Steven J. Kendall

NINE YEARS AFTER THE EXXON VALDEZ OIL SPILL: EFFECTS ON MARINE BIRD POPULATIONS IN PRINCE WILLIAM SOUND, ALASKA

Abstract We compared post Exxon Valdez oil-spill densities of marine birds in Prince William Sound from 1989–1991, 1993, 1996, and 1998 to pre-spill densities from 1984–1985. Post-spill densities of several species of marine birds were lower than expected in the oiled area of Prince William Sound when compared to densities in the unoiled area. These negative effects continued through 1998 for five taxa: cormorants, goldeneyes, mergansers, Pigeon Guillemot (Cepphus columba), and murres. Black Oystercatchers (Haematopus bachmani) and Harlequin Ducks (Histrionicus histrionicus) exhibited negative effects in 1990 and 1991. Loons showed a weak negative effect in 1993. Black-legged Kittiwakes (Rissa tridactyla) showed relative decreases in 1989, 1996, and 1998 which may have been caused by shifts in foraging distribution rather than declines in populations. Glaucous-winged Gulls (Larus glaucescens) showed positive effects in most post-spill years. Murrelets and terns showed relative increases in 1993, 1996, and 1998. Generally, taxa that dive for their food were negatively affected, whereas taxa that feed at the surface were not. Effects for some taxa were dependent upon the spatial scale at which they were analyzed. Movements of birds and the mosaic pattern of oiling reduced our ability to detect oil-spill effects, therefore our results may be conservative. Several marine bird species were negatively affected at the population level and have not recovered to pre-spill levels nine years after the oil spill. The reason for lack of recovery may be related to persistent oil remaining in the environment and reduced forage fish abundance.

Declines in Marine Bird Populations in Prince William Sound, Alaska Coincident with a Climatic Regime Shift

-Analyses of marine bird surveys conducted in Prince William Sound, Alaska in July 1972 were compared to surveys in July 1989, 1990, 1991, and 1993 and indicated that populations of several taxa of marine birds that prey on fish have declined in Prince William Sound, but most taxa that feed on other prey species, such as benthic invertebrates, have not declined. Red-throated Loon (Gavia stellata), Pacific Loon (G. pacifica), cormorant (Phalacrocorax spp.), Surf Scoter (Melanitta perspicillata), Bonapartes Gull (Larus philadelphia), terns (Sterna spp.), Pigeon Guillemot (Cepphus columba), Brachyramphus murrelets (Brachyramphus marmoratus and B. brevirostris), Parakeet Auklet (Cyclorrhynchus psittacula), Tufted Puffin (Fratercula cirrhata), and Horned Puffin (Fratercula corniculata) populations declined by >50%. Most of these are piscivores, feeding on schooling fish. Some non-piscivorous taxa, such as Harlequin Ducks (Histrionicus histrionicus), goldeneyes (Bucephala clangula and islandica), and Black Oystercatchers (Haematopus bachmani), have increased in Prince William Sound between 1972 and 1989-1993, although a portion of the population was killed by the T/VExxon Valdez oil spill. Declines in piscivorous bird populations also have been documented in the Gulf of Alaska, the Bering Sea, and along the California coast in the past two decades and have been coincidental to changes in forage fish species in the North Pacific Ocean. Many of the declines appear to be related to changes in forage fish abundance that occurred during a climatic regime shift in the north Pacific Ocean, although some taxa were also affected by the Exxon Valdez oil spill. Received 11 November 1998, accepted 6January 1999.

An evaluation of marine bird population trends following the Exxon Valdez oil spill, Prince William Sound, Alaska.

We examined post-spill trends (1989-1998) of marine bird populations in Prince William Sound (PWS) following the Exxon Valdez oil spill (EVOS) to evaluate recovery of injured taxa. Two criteria were employed. First, we examined population trends of injured taxa only in the oiled area of PWS using regression models. Second, we examined population trends of injured taxa in the oiled area relative to the unoiled area using homogeneity of the slopes tests. We considered a population recovering if there was a positive trend using either criteria. We considered a population not recovering if there was no trend using either criteria or a negative trend in the oiled area. A significant negative trend in the oiled area relative to the unoiled area was considered a continuing and increasing effect. Most taxa for which injury was previously demonstrated were not recovering and some taxa showed evidence of increasing effects nine years after the oil spill. Four taxa (loons Gavia spp, Harlequin Duck Histrionicus histrionicus, Bufflehead Bucephala spp, and North-western Crow Corvus caurinus) showed weak to very weak evidence of recovery. None of these taxa showed positive trends in both winter and summer. Nine taxa (grebes Podiceps spp, cormorants Phalacrocorax spp, Black Oystercatcher Haematopus bachmani, Mew Gull Larus canus, Glaucous-winged Gull Larus glaucescens, terns Sterna spp, murres Uria spp, Pigeon Guillemot Cepphus columba, and murrelets Brachyramphus spp) showed no evidence of recovery during summer or winter. Four taxa (scoters Melanitta spp, mergansers Mergus spp, goldeneyes Bucephala spp, and Black-legged Kittiwaka Rissa tridactyla) showed evidence of continuing, increasing effects. We showed evidence of slow recovery, lack of recovery, and divergent population trends in many taxa which utilize shoreline and nearshore habitats where oil is likely to persist. Potential lingering spill effects and natural variability appear to be acting in concert in delaying recovery of many PWS bird populations.

Abundance and distribution of Marbled and Kittlitz's Murrelets in Southcentral and Southeast Alaska

We used small boats to survey Marbled, Brachyramphus marmoratus, and Kittlitzs Murrelets, B. brevirostris (Brachyramphus murrelets) in Lower Cook Inlet, Prince William Sound, and Southeast Alaska. We estimated (± 95% CI) that there were 58,227 ± 16,058 (4.2 birds km -2 ) murrelets in Lower Cook Inlet in summer and 11,627 ± 7,410 (3.1 birds km -2 ) murrelets in the eastern half during winter. We estimated a mean of 113,652 ± 25,900 (12.7 birds km -2 ) murrelets in Prince William Sound in four summers and a mean of 24,979 ± 11,710 (2.8 birds km -2 ) murrelets in four winters. An estimated 687,061 ± 201,162 (19.4 birds km -2 ) murrelets were in Southeast Alaska in summer 1994. The summer population of all three areas was estimated to be between 655,482 and 1,062,398 murrelets. Winter abundance for the eastern portion of Lower Cook Inlet and Prince William Sound ranged from 22,646 to 50,164. Brachyramphus murrelets were distributed in low densities throughout each of the three study areas, although abundance was not uniform; there were areas of high densities within each study area. The largest densities were found in Southeast Alaska.

A Brief Response to Wiens et al., Twelve Years After the Exxon Valdez Oil Spill

Abstract We briefly address the four main issues that Wiens et al. (2001) present in their commentary on Irons et al. (2000). In summary our response is: (1) We discussed before-after control-impact design assumptions at length in our paper. Data do not exist to resolve this issue and Wiens et al. fail to shed new light on it. (2) Contrary to Wiens et al.s assertion, we discussed only statistically significant results. (3) Wiens et al. disagreed with our interpretations of a few select results. We stand by our interpretations. (4) Wiens et al. believe that the evidence we presented from other studies showing that Exxon Valdez oil still exists in Prince William Sound (PWS), and that birds are still ingesting it, is equivocal in demonstrating cause and effect. We agree, but arguments to the contrary are equally equivocal. Data from continued monitoring of marine birds in PWS support the conclusion that as of July 2000 one taxon is recovering from effects of the Exxon Valdez oil spill and eight taxa are not. Breve Respuesta a Wiens et al., Doce Años después del Derrame de Petróleo del Exxon Valdez Resumen. Nos referimos brevemente a los cuatro puntos principales que Wiens et al. (2001) presentan en su comentario sobre Irons et al. (2001). En síntesis, nuestra respuesta es: (1) En nuestro artículo abordamos de manera extensa los supuestos del diseño de evaluaciones pre y post impacto. No existen datos que permitan resolver este tema y Wiens et al. fallan en aportar nuevas ideas. (2) Contrariamente a lo afirmado por Wiens et al., solamente discutimos los resultados que son estadísticamente significativos. (3) Wiens et al. discienten con nuestras interpretaciones sobre unos pocos resultados seleccionados. Nosotros sostenemos nuestras interpretaciones. (4) Wiens et al. opinan que la evidencia que nosotros presentamos de otros estudios, que muestran que el petróleo de Exxon Valdez todavía existe en Prince William Sound (PWS) y que las aves aún están ingiriéndolo, es ambigua en demostrar causa y efecto. Coincidimos con esto, pero los argumentos en contraposición son igualmente ambiguos. Datos provenientes del monitoreo contínuo de aves marinas en PWS apoyan la conclusión que hasta julio del 2000 un taxón se está recuperando de los efectos del derrame de petróleo del Exxon Valdez y ocho taxa no lo están.

Intercontinental genetic structure and gene flow in Dunlin (Calidris alpina), a potential vector of avian influenza

Waterfowl (Anseriformes) and shorebirds (Charadriiformes) are the most common wild vectors of influenza A viruses. Due to their migratory behavior, some may transmit disease over long distances. Migratory connectivity studies can link breeding and nonbreeding grounds while illustrating potential interactions among populations that may spread diseases. We investigated Dunlin (Calidris alpina), a shorebird with a subspecies (C. a. arcticola) that migrates from nonbreeding areas endemic to avian influenza in eastern Asia to breeding grounds in northern Alaska. Using microsatellites and mitochondrial DNA, we illustrate genetic structure among six subspecies: C. a. arcticola, C. a. pacifica, C. a. hudsonia, C. a. sakhalina, C. a. kistchinski, and C. a. actites. We demonstrate that mitochondrial DNA can help distinguish C. a. arcticola on the Asian nonbreeding grounds with >70% accuracy depending on their relative abundance, indicating that genetics can help determine whether C. a. arcticola occurs where they may be exposed to highly pathogenic avian influenza (HPAI) during outbreaks. Our data reveal asymmetric intercontinental gene flow, with some C. a. arcticola short‐stopping migration to breed with C. a. pacifica in western Alaska. Because C. a. pacifica migrates along the Pacific Coast of North America, interactions between these subspecies and other taxa provide route for transmission of HPAI into other parts of North America.

Breeding habitat associations and predicted distribution of an obligate tundra-breeding bird, Smith's Longspur

ABSTRACT Smiths Longspur (Calcarius pictus) is a species of conservation concern which breeds in Arctic habitats that are expected to be especially vulnerable to climate change. We used bird presence and habitat data from point-transect surveys conducted at 12 sites across the Brooks Range, Alaska, 2003–2009, to identify breeding areas, describe local habitat associations, and identify suitable habitat using a predictive model of Smiths Longspur distribution. Smiths Longspurs were observed at seven sites, where they were associated with a variety of sedge–shrub habitats composed primarily of mosses, sedges, tussocks, and dwarf shrubs; erect shrubs were common but sparse. Nonmetric multidimensional scaling ordination of ground cover revealed positive associations of Smiths Longspur presence with sedges and mosses and a negative association with high cover of shrubs. To model predicted distribution, we used boosted regression trees to relate landscape variables to occurrence. Our model predicted that Smiths Longspurs may occur in valleys and foothills of the northeastern and southeastern mountains and in upland plateaus of the western mountains, and farther west than currently documented, over a predicted area no larger than 15% of the Brooks Range. With climate change, shrubs are expected to grow larger and denser, while soil moisture and moss cover are predicted to decrease. These changes may reduce Smiths Longspur habitat quality and limit distribution in the Brooks Range to poorly drained lowlands and alpine plateaus where sedge–shrub tundra is likely to persist. Conversely, northward advance of shrubs into sedge tundra may create suitable habitat, thus supporting a northward longspur distribution shift.