THE BREEDING SEABIRDS OF TROMELIN ISLAND (WESTERN INDIAN OCEAN): POPULATION SIZES,TRENDS AND BREEDING PHENOLOGY

Le Corre, M. 1996. The breeding seabirds of Tromelin Island (western Indian Ocean): population sizes, trends and breeding phenology. Ostrich 67: 155–159.

Formerly six or eight species of seabirds bred on Tromelin Island, but currently only two species do so: The Redfooted Booby Sula sula and the Masked Booby S. dactylatra. The last two species which became locally extinct, the Lesser Frigatebird Fregata ariel and the Greater Frigatebird F. minor, probably stopped breeding on the island as a consequence of human disturbance to breeding colonies. The populations of the two species of booby have opposing trends since 1954. The Masked Booby's population increased from 60 pairs in 1954 to 200–250 pairs in 1996 while the Red-footed Booby's population decreased from 500 pairs in 1968 to 130–180 pairs in 1996. The impacts of human settlement, introduced brown rats Rattus norvegicus, local extinction of the Greater Frigatebird and other factors are discussed to explain these changes in population sizes. New data are provided on the breeding phenology of the two species of booby. Finally, the importance of this island for the conservation of seabirds in the western Indian Ocean is discussed.     

Testing models of female reproductive migratory behaviour and population structure in the Caribbean hawksbill turtle, Eretmochelys imbricata, with mtDNA sequences

Information on the reproductive behaviour and population structure of female hawksbill turtles, Eretmochelys imbricata , is necessary to define conservation priorities for this highly endangered species. Two hypotheses to explain female nest site choice, natal homing and social facilitation, were tested by analyzing mtDNA control region sequences of 103 individuals from seven nesting colonies in the Caribbean and western Atlantic. Under the social facilitation model, newly mature females follow older females to a nesting location, and subsequently use this site for future nesting. This model generates an expectation that female lineages will be homogenized among regional nesting colonies. Contrary to expectations of the social facilitation model, mtDNA lineages were highly structured among western Atlantic nesting colonies. These analyses identified at least 6 female breeding stocks in the Caribbean and western Atlantic and support a natal homing model for recruitment of breeding females. Reproductive populations are effectively isolated over ecological time scales, and recovery plans for this species should include protection at the level of individual nesting colonies.     

Range of the Greater Flamingo, Phoenicopterus roseus , metapopulation in the Mediterranean: new insights from Turkey

Metapopulation conservation should rely on a flyway approach aiming at assessing the spatial range of metapopulations by estimating the level of exchanges among local populations. In the western Mediterranean, Greater Flamingos have been shown to constitute a metapopulation with natal and breeding dispersal among colonies. In this paper, we examine whether this metapopulation reaches Turkey using a band-resighting study. Our results are the first evidence of natal and breeding dispersal from the western Mediterranean to Turkey, and suggest that the Gediz Delta, one of the two Turkish breeding colonies, can play a significant role in the recruitment of flamingos from the western Mediterranean. In 2003 and 2004, breeders of western Mediterranean origin accounted for more than 1.2 and 1.9% of the estimated breeding population of the Gediz Delta, respectively. Our observations also indicate that the western Mediterranean and Southwest Asia may constitute two sets of populations, which overlap in Turkey. Finally, the resightings of flamingos banded in Turkey show that post-fledging dispersal from Turkey reaches both the eastern and western Mediterranean wetlands. Future data on the natal and breeding dispersal of flamingos born in Turkey could clarify further the connection between Turkey and the western Mediterranean metapopulation.     

基于基因组SNPs的南极恩克斯堡岛阿德利企鹅繁殖种群的遗传结构

我国提议在南极恩克斯堡岛新站址北侧3 km的阿德利企鹅(Pygoscelis adeliae)聚集繁殖地建立南极特别保护区, 对保护区边界的划分, 各国尚存争议, 尤其是对南湾(South Bay)的繁殖小种群是否具有遗传独特性, 是否应将其纳入保护区是重点关注的问题。本研究采集了恩克斯堡岛海景湾(Seaview Bay)和南湾的阿德利企鹅样品, 通过全基因组重测序和种群基因组学方法, 分析了恩克斯堡岛不同区域的种群遗传结构。发现恩克斯堡岛海景湾与南湾阿德利企鹅没有显著的遗传分化, 南湾阿德利企鹅不是独特的小种群; 海景湾高海拔区域个体与低海拔区域个体之间也没有显著的遗传差异, 推测该区域阿德利企鹅繁殖群体的分布格局与冰川堆积形成的阶地不具有显著相关性。本工作为恩克斯堡岛保护区和罗斯海新站建设提供了重要科技支撑。     

Population status and breeding season chronology of Heard Island fur seals

Fur seals were eliminated by sealers at Heard Island soon after its discovery in the 1850s. The first recorded breeding of Antarctic fur seals (Arctocephalus gazella) since sealing was reported in early 1963 (two pups). The most recent survey of the Heard Island fur-seal population was undertaken between November 2000 and March 2001, when 1,012 Antarctic fur-seal pups were born. This represents a fourfold increase since the last complete census in 1987/1988 (13 years), when 248 births were recorded. Pup estimates and counts available for eight breeding seasons since 1962/1963 suggest the population has been increasing at between 12 and 20% per year. Based on pup production, the breeding population is estimated to number approximately 4,100 seals. The number of fur seals on Heard Island peaked in late February/early March at 29,256 indicating that, in addition to the breeding population, a significant number of seals born elsewhere haul out on the island. Most of these are moulting sub-adult and adult males. As in 1987/1988, only one subantarctic fur-seal pup (A. tropicalis) was observed, suggesting this species is not colonising the island, as has been speculated.     

Natural immigration of brushtail possums,Trichosurus vulpecula,onto Aroha Island,Kerikeri Inlet,Bay of Islands,New Zealand

Abstract

Aroha is a 5 ha island in Kerikeri Inlet, Bay of Islands, which is joined to the North Island mainland by a 200 m long causeway. Introduced Australian brushtail possums (Trichosurus vulpecula) spread into the general area only in the mid 1970s, and were first trapped on Aroha Island in June 1979. Since then possums have regularly crossed the causeway, and have been systematically trapped to keep the island free of them. Two hundred and sixty two possums have been trapped on Aroha Island to December 1990, and the annual catch has increased steadily since 1981. About equal numbers of males and females have been trapped. Most possums were caught in March-April and fewest in July-August. Captures on the island were clustered, particularly during the breeding seasons. Average body weight was 2.2 kg; 97% were greys and 3% blacks; the young of females trapped on the island had been born in all months except December to February. In colour, body weight, and breeding pattern the possums trapped on Aroha Island were similar to other possum populations from the northern North Island. Most of the possums invading Aroha Island were 1-2 years old: in contrast to findings from previous studies of possum dispersal, Arona Island was invaded year-round by young male and female possums equally. Some older animals may also have been attracted to the island by fruits available in an orchard there. Maintenance of the possum-free state of Aroha Island will require continuous management.     

Impacts of human visitors on breeding success and long-term population trends in Adélie Penguins at Casey,Antarctica

Breeding populations of Aélie Penguins Pygoscelis adeliae have been counted at two localities near Casey Station in Wilkes Land, East Antarctica since 1959/60 and 1968/69. At Whitney Point, the breeding population increased from 1122 pairs in 14 colonies in 1959/60 to 4714 pairs in 36 colonies in 1992/93. All new colonies at Whitney Point established on relict colony sites identified in 1959/60. On Shirley Island, the total breeding population has remained at 7770 pairs ±10% between 1968/69 and 1992/93, except in 1990/91 when the population peaked at 8719 pairs. An association between the age of a colony and its rate of increase was observed at Whitney Point, with new colonies (those established since 1971/72) increasing more rapidly than colonies extant in 1959/60. At Shirley Island, where most of the colonies extant in 1968/69 have decreased in population, the establishment and growth of 13 colonies has offset this decrease; these new colonies also exhibited the association between age and rate of increase. Breeding success (chicks fledged per nest) was significantly lower for Shirley Island colonies than for those at Whitney Point. Human visitors to Shirley Island from Casey station are believed to be responsible for the observed changes in the distribution and abundance of breeding pairs and for maintaining the stable population by reducing overall breeding success through the disturbance associated with visits.     

Greater flamingo colonies around the Mediterranean form a single interbreeding population and share a common history

The greater flamingo Phoenicopterus roseus is a long‐lived colonial waterbird species, characterized by a large range encompassing three continents, a very limited number of breeding sites, and high dispersal abilities. We investigated both the phylogeographic history and the contemporary extent of genetic differentiation between eight different Mediterranean breeding colonies of greater flamingos sampled between 1995 and 2009, using both mitochondrial DNA and microsatellite markers. We found no significant differences in allelic richness or private allelic richness in relation to colony size. Overall, no genetic population differentiation was detected using either mitochondrial or microsatellite markers. F‐statistics and Bayesian clustering methods did not support any significant genetic structure. Analysis of both mitochondrial DNA and microsatellites indicated that populations have undergone a bottleneck followed by rapid growth and expansion. The average time since expansion was estimated to be 696 421 yr (90% CI: 526 316–1 131 579 yr). We discuss our results in relation to both the possible historical events accounting for the present genetic structure and relevance to conservation and management of the species.     

An assessment of the breeding range,colony sizes and population of the Westland petrel (Procellaria westlandica)

Abstract

The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs.     

Survey of Dundas Island,Auckland Islands,with particular reference to Hooker's sea lion (Phocarctos hookeri)

Abstract

Dundas Island and features of its natural history are described, following a visit on 21 January 1978. The island has by far the largest known breeding colony of Hooker's sea lion - 2767 animals were counted ashore, including approximately 1700 pups. The number of breeding females in the world population is now estimated at about 2700, but total population size remains unknown.     

Predictive habitat modelling to estimate petrel breeding colony sizes: Sooty shearwaters (Puffinus griseus) and mottled petrels (Pterodroma inexpectata) on Whenua Hou Island

Abstract

Between 2001 and 2006, we systematically sampled the entire coast of Whenua Hou, a rugged offshore island in southern New Zealand, to estimate the population densities of sooty shearwaters (Puffinus griseus) and mottled petrels (Pterodroma inexpectata) by counting the entrances of breeding burrows. A two‐step regression modelling process using binomial errors was used to predict the presence of a colony, and a normal general linear model was used to predict the density of entrances within colonies. Aerial photography, GIS and a Digital Elevation Model were used to extract relevant habitat and location variables, and a combination of both regression models was used to predict the density of breeding burrows within each 5.32 m² pixel on the island. This complex GIS and habitat prediction modelling approach gave population estimates very similar to a more traditional simple area extrapolation method and gave no improvement in precision. However, correction for the slope of the land increased our simple area estimates of population size by 11%. We estimate populations of sooty shearwater and mottled petrel breeding pairs at 173 000 (162 000–190 000) and 160 000 (123 000–197 000) respectively. Based on this number of breeding pairs, we calculate that Whenua Hou supports a total population of 868 000 (554 000–1 270 000) sooty shearwaters. Our estimate of the total mottled petrel population 202 000 pairs (162 000–242 000) is comparable with the only published estimate, but could be an underestimate because mottled petrels are sometimes found in large burrows. More research for robust estimation of population trends is needed to assess the conservation status of mottled petrels.     

Temporal and spatial variation in dispersal in the greater flamingo (Phoenicopterus ruber roseus)

We studied movements of individually marked greater flamingos (Phoenicopterus ruber roseus) born in the Camargue, southern France, between their two most important breeding colonies in the western Mediterranean (Camargue and Fuente de Piedra, Spain) from 1986 to 1992. The two sites differ in the frequency with which they offer suitable conditions for breeding. Flamingos have bred each year in the Camargue since 1974, but in only 12 of the past 22 years at Fuente de Piedra. Higher colony fidelity is thus expected in the less variable environment (Camargue), but if dispersal occurs competition might be an important factor causing this dispersal. Following years during which breeding birds in the Camrgue were disturbed (1988 and 1990) a higher proportion of adults changed colonies between breeding attempts (= breeding dispersal, 12.4%), while only 0.4% of flamingos breeding in the Camargue dispersed in the other years. As expected, flamingos breeding at Fuente de Piedra showed a higher rate of breeding dispersal (8.14%). No differences were observed between males and females. The importance of breeding failure as a factor causing breeding dispersal in flamingos was also confirmed by the movements of individual birds. The proportion of young flamingos that moved from their natal colony to start breeding at Fuente de Piedra (= natal dispersal) was independent of sex and age, but increased when breeding access to the Camargue colony was more difficult. However, natal dispersal was also higher in 1988 and 1990 (40.5%) than in the remaining years (1.2%), as was breeding dispersal. We discuss possible ways in which the increased natal dispersal among inexperienced birds could be linked with the increased breeding dispersal of adults in the same year.     

Population size and trends of southern giant petrels (<Emphasis Type="Italic">Macronectes giganteus</Emphasis>) nesting at Signy Island,South Orkney Islands

The southern giant petrel (Macronectes giganteus) has a circumpolar distribution and breeds on subantarctic islands and a few continental Antarctic sites. Although this species has recently been down-listed to “Least Concern” by the World Conservation Union (IUCN), there are strong fluctuations in abundance and variable long-term trends recorded at different sites. Systematic, long-term monitoring is essential to determine drivers underlying its population dynamics. Here, we examine long-term changes in population size and productivity of southern giant petrels at Signy Island, South Orkney Islands. Comparing estimated numbers of breeding pairs over the whole island in 2000/2001, 2005/2006, 2009/2010 and 2014/2015 with historical data revealed several phases of population change: a 64 % decline (6.2 % per annum) from 1968/1969 to 1984/1985, a 162 % increase (6.2 % per annum) to 2000/2001, stability until 2005/2006, a 56 % decline (18.3 % per annum) to 2009/2010 and stability until 2014/2015. This represents a 1.8 % decline per annum between 1968/1969 and 2014/2015. Annual counts within focal study areas suggested a more rapid increase from 1996/1997 to 2006/2007, but the same downward trend from 2006/2007 to present, underlining potential pitfalls in inferring trends from part-island counts. There was also a 20 % decline in breeding success from 1996/1997 to 2014/2015. Our results indicate substantial fluctuations in southern giant petrel abundance at Signy Island over 4–5 decades and a recent decline in breeding numbers and success. As the southern giant petrels breeding at the South Orkney Islands represents ~5–10 % of the global population, continuation of these declines would be of high conservation concern.     

Continued declines of Redshank Tringa totanus breeding on saltmarsh in Great Britain: is there a solution to this conservation problem?

Capsule: Over 50% of saltmarsh breeding Common Redshank have been lost since 1985, with current conservation management having only limited success at halting these declines.

Aims: To update population size and trend estimates for saltmarsh-breeding Redshank in Britain, and to determine whether conservation management implemented since 1996 has been successful in influencing grazing intensity and Redshank population trends.

Methods: A repeat national survey of British saltmarsh was conducted in 2011 at sites previously visited in 1985 and 1996. Redshank breeding density and grazing pressure were recorded at all sites; the presence of conservation management was additionally recorded for English sites. Results from all three national surveys were used to update population size and trend estimates, and to investigate changes in grazing pressure and breeding density on sites with and without conservation management.

Results: Of the 21 431 pairs breeding on saltmarsh in 1985, 11 946 pairs remained in 2011, with the highest proportion of this population found in East Anglia. From 1985, British breeding densities declined at a rate of 1 pair km^?2 year^?1, representing a loss of 52.8% of breeding pairs over 26 years, although regional trends varied across different time periods. Grazing pressures did not change markedly with conservation management. Redshank declines were less severe on conservation-managed sites in East Anglia and the South of England where grazing pressures remained low, though were more severe on conservation-managed sites in the North West where heavy grazing persisted.

Conclusion: Saltmarsh-breeding Redshank declines continue and are likely to be driven by a lack of suitable nesting habitat. Conservation management schemes and site protection implemented since 1996 appear not to be delivering the grazing pressures and associated habitat conditions required by this species, particularly in the North West of England, though habitat changes may not be linked to unsuitable grazing management in all regions. An in-depth understanding of grazing practices, how conservation management guidelines could be improved, and the likely success of more long-term management solutions is needed urgently.     

Distribution and abundance of elkhorn coral, Acropora palmata, and prevalence of white-band disease at Buck Island Reef National Monument, St. Croix, US Virgin Islands

In the 1970s and 1980s elkhorn coral, Acropora palmata, declined dramatically throughout the Caribbean primarily due to white-band disease (WBD). In 2005, elkhorn coral was proposed for listing as threatened under the US Endangered Species Act. WBD was first documented at Buck Island Reef National Monument (BIRNM). Together with hurricanes WBD reduced live elkhorn coral coverage by probably over 90%. In the past decade some recovery has been observed at BIRNM. This study assessed the distribution and abundance of elkhorn coral and estimated the prevalence of WBD at the monument. Within an area of 795 ha, we estimated 97,232–134,371 (95% confidence limits) elkhorn coral colonies with any dimension of connected live tissue greater than one meter, about 3% of which were infected by WBD. Despite some recovery, the elkhorn coral density remains low and WBD may continue to present a threat to the elkhorn coral population.     

Against the trend: increasing numbers of breeding Northern Lapwings Vanellus vanellus and Black-tailed Godwits Limosa limosa limosa on a German Wadden Sea island

Capsule The increase in population sizes over the last 30 years cannot be explained by reproductive success.

Aims To establish whether the positive population trends are due to increasing and self-sustaining populations or to immigration.

Methods We studied the population development of breeding lapwings from 1971 until 2005 and of godwits from 1977 until 2005 on Wangerooge, a German Wadden Sea island. Both species increased significantly during the last three decades. For each species we used a logistic growth model to derive the reproductive output required to explain the past population development without assuming immigration. We compare the values derived by this model with empirical findings of reproductive output of the respective populations.

Results For neither lapwings nor godwits can empirical reproductive success explain the observed population development.

Conclusion Our results imply that the increase in breeding pairs of Northern Lapwing and Black-tailed Godwit on Wangerooge Island is not due to reproductive output. We propose that it is mainly caused by immigration onto the island.     

Consequences of foraging trip duration on provisioning behaviour and fledging condition of common murres Uria aalgae

We examine the provisioning constraints of a pursuit‐diving seabird in a cold ocean regime by comparing the behaviour of common murres Uria aalge rearing chicks at two colonies in the Northwest Atlantic during 1998‐2000. Funk Island is the largest (340,000–400,000 breeding pairs) and most offshore (60 km) colony of common murres in eastern Canada. Seventy‐five percent of the Northwest Atlantic population of common murres breeds on this island. Great Island is one island within the Witless Bay Ecological Reserve, which is the second largest breeding aggregation (100 000 breeding pairs) and is located near‐shore (2 km). The primary forage fish species in Newfoundland waters is capelin Mallotus villosus, which spawns on or near coastal beaches during summer. Therefore, the two study colonies differ in their distance to food resources and colony size. It is within this natural context that we compare: (1) prey types and frequency of delivery (amount of prey), (2) parental time budgets, and (3) the mass and condition (mass/wing length) of fledglings at both colonies. Similarly sized female capelin (100–150 mm) were delivered to chicks at both colonies. Foraging time per day per parent, a proxy of foraging effort, was similar at both colonies (Great Island: 5.1 h; Funk Island: 5.5 h), as was the percentage of time spent with mates (Great Island: 12.3%; Funk Island: 10.9%). Foraging trips, however, were longer at Funk Island (4.1 h) than at Great Island (2.9 h). This resulted in lower feeding rates of chicks (0.17 feeds per h) and poorer condition of fledglings (2.9 g/mm) at Funk Island compared to those at Great Island (0.22 feeds per h; 3.9 g/mm). We hypothesize that provisioning efforts are constrained at Funk Island by (1) distant food resources and increased competitor density, resulting in longer foraging trip durations and (2) the time spent paired with mates at the colony, which may reflect a minimum time required to maintain breeding sites due to higher breeding densities at Funk Island compared to Great Island. Demographic consequences of this poor fledgling condition at Funk Island are unknown, but fledglings may sufficiently accelerate growth at sea due to their closer proximity to an important nursery area. If fledgling survival is compromised, however, the lower potential for growth at Funk Island will impact the entire Northwest Atlantic population of common murres.     

Cats and seabirds: effects of feral Domestic Cat Felis silvestris catus eradication on the population of Sooty Terns Onychoprion fuscata on Ascension Island, South Atlantic

The population of Sooty Terns Onychoprion fuscata breeding on Ascension Island in the Atlantic Ocean was monitored over 17 years (1990–2007). This period spanned the programme of feral Domestic Cat Felis silvestris catus eradication from the island, which commenced in 2001 with the last Cat recorded in 2004. We report on the abundance of Sooty Terns and Black Rats Rattus rattus before and after Cat eradication. The Sooty Tern breeding population in the 1990s averaged 368 000 and Cats were killing Terns at an average rate of 33 adults per night. Following Cat eradication, adult Terns are no longer predated. However, egg predation by both Rats and Common Mynas Acridotheres tristis has continued with Mynas destroying more eggs than Rats. Unexpectedly, we observed a change in Rat predatory behaviour. Following Cat eradication, Rats have become a major predator of Sooty Tern chicks. Despite this change, the Tern population has shown a season-on-season increase since Cat eradication, 48.8% in 2005, 8.2% in 2006 and 6.1% in 2007, and the breeding population increased to 420 000 birds in 2007. Incubation success improved from 66.0 to 84.4% during Cat eradication, before dropping down again to 67.9% after Cats were eradicated and Rat control measures were introduced. Index traplines were set for Rats and Rat numbers fluctuated widely immediately after Cats were eradicated but there were no significant differences that could be attributed to changes in Cat numbers. Ascension Island Sooty Terns breed every 9.6 months and juveniles defer breeding for seven seasons. Hence 2008 is the first year in which an increase in the breeding Sooty Tern population directly attributable to Cat eradication is likely to be detected. We conclude that long-term monitoring is essential to guide conservation practice even in this relatively simple predator–prey system.     

Winter Fidelity and Apparent Survival of Lesser Snow Goose Populations in the Pacific Flyway

Abstract The Beringia region of the Arctic contains 2 colonies of lesser snow geese (Chen caerulescens caerulescens) breeding on Wrangel Island, Russia, and Banks Island, Canada, and wintering in North America. The Wrangel Island population is composed of 2 subpopulations from a sympatric breeding colony but separate wintering areas, whereas the Banks Island population shares a sympatric wintering area in California, USA, with one of the Wrangel Island subpopulations. The Wrangel Island colony represents the last major snow goose population in Russia and has fluctuated considerably since 1970, whereas the Banks Island population has more than doubled. The reasons for these changes are unclear, but hypotheses include independent population demographics (survival and recruitment) and immigration and emigration among breeding or wintering populations. These demographic and movement patterns have important ecological and management implications for understanding goose population structure, harvest of admixed populations, and gene flow among populations with separate breeding or wintering areas. From 1993 to 1996, we neckbanded molting birds at their breeding colonies and resighted birds on the wintering grounds. We used multistate mark-recapture models to evaluate apparent survival rates, resighting rates, winter fidelity, and potential exchange among these populations. We also compared the utility of face stain in Wrangel Island breeding geese as a predictor of their wintering area. Our results showed similar apparent survival rates between subpopulations of Wrangel Island snow geese and lower apparent survival, but higher emigration, for the Banks Island birds. Males had lower apparent survival than females, most likely due to differences in neckband loss. Transition between wintering areas was low (<3%), with equal movement between northern and southern wintering areas for Wrangel Island birds and little evidence of exchange between the Banks and northern Wrangel Island populations. Face staining was an unreliable indicator of wintering area. Our findings suggest that northern and southern Wrangel Island subpopulations should be considered a metapopulation in better understanding and managing Pacific Flyway lesser snow geese. Yet the absence of a strong population connection between Banks Island and Wrangel Island geese suggests that these breeding colonies can be managed as separate but overlapping populations. Additionally, winter population fidelity may be more important in lesser snow geese than in other species, and both breeding and wintering areas are important components of population management for sympatric wintering populations.