Population trends and breeding success of albatrosses and giant petrels at Gough Island in the face of at-sea and on-land threats

AbstractSeveral factors threaten populations of albatrosses and giant petrels, including the impact of fisheries bycatch and, at some colonies, predation from introduced mammals. We undertook population monitoring on Gough Island of three albatross species (Tristan albatross Diomedea dabbenena L., sooty albatross Phoebetria fusca Hilsenberg, Atlantic yellow-nosed albatross Thalassarche chlororhynchos Gmelin) and southern giant petrels Macronectes giganteus (Gmelin). Over the study period, numbers of the Critically Endangered Tristan albatross decreased at 3.0% a year. Breeding success for this species was low (23%), and in eight count areas was correlated (r2 = 0.808) with rates of population decline, demonstrating chick predation by house mice Mus musculus L. is driving site-specific trends and an overall decline. Numbers of southern giant petrels were stable, contrasting with large increases in this small population since 1979. Significant population declines were not detected for either the Atlantic yellow-nosed or sooty albatross, however, caution should be applied to these results due to the small proportion of the population monitored (sooty albatross) and significant interannual variation in numbers. These trends confirm the Critically Endangered status of the Tristan albatross but further information, including a more accurate estimate of sooty albatross population size, is required before determining island wide and global population trends of the remaining species.

Download Full-text

Low burrow occupancy and breeding success of burrowing petrels at Gough Island: a consequence of mouse predation

Bird Conservation International ◽

10.1017/s0959270912000494 ◽

2013 ◽

Vol 23 (2) ◽

pp. 113-124 ◽

Cited By ~ 22

Author(s):

RICHARD J. CUTHBERT ◽

HENK LOUW ◽

JEROEN LURLING ◽

GRAHAM PARKER ◽

KALINKA REXER-HUBER ◽

...

Keyword(s):

Mus Musculus ◽

Breeding Success ◽

House Mice ◽

Population Declines ◽

Predatory Behaviour ◽

Breeding Parameters ◽

Gough Island ◽

The Impact ◽

Detrimental Impact ◽

Winter Breeding

SummaryThe predatory behaviour of introduced house mice Mus musculus at Gough Island is known to impact on albatross and petrels, resulting in the Tristan Albatross Diomedea dabbenena and Atlantic Petrel Pterodroma incerta being listed as “Critically Endangered” and “Endangered”, respectively. Although predation has been documented for two burrowing petrels and one albatross species, the impact of house mice on other burrowing petrels on Gough Island is unknown. We report burrow occupancy and breeding success of Atlantic Petrels, Soft-plumaged Petrels Pterodroma mollis, Broad-billed Prions Pachyptila vittata, Grey Petrels Procellaria cinerea and Great Shearwaters Puffinus gravis. With the exception of the Great Shearwater, breeding parameters of burrowing petrels at Gough Island were very poor, with low burrow occupancy (range 4–42%) and low breeding success (0–44%) for four species, and high rates of chick mortality in Atlantic Petrel burrows. Breeding success decreased with mass, suggesting that smaller species are hardest hit, and winter-breeding species had lower breeding success than summer breeders. The results indicate that introduced house mice are having a detrimental impact on a wider range of species than previously recorded and are likely to be causing population declines among most burrowing petrels on Gough Island. The very low values of burrow occupancy recorded for Soft-plumaged Petrels and Broad-billed Prions and greatly reduced abundance of burrowing petrels in comparison to earlier decades indicate that Gough Island’s formerly abundant petrel populations are greatly threatened by the impact of predatory house mice which can only be halted by the eradication of this species from the island.

Download Full-text

Population trends and conservation status of the Northern Rockhopper PenguinEudyptes moseleyiat Tristan da Cunha and Gough Island

Bird Conservation International ◽

10.1017/s0959270908007545 ◽

2009 ◽

Vol 19 (1) ◽

pp. 109-120 ◽

Cited By ~ 19

Author(s):

RICHARD CUTHBERT ◽

JOHN COOPER ◽

MARIE-HELENE BURLE ◽

CONRAD J. GLASS ◽

JAMES P. GLASS ◽

...

Keyword(s):

Indian Ocean ◽

Conservation Status ◽

Sharp Decrease ◽

Population Trends ◽

Tristan Da Cunha ◽

Fur Seals ◽

Introduced Predators ◽

Gough Island ◽

The Indian Ocean ◽

The Impact

SummaryPopulations of the recently split Northern Rockhopper PenguinEudyptes moseleyiare restricted to Tristan da Cunha and Gough Island in the South Atlantic, and Amsterdam and St Paul in the Indian Ocean. The majority of the population is in the Atlantic (> 80%), but population trends at Tristan da Cunha and Gough are uncertain. Early records indicate “millions” of penguins used to occur at Tristan da Cunha and Gough Island. The most recent estimates indicate declines in excess of 90% for both Gough and the main island of Tristan that have occurred over at least 45 and 130 years, respectively. Numbers breeding at Inaccessible and Nightingale islands (TDC) also may have declined since the 1970s, albeit modestly, whereas numbers on Tristan appear stable over the last few decades. Current population estimates are 32,000–65,000 pairs at Gough, 18–27,000 at Inaccessible, 19,500 at Nightingale, and 3,200–4,500 at Tristan. Numbers and trends at Middle Island (TDC) are unknown. Middle Island supported an estimated 100,000 pairs in 1973, and recent observations suggest this colony is being impacted by competition for space with recently recolonising Subantarctic Fur SealsArctocephalus tropicalis. Past human exploitation and the impact of introduced predators may be responsible for the historical decline in numbers at Tristan, but these factors cannot explain the sharp decrease (since the 1950s) at Gough Island. Overall, declines at Gough, Tristan, Nightingale and Inaccessible islands indicate a three-generation decline of > 50%. Taken in combination with recent decreases in Indian Ocean populations, the Northern Rockhopper Penguins is now categorised as globally ‘Endangered’. Determining the causal factors responsible for these recent declines is an urgent priority.

Download Full-text

Mouse eradication is required to prevent local extinction of an endangered seabird on an oceanic island

10.1101/2020.11.16.385997 ◽

2020 ◽

Author(s):

Christopher W. Jones ◽

Michelle M. Risi ◽

Alexis M. Osborne ◽

Peter G. Ryan ◽

Steffen Oppel

Keyword(s):

Breeding Success ◽

Extinction Risk ◽

Oceanic Islands ◽

Adult Survival ◽

House Mice ◽

Breeding Populations ◽

Gough Island ◽

Invasive Mammals ◽

Population Trajectory ◽

The Impact

AbstractPetrels (Procellariidae) are a highly diverse family of seabirds, many of which are globally threatened due to the impact of invasive species on breeding populations. While predation by invasive cats and rats has led to the extinction of petrel populations, the impact of invasive house mice Mus musculus is slower and less well documented. However, mice impact small burrow-nesting species such as MacGillivray’s prion Pachyptila macgillivrayi, a species classified as endangered because it has been extirpated on islands in the Indian Ocean by introduced rodents. We use historic abundance data and demographic monitoring data from 2014 to 2020 to predict the population trajectory of MacGillivray’s prion on Gough Island with and without a mouse eradication using a stochastic integrated population model. Given very low annual breeding success (0.01 fledglings per breeding pair in ‘poor’ years (83%) or 0.38 in ‘good’ years (17%), n = 320 nests over 6 years) mainly due to mouse predation, our model predicted that the population collapsed from ~3.5 million pairs in 1956 to an estimated 175,000 pairs in 2020 despite reasonably high adult survival probability (ϕ = 0.901). Based on these parameters, the population is predicted to decline at a rate of 9% per year over the next 36 years without a mouse eradication, with a 31% probability that by 2057 the MacGillivray’ prion population would become extremely vulnerable to extinction. Our models predict population stability (λ = 1.01) and a lower extinction risk (<10%) if mouse eradication on Gough Island restores annual breeding success to 0.519, which is in line with that of closely-related species on predator-free islands. This study demonstrates the devastating impacts that introduced house mice can have on small burrowing petrels and highlights the urgency to eradicate invasive mammals from oceanic islands.

Download Full-text

Quantifying the impact of protected areas on near-global waterbird population trends, a pre-analysis plan

10.7287/peerj.preprints.27741 ◽

2019 ◽

Author(s):

Hannah S Wauchope ◽

Julia P G Jones ◽

Tatsuya Amano ◽

Jonas Geldmann ◽

Daniel Blanco ◽

...

Keyword(s):

Protected Areas ◽

Positive Impact ◽

Association Studies ◽

Population Decline ◽

Population Trends ◽

Complex Data ◽

Waterbird Species ◽

Before And After ◽

And Performance ◽

The Impact

There is increasing interest in the effectiveness of protected areas (PAs) for supporting populations of wildlife. While there are a number of association studies showing a relationship between protected areas and abundance or trends in wild species, studies with an appropriate counterfactual (what would have happened in the absence of protection) are rare. We use the world’s largest database on waterbird counts (covering 587 species at 21,989 sites globally) to answer three questions: 1) Do PAs have a positive impact on waterbird population trends relative to a counterfactual (this includes cases where a PA has lessened, but not halted, a population decline)?; 2) are PAs performing successfully by maintaining or increasing populations? and 3) what factors contribute to PA impact and performance? We selected 15,703 waterbird populations (here defined as a site species combination), consisting of 311 species at 870 protected sites, where PA designation occurred at least 5 years after the first survey date, and 5 years before the last. We will use this to compare trends before PA designation to those afterwards. We then matched these sites to unprotected sites with similar covariates in the years before PA designation, resulting in a matching dataset of 6,451 populations pairs consisting of 39 species at 769 pairs of protected and unprotected sites. We will use this to compare trends both before and after PA designation and inside and outside of PAs. Our results will shed light on the impact of PA on hundreds of waterbird species, providing much needed evidence regarding PA effectiveness. As PA performance is a sensitive subject and it is important to develop hypotheses before knowing the results (especially for the relatively complex data analysis used in matching protected and unprotected sites), we present a pre-analysis plan. This will ensure that the final paper’s analyses are hypotheses testing, rather than generating, and avoids the risk of, or perception of, data dredging.

Download Full-text

Population monitoring of an urban gliding mammal in eastern Australia

Australian Mammalogy ◽

10.1071/am17029 ◽

2018 ◽

Vol 40 (2) ◽

pp. 214

Author(s):

Ross L. Goldingay

Keyword(s):

Adult Population ◽

Population Decline ◽

Species Conservation ◽

Population Monitoring ◽

Small Population ◽

Population Modelling ◽

Forest Remnant ◽

Eastern Australia ◽

Squirrel Glider

Long-term monitoring is an important element of species conservation. This study describes changes in the size of a squirrel glider (Petaurus norfolcensis) population over a 10-year period. The population occupied a 45-ha forest remnant within the urban area of Brisbane. Gliders were tagged from 25 nights of trapping during 2006–08 and from 16 nights of trapping in 2015. Population modelling was used to estimate adult population size. This suggested the adult population comprised 30–40 individuals at the beginning and end of the 10-year period. It reached a peak of 70 individuals in mid-2007. These data suggest that the study area contains a small population that is prone to interannual variation but there was no evidence of it being in decline. Survival estimates during 2006–08 were equivalent to those estimated for a larger population in Victoria. Population monitoring should be continued to determine how resilient this population is to population decline and to investigate factors that may cause decline. This study provides an example of an approach that could be used to monitor threatened populations of the squirrel glider.

Download Full-text

Positive association between rat abundance and breeding success of the Critically Endangered Mariana Crow Corvus kubaryi

Bird Conservation International ◽

10.1017/s095927091300018x ◽

2013 ◽

Vol 24 (2) ◽

pp. 192-200 ◽

Cited By ~ 2

Author(s):

ARJUN AMAR ◽

JACOB A. ESSELSTYN

Keyword(s):

Breeding Success ◽

Nest Predation ◽

Wild Population ◽

Positive Association ◽

Critically Endangered ◽

Mariana Islands ◽

Population Declines ◽

Nest Sites ◽

Plausible Hypothesis ◽

Shared Predator

SummaryDiagnosing the causes of population declines of highly endangered species is vital to ensure that appropriate conservation measures are undertaken. Although experiments can provide critical information on potential causes, these can be time consuming and costly, and so it is important to determine the most plausible hypothesis for such tests. The last wild population of the Critically Endangered Mariana Crow Corvus kubaryi has been declining rapidly on Rota in the Mariana Islands. Because nest predation by introduced rats Rattus spp. has been implicated in the declines of other Pacific island birds, we tested for a correlation between breeding success of Mariana Crows and abundance of rats R. diardii surrounding their nest sites. If rats are a contributing factor in this species’s decline, we predicted that breeding success would be lower in areas where rats were more abundant. In complete contrast to this prediction, we found that breeding success was significantly higher where rats were most abundant, suggesting that rats are unlikely to be a major driving force behind the decline in this species. The positive association between crow breeding success and rat abundance suggests these species may be responding to similar habitat needs or a shared predator. This study illustrates the importance of gathering sufficient knowledge on the ecology of a species prior to undertaking costly, logistically difficult and time consuming experiments.

Download Full-text

Investigating effect of climate warming on the population declines of Sympetrum frequens during the 1990s in three regions in Japan

Scientific Reports ◽

10.1038/s41598-020-69532-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Kosuke Nakanishi ◽

Dai Koide ◽

Hiroyuki Yokomizo ◽

Taku Kadoya ◽

Takehiko I. Hayashi

Keyword(s):

Climate Warming ◽

Population Decline ◽

Population Monitoring ◽

Rice Paddy ◽

Adult Mortality ◽

Monitoring Data ◽

Population Declines ◽

Key Factor ◽

Sympetrum Frequens ◽

Summer Temperatures

AbstractClimate warming is of concern as a key factor in the worldwide decline in insect populations. In Japan, numbers of a common dragonfly in rice paddy fields, Sympetrum frequens, decreased sharply in the 1990s. Because S. frequens migrates to cooler mountains in summer, climate warming has been suggested as one of the main causes of the population decline in addition to agronomic factors. Here, we analysed the relation between summer temperatures and population densities of S. frequens and the related S. infuscatum, which does not migrate to mountains in summer, using published population monitoring data and temperature data from three regions (Toyama, Ishikawa, and Shizuoka) in Japan. Decadal differences in summer temperatures lay within the range of fluctuations among years, suggesting that an increase in summer temperatures cannot explain the past sharp population declines. However, regression analyses using monitoring data from Toyama showed that the population dynamics of both species in autumn are negatively correlated with summer temperatures in the same year. These results suggest that high temperatures in summer directly affect adult mortality to an extent that results in a decrease in population growth.

Download Full-text

Rapid population declines of Himalayan Griffon Gyps himalayensis in Upper Mustang, Nepal

Bird Conservation International ◽

10.1017/s0959270908007417 ◽

2009 ◽

Vol 19 (1) ◽

pp. 99-107 ◽

Cited By ~ 10

Author(s):

RAJU ACHARYA ◽

RICHARD CUTHBERT ◽

HEM SAGAR BARAL ◽

KARAN BAHADUR SHAH

Keyword(s):

South Asia ◽

Conservation Status ◽

Population Decline ◽

Population Trends ◽

Himalayan Region ◽

Veterinary Drug ◽

Mountainous Region ◽

Population Declines ◽

Breeding Area ◽

Population Collapse

SummaryThe population collapse of resident Gyps vulture species in South Asia, caused by the use of a veterinary drug diclofenac, has highlighted an urgent need to monitor numbers of other vulture species in the region. This study assessed population trends of Himalayan Griffon Gyps himalayensis in the mountainous region of Upper Mustang, Nepal, which is an important breeding area for the species. Vultures were surveyed in 2002, 2004 and 2005 by recording the number of birds sighted along 188 km of transects, and observing numbers of birds at breeding colonies. The number of birds recorded per day and per kilometre of transect declined by 67% and 70% respectively over the period of study. The number of active nests declined by 84% from 2002 to 2005. The veterinary drug diclofenac was available in pharmacies in the Mustang region. Young Himalayan Griffons, which migrate to the lowland areas of Nepal and, in increasing numbers to India, are highly likely to be subject to diclofenac poisoning. If this rate of population decline occurs throughout the Himalayan region, the conservation status of the species will need to be urgently reassessed.

Download Full-text

Failure to account for behavioral variability overestimates bonobo populations and compromises accuracy in population monitoring

10.1101/2021.12.22.473935 ◽

2021 ◽

Author(s):

Erin G Wessling ◽

Martin Surbeck

Keyword(s):

Population Change ◽

Pan Paniscus ◽

Population Decline ◽

Population Monitoring ◽

Population Estimation ◽

Behavioral Variability ◽

Nest Construction ◽

Wildlife Population ◽

Time Space ◽

The Impact

Wildlife population monitoring depends on accurate counts of individual animals or artefacts of behavior (e.g., nests or dung), but also must account for potential biases in the likelihood to encounter these animals or artefacts. In indirect surveying, which depends largely upon artefacts of behavior, likelihood to encounter indirect signs of a species is derived from both artefact production and decay. Although environmental context as well as behavior contribute to artefact abundance, variability in behaviors relevant to artefact abundance is rarely considered in population estimation. Here we demonstrate how ignoring behavioral variability contributes to overestimation of population size of a highly endangered great ape endemic only to the Democratic Republic of the Congo, the bonobo (Pan paniscus). Variability in decay of signs of bonobo presence (i.e., nests) is well documented and linked to environmental determinants. Conversely, a single metric of sign production (i.e., nest construction) is commonly used to estimate bonobo density, assumed to be representative of bonobo nest behavior across all contexts. We estimated nest construction rates from three bonobo groups within the Kokolopori Bonobo Reserve and found that nest construction rates in bonobos to be highly variable across populations as well as seasonal within populations. Failure to account for behavioral variability in nest construction leads to potentially severe degradation in accuracy of bonobo population estimates of abundance, accounting for a likely overestimation of bonobo numbers by 34%, and in the worst cases as high as 80% overestimation. Using bonobo nesting as an example, we demonstrate that failure to account for inter- and intra-population behavioral variation compromises our ability to monitor population change or reliably compare contributors to population decline or persistence. We argue that variation in sign production is but one of several potential ways that behavioral variability can affect conservation monitoring, should be measured across contexts whenever possible, and must be considered in population estimation confidence intervals. With increasing attention to behavioral variability as a potential tool for conservation, conservationists must also account for the impact that behavioral variability across time, space, individuals, and populations can play upon precision and accuracy of wildlife population estimation.

Download Full-text

Quantifying the impact of protected areas on near-global waterbird population trends, a pre-analysis plan

10.7287/peerj.preprints.27741v1 ◽

2019 ◽

Author(s):

Hannah S Wauchope ◽

Julia P G Jones ◽

Tatsuya Amano ◽

Jonas Geldmann ◽

Daniel Blanco ◽

...

Keyword(s):

Protected Areas ◽

Positive Impact ◽

Association Studies ◽

Population Decline ◽

Population Trends ◽

Complex Data ◽

Waterbird Species ◽

Before And After ◽

And Performance ◽

The Impact

There is increasing interest in the effectiveness of protected areas (PAs) for supporting populations of wildlife. While there are a number of association studies showing a relationship between protected areas and abundance or trends in wild species, studies with an appropriate counterfactual (what would have happened in the absence of protection) are rare. We use the world’s largest database on waterbird counts (covering 587 species at 21,989 sites globally) to answer three questions: 1) Do PAs have a positive impact on waterbird population trends relative to a counterfactual (this includes cases where a PA has lessened, but not halted, a population decline)?; 2) are PAs performing successfully by maintaining or increasing populations? and 3) what factors contribute to PA impact and performance? We selected 9,650 waterbird populations (here defined as a site species combination), consisting of 262 species at 546 protected sites, where PA designation occurred at least 5 years after the first survey date, and 5 years before the last. We will use this to compare trends before PA designation to those afterwards. We then matched these sites to unprotected sites with similar covariates in the years before PA designation, resulting in a matching dataset of 3,677 populations consisting of 94 species at 514 pairs of protected and unprotected sites. We will use this to compare trends both before and after PA designation and inside and outside of PAs. Our results will shed light on the impact of PA on hundreds of waterbird species, providing much needed evidence regarding PA effectiveness. As PA performance is a sensitive subject and it is important to develop hypotheses before knowing the results (especially for the relatively complex data analysis used in matching protected and unprotected sites), we present a pre-analysis plan. This will ensure that the final paper’s analyses are hypotheses testing, rather than generating, and avoids the risk of, or perception of, data dredging.

Download Full-text