Avian Predator Control Led to Increased Breeding Success of Common Murre Uria aalge on Teuri Island, Hokkaido

The Common Murre Uria aalge is listed as an endangered species in Japan and breeds only on Teuri Island, Hokkaido. The Teuri Island population has decreased from 8,000 birds in 1963 to 19 in 2010. They bred on sea-stack and cliff ledges (open habitat) before 1994, but mostly in cliff caves (closed habitat) after 1994. In closed habitat, the fledging rate was greater and the rate of population decrease was smaller than in open habitat. Restoration actions (decoys and sounds) were effective in attracting murres, but did not enhance the fledging rate sufficiently to raise their population, possibly because of predation by avian predators (Slatybacked Gulls Larus schistisagus and Jungle Crows Corvus macrorhynchos). Using the fledging rate observed in closed habitat and other demographic parameters found in references, Population Viability Analysis shows that the probability of extinction of the Teuri population within 50 years is 66%. To improve the fledging rate and make the restoration actions more effective, we recommend the control of avian predators.

(1) The influence of predation by Slaty-backed Gulls Larus schistisagus on the fledging success of Black-tailed Gulls L. crassirostris was studied on Teuri Island off Haboro, Hokkaido, in 1980 and 1981. (2) Four quadrats were set in the breeding colony of Black-tailed Gulls in which 326 chicks were colour ringed and their biomass was measured. The analysis of food remains collected from forty nests of Slaty-backed Gulls was made for the estimation of the amount of predation. (3) The amount of predation reached a maximum later than the time when the biomass of prey reached a maximum. (4) Slaty-backed Gulls selectively hunt smaller chicks because of low hunting successs of large prey. (5) Later broods of Black-tailed Gulls were exposed to higher predation pressure by Slaty-backed Gulls. (6) The fledging success of Black-tailed Gulls was lower in late (14%) than in early (31%) and middle broods (41%). This trend could partly be explained by predation by Slaty-backed Gulls.

Sea‐surface temperature (SST) directly and indirectly affects the distribution and abundance of prey species for seabirds, so we expect variation in SST to be associated with variation in seabird life history traits. In black‐tailed gulls (Larus crassirostris) at Teuri Island in northern Hokkaido, Japan, we investigated the diet of the gulls prior to egg laying in 2004 and 2005, and examined the influences of SST in March or April, when the gulls congregate in the colony, on egg‐laying parameters using 13 years of data (1992–2004). The gulls fed on krill (Thysanoessa inermis) and fish prior to the egg laying. Mean first egg dates and clutch sizes were significantly and quadratically related to SST anomalies in March, but were not influenced by SST anomalies in April. There was no significant effect of SSTs in either March or April on egg volume. Sea‐surface temperature anomalies in March of the years of early laying (−1 to 1°C) were higher than those in 2001 (−2.2°C), but lower than those in 1992 (+1.2°C) and 2004 (+1.1°C). Thysanoessa inermis congregates to spawn at the sea surface, when SSTs rise 3−4°C. Thus, a mismatch between food availability and the timing of egg production in the gulls could have occurred in these 3 years. This study suggests that SST fluctuations prior to laying are important in breeding success of black‐tailed gulls.

Interannual variations of the occurrence of epipelagic fish in the diets of the seabirds breeding on Teuri Island, northern Hokkaido, Japan

Artificial nest experiment reveals inter-guild facilitation in duck nest predation

Predation has been suggested to be especially important in simple food webs and less productive ecosystems such as the arctic tundra, but very few data are available to evaluate this hypothesis. We examined the hypothesis that avian predators could drive the population dynamics of two cyclic lemming species in the Canadian Arctic. A dense and diverse suite of predatory birds, including the Snowy Owl (Bubo scandiacus), the Rough-legged Hawk (Buteo lagopus), and the Long-tailed Jaeger (Stercorarius longicaudus), inhabits the arctic tundra and prey on collared (Dicrostonyx groenlandicus) and brown (Lemmus trimucronatus) lemmings during the snow-free period. We evaluated the predation pressure exerted by these predators by combining their numerical (variation in breeding and fledgling numbers) and functional (variation in diet and daily consumption rates) responses to variations in lemming densities over the 2004-2010 period. Breeding density and number of fledglings produced by the three main avian predators increased sharply without delay in response to increasing lemming densities. The proportion of collared lemmings in the diet of those predators was high at low lemming density (both species) but decreased as lemming density increased. However, we found little evidence that their daily consumption rates vary in relation to changes in lemming density. Total consumption rate by avian predators initially increased more rapidly for collared lemming but eventually leveled off at a much higher value for brown lemmings, the most abundant species at our site. The combined daily predation rate of avian predators exceeded the maximum daily potential growth rates of both lemming species except at the highest recorded densities for brown lemmings. We thus show, for the first time, that predation pressure exerted without delay by avian predators can limit populations of coexisting lemming species during the snow-free period, and thus, that predation could play a role in the cyclic dynamic of these species in the tundra.

For seabirds, nest site features are an important factor that determines reproductive success. During three breeding seasons (2010–2012), we visited two coastal cliff colonies of Red-legged Cormorants Phalacrocorax gaimardi in the Ria Deseado, Argentina, and studied how nest site characteristics influenced their breeding success. We measured six physical characteristics at 46 nest sites, and we counted the number of fledglings produced each year from each nest (breeding success). We also related nest site temperature and wind exposure with nest site orientation. Breeding success was higher at nest sites with a broad base (greater capacity for holding young) and at nests that were less exposed to winds greater than 25 knots (46.25 km/h), which were sites with a north orientation. The lowest breeding success was observed in nest sites that were exposed to the strongest winds (i.e., sites with a south orientation). Strong winds often blow eggs and chicks away from the nests and increase opportunistic predation by gulls Larus sp. No significant relationship was found between nest site orientation and nest site temperature. Breeding success decreased with the distance to the nearest nest, which agrees with the idea that higher density of reproductive individuals reduces effectiveness of predators. Nest cover, distance from the top of the cliff, and distance from the tide line had no effect on breeding success at this study scale. Our results suggested that nest site characteristics that were related to protection against adverse weather conditions (e.g., strong winds) and avian predation, in combination with a suitable nest space, determined the breeding success of Red-legged Cormorants.

Post-logging effects on nest predation and avian predator assemblages in a subtropical forest

The global loss of biodiversity has inspired actions to restore nature across the planet. Translocation and social attraction actions deliberately move or lure a target species to a restoration site to reintroduce or augment populations and enhance biodiversity and ecosystem resilience. Given limited conservation funding and rapidly accelerating extinction trajectories, tracking progress of these interventions can inform best practices and advance management outcomes. Seabirds are globally threatened and commonly targeted for translocation and social attraction ("active seabird restoration"), yet no framework exists for tracking these efforts nor informing best practices. This study addresses this gap for conservation decision makers responsible for seabirds and coastal management. We systematically reviewed active seabird restoration projects worldwide and collated results into a publicly accessible Seabird Restoration Database. We describe global restoration trends, apply a systematic process to measure success rates and response times since implementation, and examine global factors influencing outcomes. The database contains 851 active restoration events in 551 locations targeting 138 seabird species; 16% of events targeted globally threatened taxa. Visitation occurred in 80% of events and breeding occurred in 76%, on average 2 y after implementation began (SD = 3.2 y). Outcomes varied by taxonomy, with the highest and quickest breeding response rates for Charadriiformes (terns, gulls, and auks), primarily with social attraction. Given delayed and variable response times to active restoration, 5 y is appropriate before evaluating outcomes. The database and results serve as a model for tracking and evaluating restoration outcomes, and is applicable to measuring conservation interventions for additional threatened taxa.

Predators are often the focus of conservation efforts. They can be useful sentinel species, umbrella species, and flagship species. Predators can also be the first guild lost when ecosystems are under stress, especially from anthropogenic land-use change. Avian predators (raptors) can be an exception to this trend, filling the role of apex predators across the urban gradient. South Florida contains the Everglades ecosystem and one of the fastest growing human populations in the country. In the current study, I investigated the population dynamics of South Florida’s most abundant hawk: the Red-shouldered Hawk (Buteo lineatus, RSHA) across the urban gradient. South Florida is home to its own subspecies of RSHA (Buteo lineatus extimus), which has heretofore received little formal study. I first observed breeding attempts to quantify the productivity of the southern subspecies. South Florida RSHAs were found to be equally productive in urban and exurban areas and produced 1.8 ± 0.6 fledglings per successful nest, about average for this species. I developed habitat maps around each nest using remote sensing, but land cover was not related to the likelihood of nest success. I then placed cameras in nests to observe the prey items fed to chicks. Adults fed primarily reptiles (58%) and amphibians (18%). I also partnered with three wildlife rehabilitation hospitals to screen RSHAs that perished in their care for anticoagulant rodenticides (ARs). The Environmental Protection Agency restricted the sale of ARs to the public in 2008 in part to reduce secondary poisoning to wildlife like raptors. Despite these restrictions and the low rate of mammal consumption among local birds, 49% of RSHAs screened had been exposed to ARs. Finally, I investigated the genetic diversity of RSHAs and found evidence for a genetic bottleneck, reduced genetic diversity, and inbreeding in the focal population. My study found RSHAs in South Florida to be very flexible in their diet and nest sites but also found reduced genetic diversity and high rates of exposure to toxins. Additional research is needed to determine whether the population is increasing, stable, or declining in the rapidly urbanizing region.

We ringed a female House Sparrow (Passer domesticus) at the Teuri Island, off Haboro, northern Hokkaido on 3 May 1998. Although there are several observation records of the species in northeastern Japan (Hokkaido, Akita and the satellite islands in the Japan Sea), this was the first House Sparrow ringed in Japan.

48. On the Shelterbelt Establishment on Teuri Island, Northern Hokkaido

We evaluated characteristics at Red-shouldered Hawk (Buteo lineatus) nest sites at two study areas with different topography and forest types in north-central and central Minnesota to identify nest site commonalities across geographically distinct areas. During the breeding seasons of 1994–1995, we located nests of Red-shouldered Hawks at the Camp Ripley Army National Guard Training Site and the Chippewa National Forest using a combination of broadcast surveys, helicopter searches, and systematic foot searches. All 38 nests at Camp Ripley and 18 nests in the Chippewa National Forest were in upland hardwood stands; the remaining two nests in the Chippewa National Forest were in aspen (Populus spp.) stands. We aged cores from 19 nest trees at Camp Ripley and measured habitat characteristics in a 0.04 ha circle centered on each nest tree and at a paired random site within the nest stand. We compared habitat variables at nest and random sites to identify habitat characteristics that were consistent predictors of nest sites versus random sites for each study area and for all nests combined. Compared to random sites, nest sites in the Chippewa National Forest had larger diameters at breast height (dbh) of the nest tree, taller nest tree height, and higher canopy height. At Camp Ripley, nest sites differed from random sites with regard to many more variables; nests were located in portions of the stand with larger trees and closer to surface water. Nest trees ranged in age from 50–89 years. Logistic regression models indicated that, for both study areas combined, nest tree dbh, basal area, canopy height, and distance to water were the most important variables in distinguishing nest sites from random sites.

SummaryGlobal seabird populations are in decline, with nearly half of all seabird species currently in an extinction crisis. Understanding long-term seabird population trends is an essential first step to inform conservation actions. In this study, we assembled historical breeding records of seabirds throughout the Japanese archipelago and quantified the long-term population trends of 10 major breeding seabird species using a hierarchical Bayesian state-space model. The model revealed that six species had increasing or no detectable trends (Short-tailed Albatross Phoebastria albatrus, Leach’s Storm Petrel Oceanodroma leucorhoa, Pelagic Cormorant Phalacrocorax pelagicus, Japanese Cormorant Phalacrocorax capillatus, Spectacled Guillemot Cepphus carbo, and Rhinoceros Auklet Cerorhinca monocerata). However, decreasing trends were found not only in nationally threatened species (Common Murre Uria aalge, and Tufted Puffin Fratercula cirrhata) but also common species that are often described as abundant (Black-tailed Gull Larus crassirostris and Slaty-backed Gull Larus schistisagus). These declining species have declined to 3–35% of baseline levels over the past 30 years. This study provides the first evidence of long-term declines in common and widespread seabirds in Japan.

Breeding ecology of the Cattle Egret (Bubulcus ibis) in Guerbes-Sanhadja wetlands of Algeria