (P = 0.572) or during the LMP (P = 0.965). When we censored hunting losses for combined years for each period. EMP or LMP, all survival estimates exceeded 0.800 (0.809-0.965). These data emphasize need for an improved harvest strategy for American black ducks in North America to allow for increases in breeding populations to achieve population goals.

Survival of postfledging female American black ducks

We equipped 106 hatching-year (HY), female, black ducks (Anas rubripes) with transmitters during 1985-87 and monitored survival from late August to mid-December on a lightly hunted area on the Maine-New Brunswick border. The 1985-87 estimate of survival (hunting losses included) was 0.593, and when losses from hunting were censored it was 0.694. Survival in August-September was 0.987; by 31 October survival declined to 0.885, and by 30 November it was 0.718. Most nonhunting mortality was caused by predators (21/41, 53.2%); there were 14 deaths (34.1%) from mammals or unknown predators and 7 (17.1%) from raptors. Hunting caused 13 (31.7%) deaths. Ducks with lowest mass had the lowest survival. The estimate of survival for postfledging female black ducks, when multiplied with interval survival rates for hunting, winter, and breeding periods, produced an annual survival estimate of 0.262, about 12% lower than that (0.38) based on analysis of banding data

Foods of juvenile ring-necked ducks: Relationship to wetland pH

Foods of 37 juvenile ring-necked ducks (Aythya collaris) from 16 different wetlands were examined in eastcentral Maine in 1983-85. Invertebrates made up 70% aggregate dry weight (100% occurrence) of the foods of Class Ia-IIa (-24 days old) ducklings and 32% (86% occurrence) of Class IIb-III (>25 days old) ducklings. These percentages may be as high as 85% for Ia-IIa ducklings and 47% for IIb-III ducklings after adjusting for insect sclerites. Ducklings ate invertebrates from 44 taxa and seeds or fibers from 23 plant taxa. Freshwater sponges (Porifera) were the most important invertebrate and constituted 23% of the foods of all ducklings. Seeds of pondweeds (Potamogeton spp.) were the most important plant foods. Diets of ducklings from high-pH (26.1) wetlands were more diverse (t = 2.54, P = 0.021) than those from low-pH (<6.1) wetlands and consisted of 33 invertebrate taxa. Only 17 taxa occurred in ducklings from low-pH ponds. Class Ia-IIa ducklings from high-pH wetlands ate more invertebrates (77%) than ducklings from lower-pH wetlands (61%), although the difference was not significant (P = 0.21). Sponges made up the largest percentage of the diets and occurred in similar amounts in high(34%) and low(31.5%) pH wetlands. J. WILDL. MANAGE. 52(2):177-185 Aquatic invertebrates are important foods for young ducklings (Bartonek and Hickey 1969, Sugden 1973, Reinecke 1979), and retarded growth and low survival have been associated with low invertebrate abundance (Street 1977). Aquatic invertebrates are important in the diet of ring-necked duck ducklings in Minnesota (Hohman 1985). Mendall (1958) reported the foods eaten by ring-necked ducks in Maine, but his data included only gizzard contents, which bias results toward the less digestible plant foods (Swanson and Bartonek 1970). Ring-necked duck habitats in Maine consist primarily of permanent wetlands that have lower productivities than newly-flooded or seasonally-flooded wetlands (Whitman 1974). Many wetlands in Maine are vulnerable to acidification, a process that can adversely affect invertebrates (Bell 1971, Haines 1981, Eilers et al. 1984). Reinecke (1977) reported no difference in the nutrient content of duck foods in Maine wetlands versus richer, prairie wetlands, and he believed that food quantity rather than quality limited waterfowl in the Northeast. Low invertebrate diversity or biomass in wetlands could adversely affect duckling diets. The purpose of our study was to document food habits of ring-necked duck ducklings in Maine and to determine if diets differed between wetlands of high and low pH. We thank A. G. LaRochelle, P. E. Malicky, D. D. Eggeman, and R. R. Roy for their assistance in the field. T. M. Mingo identified invertebrates and J. E. Longcore identified sponges. K. L. Stromborg analyzed water samples. M. A. Howe, K. J. Reinecke, T. W. Custer, and 2 anonymous referees gave helpful reviews of the manuscript. STUDY AREA AND METHODS Our study area consisted of isolated broodrearing wetlands in a 17,800-km2 area (McAuley 1986) that extended from eastern Waldo County through Hancock and Washington counties and into northern Penobscot and southwestern Aroostook counties in Maine. This area included most of the wetlands that were studied by Mendall (1958). Bedrock types (i.e., sensitivity class 1 and 2 [no-low and low-medium acid neutralizing capacity]) (Norton et al. 1982a,b) indicated wetlands were vulnerable to acidification (alkalinity 5200 geq/L [Hendrey et al. 1980]). Ducklings were collected from 16 wetlands. Most water samples were collected in July 1983-84. Measurements of water chemistry followed Haines and Akielaszek (1983), except alkalinity was determined by the Gran plot method (Stumm and Morgan 1970) only. During 1983-85, we attempted to collect Class I (?16 days old), II (17-38 days old), and III (39-49 days old) ducklings (Gollop and Marshall 1954) from as many wetlands as possible. We tried to observe ducklings feeding before collecting (Swanson and Bartonek 1970), but because broods were sparsely distributed and often

EFFECTS OF HUNTING ON SURVIVAL OF AMERICAN WOODCOCK IN THE NORTHEAST

Abstract Numbers of American woodcock (Scolopax minor) males counted on the annual singing ground survey (SGS) have declined over the last 35 years at an average rate of 2.3% per year in the Eastern Region and 1.8% per year in the Central Region. Although hunting was not thought to be a cause of these declines, mortality caused by hunters can be controlled. Furthermore, there has been no research on effects of hunting mortality on woodcock populations at local and regional levels on the breeding grounds. We used radiotelemetry to determine survival rates and causes of mortality for 913 woodcock captured during fall 1997–2000 on 7 areas in Maine, New Hampshire, Pennsylvania, and Vermont, USA. Three of 7 sites were closed to hunting. For all sites and all years combined, 176 woodcock died, and 130 were censored, of which 39 were censored mortalities. Predation was the major (n = 134, 76%) cause of mortality. Mammals accounted for 56% of the predation, raptors accounted for 25%, and 19% was attributed to unknown predators. On hunted sites, 36% of the total mortality (n = 102) was caused by hunting, 63% by predation, and 1 bird starved. Kaplan-Meier survival curves did not differ between hunted and non-hunted sites among years (P = 0.46). Overall, point estimates of survival did not differ (P = 0.217) between hunted (SR = 0.636, SE = 0.04) and nonhunted sites (SR = 0.661, SE = 0.08). We modeled hazard rates from hunting and natural mortality events using program MARK. Akaikes Information Criterion supported using a model with common constant hazards from both hunting and natural causes for groups of sites. Groupings of sites for hazard rates from natural causes were not influenced by whether a site was hunted or not. Models detected no effects of woodcock age and sex (P = 0.52) on survival. Proportional hazards models comparing hunted and nonhunted sites found no effects of age and sex (P = 0.45), interactions of age, sex, capture weight, and bill length (P ≥ 0.269). Our data suggest that current hunting regulations are not causing lower survival of woodcock.

Outcome of aggressive interactions between American black ducks and mallards during the breeding season

American black duck (Anas rubripes) numbers have declined during the past several decades, while mallards (A. platyrhynchos) have expanded their range eastward. Competitive exclusion of black ducks from wetlands by mallards has been proposed as a principal cause of the decline. We studied a sympatric population of black ducks and mallards in Maine during the early breeding season to document behavior and interactions. We observed 832 aggressive interactions; most (72%) were interspecific. When a choice was available, both species interacted more often with conspecifics than with the other species (P < 0.028). On wetlands occupied simultaneously by both species, numbers of intraspecific interactions initiated by each species were similar (P = 0.470). The proportions of won (initiator displaces recipient of attack), lost (initiator displaced), and no change outcomes of these interactions were different (P < 0.001). When black ducks initiated interactions with mallards, black ducks did not lose any interactions and displaced mallards 87.2% of the time; no change occurred during 12.8% of the interactions. When mallards initiated interactions with black ducks, mallards displaced black ducks 63.3% of the time but were displaced by black ducks 15.0% of the time; no change occurred during 21.7% of the interactions. Displacement from wetlands was rare (38 of 229 interspecific interactions) and was equal between species.

Habitat Characteristics of American Woodcock Nest Sites on a Managed Area in Maine

We measured characteristics of habitat near 89 nests of American woodcock (Scolopax minor) and 100 randomly selected points on Moosehorn National Wildlife Refuge, Calais, Maine, an area managed for woodcock. At nest sites, basal area was lower (P 0.05) or between sites of successful nests and nests destroyed by predators, although the large variances of the variables reduced our power to detect differences. Habitat around sites of renests differed from sites of first nests. Sites around first nests had lower basal area of dead trees (P = 0.05) and higher stem densities of aspen (P = 0.03) and cherry saplings (Prunus spp.) (P = 0.001), and viburnum (Viburnum spp.) (P = 0.05), while renest sites had taller trees (P = 0.02). The change from nest sites in areas dominated by alders and tree-size gray birch used in 1977-80 to sites dominated by sapling trees, especially aspen, used during 1987-90 suggests that woodcock in the expanding population at the refuge are selecting nest sites created by habitat management since 1979.

Dynamic use of wetlands by black ducks and mallards: evidence against competitive exclusion

Abstract The decline of the American black duck (Anas rubripes) has been attributed to competition from mallards (A. platyrhynchos) that led to exclusive use of fertile wetlands by mallards. Data from annual breeding waterfowl surveys provide instantaneous, single observations of breeding pairs, which are used to estimate breeding population size and evaluate the condition of habitat. Data from these surveys have been used to document habitat use by black ducks and mallards. We used quiet-observation surveys from elevated platforms to study sympatric black ducks and mallards in northern Maine during the breeding season. Our objectives were to document occupancy of wetlands by breeding black ducks and mallards throughout the day during prenesting and early nesting periods to determine whether 1) wetlands were occupied by only a single species, 2) pairs of the same species occupied wetlands throughout the period, and 3) single observations of short duration adequately determine numbers and species using a wetland. We observed ducks at 5-minute intervals from elevated platforms on wetland margins to determine numbers and species of indicated pairs using each wetland over time. We visited 80% of the wetlands ≥2 times, with mean total time per wetland averaging 267 minutes. For each wetland we determined the most frequently observed grouping of black ducks and mallards from all combinations recorded during all intervals (e.g., 1 black duck [BD] pair during 9 intervals; 2 mallard [MA] pairs and 1 BD pair during 22 intervals; 0 pairs during 3 intervals). A single pair, a lone male, or no ducks were recorded during 34% of the 5-minute intervals. For wetlands with ≥2 hours of observations (n=65), all but 2 were used by ≥2 different combinations of ducks. On most wetlands, the most frequent grouping was observed during <40% of the intervals. To simulate aerial surveys, we randomly selected 1 5-minute interval for each wetland. On average, the number of indicated pairs recorded during random 5-minute intervals was less than half of the total black duck pairs (2.0 vs. 4.4, P= 0.009), total mallard pairs (1.1 vs. 2.6, P=0.0001), and pairs of both species combined (3.2 vs. 7.0, P=0.0001) determined for each wetland based on total observations. On wetlands used by both species, random counts detected one or both species 49% of the time. Although 53 of the 65 wetlands observed ≥2 hours were used by both species, random visits detected both species on only 27 wetlands. Our data do not support assertions that the mallard has caused the decline of black ducks through interspecific competition for habitat, or that wetlands are occupied continuously by single pairs that aggressively exclude conspecifics. Our data indicated that single, short-duration visits with disturbance to wetlands are unreliable and inappropriate to document seasonal use of wetlands by breeding black ducks and mallards.