Stephen W. Kress

Invasive mammal eradication on islands results in substantial conservation gains.

Significance Global conservation actions to prevent or slow extinctions and protect biodiversity are costly. However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions. Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species. This research quantifies the benefits to native island fauna of removing invasive mammals from islands. Our results highlight the importance of this conservation measure for protecting the worlds most threatened species. More than US

Marine Foraging Birds As Bioindicators of Mercury in the Gulf of Maine

21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the worlds most imperiled fauna.

Assessment of Social Attraction Techniques Used to Restore a Common Murre Colony in Central California

From existing databases, we compiled and evaluated 604 total mercury (Hg) levels in the eggs and blood of 17 species of marine foraging birds from 35 Gulf of Maine islands to provide baseline data and to determine the best tissue, age class, and species for future biomonitoring. While mean Hg levels in most species did not exceed adverse effects thresholds, levels in some individual eggs did; for all species arithmetic mean egg Hg levels ranged from 0.04 to 0.62 (μg/g, wet weight). Piscivorous birds had higher Hg levels than invertivores. Leach’s storm-petrel (Oceanodroma leucorhoa), razorbill (Alca torda), and black guillemot (Cepphus grylle) adult blood and egg Hg levels were higher than other species. Our results indicate that adult blood is preferable to chick blood for detecting long-term temporal trends because adult levels are higher and not confounded by metabolic effects. However, since we found that eggs and adult blood are comparable indicators of methylmercury bioavailability, we determined that eggs are the preferred tissue for long-term Hg monitoring because the relative ease in collecting eggs ensures consistent and robust datasets. We suggest specific sampling methods, and based on our results demonstrate that common eider (Somateria mollissima), Leach’s storm-petrel, double-crested cormorant, and black guillemot are the most effective bioindicators of Hg of the Gulf of Maine.

ENCOUNTER, SURVIVAL, AND MOVEMENT PROBABILITIES FROM AN ATLANTIC PUFFIN (FRATERCULA ARCTICA) METAPOPULATION

Abstract Colonial seabirds such as alcids often do not rapidly recolonize former breeding habitat following extirpation of nesting colonies. Social attraction (e.g., use of decoys, recorded vocalizations and mirrors) artificially stimulates nesting by providing social cues that encourage colonization. Common Murres (Uria aalge) stopped breeding at Devil’s Slide Rock, San Mateo County, California following the 1986 Apex Houston oil spill. Natural recolonization did not occur between 1987 and 1995. Common Murres began regular visits to Devil’s Slide Rock within 24 hours of social attraction equipment installation in January 1996 and six pairs nested by June 1996. Over 90% of murre observations were in decoy plots in contrast to control plots and outside of plots where few murre observations occurred. Significantly more murre presences versus absences were recorded in low density decoy plots and these birds most often frequented open areas (aisles) within decoy clusters. Significantly larger groups of murres visited high density decoy plots and aisle sub-plots. Murre densities were significantly greater within 30 cm of mirrors. Five of six nests were within 60 cm of mirrors. Nests coincided with areas where prior nesting and last pre-1996 attendance had been concentrated. Rapid breeding response combined with recent nonbreeding attendance suggests that the first colonists may have been surviving breeders from the original colony or young produced at the rock prior to the oil spill. The initial recolonization event and continued restoration efforts have prompted further colony growth to 190 pairs nesting by 2004. This study suggests that social stimuli can limit natural colonization of otherwise suitable habitat.

Attraction of the endangered dark-rumped petrel to recorded vocalizations in the Galápagos Islands

Several weaknesses in our understanding of long-lived animal populations have persisted, mainly due to a prevalence of studies of a single local population at the expense of multisite studies. We performed a multisite capture–mark–resight analysis using 2050 Atlantic Puffins (Fratercula arctica) banded as chicks on four islands (colonies) over 24 years in the Gulf of Maine, USA and Canada. Within program MARK, encounter, apparent survival, pre-breeding movement (PBM; annual movements between colonies prior to breeding), and natal dispersal (ND) probabilities were modeled as functions of age, colony, and several covariates. Information-theoretic model selection criteria and estimated model effect sizes were used to identify important effects and select models to estimate parameters. Encounter probabilities were extremely variable (0.10–0.95) and declined annually starting six years after bands were applied, due to changes in resighting effort, and band wear, respectively. Colony-dependent survival probabil...

Breeding Dispersal and Survival of Arctic Terns (Sterna Paradisaea) Nesting in the Gulf of Maine

We report the attraction of Dark-rumped Petrels (Pterodroma phaeopygia), an endangered seabird of the Galapagos Islands, to playbacks of vocalizations and compare results during playback to results using control periods when no vocalizations were presented. From May to August in 1988 and 1989, during a total of 868 hours ofplayback, we captured 600 petrels in mist nets and observed 11,020 passes of petrels over the mist nets. Playback of vocalizations resulted in a mean capture rate of 0.83 petrels per hour whereas control periods yielded a mean capture rate of 0.38 petrels per hour. Playback of vocalizations resulted in a mean passing rate of 15.13 petrels per hour whereas control periods yielded a mean capture rate of 7.3 petrels per hour. Playback of vocalizations recorded from petrel colonies (groups of birds) usually resulted in higher capture and passing rates compared to rates during playback of vocalizations from single birds. These results demonstrate the potential of acoustic playback for luring seabirds to nondegraded habitat or to restored habitat. In addition to having management implications for a variety of threatened colonial nesting birds, the results reported here also suggest that certain Dark-rumped Petrel vocalizations function as indicators to the quality of nesting habitat.

Effects of Gull Predation and Predator Control on Tern Nesting Success at Eastern Egg Rock, Maine

Abstract We used capture–mark–recapture (or re-encounter) analysis of a metapopulation to estimate the probability of survival, re-encounter, and dispersal of Arctic Terns (Sterna paradisaea) nesting in the Gulf of Maine and the Bay of Fundy. Before our study, there were only a few anecdotal accounts of breeding dispersal, and the only estimates of survival for this species were calculated in the 1950s and 1960s in the United Kingdom, using return rates unadjusted for recapture probability. Approximately 45% of the North American breeding population nests in the Gulf of Maine region; 95% of these nest on the four islands studied. Re-encounter observations of 2,295 adult Arctic Terns banded on these four key islands were collected from 1999 to 2005. An information-theoretic approach was used to determine the model best describing survival and movement patterns. Models using the program M-SURGE suggested that the apparent survival of adult Arctic Terns was colony- and year-specific, ranging from 0.704 to 0.960 when transient individuals were accounted for. Re-encounter probabilities were generally low, ranging from 0.12 to 0.74, depending on colony and year. Fidelity to previous breeding colonies was high; estimated probability of movement among colonies ranged from 0.000 to 0.015. Breeding dispersal was negatively correlated with distances among islands, but not with colony size. There was no difference between male and female Arctic Terns in survival, re-encounter, or breeding dispersal.

Diet of Nestling Black-crowned Night-herons in a Mixed Species Colony: Implications for Tern Conservation

Abstract Gull predation is an important source of egg and chick mortality for many seabirds. From 2003-2005, the effects of gull predation and a predator control program on tern nesting success were studied at Eastern Egg Rock, Maine. In 2003, gull predation was uncontrolled, and in 2004 and 2005, attempts were made to shoot Herring (Larus argentatus), Great Black-backed (L. marinus), and Laughing (L. atricilla) gulls that preyed on Common (Sterna hirundo), Arctic (S. paradisaea), and Roseate (S. dougallii) tern adults, eggs, and chicks. To evaluate the effectiveness of gull removal, daily watches were performed from an observation tower and tern hatching and fledging success were measured annually. Despite shooting efforts in 2004-2005, many known predators could not be removed. Great Black-backed Gull predation was a function of year, tidal state, and visibility, while Herring Gull predation depended only on the stage of the tern breeding cycle. Using disappearance of eggs and chicks from monitored nests as a proxy for gull predation pressure, an estimated 23% of Common, 32% of Arctic, and 6% of Roseate tern nests were depredated by gulls during the study period. Predation risk depended on nest position within the colony, but not year, with some areas consistently more vulnerable to gulls than others. We discuss the difficulty of removing predatory gulls from a tern colony lacking nesting Herring and Great Black-backed gulls and suggest the importance of human presence and associated research activities for reducing gull predation at this site.

ADULT SURVIVAL ESTIMATES FROM TWO ATLANTIC PUFFIN (FRATERCULA ARCTICA) COLONIES IN THE GULF OF MAINE

Abstract Boluses were collected from Black-crowned Night-heron (Nycticorax nycticorax) nestlings in 1992 to examine the impact of night-heron predation on a restored tern colony. Boluses (n = 101) were collected from 18 nests. Fish remains occurred in 89% of nests, sand shrimp (Crangon septemspinosa) in 50%, birds in 28%, and amphibians in 16% of nests sampled; mammalian, eel, squid, and marine invertebrate remains were also noted. Regurgitated bird remains were found in five nests and included four species, Common Terns (Sterna hirundo), Common Eiders (Somateria mollissima), Gulls (Larus sp.), and the legs of an unknown wading bird. Nestling night-herons from three nests were fed tern chicks, but 92% of tern chicks known to have been eaten were fed to nestling Black-crowned Night-herons in one nest. No tern chicks fledged in 1992 and night-herons were observed in the tern colony on multiple occasions. This study suggests that individual night-herons will specialize on waterbird prey. The subsequent removal of a specialist night-heron predator resulted in improved tern productivity.

Comparison of Common Tern Reproductive Performance at Four Restored Colonies along the Maine Coast, 1991-2002

Abstract We report survival probabilities for 148 breeding adult Atlantic Puffins (Fratercula arctica) monitored through capture-mark-resight at two colonies for 11 years (1992–2003). The colonies, Eastern Egg Rock and Seal Island, are ∼42 km apart in the Gulf of Maine. Support for competing models in the program MARK suggests constant survival of 0.95 ± 0.01 (SE) that is independent of colony. Our high survival probability is consistent with published estimates for Atlantic Puffins and other long-lived seabirds. No time-variance contrasts with many long-term seabird studies, which often report high survival in most years, broken occasionally by low-survival events. However, a post-hoc observation of survival estimates from the time-dependent model suggests that there may have been at least two low-survival events in our time-series; sparse data may have precluded detection by our models. In this study, each bird received an individually engraved, plastic, field-readable leg band, as well as the standard metal band. Using an index of band readability, we show that plastic bands wore rapidly, resulting in accumulating losses of engraved characters through time. Degradation and loss of marks is a common source of overdispersion in capture-mark-re-encounter data and results in underestimated sampling variances. In the presence of a 70% reduction in band readability over eight years, an estimate of the adjusted overdispersion factor (ĉ = 1.14) identified very little overdispersion in our data. Overdispersion was avoided by double banding and intensively resighting metal bands. Estimation de la Survie Adulte de Deux Colonies de Fratercula arctica dans le Golfe du Maine