Impoundment Drawdown and Artificial Nest Structures as Management Strategies for Snowy Plovers

This paper presents preliminary work on two potential management techniques that might enhance populations of Snowy Plovers (Charadrius alexandrines). Large tracts of suitable plover nesting habitat are being degraded by vegetation encroachment at Great Sale Lake, Utah. Therefore, we used impoundment drawdown to create shorebird nesting habitat by eliminating unwanted vegetation at a diked wetland. Twenty-two pairs of Snowy Plovers, four pairs of American Avocets (Recurvirosta Americana), and one pair of Long-billed Curlew (Numenius americanus) nested in a 12-ha drawdown impoundment. Also, some apparently suitable nesting macrohabitants (sparsely vegetation salt flats) were not used by breeding plovers. We thought increasing the availability of potential nest-site microhabitants in these suitable macrohabitants might increase their use. We placed 1-m2 gravel pads on selected barren salt flats at Great Salt Lake, and Snowy Plovers readily used these artificial substrates; 50% of 32 small-grained structures were used for building scrapes and three structures had clutches initiated on them. These strategies represent potential management techniques that should be field tested by land managers to determine their effectiveness to enhance Snowy Plover populations

Factors Affecting Interannual Movements of Snowy Plovers

We studied the interannual movements of 361 individually color-banded adult Snowy Plovers (Charadrius alexandrinus nivosus) at Great Salt Lake, Utah from 1990 to 1993. In northern Utah, Snowy Plovers nested in a dynamic environment; suitable breeding habitat declined by 50% at two study areas in four years. Male Snowy Plovers were more site faithful than females; 40% of males exhibited fidelity compared with 26% of females (P \u3c 0.01). However, as the amount of available suitable nesting habitat declined, male site fidelity diminished, whereas female fidelity remained relatively constant. We found strong evidence that female site fidelity was affected by nesting success in the previous year. Females that nested unsuccessfully were less likely than successful females to exhibit site fidelity the following year; males did not exhibit this nest-success bias. In addition, unsuccessful females breeding at sites with high densities of nests tended to disperse the following year, whereas male site fidelity did not appear to be affected by either a study site\u27s overall nesting success the previous year or a study site\u27s nest density the previous year. Female avoidance of areas with high densities of nests may be an antipredator strategy. Snowy Plovers in northern Utah have biparental incubation duties, but only males care for broods. Familiarity with brood-rearing areas was one plausible explanation for male-biased fidelity. However, we could not eliminate an alternative hypothesis that both focal study sites represented scarce breeding areas due to the presence of freshwater, and male Snowy Plovers preferred to use the same areas rather than disperse. We propose that more landscape-level studies are needed to address questions concerning local and regional movement patterns

Responses of Birds to Humans at a Coastal Barrier Beach: Napatree Point, Rhode Island

Human activity is one of the most important factors affecting disturbance to birds that use coastal barrier beaches in southern New England. The barrier beach at Napatree Point, RI, provides important breeding habitat for several bird species, key stopover habitat for thousands of migrating shorebirds, and is also a popular destination for people. Anecdotal evidence suggested that walkers, joggers, dogs, and watercraft were disrupting birds that foraged and roosted at this site. Our objectives were to characterize the frequency and sources of disturbance to birds and use this information to develop management recommendations to minimize the frequency of human disturbances to birds at Napatree Point. We conducted 106 hours of observation from May through August in 2013. Of 211 flight responses, the most common sources of disturbance to birds were beach walkers (57.8%), motorboats (8.5%), kayaks (8.5%), bird watchers (7.6%), and anglers (6.2%). Birds typically flushed when pedestrians (e.g., walkers, bird watchers, and anglers) were within 39 ± 24 m (median ± inter-quartile range) and watercraft (e.g., motorboats and kayaks) were within 38 ± 33 m. Flight responses were positively correlated with the number of people on the beach and the number of boats in the area. Disturbances to birds peaked in July when human visitation was highest. Using a spatially explicit density map of flight-initiation distance vectors, we identified the most important area to set as a buffer zone for human access if managers seek to reduce the frequency of human disturbances to birds at Napatree Point

Using Long-Term Constant-Effort Banding Data to Monitor Population Trends of Migratory Birds: A 33-Year Assessment of Adjacent Coastal Stations

One technique for monitoring population trends of many species of migratory songbirds is to assess changes in population indices at constant-effort mist-netting stations located at sites of migration stopover. However, few studies have attempted to validate this approach. We compared long-term (1969–2001) population trends based on annual variation in capture rates at two banding stations located 30 km apart in southern Rhode Island, with one on the mainland, the other on an offshore island. Of 24 species with sufficient sample sizes, 21 species exhibited a significant linear decline at one or both stations. There was a high degree of conformity in trend-slope directions observed at each station. Annual fluctuations and trend magnitude conformed less well, although there was more concordance for nine transient species that do not breed in southern New England. At both stations trends were similar to those at a migration-monitoring station ~95 km away in coastal Massachusetts. The trends at this network of three migration-monitoring stations were more negative than those of Breeding Bird Surveys in northern New England and southeastern Canada. Our results demonstrate that constant-effort mist-netting stations could be used to monitor population trends of many species of migratory songbirds, although it is not clear which breeding populations are being monitored. This suggests that banding stations could be used to supplement existing large-scale monitoring programs

Breeding Ecology and Behavior of the Hawaiian Hawk

We studied the ecology of the endangered Hawaiian Hawk (Buteo solitarius) on the island of Hawaii for three breeding seasons. Their breeding strategy is a prime example of a K-selected species characteristic of many birds in tropical environments: clutch size was one and brood-rearing was among the longest reported for any diurnal raptor. Twenty-eight nests were found in a variety of native and exotic habitats. Incubation lasted 38 days, nestlings fledged after 59-63 days, and parents cared for fledglings for an average of 30.2 weeks, which was 2.5 to 10 times longer than similar-size temperate zone raptors. Males assisted females with incubation, but only females brooded young. Radio-tagged juveniles remained within 0.63 km of their nests for the first two months after fledging, after which dispersal distances expanded gradually. Avian (45%) and mammalian (54%) prey dominated the diet of nestlings. There was no evidence that avian malaria, introduced predators, or environmental contaminants were affecting their population. Based upon estimates of population size, the availability of suitable nesting habitat, and reproductive success, we suggest the species be considered for downlisting from endangered to threatened status

Are Wetland Regulations Cost Effective for Species Protection? A Case Study of Amphibian Metapopulations

Recent declines in amphibian populations have raised concern among conservation biologists, with habitat loss and degradation due to human activities among the leading causes. The most common policies used to protect the habitat of pond-breeding amphibians are wetland regulations that safeguard the wetland itself. However, many amphibians spend much of their adult lives foraging and over-wintering in upland habitats and exist as metapopulations with dispersal among ponds. With no consideration of lands in the dispersal matrix, wetland policies may be ineffective at protecting amphibians or other wetland species that disperse across the landscape. This paper examined the adequacy and cost effectiveness of alternative conservation policies and their corresponding land use patterns on the long-term persistence of pond-breeding amphibians in exurban landscapes. We used computer simulations to compare outcomes of wetland buffer policies and broader landscape wide conservation policies across a variety of landscape scenarios, and we conducted sensitivity analyses on the model\u27s species parameters in order to generalize our results to other wetland species. Results showed that, in the majority of human-dominated landscapes, some amount of dispersal matrix protection is necessary for long-term species persistence. However, in landscapes with extremely low-intensity land use (e.g., low-density residential housing) and high pond density, wetland buffer policies may be all that is required. It is not always more cost effective to protect core habitat over the dispersal matrix, a common conservation practice. Conservation costs that result from forgone residential, commercial, or agricultural activities can vary substantially but increase in a nonlinear manner regardless of land use zoning. There appears to be a threshold around an average habitat patch occupancy level of 80%, after which opportunity costs rise dramatically

Distributing transmitters to maximize population-level representativeness in automated radio telemetry studies of animal movement

Telemetry is a powerful and indispensable tool for evaluating wildlife movement and distribution patterns, particularly in systems where opportunities for direct observation are limited. However, the effort and expense required to track individuals often results in small sample sizes, which can lead to biased results if the sample of tracked individuals does not fully capture spatial, temporal, and individual variability within the target population. To better understand the influence of sampling design on results of automated radio telemetry studies, we conducted a retrospective power analysis of very high frequency (VHF) radio telemetry data from the Motus Wildlife Tracking System for two species of birds along the United States Atlantic coast: a shorebird, the piping plover (Charadrius melodus), and a nearshore seabird, the common tern (Sterna hirundo). We found that ~ 100–150 tracked individuals were required to identify 90% of locations known to be used by the tracked population, with 40–50 additional individuals required to include 95% of used locations. For any number of individuals, the percentage of stations included in the sample was higher for common terns than for piping plovers when tags were deployed within a single site and year. Percentages of stations included increased for piping plovers when birds were tagged over multiple sites and, to a lesser extent, years, and increased with average length of the tracking period. The probability that any given receiver station used by the population would be included in a subsample increased with the number of birds tracked, station proximity to a migratory stopover or staging site, number of receiving antennas per station, and percentage of the tracked population present. Our results provide general guidance for the number and distribution of tagged birds required to obtain representative VHF telemetry data, while also highlighting the importance of accounting for station network configuration and species-specific differences in behavior when designing automated radio telemetry studies to address specific research questions. Our results have broad applications to remotely track movements of small-bodied migratory wildlife in inaccessible habitats, including predicting and monitoring effects of offshore wind energy development