Daniel Gibson

Migrant Birds at Shemya Island, Aleutian Islands, Alaska

-A five-season study of bird migration in the Near Islands, western Aleutian Islands, Alaska, resulted in data that suggest that some 30 Palearctic and Aleutican taxa that are of irregular occurrence or are virtually unknown in Alaska east of 180” occur regularly on passage in this area in small numbers, some of them both spring and autumn. Most of these forms are apparently en route in spring to the Koryak Highlands or the Anadyr River basin, both of which areas lie directly north of the Near Islands, in the U.S.S.R. An annotated list of 147 taxa discusses all forms recorded. The Near Islands, named by Russian explorers for their proximity to Asia, are five islands-Attu, Agattu, Alaid, Nizki, and Shemya-that make up the westernmost group of the Aleutian Islands, Alaska. Shemya is the easternmost of the group (52”43’ N, 174”07’ E). It is situated 1,500 km west and south of the Alaska mainland, 630 km south and east of Cape Olyutorsk, Koryak Highlands, and 600 km east of Kamchatka (Fig. 1). It is 320 km southeast of the Commander Islands. Shemya is a small, low-lying island, a “raised, wave-cut platform” (Gates et al. 1971) of 14.2 km2 with a coastline of 21.5 km. It is treeless, as are all of the Aleutians, but it differs from many of the others in being quite flat-a gently rolling, meadowcovered plateau that drops from elevations of 70-80+ m above North Beach to lo-15 m above South Beach. Fifteen permanent lakes regularly support transient waterfowl populations, but three of the largest (Upper, Lower, and Laundry lakes) support a diversity of birds not seen at the others. The steep bluffs along the irregularly sculpted north shore (Fig. 2), with its protected amphitheaters and bays and dense tall forb vegetation, are most important to transient passerines. Shemya has a maritime climate. Fog and rain are characteristic, and violent storms, often with sustained winds over 50 kph, occur frequently, usually arriving from the southwest or west in spring, from the northwest or west in fall. Eleven of the 29 avian habitats described for Alaska by Kessel (1979) were identified at Shemya: Lacustrine Waters and Shorelines, Fluviatile Waters and Shorelines, Inshore Waters, Rocky Shores and Reefs, Beaches, Cliffs (coastal), Wet Meadows, Dwarf Shrub Meadows, Grass Meadows, Tall Forb Meadows, and Artificial (e.g., buildings, garbage dumps, World War II wreckage). Their relative importance to migrants on the island was not determined systematically, partly because most migrants were waterfowl or shorebirds, whose habitat uses were straightforward, and partly because the availability of any cover and food on this small island were often the only criteria that seemed important (i.e., the substrate many migrants used depended on the topography and its function in protecting them from the weather). The island is part of the Aleutian Islands National Wildlife Refuge, and since 1943 the U.S. Air Force has maintained it as a military installation. During the periods 9-23 May 1975, 30 April-31 May 1976, 29 April-7 June 1977, 31 August-3 October 1977, and 15 August13 October 1978 I conducted fieldwork on the island, under cooperative agreements between the University of Alaska Museum and the U.S. Fish and Wildlife Service, and with the cooperation of the U.S. Air Force, in an effort to inventory the migrant bird forms that occur in this poorly-known and westernmost part of Alaska and of the Refuge. I was accompanied in the field in different seasons by George E. Hall, Theodore G. Tobish, and Raymond S. Hadley, all experienced Alaskan field ornithologists. Fieldwork was conducted on foot, except in spring 1977, when a truck was available. We wanted to inventory all migrants on the island, so we surveyed it in an opportunistic fashion, monitoring habitats and topography in daily response to weather conditions and to the stage of migration. The small size of the island enabled us to survey carefully the entire perimeter on days when we deemed it profitable to do so. Experience elsewhere in the Aleutians had taught that most through-migrants make landfall and remain at the perimeter of an island, so that, except to check prominent features elsewhere on

The Birds of Adak Island Alaska

Adak Island lies between 51”35’ and 52”Ol’ N. and 176”25’ and 176”59’ W, in the Andreanof Group, Aleutian Islands. Although Taber (1946) provides an annotated list of birds he observed at Adak in winter, year-round observations have not been previously published. Since Adak lies near the middle of the axis formed by the Alaska Peninsula and the Aleutian and Commander islands (fig. l), which links North America and Asia, its avifauna is composed of species with varied geographic origins. Closely paralleling the findings of Emison et al. (1971), who discuss the geographic origins of 100 species of birds known from Amchitka Island, 65% (81 species) of the birds recorded at Adak have contemporary breeding distributions in both North America and Asia (vs. 68% at Amchitka) ; 19% (24 spp.) have affinities only to Asia (vs. 15%); 12% (15 spp.) have affinities only to North America (vs. 13%); and 3% (4 spp.) breed only on midand south Pacific islands (vs. 4%). Of the 124 species included in the following annotated list, two, Anas poecilorhyncha zonorhyncha and Cuculus canorus canorus, are new to North America. Seventeen additional forms are represented by few North American records, and well over half of the species listed have not been previously recorded on Adak.

Seventy-Four New Avian Taxa Documented in Alaska 1976-1991

The occurrence in Alaska of 74 avian taxa was documented for the first time during 1976-1991, bringing the number of species known to have occurred in Alaska to 436. These added taxa include 20 species and eight subspecies documented for the first time in North America.

Summer distribution of pelagic birds in Bristol Bay Alaska

Bristol Bay and its islands, the embayments, lagoons, and other estuaries along the north side of the Alaska Peninsula, and the nesting cliffs on the north shore, are seasonally important to vast numbers of seabirds, waterfowl, and shorebirds that either breed, summer, winter, or stopover there during migration. This productive southeast corner of the Bering Sea is also used by sea otters and several species of pinnipeds and cetaceans, and it is the site of the worlds largest salmon fishery. Petroleum development is planned for this area and, judging from the past history of numerous oil spills in nearby Cook Inlet, could have deleterious effects on this rich fauna. This possibility prompted investigations of the migratory birds, including the pelagic species, that could provide the year-round information on distribution and numbers nec-

Evaluating vegetation effects on animal demographics: the role of plant phenology and sampling bias

Abstract Plant phenological processes produce temporal variation in the height and cover of vegetation. Key aspects of animal life cycles, such as reproduction, often coincide with the growing season and therefore may inherently covary with plant growth. When evaluating the influence of vegetation variables on demographic rates, the decision about when to measure vegetation relative to the timing of demographic events is important to avoid confounding between the demographic rate of interest and vegetation covariates. Such confounding could bias estimated effect sizes or produce results that are entirely spurious. We investigated how the timing of vegetation sampling affected the modeled relationship between vegetation structure and nest survival of greater sage‐grouse (Centrocercus urophasianus), using both simulated and observational data. We used the height of live grasses surrounding nests as an explanatory covariate, and analyzed its effect on daily nest survival. We compared results between models that included grass height measured at the time of nest fate (hatch or failure) with models where grass height was measured on a standardized date – that of predicted hatch date. Parameters linking grass height to nest survival based on measurements at nest fate produced more competitive models, but slope coefficients of grass height effects were biased high relative to truth in simulated scenarios. In contrast, measurements taken at predicted hatch date accurately predicted the influence of grass height on nest survival. Observational data produced similar results. Our results demonstrate the importance of properly considering confounding between demographic traits and plant phenology. Not doing so can produce results that are plausible, but ultimately inaccurate.

Senescence and carryover effects of reproductive performance influence migration, condition, and breeding propensity in a small shorebird

Abstract Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animals breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; βsex = −0.21, 95% CI: −0.38 to −0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.

Discovery of an Important Stopover Location for Migratory Piping Plovers (Charadrius melodus) on South Point, Ocracoke Island, North Carolina, USA

Abstract. Piping Plovers (Charadrius melodus) undertake comparatively short migrations for a shorebird and were not previously thought to congregate in large numbers during migration. Superpopulation size (individuals occurring at the study site during the study period) and stopover duration were estimated for migratory Piping Plovers on South Point, Ocracoke Island, North Carolina, USA, from 3 July–28 October 2016 by integrating a Jolly-Seber model and a binomial model of resighting and count data. We estimated 569 Piping Plovers (95% CI: 502–651) used South Point during fall migration in 2016, approximately 10% of the global population and approximately 15% of the Atlantic Coast population. Stopover duration differed between Piping Plovers that bred on or near our study site (Southern USA, 46 days, SD = 1.7) compared to individuals that bred in the northern area of the breeding range (Atlantic Canada, 41 days, SD = 2.0; New England States, USA, 44 days, SD = 1.8) and the central area of the breeding range (New York and New Jersey, USA, 26 days, SD = 1.4). South Point may be unique in that no other areas are known to host similar numbers of Piping Plovers during fall migration.

Impacts of anthropogenic disturbance on body condition, survival, and site fidelity of nonbreeding Piping Plovers

ABSTRACT The impact of habitat loss on shorebirds may be exacerbated by disturbance from human recreational use, which further reduces the amount of coastal habitat that is functionally available. This can have consequences for the condition of individual birds or for population processes, both of which should be considered in strategies to reduce conflict between shorebirds and recreational users of coastal habitat. Our objectives were to determine the associations between human recreational use, coastal habitat modifications, and Piping Plover (Charadrius melodus) body condition and demography. We monitored banded Piping Plovers throughout their annual cycle to assess variation in body condition, true survival, and site fidelity related to disturbance regimes in 8 geographically proximate, nonbreeding areas along the southeastern Atlantic Coast of North America from 2012 to 2016. Piping Plovers in disturbed sites were 7% lighter than those in less disturbed sites. Additionally, true annual survival was lower in more disturbed areas. However, site fidelity was less influenced by disturbance than were body mass and survival. Movements away from specific nonbreeding areas were uncommon, regardless of disturbance regime, but individuals that moved to new wintering locations had high probabilities of annual survival (S̄ = 0.80) relative to their site-faithful counterparts (S̄ = 0.67). Associations among nonbreeding conditions, body condition, and demography highlight the importance of nonbreeding habitats to annual population dynamics of migratory species. Conservation strategies for Piping Plovers that focus solely on breeding season dynamics may not account for some of the mechanisms that influence demographic rates and population trajectories.