Landbird Species Research Articles

Exploratory Surveys of Migratory Birds Breeding in the Western and Central Canadian Arctic 2005–2011

Abstract The Canadian Arctic and subarctic are the primary breeding areas of many species of North American water and land birds. Because of the remote location and the logistical difficulties of working there, wildlife biologists have not systematically surveyed most important areas for wildlife, nor have they surveyed these areas very frequently. During the summers of 2005–2011, various Joint Ventures, and U.S., Canadian, and state wildlife agencies and other partners funded exploratory fixed-wing aircraft surveys of migratory birds (excluding passerines and shorebirds) in important habitats in Canada's western and central Arctic. Our objectives were to provide access to the complete survey dataset (all bird and mammal observations and associated location data) and summarize information on several species. Thus, we produced maps of average relative density and estimates of abundance in the survey area for cackling geese Branta hutchinsii, greater white-fronted geese Anser albifrons, tundra swans Cygnus columbianus, king eiders Somateria spectabilis, long-tailed ducks Clangula hyemalis, white-winged Melanitta fusca and surf Melanitta perspicillatas scoters, and yellow-billed Gavia adamsii, red-throated Gavia stellata, and Pacific Gavia pacifica loons. We reviewed previous survey efforts in the area and, where possible, compared them with our results.

Niche modeling reveals life history shifts in birds at La Brea over the last twenty millennia

A species presence at a particular site can change over time, resulting in temporally dynamic species pools. Ecological niche models provide estimates of species presence at different time intervals. The avifauna of La Brea includes approximately 120 species dating to approximately 15,000 years ago. Niche models predicted presence at the Last Glacial Maximum for over 90% of 89 landbird species. This confirms that niche modeling produces sensible range estimates at the Last Glacial Maximum. For 97 currently local species that are as yet undocumented at La Brea over 90% were predicted to occur; absence is due to insufficient study, lack of the ecological niche, transient occurrence or a behavioral ability to avoid entrapment. Our 366 niche models provide a prospective checklist of the landbird fauna of La Brea. The models indicate fluidity in life history strategies and a higher proportion of resident birds at the LGM (88% to 60%). We evaluated a subset of 103 species in breeding and winter periods using two climate models (MIROC−ESM, CCSM4) with a variety of differing parameters, finding differences in 5% of the niche models. Niche breadths in bark-foraging birds changed little between the present and LGM, suggesting that greater species diversity at the LGM was due to greater niche availability rather than contractions of niche breadths (i.e., niche partitioning).

A collaborative bird survey of East Kwaio, Malaita, Solomon Islands

We surveyed the birds of East Kwaio, Malaita, Solomon Islands from 20 October to 2 November 2018. We conducted 66 point counts and recorded or observed 58 species of resident landbirds, including 23 of the 24 passerine species known from the island of Malaita and 15 waterbird species. We collected some form of samples (e.g., whole specimens and/or blood samples) from 61 individuals of 17 species, including representatives of the four species-level endemics: Malaita Fantail Rhipidura malaitae (Mayr, 1931), Malaita Dwarf-Kingfisher Ceyx malaitae (Mayr, 1935), Malaita White-eye Zosterops stresemanni (Mayr, 1931), and Red-bellied Myzomela Myzomela malaitae (Mayr, 1931). We demonstrate the considerable potential for conservation of the Malaitan avifauna on traditional lands in the mountains of East Kwaio. The extensive knowledge of the local people was a key factor in the success of the expedition. To facilitate ongoing conservation efforts, we documented the local Kwaio names of the birds we encountered.

Can invasive species replace native species as a resource for birds under climate change? A case study on bird-fruit interactions

Wild fruits are an important food source for many north temperate-breeding landbirds during autumn migration and, in turn, birds provide the service of seed dispersal. Despite the importance of these autumn interactions, their potential to shift with climate change and species invasions remains poorly understood. As invasive fleshy-fruited shrubs spread across the Northeast USA and many landbird species pass through stopover sites later with warming temperatures, the potential for changes in bird-fruit interactions depends on the phenology and availability of native and invasive wild fruits, and bird preferences across the autumn season. We observed the fruiting phenology of 25 native and invasive fleshy-fruited wild plant species at Manomet, a migratory stopover site on the coast of Massachusetts, USA, during the autumn migration season (August to November) in 2014 and 2015. We also monitored fruit availability across Manomet in 2015. To determine whether fruit consumption reflected phenology and availability, we identified seeds from 469 fecal samples collected from songbirds captured during the 2014 and 2015 autumn banding seasons. We found that while invasive shrubs fruited later, on average, than native plants, and comprised a large proportion of the total available fruits in late-autumn, birds primarily consumed the fruits of native species throughout the autumn season. Our results demonstrate that native fruits are an important food resource for birds during the autumn migration season and are unlikely to be replaced by abundant fruits of late-season invasive species under climate change.

Landbird trends in protected areas using time‐to‐event occupancy models

AbstractGlobal populations of wildlife are affected by human activity, land cover change, and climate change. Long‐term monitoring programs across large spatial scales are required to understand how these and other factors affect wildlife populations. Occupancy models are frequently used to monitor changes in species distribution while accounting for imperfect detection. Occupancy surveys can be expensive because they typically require multiple surveys to estimate the probability of detection. Time‐to‐detection models provide a promising approach for estimating occupancy because they require just one visit; however, few studies have tested or applied these models to wildlife data. We ran a simulation study to assess biases of time‐to‐event occupancy models for standardized avian point‐count surveys and then applied the models to 10 yr of data. Time to first detection occupancy models had minimal bias and almost nominal coverage for species with a mean time to first detection <8 min on surveys with 10 min of sampling. Biases and root mean squared error increased with increasing time to first detection. We applied a single species, multi‐year occupancy model to 34,665 detections of 77 landbird species collected across 500 km of latitude in five protected areas along the Rocky Mountains. Models from 64 species converged and had mean times to first detection <8 min. Average time to first detections was 3.2 min, which reflected a cumulative probability of detection of 0.96. Occupancy rates increased, decreased, and remained unchanged for 53%, 9%, and 38% of species, respectively. Overall, occupancy rates increased in 2015 and 2016 for short‐ and long‐distance migrants and decreased slightly for winter residents. Average decadal temperature and precipitation were important predictors for almost half of the species, while annual changes in spring temperature and precipitation affected 23% of species. Our studies demonstrate that time to first event occupancy models provide an efficient method for monitoring changes in distribution so long as encounter rates are much shorter than the survey duration. Our stable to increasing trends and strong responses to spring temperature and precipitation highlight the value of long‐term monitoring for understanding how changing climatic conditions affect wildlife.

Additive and interactive cumulative effects on boreal landbirds: winners and losers in a multi‐stressor landscape

Stressors created by multiple resource industries can result in cumulative effects over time and space. Many studies have evaluated single stressors and assumed that cumulative effects can be understood by adding stressors together. However, there is growing evidence that interactive effects are important in structuring biological communities. We evaluated whether the effects of multiple stressors in the boreal forest (linear features, energy, forestry) combine additively or interactively by testing a candidate model set of 12 cumulative effects models of abundance for 27 landbird species. We fitted paired additive and interactive Generalized Additive Models and examined model predictions in the Athabasca Oil Sands Area of Alberta, Canada, and a theoretical no‐disturbance version of the study area. Of the 27 species examined, an additive disturbance model was the best for nine species, while an interactive disturbance model was the best for 11 species. In the current study area, disturbance models predicted strong increases in abundance for species associated with deciduous forest and open habitats (winning species) and moderate decreases for species associated with conifer forest (losing species). We found a 15% change in landbird community composition between the current study area, with 8.4% disturbance, and the theoretical no‐disturbance study area. Complex synergistic and antagonistic interactions among stressors were observed for 39% of landbird species, with the majority of interactions observed being synergistic. Stressors with relatively small disturbance areas, such as narrow linear disturbances, frequently interacted with other stressors to affect species’ responses, and energy sector stressors often had additive or interactive effects with forestry stressors. Interactive cumulative effects from multiple sectors will make it increasingly difficult for industry and land managers to manage impacts unless interactions among stressors are incorporated into cumulative effects assessments and regional land use planning processes.

The conservation value of secondary vegetation for Fijian woodland birds

ABSTRACT Half of Fiji’s 66 land bird species are endemic and 15 species are threatened with extinction following ~70% deforestation. Under conditions of large-scale habitat loss, secondary vegetation can be important for woodland biodiversity conservation. This study compares avian abundance and diversity in secondary vegetation on Viti Levu, Fiji. We use avian point surveys at replicate sites in regenerating mahogany plantation (Colo-i-Suva; eastern lowlands), regenerating native forest (Koroyanitu National Heritage Park; western highlands) and grassland (Koroyanitu National Heritage Park). We ask if there are differences in avian abundance and species richness across habitat types. In total, we recorded 1063 birds from 33 bird species. Regenerating forest sites had the greatest species richness with mostly endemic and native woodland bird species and few introduced species. Regenerating plantation sites harboured a comparable number of endemic species and threatened species as regenerating forest sites but had significantly fewer native species and no introduced species. We recorded the most birds at grassland sites as well as the most introduced species. The findings of this study underscore the importance of regenerating native forest and regenerating plantation as habitats for Fiji’s endemic woodland birds. Increasing the expanse of regenerating forest sites should be considered for conservation planning to sustain Fiji’s extant birds.

Ornithological observations from Maratua and Bawean Islands, Indonesia

Indonesia’s many islands, large and small, make it an important center of avian diversity and endemism. Current biogeographic understanding, however, is limited by the lack of modern genetic samples for comparative analyses from most of these islands, and conservation efforts are hampered by the paucity of recent information from small islands peripheral to major, more commonly visited islands. In November and December 2016, we visited Maratua, an oceanic coral atoll 50 km east of Borneo, and Bawean, a volcanic island on the Sunda continental shelf 150 km north of Java, to survey birds and collect specimens for morphological and genetic analysis. We detected many of the birds on Maratua’s historical lists and added several new resident and migratory species. Notably, we did not detect the Maratua White-rumped Shama (Copsychus malabaricus barbouri). On Bawean, we found the forests to be nearly silent and detected remarkably few resident land-bird species overall. The severe population reduction of C. m. barbouri on Maratua and the drastic reduction of forest birds on Bawean probably result from overexploitation by the cage-bird trade in the first case and a combination of the cage-bird trade and pellet-gun hunting in the second.

Trends in Landbird Density at Two National Parks in Fragmented, Mixed-Use Landscapes of the Pacific Northwest

National parks play a key role in conserving species by providing landscapes where threats from anthropogenic disturbance are reduced. In a recent study of 3 large wilderness parks in the Pacific Northwest, nearly all landbird species were found to be stable or increasing. Nonetheless, contemporary results from the Breeding Bird Survey and mark-recapture studies fuel concerns that some landbirds in the Pacific Northwest are trending in sync with many North America species in widespread decline. Although landbird populations might be thriving in large parks with extensive old-growth forest, those in smaller parks with less intact wilderness and higher ratios of edge-to-interior habitat might reflect the stressors inherent in more human-dominated landscapes. We conducted landbird point-count surveys from 2005 to 2016 in 2 national historical parks situated in the more human-dominated landscapes of this region, San Juan Island National Historical Park and Lewis and Clark National Historical Park. Established primarily to protect cultural resources, these parks lack old-growth forest and consist of relatively small parcels embedded in fragmented, multi-use landscapes. Here, we apply recent developments in point-count analysis to estimate trends in population density for 50 landbird species commonly detected in these small parks, including lagged effects of precipitation and temperature on the annual density of each species, and effects of survey conditions on species detection. All but 3 species exhibited stable densities in both parks, and more than half of the populations analyzed clearly increased in density over the study period. Notable exceptions were single-park declines in Olive-sided Flycatcher (Contopus cooperi), Northern Flicker (Colaptes anratus), and Hutton's Vireo (Vireo huttoni). Annual variation in population density was often related to climate, with generally positive responses to a recent deficit in annual precipitation-as-snow, and more variable responses to higher mean spring temperature. These results reinforce trends estimated for 3 large national parks in the Pacific Northwest, suggesting recent stability of landbird populations in parks of this region, independent of park size or setting.

Occurrence and diversity of avian haemosporidia in Afrotropical landbirds.

Avian haemosporidian infections are widespread and can result in the decline of wild bird populations or in some cases contribute to extinction of species. We determined the prevalence and genetic diversity of avian haemosporidia in 93 samples from 22 landbird species from South Africa (N = 76) and West Africa (N = 17), of which six are intra-African migrants and one is a Palearctic migrant. The samples were analysed for the presence of avian haemosporidian DNA using real-time quantitative PCR (qPCR) and nested PCR assays targeting specific mitochondrial genes of these parasites. The cytochrome b (cytb) gene was sequenced for all samples that tested positive and phylogenetic analysis was conducted in order to determine the relationship of the new sequences with previously published sequences from the MalAvi database. The overall prevalence of avian haemosporidiosis was 68.82% (95% CI: 56.4%–78.87%) and 82.80% (95% CI: 65.68%–86.11%) as determined by qPCR and nested PCR respectively. Eighteen (19.36%; 95% CI; 10.78%–29.97%) samples had mixed infections. Infection prevalence of all haemosporidian spp. were significantly higher (p < 0.05) in samples from West Africa. Forty-six mitochondrial sequences obtained from 14 avian species grouped into three distinct clusters of Haemoproteus (36), Leucocytozoon (8) and Plasmodium (2). These represent eight published and nine new cytb lineages. The most common lineage was Haemoproteus sp. (VIMWE1) which was identified in two bird species from West Africa and seven bird species from South Africa. This study adds to our knowledge of host-parasite relationships of avian haemosporidia of Afrotropical birds.

Allometry and integration do not strongly constrain beak shape evolution in large-billed (Corvus macrorhynchos) and carrion crows (Corvus corone).

A recent geometric morphometric study on certain landbird lineages revealed that a major part of the variation in beak shape is accounted for by skull size and cranial shape. The study interpreted this result as evidence for the presence of strong evolutionary constraints that severely prevented beak shape from evolving substantially away from predictions of allometry and morphological integration. However, there is another overlooked but similarly plausible explanation for this result: The reason why beak shape does not depart much from predictions might simply be that selection pressures favoring such changes in shape are themselves rare. Here, to evaluate the intensity of evolutionary constraints on avian beak shape more appropriately, we selected large‐billed (Corvus macrorhynchos) and carrion crows (Corvus corone) as study objects. These landbird species seem to experience selection pressures favoring a departure from an allometric trajectory. A landmark‐based geometric morphometric approach using three‐dimensional reconstructions of CT scan images revealed that only 45.4% of the total shape variation was explained by allometry and beak–braincase integration. This suggests that when a selection pressure acts in a different direction to allometry and integration, avian beak shape can react to it and evolve flexibly. As traditionally considered, evolutionary constraints on avian beak shape might not be all that strong.

Temporal changes in abundance exhibit less spatial structure than abundance itself in North American birds

Species abundance is often spatially structured such that, within a species’ distribution, abundance peaks at one or more areas and declines from those points. Abundance may also increase or decrease over time, but the spatial structure of temporal changes in abundance has been infrequently examined. Here we use count data from the North American Breeding Bird Survey (BBS) to describe the spatial structure of yearly changes in abundance across the distributions of 135 species of land birds. For each species, we calculated the difference in the logarithms of the number of birds counted from one year to the next at survey routes within their distributions. We assessed the spatial structure of yearly changes in abundance using Moran’s I, a measure of spatial autocorrelation. For comparison, we also calculated Moran’s I for abundance, i.e., the logarithm of the number of birds counted on survey routes in each year. As expected, abundance was positively spatially autocorrelated (i.e. closer routes were more similar than expected by chance) at distances of up to a few hundred kilometers for most species. In contrast, changes in abundance showed little to no spatial autocorrelation. Resident species exhibited greater spatial structure in abundance than migrant species; however, the two groups did not differ in the degree of spatial structure in change in abundance. Variation in abundance over multiple years was mostly unrelated to the distance from the abundance-weighted center of species’ distributions. Temporal changes in abundance can occur at fine spatial scales for many species, but understanding the causes of such changes is challenging. These results fill a gap in the ecological literature and may have important implications for conservation planning.

Avian community characteristics and demographics reveal how conservation value of regenerating tropical dry forest changes with forest age.

Expansion of secondary forests following the abandonment of agriculture may have important implications for bird conservation, but few studies have examined the dynamics of this process. We studied bird use of a chronosequence of differently-aged abandoned pastures regenerating to dry forest to better understand how the value of these habitats to birds changes over time. In a five year study on Hispaniola, we recorded 7,315 net captures of 60 species of landbirds in sites that began the study at two, five, 10, and 20 years post-abandonment, and in mature native dry forest. Twenty-five species made up 97% of all net captures. Highest capture rates were in the two youngest sites. These early-successional habitats had many over-wintering Neotropical migrants; among residents, granivores and frugivores predominated. In contrast, both the twenty-year-old and mature forest sites had few migrants, more resident insectivores and omnivorous species, and a greater proportion of endemics. Age and sex ratios, body condition and site persistence suggest early successional sites were sub-optimal for most over-wintering migrants, but habitat improved with age for three migratory species; results for permanent residents varied among species. Remnant trees and understory shrubs in the agroecological matrix likely contributed to avian diversity in regenerating dry forest sites, and proximity to mature forest also likely affected the diversity and abundance of birds in regenerating habitat. Our study shows that regenerating forests do not fully compensate for loss of mature dry forest habitat, even after 24 years of regeneration; natural restoration of complex microhabitats in dry forest sites converted to agriculture may take decades or longer. The highest value of regenerating forests may be as habitat for some over-wintering Neotropical migrants, and in creating a buffer zone that enhances biodiversity conservation by re-integrating these lands into the protected tracts of mature forest needed by the islands more unique and endemic bird species.

Population status of four endemic land bird species after an unsuccessful rodent eradication on Henderson Island

SummaryInvasive rodents detrimentally affect native bird species on many islands worldwide, and rodent eradication is a useful tool to safeguard endemic and threatened species. However, especially on tropical islands, rodent eradications can fail for various reasons, and it is unclear whether the temporary reduction of a rodent population during an unsuccessful eradication operation has beneficial effects on native birds. Here we examine the response of four endemic land bird species on subtropical Henderson Island in the Pitcairn Island Group, South Pacific Ocean, following an unsuccessful rodent eradication in 2011. We conducted point counts at 25 sampling locations in 14 survey periods between 2011 and 2015, and modelled the abundance trends of all species using binomial mixture models accounting for observer and environmental variation in detection probability. Henderson Reed Warbler Acrocephalus taiti more than doubled in abundance (2015 population estimate: 7,194-28,776), and Henderson Fruit Dove Ptilinopus insularis increased slightly between 2011 and 2015 (2015 population estimate: 4,476–10,072), while we detected no change in abundance of the Henderson Lorikeet Vini stepheni (2015 population estimate: 554–3014). Henderson Crake Zapornia atra increased to pre-eradication levels following anticipated mortality during the operation (2015 population estimate: 4,960–20,783). A temporary reduction of rat predation pressure and rat competition for fruit may have benefitted the reed warbler and the fruit dove, respectively. However, a long drought may have naturally suppressed bird populations prior to the rat eradication operation in 2011, potentially confounding the effects of temporary rat reduction and natural recovery. We therefore cannot unequivocally ascribe the population recovery to the temporary reduction of the rat population. We encourage robust monitoring of island biodiversity both before and after any management operation to better understand responses of endemic species to failed or successful operations.

Bird Diversity Patterns in the Nuclear Central American Highlands: A Conservation Priority in the Northern Neotropics

The Nuclear Central American Highlands (NCAH) is a mountainous region located within a complex transition zone. Here, we analyzed the distribution patterns of 282 species of resident land birds of the NCAH. We gathered a database with records of presence of species, from which we generated realized ecological niche models using the Genetic Algorithm for Rule Set Production. These ecological niche models were used to obtain maps of each species’ potential distribution and generated species richness maps that were also compared to the map of protected areas. In addition, the maps were overlaid with a 0.25° diameter hexagonal grid to generate a presence–absence matrix to create regionalizations through (a) a Parsimony Analysis of Endemism and (b) a phenogram. Results show contrasting patterns of distribution between total species richness and endemic species richness. The regionalizations show groups influenced by slope and altitude. Species composition is mainly Mesoamerican and Neotropical species. Our results offer a new view of the regional understanding of bird diversity patterns and biogeographical processes that have shaped regional richness, like the effects of the Great American Biotic Interchange that are visible in the species composition of the NCAH. We believe that these maps of both species richness and regionalization can serve as useful tools for conservation biologists and authorities in implementing strategies for the protection of natural areas in the NCAH.

Avian monitoring – comparing structured and unstructured citizen science

Context Citizen science is increasingly used to collect biodiversity data to inform conservation management, but its validity within urban greenspaces remains largely unresolved. Aims To assess the validity of eBird data for generating biodiversity estimates within an urban greenspace. Methods We compared data from structured avian surveys with eBird data at an urban greenspace in Sydney during 2012–16, using species richness and Shannon diversity indices. We also compared community composition, using non-metric multidimensional scaling (NMDS) and dissimilarities using non-parametric MANOVA. Key results Structured surveys had a lower overall species richness (80 versus 116) and Shannon diversity (3.64 versus 3.94) than eBird data, but we found no significant differences when using years as replicates. After standardising the richness and diversity indices by time spent surveying in a given year, structured surveys produced significantly higher biodiversity estimates. Further, when grouped into species occupying different broad habitats, there were no significant differences in waterbird or landbird species richness, or in Shannon diversity between data sources. Conclusions The most likely explanation for the larger magnitudes of the biodiversity indices from the eBird data is the increase in effort manifested in the number of observers, time spent surveying and spatial coverage. This resulted in increased detection of uncommon species, which in turn accounted for a significant difference (R2 = 0.21, P = 0.015) in overall community composition measured by the two methods. Implications Our results highlight the opportunities provided by eBird data as a useful tool for land managers for monitoring avian communities in urban areas.

Major stopover regions and migratory bottlenecks for Nearctic-Neotropical landbirds within the Neotropics: a review

SummaryNearly 300 species of landbirds, whose populations total billions, migrate between the Neotropics and North America. Many migratory populations are in steep decline, and migration is often identified as the greatest source of annual mortality. Identifying birds’ needs on migration is therefore central to designing conservation actions for Nearctic-Neotropical migratory birds; yet migration through the Neotropics is a significant knowledge gap in our understanding of the full annual cycle. Here, we synthesise current knowledge of Neotropical stopover regions and migratory bottlenecks, focusing on long-distance, migratory landbirds that spend the boreal winter in South America. We make the important distinction between “true” stopover—involving multi-day refuelling stops—and rest-roost stops lasting &lt; 24 hours, citing a growing number of studies that show individual landbirds making long stopovers in just a few strategic areas, to accumulate large energy reserves for long-distance flights. Based on an exhaustive literature search, we found few published stopover studies from the Neotropics, but combined with recent tracking studies, they describe prolonged stopovers for multiple species in the Orinoco grasslands (Llanos), the Sierra Nevada de Santa Marta (Colombia), and the Yucatan Peninsula. Bottlenecks for diurnal migrants are well described, with the narrowing Central American geography concentrating millions of migrating raptors at several points in SE Mexico, Costa Rica, Panama and the Darién. However, diurnally migrating aerial insectivores remain understudied, and determining stopover/roost sites for this steeply declining group is a priority. Despite advances in our knowledge of migration in the Neotropics, we conclude that major knowledge gaps persist. To identify stopover sites and habitats and the threats they face, we propose a targeted and collaborative research agenda at an expanded network of Neotropical sites, within the context of regional conservation planning strategies.

Darker where cold and wet: Australian birds follow their own version of Gloger's rule

Gloger's rule is usually interpreted as predicting darker coloured animals in warmer and more humid/vegetated regions. The relative importance of temperature and rainfall or vegetation is however unclear, and often only one variable is tested at a time, mainly through proxies. Here, I assess the predictions of Gloger's rule for interspecific achromatic plumage variation (dark to light variation) for an entire avifauna (551 species of Australian landbirds). I tested the effects of climatic variables (temperature and rainfall) and vegetation structure on plumage reflectance at species and assemblage level (100 × 100 km cells), controlling for phylogenetic relatedness and spatial autocorrelation. To assess the robustness of these results I compared observed results with those of a null distribution of effects obtained from repeatedly simulating random plumage reflectance evolution on the phylogeny. At both the species and assemblage level, darker coloured birds were found in wetter and colder regions and in more densely vegetated habitats. Simulations confirm results at the species level and the effect of temperature at the assemblage level, but rainfall and vegetation effects at the assemblage level fall within the distribution of simulated effects and should be interpreted with care. Interspecific colour variation in Australian birds supports Gloger's rule for rainfall/vegetation, but shows the opposite pattern for temperature. Darker colours in wet and vegetated environments are consistent with the role of melanin pigmentation in preventing feather degradation by bacteria, but also with background‐matching for camouflage. Darker plumage might be beneficial in colder regions or detrimental in warmer regions if it affects thermoregulation, a selective force often only assumed to be of importance for ectotherms. The data highlight the need to test the generality of biogeographic rules across levels and at broad scale. Experimental work is needed to confirm the mechanisms linking plumage achromatic variation to climate.

Avian population trends inScalesiaforest on Floreana Island (2004-2013): Acoustical surveys cannot detect hybrids of Darwin’s tree finchesCamarhynchusspp.

SummaryFloreana Island has the highest proportion of local land bird extinctions on the Galápagos Archipelago, and is home to the range-restricted and critically endangered Medium Tree FinchCamarhynchus pauper. We used acoustic surveys during 2004, 2008 and 2013 to compare the estimated population size ofC. pauperand other land bird species in a remnant patch ofScalesiaforest. First, we compared song inC. pauperandC. parvulusand the recently discoveredCamarhynchushybrid group to justify our use of acoustic surveys to detect population trends given contemporary hybridisation betweenC. pauperandC. parvulus. Song differed significantly betweenC. pauperversusC. parvulusand hybrid birds, but not betweenC. parvulusversus hybrid birds. Second, we compared population size estimates.Camarhynchus pauperdeclined by 52% between 2004 and 2013 (with a 10% increase since 2008);C. parvulus/hybrid increased by 45% between 2004 and 2013 (with 28% decrease since 2008). In 2013, there were ∼ 419C. paupermales in theScalesiaforest (estimate forScalesiahabitat only) and ∼ 2,537 males on Floreana Island (estimate for the entire available highland habitat). Not all species showed a pattern of decline in the highlandScalesiahabitat between 2004 and 2013:Dendroica petechia(+256%),Crotophaga ani(+254%)Geospiza fuliginosa(+23%), andMyiarchus magnirostris(+11%) increased, while the ground finchG. fortis(-76%) decreased. Understanding whyC. pauperis declining while other land bird species are increasing in the same habitat requires continued inquiry and monitoring efforts.

Le renouvellement récent des faunes de vertébrés sur l’île de Cavallo (archipel des Lavezzi, Corse)

We present a recent survey of the vertebrate fauna of Cavallo, a small island belonging to the Lavezzi archipelago located between Corsica and Sardinia. This island is the only inhabited one off the coast of Corsica and underwent deep landscape and ecosystem changes in the past 50 years induced by touristic development. The herpetofauna of the Cavallo island has changed with two recent colonisations, one green frog and one gecko. Two amphibian species and four reptiles live nowadays on this island. Concerning the breeding landbirds, this island has been visited by ornithologists more or less regularly since 1955. Several species have colonized the island while others have left. These changes are due to important modifications of the habitats, such as urbanization, the decline of high matorral and grasslands, but also the development of gardens and the creation of a permanent wetland. Today, 13 species of landbirds breed on Cavallo. Several introduced mammal species recorded in the 1980s seem to have vanished, and today the list is restricted to the introduced Black rat and two or three bat species.