Brad A. Andres

Effects of persistent shoreline oil on breeding success and chick growth in black oystercatchers

To determine if Black Oystercatchers (Haematopus bachmani) were affected by persistent shoreline oil from the T/V Exxon Valdez oil spill, I identified contaminated for- aging sites of oystercatchers, quantified diet and foraging behavior, assessed hydrocarbon uptake, and measured breeding success and mass gain of chicks. Hydrocarbon concentra- tions in sediments at foraging sites indicated that some oystercatchers potentially were ex- posed to shoreline oil that persisted into 1992 or 1993. Direct evidence of hydrocarbon ex- posure was obtained from feces of chicks raised on persistently oiled shorelines. Elevated concentrations of total hydrocarbons, even-numbered aliphatics, and unresolved complex mixtures were indicative of petroleum hydrocarbon exposure. Mussels (Mytilus trossulus) were an important component of the diet of adults and chicks. Oystercatchers foraged for mussels on low-sloping, mixed sand-and-gravel beaches that often retained oil but spent less time foraging on contaminated substrates than on unoiled substrates. Effects of persistent shoreline oil on measures of breeding success were negligible and likely were overridden by the influence of egg and chick predation. Chicks raised on shorelines that were heavily oiled in 1989 gained mass at a slower rate than did chicks raised on shorelines that were not heavi- ly oiled; however, slower mass gain did not translate into reduced fiedging success of chicks raised on heavily oiled shorelines. Although some oystercatchers were exposed to persistent shoreline oil, areas of contamination were patchily distributed, and relatively few adults and young were exposed. The lack of a large-scale change in oystercatcher numbers inhabiting the oiled area of Prince William Sound suggests that the negative effects of oil exposure operated locally. Consequently, oiled mussel beds present little additional risk to the pop- ulation of Black Oystercatchers inhabiting Prince William Sound. Received 4 February 1998,

Population Size of Snowy Plovers Breeding in North America

Abstract. Snowy Plovers (Charadrius nivosus) may be one of the rarest shorebirds in North America yet a comprehensive assessment of their abundance and distribution has not been completed. During 2007 and 2008, 557 discrete wetlands were surveyed and nine additional large wetland complexes sampled in México and the USA. From these surveys, a population of 23,555 (95% CI = 17,299 – 29,859) breeding Snowy Plovers was estimated. Combining the estimate with information from areas not surveyed, the total North American population was assessed at 25,869 (95% CI = 18,917 – 32,173). Approximately 42% of all breeding Snowy Plovers in North America resided at two sites (Great Salt Lake, Utah, and Salt Plains National Wildlife Refuge, Oklahoma), and 33% of all these were on wetlands in the Great Basin (including Great Salt Lake). Also, coastal habitats in central and southern Texas supported large numbers of breeding plovers. New breeding sites were discovered in interior deserts and highlands and along the Pacific coast of México; approximately 9% of the North American breeding population occurred in México. Because of uncertainties about effects of climate change and current stresses to breeding habitats, the species should be a management and conservation priority. Periodic monitoring should be undertaken at important sites to ensure high quality habitat is available to support the Snowy Plover population.

Population Size and Stopover Duration Estimation Using Mark-Resight Data and Bayesian Analysis of a Superpopulation Model

We present a novel formulation of a mark-recapture-resight model that allows estimation of population size, stopover duration, and arrival and departure schedules at migration areas. Estimation is based on encounter histories of uniquely marked individuals and relative counts of marked and unmarked animals. We use a Bayesian analysis of a state-space formulation of the Jolly-Seber mark-recapture model, integrated with a binomial model for counts of unmarked animals, to derive estimates of population size and arrival and departure probabilities. We also provide a novel estimator for stopover duration that is derived from the latent state variable representing the interim between arrival and departure in the state-space model. We conduct a simulation study of field sampling protocols to understand the impact of superpopulation size, proportion marked, and number of animals sampled on bias and precision of estimates. Simulation results indicate that relative bias of estimates of the proportion of the population with marks was low for all sampling scenarios and never exceeded 2%. Our approach does not require enumeration of all unmarked animals detected or direct knowledge of the number of marked animals in the population at the time of the study. This provides flexibility and potential application in a variety of sampling situations (e.g., migratory birds, breeding seabirds, sea turtles, fish, pinnipeds, etc.). Application of the methods is demonstrated with data from a study of migratory sandpipers.

Estimating Eastern Pacific Coast Populations of Whimbrels and Hudsonian Godwits, with an Emphasis on Chiloé Island, Chile

Abstract. A large proportion of the Hudsonian Godwits (Limosa haemastica) spending the boreal winter along the eastern Pacific Ocean coast are known to occur in the vicinity of Chiloé Island, Chile, but the importance of the region to Whimbrels (Numenius phaeopus) is less known. Ground counts conducted in 2007 and 2008 increased published estimates, at a minimum, of Pacific coast populations by 27% for Whimbrels (33,150 individuals) and 51% for Hudsonian Godwits (21,161 individuals). Bays and shorelines in the Chiloé Island region supported 99% of Hudsonian Godwits and, perhaps, 61% of Whimbrels estimated to occur along the Pacific coast during the boreal winter. Whereas Hudsonian Godwits aggregated in shallow bays on the eastern and northern coast of Chiloé Island, Whimbrels were more dispersed along the islands coastline and reached a density of 7.5 birds/km along sheltered gravel shorelines. Bays in the vicinity of Chiloés capital, Castro, provided important foraging and roosting habitat for non-breeding birds; these sites supported 52% of the Pacific coast population of Hudsonian Godwits and >4,000 Whimbrels. Low human disturbance in Pullao and Putemún bays makes these sites particularly attractive to nonbreeding Hudsonian Godwits, and their permanent protection is urged.

Large-scale monitoring of shorebird populations using count data and N-mixture models: Black Oystercatcher ( Haematopus bachmani ) surveys by land and sea

ABSTRACT. Large-scale monitoring of bird populations is often based on count data collected across spatial scales that may include multiple physiographic regions and habitat types. Monitoring at large spatial scales may require multiple survey platforms (e.g., from boats and land when monitoring coastal species) and multiple survey methods. It becomes especially important to explicitly account for detection probability when analyzing count data that have been collected using multiple survey platforms or methods. We evaluated a new analytical framework, N-mixture models, to estimate actual abundance while accounting for multiple detection biases. During May 2006, we made repeated counts of Black Oystercatchers (Haematopus bachmani) from boats in the Puget Sound area of Washington (n = 55 sites) and from land along the coast of Oregon (n = 56 sites). We used a Bayesian analysis of N-mixture models to (1) assess detection probability as a function of environmental and survey covariates and (2) estimate total Black Oystercatcher abundance during the breeding season in the two regions. Probability of detecting individuals during boat-based surveys was 0.75 (95% credible interval: 0.42–0.91) and was not influenced by tidal stage. Detection probability from surveys conducted on foot was 0.68 (0.39–0.90); the latter was not influenced by fog, wind, or number of observers but was ∼35% lower during rain. The estimated population size was 321 birds (262–511) in Washington and 311 (276–382) in Oregon. N-mixture models provide a flexible framework for modeling count data and covariates in large-scale bird monitoring programs designed to understand population change.

Predicting breeding shorebird distributions on the Arctic Coastal Plain of Alaska

The Arctic Coastal Plain (ACP) of Alaska is an important region for millions of migrating and nesting shorebirds. However, this region is threatened by climate change and increased human development (e.g., oil and gas production) that have the potential to greatly impact shorebird populations and breeding habitat in the near future. Because historic data on shorebird distributions in the ACP are very coarse and incomplete, we sought to develop detailed, contemporary distribution maps so that the potential impacts of climate-mediated changes and development could be ascertained. To do this, we developed and mapped habitat suitability indices for eight species of shorebirds (Black-bellied Plover [Pluvialis squatarola], American Golden-Plover [Pluvialis dominica], Semipalmated Sandpiper [Calidris pusilla], Pectoral Sandpiper [Calidris melanotos], Dunlin [Calidris alpina], Long-billed Dowitcher [Limnodromus scolopaceus], Red-necked Phalarope [Phalaropus lobatus], and Red Phalarope [Phalaropus fulicarius]) that commonly breed within the ACP of Alaska. These habitat suitability models were based on 767 plots surveyed during nine years between 1998 and 2008 (surveys were not conducted in 2003 and 2005), using single-visit rapid area searches during territory establishment and incubation (8 June–1 July). Species-specific habitat suitability indices were developed and mapped using presence-only modeling techniques (partitioned Mahalanobis distance) and landscape environmental variables. For most species, habitat suitability increased at lower elevations (i.e., near the coast and river deltas) and decreased within upland habitats. Accuracy of models was high for all species, ranging from 65–98%. Our models predicted that the largest fraction of suitable habitat for the majority of species occurred within the National Petroleum Reserve-Alaska, with highly suitable habitat also occurring within coastal areas of the Arctic National Wildlife Refuge west to Prudhoe Bay.

Black Oystercatchers and Campsites in Western Prince William Sound, Alaska

Abstract. Black Oystercatchers (Haematopus bachmani) have been identified as a species of concern by government agencies and conservation organizations because they have small populations and are sensitive to disturbance caused by shoreline and near-shore human activity. Expanding human recreation in Prince William Sound (PWS) may have potential negative consequences on Black Oystercatcher reproduction and on the population as a whole. Almost 2000 km of shoreline in western PWS was inventoried to assess density, distribution and habitat use of breeding Black Oystercatchers each June and July from 2001 to 2004. These efforts identified 94 territories (density 0.030.38 pairs/km). Black Oystercatcher territories were preferentially located on wave-cut platforms and rocky islets as well as gravel beaches but they avoided salt marsh, tide flats and sheltered rocky shores. Within western PWS 186 shoreline campsites were documented and people preferred to camp on gravel beaches. The association between campsites and territories was evaluated, and although there was a positive correlation at the landscape level, direct overlap only occurred on four sites and territories were separated from campsites, on average, by 1.8 km. Impacts associated with direct overlap (e.g., trampling of nests or direct displacement of pairs) may be rare for this remote area.

BREEDING BIRDS OF RESEARCH NATURAL AREAS IN SOUTHEASTERN ALASKA

Abstract The Tongass National Forest encompasses a large expanse of temperate rainforest in southeastern Alaska and contains 12 designated Research Natural Areas (RNAs). Existing in as near a natural condition as possible, RNAs receive minimal commercial and recreational use. Because few bird studies have been conducted on RNAs, we used point counts and area searches to determine the occurrence and abundance of breeding landbirds present in vegetation communities of RNAs. Of 49 species of small landbirds detected during area searches, the most widely distributed birds among RNAs were rufous hummingbird (Selasphorus rufa), chestnut-backed chickadee (Poecile rufescens), winter wren (Troglodytes troglodytes), golden-crowned kinglet (Regulus satrapa), Swainsons thrush (Catharus ustulatus), hermit thrush (C. guttatus), varied thrush (Ixoreus naevius), and Townsends warbler (Dendroica townsendi). The 8 most abundant species recorded on 187 point counts (>0.5 birds/point) were Pacific-slope flycatcher (Empidonax difficilis), hermit thrush, varied thrush, winter wren, golden-crowned kinglet, Townsends warbler, and chestnut-backed chickadee. Several species had significant differences in abundance between low-elevation hemlock-spruce forest and their abundance in either high-elevation fir-spruce forest or mixed conifer-shore pine muskeg. Because RNAs provide forests that are not disturbed by human activities, these sites could provide a standard to evaluate changes in bird abundance and richness that may occur on developed land in southeastern Alaska.

Birds of the major mainland rivers of southeast Alaska.

Johnson, James A.; Andres, Brad A.; Bissonette, John A. 2008. Birds of the major mainland rivers of southeast Alaska. Gen. Tech. Rep. PNW-GTR-739. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 88 p. This publication describes the bird communities of major mainland rivers of southeast Alaska and is based on a review of all known relevant studies as well as recent fieldwork. We synthesized information on the composition, structure, and habitat relationships of bird communities at 11 major mainland rivers. Information on current management concerns and research needs are also included.