Recent recovery and expansion of Guam’s locally endangered Såli (Micronesian Starling) Aplonis opaca population in the presence of the invasive brown treesnake

Summary Assessing the impacts of invasive predators on the demography and distribution of native species is critical for understanding mechanisms of species persistence and informing the design of recovery programmes. On the oceanic island of Guam, the introduction of the predatory brown treesnake Boiga irregularis after World War II caused the near-total loss of the native forest avifauna. Localised snake control measures have been implemented since the early 1990s, yet it remains poorly understood how they have impacted Guam’s remaining native bird populations. To address this question, we combined intensive area searches of Andersen Air Force Base (AAFB) with island-wide transect surveys and opportunistic sightings to provide a comprehensive update on the distribution and abundance of Såli (Micronesian Starling, Aplonis opaca) – one of Guam’s last extant native bird species. Area searches of AAFB, where the largest remnant of the Såli population persists, revealed a 15-fold population increase since the last survey in the early 1990s, and transect surveys and opportunistic sightings indicate incipient recolonisation of other urbanised areas of northern and central Guam. We estimate the current island-wide population size at ~1,400 individuals. The population increase can likely be attributed to a combination of snake control measures and the Såli’s ability to exploit urban refugia for nesting and roosting. Although these trends demonstrate some population recovery, a skewed age ratio (>90% adults and subadults) at AAFB and a highly urbanised distribution and low abundance outside AAFB indicate that snake predation continues to strongly impact the population. More intensive snake suppression efforts, particularly in forested areas, may allow for the Såli population to attain its former distribution and abundance on Guam. More broadly, our findings reinforce the importance of urban areas as refugia for some threatened species.

Download Full-text

Determination of the presence of Mycobacterium avium on Guam as a precursor to reintroduction of indigenous bird species

Pacific Conservation Biology ◽

10.1071/pc980227 ◽

1998 ◽

Vol 4 (3) ◽

pp. 227

Author(s):

Ilse Silva-Krott ◽

M. Kelly Brock ◽

Randall E. Junge

Keyword(s):

Mycobacterium Avium ◽

Captive Breeding ◽

Bird Species ◽

Animal Husbandry ◽

Breeding Population ◽

Native Forest ◽

Captive Population ◽

Boiga Irregularis ◽

Bird Populations ◽

High Degree

Eight of 11 native forest bird species on Guam were extirpated by the introduction of the Brown Tree Snake Boiga irregularis. Emergency measures necessary to rescue the Guam subspecies of Micronesian Kingfisher Halcyon cinnamomina cinnamomina from extinction involved translocation and captive breeding in American mainland zoos. Soon after the establishment of a captive breeding population, the kingfisher demonstrated a high degree of susceptibility to avian tuberculosis (ATB), a disease that proved to be a major threat to the preservation of the species. The cause of ATB is Mycobacterium avium which produces a prolonged course of infection in kingfishers and other birds. Kingfishers infected with M. avium are difficult to detect until late in the course of the disease, thereby potentially posing a risk of transmitting ATB to the Guam captive population of Guam Rails Gallirallus owstoni, if kingfishers are repatriated. M. avium is considered to be ubiquitous in nature. However, there are no reported mortalities due to ATB in any bird species on Guam. In this study, six of twenty-one cultures yielded Mycobacterium spp., two of which were further identified as M. avium. Since this study demonstrates that M. avium already exists on Guam, repatriating kingfishers to Guam poses no threat of introducing a new pathological agent to the island's ecosystem. Strict quarantine procedures along with rigorous animal husbandry protocols should minimize risks of repatriating infected kingfishers to Guam, and prevent transmission of ATB to the captive population of Guam Rails and other bird populations on Guam.

Download Full-text

Increased nesting success of Hawaii Elepaio in response to the removal of invasive black rats

The Condor ◽

10.1093/condor/duz003 ◽

2019 ◽

Vol 121 (2) ◽

Author(s):

Paul C Banko ◽

Kelly A Jaenecke ◽

Robert W Peck ◽

Kevin W Brinck

Keyword(s):

Forest Restoration ◽

Nest Success ◽

Rattus Rattus ◽

Bird Species ◽

Oceanic Islands ◽

Nesting Success ◽

Native Forest ◽

Forest Bird ◽

Bird Populations ◽

Black Rats

Abstract In Hawaii and other oceanic islands with few native land mammals, black rats (Rattus rattus) are among the most damaging invasive vertebrate species to native forest bird populations and habitats, due to their arboreal behavior and generalist foraging habits and habitat use. We evaluated the nesting response of Hawaii Elepaio (Chasiempis sandwichensis; Monarchidae), a generalist insectivore, to the removal of black rats using rodenticide in a before-after-control-impact study in high- and low-elevation mesic montane habitat recovering from long-term damage from introduced ungulates and weeds. We monitored nesting success and rat abundance during 2015–2016 before applying rodenticide bait in 2017 to remove rats from two 700 × 700 m treatment plots that were paired with 2 nontreatment plots of the same size. Rat abundance was reduced by 90% during treatment, with combined variables treatment and elevation best explaining the change using GLM methods and AIC model selection. The daily survival rate (DSR) of nests (n = 191) was greater on treated plots after rodenticide application (mean ± SE = 0.980 ± 0.004 treatment; 0.964 ± 0.004 nontreatment), modeled nest success increased from 29% to 50%, and apparent nest success (number of successful nests per total nests) increased from 37% to 52%. The most informative model for predicting DSR included the effect of treatment. Predation by rats was documented at 3 of 16 nests using video surveillance, and we observed additional evidence of rat predation during in-person nest monitoring. Rats targeted adults on the nest and sometimes removed intact eggs, leaving little trace of their activity. Our results demonstrate that reducing rat predation can immediately improve the nesting success of even a common bird species in habitat with a long history of forest restoration. Sustained predator control may be critical to accelerating the recovery of native forest bird communities.

Download Full-text

Sustaining biodiversity in ancient tropical countryside: Fig. 1.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0808874105 ◽

2008 ◽

Vol 105 (46) ◽

pp. 17852-17854 ◽

Cited By ~ 107

Author(s):

Jai Ranganathan ◽

R. J. Ranjit Daniels ◽

M. D. Subash Chandran ◽

Paul R. Ehrlich ◽

Gretchen C. Daily

Keyword(s):

Native Species ◽

Production Systems ◽

Bird Species ◽

Structural Complexity ◽

Bird Diversity ◽

Native Forest ◽

Conservation Value ◽

Tropical Agriculture ◽

Agricultural Ecosystem ◽

Bird Species Richness

With intensifying demands for food and biofuels, a critical threat to biodiversity is agricultural expansion into native tropical ecosystems. Tropical agriculture, particularly intensive agriculture, often supports few native organisms, and consequently has been largely overlooked in conservation planning; yet, recent work in the Neotropics demonstrates that tropical agriculture with certain features can support significant biodiversity, decades after conversion to farmland. It remains unknown whether this conservation value can be sustained for centuries to millennia. Here, we quantify the bird diversity affiliated with agricultural systems in southwest India, a region continuously cultivated for >2,000 years. We show that arecanut palm (Areca catechu) production systems retain 90% of the bird species associated with regional native forest. Two factors promote this high conservation value. First, the system involves intercropping with multiple, usually woody, understory species and, thus, has high vertical structural complexity that is positively correlated with bird species richness. Second, the system encompasses nearby forests, where large quantities of leaf litter are extracted for mulch. The preservation of these forests on productive land traces back to their value in supplying inputs to arecanut cultivation. The long-term biodiversity value of an agricultural ecosystem has not been documented in South and Southeast Asia. Our findings open a new conservation opportunity for this imperiled region that may well extend to other crops. Some of these working lands may be able to sustain native species over long-time scales, indicating that conservation investments in agriculture today could pay off for people and for nature.

Download Full-text

Habitat use by grey-crowned babbler, Pomatostomus temporalis, in urban and peri-urban environments

Pacific Conservation Biology ◽

10.1071/pc16023 ◽

2017 ◽

Vol 23 (1) ◽

pp. 88

Author(s):

Kathryn Teare Ada Lambert ◽

Hugh Ford

Keyword(s):

Habitat Use ◽

Urban Areas ◽

Native Species ◽

Woody Debris ◽

Bird Species ◽

Ground Cover ◽

Urban Environments ◽

High Rate ◽

Habitat Requirements ◽

Urban Landscapes

Habitat loss in the urban environment leads to a high rate of local extinction of native fauna. In contrast, where key habitat structures, such as woody debris, shrubs and trees, are maintained, urban landscapes can retain many native species. To manage urban habitats successfully for urban bird communities, it is, therefore, necessary to understand the habitat requirements of the species using them. We have previously shown that the grey-crowned babbler, Pomatostomus temporalis, exhibits similar mean weight, sex ratio and group size in natural and altered habitat in and around Dubbo, New South Wales. In the present study, we detail the movements and habitat use of the groups that inhabit urban areas. We found that groups behaved similarly in urban and peri-urban areas, but showed small differences in the frequency of behaviours, based on the habitat feature that was available. The results suggested that, despite the decline of the grey-crowned babbler in the southern parts of its range, this species is able to survive in altered habitats, if nesting habitat and ground cover remain available and neighbouring groups persist nearby. Because other woodland bird species have shown similar responses to urban environments, managers of urban parkland should provide foraging substrates for a variety of woodland bird species, including vulnerable species, to ameliorate threatening processes and protect key habitat requirements.

Download Full-text

Sugar water feeding practices are associated with bird species composition in urban backyards

Journal of Urban Ecology ◽

10.1093/jue/juab018 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Daria A Erastova ◽

Josie A Galbraith ◽

Kristal E Cain ◽

Yolanda van Heezik ◽

Antoine Filion ◽

...

Keyword(s):

Species Composition ◽

Urban Areas ◽

Native Species ◽

Bird Species ◽

Feeding Practices ◽

Future Research ◽

Online Questionnaire ◽

Sugar Water ◽

Individual Bird ◽

Backyard Birds

Abstract Feeding backyard birds with sugar water is increasingly popular in urban areas, but it has poorly understood effects on bird assemblages. In New Zealand, ca. 20% of households engaged in feeding wild birds use sugar water, often in an attempt to attract native, nectarivorous birds. Developing best practices for sugar water feeding could be a powerful tool for attracting these species in urban areas. However, it is currently unclear whether these feeders actually support native species, and, if so, which feeding practices are most effective in increasing visitation. We surveyed New Zealanders who provide sugar water to birds about their feeding practices via an online questionnaire. The aim of our research was to understand existing practices and their effect on attracting native species, as well as the motivations and social factors behind urban sugar water bird feeding. Our results show that this practice is popular throughout the country with the majority of households successful in attracting native nectarivorous species to their gardens. Sugar water feeder type had the largest effect on reported species richness at feeders in comparison to other factors (e.g. sugar concentration). Feeders specifically designed for nectarivorous birds, namely the Tui Nectar Feeder™, are more successful at attracting natives in comparison to other commonly used feeder types. Thus, individual householder decisions around feeder use can have important consequences for bird species composition in urban gardens. Future research is needed to understand the consequences of sugar water feeding for bird communities and individual bird health.

Download Full-text

Urban trees facilitate the establishment of non-native forest insects

NeoBiota ◽

10.3897/neobiota.52.36358 ◽

2019 ◽

Vol 52 ◽

pp. 25-46 ◽

Cited By ~ 6

Author(s):

Manuela Branco ◽

Pedro Nunes ◽

Alain Roques ◽

Maria Rosário Fernandes ◽

Christophe Orazio ◽

...

Keyword(s):

European Country ◽

Urban Areas ◽

Native Species ◽

Urban Forest ◽

First Record ◽

Urban Trees ◽

Tree Cover ◽

Suitable Habitat ◽

Native Forest ◽

Forest Pests

Cities, due to the presence of ports and airports and the high diversity of trees in streets, parks, and gardens, may play an important role for the introduction of invasive forest pests. We hypothesize that areas of urban forest facilitate the establishment of non-native forest pests. Based on scientific literature and a pan-European database on non-native species feeding on woody plants, we analysed where the first detections occurred in European countries. We collected site data for 137 first detections in Europe and 508 first European country-specific records. We also estimated the percentage of tree cover and suitable habitat (green areas with trees) in buffers around detection points. The large majority of first records (89% for first record in Europe and 88% for first records in a European country) were found in cities or suburban areas. Only 7% of the cases were in forests far from cities. The probability of occurrence decreased sharply with distance from the city. The probability to be detected in urban areas was higher for sap feeders, gall makers, and seed or fruit feeders (>90%) than for bark and wood borers (81%). Detection sites in cities were highly diverse, including public parks, street trees, university campus, arboreta, zoos, and botanical gardens. The average proportion of suitable habitat was less than 10% in urban areas where the species were detected. Further, more than 72% of the cases occurred in sites with less than 20% of tree cover. Hotspots of first detection were identified along the coastal regions of the Mediterranean and Atlantic, and near industrial areas of central Europe. We conclude that urban trees are main facilitators for the establishment of non-native forest pests, and that cities should thus be intensely surveyed. Moreover, as urban areas are highly populated, the involvement of citizens is highly recommended.

Download Full-text

Pervasive impacts of invasive brown treesnakes drive low fledgling survival in endangered Micronesian Starlings (Aplonis opaca) on Guam

The Condor ◽

10.1093/condor/duz014 ◽

2019 ◽

Vol 121 (2) ◽

Cited By ~ 3

Author(s):

Henry S Pollock ◽

Julie A Savidge ◽

Martin Kastner ◽

Thomas F Seibert ◽

Todd M Jones

Keyword(s):

Survival Rates ◽

Bird Species ◽

Forest Edge ◽

Life History Stage ◽

Native Forest ◽

Boiga Irregularis ◽

Nest Location ◽

Nest Boxes ◽

Invasive Predators ◽

Fledgling Survival

Abstract Invasive predators have caused widespread loss of biodiversity in island ecosystems, yet certain species are able to tolerate the presence of generalist invaders. For example, the invasive brown treesnake (BTS; Boiga irregularis) caused the extirpation of 10 of 12 native forest bird species on the island of Guam, but a remnant population of the Micronesian Starling (Aplonis opaca), or Såli, has managed to persist on a military installation in northern Guam. Understanding how Micronesian Starlings are coping with the presence of BTS can inform conservation efforts for island bird populations facing invasive predators and provide insight into strategies for expanding the starling population. We monitored the survival, movements, and habitat use of 43 radio-tagged starling fledglings during this vulnerable life-history stage. Invasive predators accounted for 75% of fledgling mortality (56% from BTS; 19% from feral cats) and contributed to one of the lowest post-fledging survival rates (38% through day 21 post-fledging) recorded for passerine birds. Predation by BTS persisted at elevated rates following natal dispersal, further reducing cumulative survival to 26% through 53 days post-fledging. Nest location was an important predictor of survival: fledglings from nest boxes closer to the forest edge were more likely to use forest habitat at younger ages and more likely to be depredated by BTS. Overall, our findings indicate that BTS continue to severely impact Guam’s starling population, even more so than invasive predators affect native birds in other island systems. We recommend deploying nest boxes farther from the forest to improve fledgling survival and implementing urban predator control to promote growth of the Micronesian Starling population on Guam and facilitate future reintroductions of other species.

Download Full-text

Non-native species in Canada’s boreal zone: diversity, impacts, and risk

Environmental Reviews ◽

10.1139/er-2013-0083 ◽

2014 ◽

Vol 22 (4) ◽

pp. 372-420 ◽

Cited By ~ 25

Author(s):

David W. Langor ◽

Erin K. Cameron ◽

Chris J.K. MacQuarrie ◽

Alec McBeath ◽

Alec McClay ◽

...

Keyword(s):

Urban Areas ◽

Native Species ◽

Soil Nutrient ◽

Classical Biological Control ◽

Agricultural Landscapes ◽

Ecological Impacts ◽

Control Measures ◽

Boreal Zone ◽

Natural Habitats ◽

Management Measures

More than 1180 non-native species, mostly of Palaearctic origin, have been recorded from the boreal zone of Canada, with the highest diversity on the island of Newfoundland and in the southern boreal zone of Ontario and Quebec. The non-native biota of the boreal zone (and of Canada in general) is poorly known in terms of species composition and distribution. A large proportion of species are associated with disturbed anthropogenic habitats such as urban areas, agricultural landscapes, transportation and communication corridors, and industrial developments. Natural habitats in the boreal zone have a high degree of resistance to invasion compared with those of other Canadian zones, likely owing to harsh climates, low light levels, poor soil nutrient availability, low soil pH, low productivity, and dense covering of the ground by plants, especially bryophytes. Of the relatively few non-native species that have successfully colonized the boreal zone, many decline greatly in abundance after a few years, suggesting biotic resilience. To date the boreal zone has shown the least resistance and resilience to large vertebrates (moose and white-tailed deer) translocated to islands, diseases of vertebrates, and earthworms. In general, the ecological impacts of non-native species on the boreal zone have been poorly studied, and there are few examples where such impacts are evident. Likewise, there has been little attempt to quantify the economic impacts of non-native species in either the boreal zone or in Canada as a whole. In the few cases where management measures have been implemented for highly destructive non-native species, results have been somewhat successful, especially where classical biological control measures have been implemented against insects on trees. Chemical and mechanical management measures have had only limited success in localized situations. Management resources are most effectively applied to reducing the risk of introduction. The risk to the boreal zone posed by future new non-native species is increasing with the warming climate and the fast and direct transport of goods into the boreal zone from points of origin. Five recommendations are provided to address recognized gaps concerning non-native species.

Download Full-text

Birds of remnant vegetation on the Mornington Peninsula, Victoria, Australia: the role of interiors, edges and roadsides

Pacific Conservation Biology ◽

10.1071/pc040294 ◽

2003 ◽

Vol 9 (4) ◽

pp. 294 ◽

Cited By ~ 7

Author(s):

Mark J. Antos ◽

John G. White

Keyword(s):

Introduced Species ◽

Native Species ◽

Agricultural Land ◽

Local Level ◽

Bird Species ◽

Forest Edges ◽

Forest Patches ◽

Bird Populations ◽

Remnant Vegetation ◽

Roadside Vegetation

Habitat loss and fragmentation on the Mornington Peninsula, Victoria, Australia, has resulted in a mosaic of forest patches, forest edges abutted by agricultural land and linear habitat strips amidst a human-modified land matrix. To examine the use of forest elements by the avifauna in this landscape, bird populations were sampled along fixed transects established within forest interiors, on forest edges and along forested roadsides. A total of 60 species was recorded during this study, five of which were introduced. Species richness and diversity did not differ significantly between the three habitat elements, but avifaunal composition varied considerably. The species assemblages of all habitat elements differed significantly, with forest interiors and roadsides showing the greatest difference and forest interiors and forest edges showing the least degree of difference. Forest-dependent bird species used both interiors and edges. Interiors differed from edges and roadsides in having lower abundances of open country species, predatory species and introduced species, A clear gradient of change in bird communities from forest interiors to roadside vegetation was observed. This study suggests that the interiors of medium-sized (<1 000 ha) patches may play an important role in conserving bird biodiversity on a local level as they provide refuge for forest-dependent native species in extensively cleared landscapes.

Download Full-text

Weak Effects of Owned Outdoor Cat Density on Urban Bird Richness and Abundance

Land ◽

10.3390/land10050507 ◽

2021 ◽

Vol 10 (5) ◽

pp. 507

Author(s):

Genevieve C. Perkins ◽

Amanda E. Martin ◽

Adam C. Smith ◽

Lenore Fahrig

Keyword(s):

Urban Areas ◽

Bird Species ◽

Lethal Effect ◽

Bird Communities ◽

Domestic Cats ◽

Urban Birds ◽

Negative Effects ◽

Bird Populations ◽

Bird Richness ◽

Urban Bird

Domestic cats (Felis catus) are ubiquitous predators of birds in urban areas. In addition to the lethal effect of predation, there can also be sublethal, negative effects of domestic cats on individual birds. These effects have led to the inference that reducing outdoor cat densities would benefit urban bird communities. Here we estimate the likely result of policies/programs designed to reduce densities of owned outdoor cats in urban areas, estimating relationships between bird richness/abundance and cat densities across 58 landscapes in Ottawa, Ontario, Canada. We estimate that we would most likely observe one additional bird species, and 0.003 additional individuals per species, if policies/programs reduced owned outdoor cat densities to zero in an average landscape in Ottawa (with 130.2 cats/km2). However, these effects of cat density on birds were uncertain, with 95% confidence intervals crossing zero. Our findings—in combination with those of previous studies—suggest a need for research to resolve the apparent disconnect between the strong, negative effects of cats on individual urban birds and the weak, uncertain effects of cats on bird populations. Although measures that reduce owned outdoor cat densities are justified based on the precautionary principle, evidence to date does not support prioritizing these measures over those addressing threats that have consistently strong effects on bird populations.

Download Full-text