Avian Island Research Articles

Avian Island Radiations Shed Light on the Dynamics of Adaptive and Nonadaptive Radiation.

Understanding the mechanisms underlying species formation and differentiation is a central goal of evolutionary biology and a formidable challenge. This understanding can provide valuable insights into the origins of the astonishing diversity of organisms living on our planet. Avian evolutionary radiations on islands have long fascinated biologists as they provide the ideal variation to study the ecological and evolutionary forces operating on the continuum between incipient lineages to complete speciation. In this review, we summarize the key insights gained from decades of research on adaptive and nonadaptive radiations of both extant and extinct insular bird species. We present a new comprehensive global list of potential avian radiations on oceanic islands, based on published island species checklists, taxonomic studies, and phylogenetic analyses. We demonstrate that our understanding of evolutionary processes is being greatly enhanced through the use of genomic tools. However, to advance the field, it is critical to complement this information with a solid understanding of the ecological and behavioral traits of both extinct and extant avian island species.

The island syndrome in birds

AbstractThe island syndrome is a widespread biological phenomenon that describes a suite of morphological, behavioural, demographic and life‐history changes associated with island dwelling. These similar evolutionary responses among disparate groups of animals and plants represent a remarkable case of convergent evolution. Among animals, birds are a highly suitable group to study the island syndrome; they are a comparatively data‐rich taxon, are frequent island colonisers, and sometimes display extreme adaptations such as the loss of flight. However, the avian island syndrome literature is fragmented, and multiple components are rarely considered together even though many are inextricably linked. We reviewed multi‐species comparative studies, single‐species or population‐level studies and anecdotal accounts, to summarise and assess the support for individual components of the island syndrome for birds, and to identify suites of traits that should be considered together. The weight of evidence for island syndrome patterns in morphology is substantial, but is more partial or even anecdotal for various aspects of behaviour, life history and physiology. Full validation of the island syndrome in birds will require the less‐studied components to be treated in a comparative framework, and for covarying components to be examined in an integrated way. An improved description of the scope of the syndrome will pave the way to understanding its drivers.

A global analysis of avian island diversity-area relationships in the Anthropocene.

Research on island species-area relationships (ISAR) has expanded to incorporate functional (IFDAR) and phylogenetic (IPDAR) diversity. However, relative to the ISAR, we know little about IFDARs and IPDARs, and lack synthetic global analyses of variation in form of these three categories of island diversity-area relationship (IDAR). Here, we undertake the first comparative evaluation of IDARs at the global scale using 51 avian archipelagic data sets representing true and habitat islands. Using null models, we explore how richness-corrected functional and phylogenetic diversity scale with island area. We also provide the largest global assessment of the impacts of species introductions and extinctions on the IDAR. Results show that increasing richness with area is the primary driver of the (non-richness corrected) IPDAR and IFDAR for many data sets. However, for several archipelagos, richness-corrected functional and phylogenetic diversity changes linearly with island area, suggesting that the dominant community assembly processes shift along the island area gradient. We also find that archipelagos with the steepest ISARs exhibit the biggest differences in slope between IDARs, indicating increased functional and phylogenetic redundancy on larger islands in these archipelagos. In several cases introduced species seem to have 're-calibrated' the IDARs such that they resemble the historic period prior to recent extinctions.

The island biogeography of the eBird citizen‐science programme

AbstractAimIsland biotas face an array of unique challenges under global change. Monitoring and research efforts, however, have been hindered by the large number of islands, their broad distribution and geographical isolation. Global citizen‐science initiatives have the potential to address these deficiencies. Here, we determine how the eBird citizen‐science programme is currently sampling island bird assemblages annually and how these patterns are developing over time.LocationGlobal.TaxaBirds.MethodsWe compiled occurrence information of non‐marine bird species across the world's islands (n = 21,813) over an 18‐year period (2002–2019) from eBird. We estimated annual survey completeness and species richness across islands, which we examined in relation to six geographical and four climatic features.ResultseBird contained bird occurrence information for ca. 20% of the world's islands (n = 4,205) with ca. 8% classified as well surveyed annually (n = 1,644). eBird participants tended to survey larger islands that were more distant from the mainland. These islands had lower proximity to other islands and contained a broader range of elevations. Temperature, precipitation and temperature seasonality were at intermediate levels. Precipitation seasonality was at low and intermediate levels. Islands located between 10 and 60° N latitude and 20 and 40° S latitude were overrepresented, and islands located in Southeast Asia were underrepresented. From 2002 to 2019, the number of islands surveyed annually increased by ca. 96.4 islands/year. During this period, island size decreased, distance from mainland did not change, proximity to other islands increased and elevation range decreased.Main conclusionsThe eBird programme tends to survey larger islands containing intermediate climates that are more isolated from the mainland and other islands. These findings provide a framework to support the informed application of the eBird database in avian island biogeography. Our findings emphasize citizen science as an empirical resource to support long‐term ecological research, conservation and monitoring efforts across remote regions of the globe.

A Semi-Automated Method for Estimating Adélie Penguin Colony Abundance from a Fusion of Multispectral and Thermal Imagery Collected with Unoccupied Aircraft Systems

Monitoring Adélie penguin (Pygoscelis adeliae) populations on the Western Antarctic Peninsula (WAP) provides information about the health of the species and the WAP marine ecosystem itself. In January 2017, surveys of Adélie penguin colonies at Avian Island and Torgersen Island off the WAP were conducted via unoccupied aircraft systems (UAS) collecting optical Red Green Blue (RGB), thermal, and multispectral imagery. A semi-automated workflow to count individual penguins using a fusion of multispectral and thermal imagery was developed and combined into an ArcGIS workflow. This workflow isolates colonies using multispectral imagery and detects and counts individuals by thermal signatures. Two analysts conducted manual counts from synoptic RGB UAS imagery. The automated system deviated from analyst counts by −3.96% on Avian Island and by 17.83% on Torgersen Island. However, colony-by-colony comparisons revealed that the greatest deviations occurred at larger colonies. Matched pairs analysis revealed no significant differences between automated and manual counts at both locations (p > 0.31) and linear regressions of colony sizes from both methods revealed significant positive relationships approaching unity (p < 0.0002. R2 = 0.91). These results indicate that combining UAS surveys with sensor fusion techniques and semi-automated workflows provide efficient and accurate methods for monitoring seabird colonies in remote environments.

Marine subsidies mediate patterns in avian island biogeography

The classical theory of island biogeography, which predicts species richness using island area and isolation, has been expanded to include contributions from marine subsidies, i.e. subsidized island biogeography (SIB) theory. We tested the effects of marine subsidies on species diversity and population density on productive temperate islands, evaluating SIB predictions previously untested at comparable scales and subsidy levels. We found that the diversity of terrestrial breeding bird communities on 91 small islands (approx. 0.0001–3 km2) along the Central Coast of British Columbia, Canada were correlated most strongly with island area, but also with marine subsidies. Species richness increased and population density decreased with island area, but isolation had no measurable influence. Species richness was negatively correlated with marine subsidy, measured as forest-edge soil δ15N. Density, however, was higher on islands with higher marine subsidy, and a negative interaction between area and subsidy indicates that this effect is stronger on smaller islands, offering some support for SIB. Our study emphasizes how subsidies from the sea can shape diversity patterns on islands and can even exceed the importance of isolation in determining species richness and densities of terrestrial biota.

Novel penguin Avian avulaviruses 17, 18 and 19 are widely distributed in the Antarctic Peninsula.

Three novel Avian avulavirus species were discovered and isolated during 2017 from Gentoo penguins (Pygoscelis papua) at Kopaitic island in the Northwestern region of the Antarctic Peninsula. The viruses were officially named as Avian avulavirus 17 (AAV17), Avian avulavirus 18 (AAV18) and Avian avulavirus 19 (AAV19), collectively referred to as penguin avulaviruses (PAVs). To determine whether these viruses are capable of infecting the three species of Pygoscelis spp. penguins (Gentoo, Adelie and Chinstrap) and assess its geographical distribution, serum samples were collected from seven locations across the Antarctic Peninsula and Southern Shetland Islands. The samples were tested by Hemagglutination inhibition assay using reference viruses for AAV17, AAV18 and AAV19. A total of 498 sera were tested, and 40 were positive for antibodies against AAV17, 20 for AAV18 and 45 for AAV19. Positive sera were obtained for the penguin's species for each virus; however, antibodies against AAV18 were not identified in Adelie penguins. Positive penguins were identified in all regions studied. Positive locations include Ardley Island and Cape Shirreff at Livingston Island (Southern Shetland Region); Anvers Island, Doumer Island and Paradise Bay in the Central Western region; and Avian Island at Southwestern region of the Antarctic Peninsula. The lowest occurrence was observed at the Southwestern region at Lagotellerie Island, where all samples were negative. On the other hand, Cape Shirreff and Paradise Bay showed the highest antibody titres. Field samples did not evidence cross-reactivity between viruses, and detection was significantly higher for AAV19 and lower for AAV18. This is the first serologic study on the prevalence of the novel Avian avulaviruses including different locations in the white continent. The results indicate that these novel viruses can infect the three Pygoscelis spp. penguins, which extend across large distances of the Antarctic Peninsula.

Reconciling supertramps, great speciators and relict species with the taxon cycle stages of a large island radiation (Aves: Campephagidae)

AbstractAimThe taxon cycle concept provides a geographically explicit and testable set of hypotheses for exploring the evolutionary processes underlying the distribution of species in space and time. Here, we test taxon cycle predictions within a large avian island radiation, the core Campephagidae and explicitly integrate the concepts of ‘supertramps’, ‘great speciators’ and relictualization.LocationThe Indo‐Pacific, Australia, Asia and Africa.TaxonCorvoid passerine birds.MethodsWe constructed a new time‐calibrated molecular phylogeny of the core Campephagidae (cuckooshrikes, cicadabirds and trillers) using Bayesian phylogenetic methods. Ancestral range estimation methods and diversification rate analyses were used to explore the dispersal and diversification history of the group. We used an extensive dataset on wing morphology and range distributions to test for correlations between evolutionary age of species and dispersal capacity, diversification and distribution, while accounting for phylogenetic non‐independence.ResultsThe core Campephagidae represents an ecologically homogeneous radiation distributed across the Indo‐Pacific, Australia, Southeast Asia and Africa. Its members represent a continuum of dispersal abilities; some species are widespread and undifferentiated (‘supertramps’) or show strong differentiation of local populations (‘great speciators’), and a few are endemic to single islands (relicts). We show that older species relative to younger species inhabit fewer and larger islands at higher elevations. The level of intraspecific variation measured as the number of subspecies also decreases with species age, and is highest in ‘great speciators’ with intermediate levels of dispersal abilities (as per hand‐wing index).Main conclusionsBased on trait correlations with species age, we infer phases of range expansion and contraction over millions of years (taxon cycles), within a single monophyletic group of birds. These observations demonstrate reconciliation of the concepts of ‘supertramps’, ‘great speciators’ and relictual palaeoendemics within the temporal stages of the taxon cycle.

Dietary niche and the evolution of cranial morphology in birds.

Cranial morphology in birds is thought to be shaped by adaptive evolution for foraging performance. This understanding of ecomorphological evolution is supported by observations of avian island radiations, such as Darwin's finches, which display rapid evolution of skull shape in response to food resource availability and a strong fit between cranial phenotype and trophic ecology. However, a recent analysis of larger clades has suggested that diet is not necessarily a primary driver of cranial shape and that phylogeny and allometry are more significant factors in skull evolution. We use phenome-scale morphometric data across the breadth of extant bird diversity to test the influence of diet and foraging behaviour in shaping cranial evolution. We demonstrate that these trophic characters are significant but very weak predictors of cranial form at this scale. However, dietary groups exhibit significantly different rates of morphological evolution across multiple cranial regions. Granivores and nectarivores exhibit the highest rates of evolution in the face and cranial vault, whereas terrestrial carnivores evolve the slowest. The basisphenoid, occipital, and jaw joint regions have less extreme differences among dietary groups. These patterns demonstrate that dietary niche shapes the tempo and mode of phenotypic evolution in deep time, despite a weaker than expected form–function relationship across large clades.

Gastrointestinal helminths of Adélie penguins (Pygoscelis adeliae) from Antarctica

Knowledge about parasitic organisms in Antarctica is scarce and fragmentary. The study reported here adds to the knowledge of gastrointestinal parasites of the Adelie penguin ( Pygoscelis adeliae ) (Sphenisciformes), from 25 de Mayo/King George Island (South Shetlands), Bahia Esperanza (Hope Bay) and Avian Island (Antarctica). Thirty-five freshly dead specimens (20 chicks and 15 adults) were collected from December 2007 to December 2014 and examined for internal macroparasites. Three adult parasite species were found: one Cestoda, Parorchites zederi , and two Nematoda, Stegophorus macronectes and Tetrameres sp. Immature Tetrabothrius sp. were found in hosts from Avian Island. Helminth communities are known to be related to host feeding behaviours. Low parasite richness observed in Adelie penguins could be related to the stenophagic and pelagic diet of this host species, which feeds almost exclusively on krill. Keywords: Parorchites zederi ; Stegophorus macronectes ; Tetrameres sp.; parasites; ecosystem health. (Published: 16 June 2016) Citation: Polar Research 2016, 35 , 28516,http://dx.doi.org/10.3402/polar.v35.28516

Erythrocytic abnormalities in three Antarctic penguin species along the Antarctic Peninsula: biomonitoring of genomic damage

Pollutants and toxic contaminants produced in all parts of the world are transported to remote regions including Antarctica. Tourism, research, and fishing activities on this continent are another source of contamination. Toxic substances affect Antarctic species, and some produced genomic damage to the fauna. The genetic damage can be detected by microscopic observation of erythrocytic nuclear abnormalities (ENAs). We counted the number of ENAs in seven populations of three Pygoscelid penguin species, Adélie (Pygoscelis adeliae), Chinstrap (Pygoscelis antarctica), and Gentoo (Pygoscelis papua), and found important differences among species exposed to the same conditions. ENAs were more frequent in Adélie penguins than in the other two species. Inter-population comparisons within species showed remarkable differences in Adélie and Chinstrap penguins but not in Gentoo penguin. Frequency of ENAs in Adélie penguins was the highest in Yalour Island population, intermediate in King George Island population, and the lowest in Torgersen Island and Avian Island populations. In Chinstrap penguins, the highest number of ENAs was found on Deception Island, and significant differences were found only between Deception Island and King George Island populations. This information will provide baseline data to be used for assessing the evolution of genomic damage of penguins along the Antarctic Peninsula in the future.

A new high-latitude record for the macaroni penguin (Eudyptes chrysolophus) at Avian Island, Antarctica

On 20 and 22 January 2007, we observed macaroni penguins (Eudyptes chrysolophus) on Avian Island, Antarctica, approximately 1° south of the Antarctic Circle along the Western Antarctic Peninsula (WAP) near Adelaide Island, a new high-latitude observational record for the species within this region of the continent. Additionally, we report several extra-limital sightings of macaroni penguins over the last decade at relatively lower latitudes along the WAP near Anvers Island, including observations of breeding attempts. Although vagrancy cannot be ruled out as a possible causal factor in our observations, we hypothesize that a climate-induced shift in the species’ bio-geographic range may be in progress. In this context, our observations are similar to the well-documented range shifts and eventual establishment of breeding populations by other sub-Antarctic penguin species along the WAP, over the last three decades, in response to regional climate warming. We highlight that the few observations reported here do not provide conclusive evidence for any putative causal mechanism explaining the presence of macaroni penguins at locations outside their natural geographic range. However, our observations are important for developing a better understanding of the natural history of the species along the WAP.

Neutral markers mirror small-scale quantitative genetic differentiation in an avian island population

We still know remarkably little about the extent to which neutral markers can provide a biologically relevant description of population structure. In the present study, we address this question, and quantify microsatellite differentiation among a small, structured island population of great tits (Parus major), and a large mainland population 150 km away. Although only a few kilometres apart, we found small but statistically significant levels of differentiation between the eastern and the western part of the island. On the other hand, there was no differentiation between the western part of the island and the mainland population, whereas the eastern part and the mainland did differ significantly. This initially counterintuitive result provides powerful support for the hypothesis that the large genetic difference in clutch size between both parts of the island found earlier is maintained by different levels of gene flow into both parts of the island, and illustrates the capac! ity of microsatellites to provide a meaningful description of population structure. Importantly, because the level of microsatellite differentiation is very low, we were unable to infer any population structure without grouping individuals a priori. Hence, these low levels of differentiation in neutral markers could easily remain undetected, or incorrectly be dismissed as biologically irrelevant. Thus, although microsatellites can provide a powerful tool to study genetic structure in wild populations, they should be used in conjunction with a range of other sources of information, rather than as a replacement.

Consequences of dispersal for the quantitative study of adaptation in small-scale plots: a case study of an avian island population

Lifetime recruitment of breeding offspring estimated in small-scale study plots (i.e. local recruitment) is considered to be the best available ecological measure of contributions to following generations, and sufficient for the quantitative study of adaptation in natural populations. Recent investigations suggest that local recruitment of breeding offspring does not always reflect the total recruitment in the whole population, especially in small-scale plots where the majority of locally-born offspring leave these plots to breed elsewhere. We examined in an avian island population whether study plot size has an important impact on different population and fitness measures. We defined around a central nestbox seven plots, varying in radius from 100 to 700 m. We show that in the smallest plots, the local replacement rate of adults by breeding offspring is low, the number of locally-born offspring settling beyond the limits of a plot is high, and relationships between local and total recruitment are weak. This is especially true for daughters as more daughters than sons settle beyond the limits of local plots for breeding. Our interpretation is that the lifetime recruitment of breeding offspring in local plots does not necessarily reflect the lifetime recruitment of breeding offspring in the whole population, especially when plots do not cover the natal dispersal distance. Consequences of dispersal for the quantitative study of adaptation are discussed.

Influential factors for natal dispersal in an avian island metapopulation

Dispersal is a key parameter in evolutionary, demographic and conservation theory, but the factors influencing dispersal between populations are rarely known, and the contribution of immigrants to population stability remains uncertain. Using dispersal data from nine island populations of song sparrows, we show that female and male immigrants responded differently to population structure: in females, immigration varied with adult sex ratio; whereas immigration by males was more influenced by population density. These patterns are consistent with the hypothesis that intra‐sexual competition for breeding resources influenced recruitment patterns. Immigrants often constituted a substantial fraction of local population size, and in six cases immigration by females prevented the extirpation of that sex from the island. Breeding vacancies and extirpations may have been more likely in females because their apparent survival was lower than in males. Local recruitment and immigration varied markedly among islands, perhaps as consequence of island size and isolation. Overall, our results suggest that immigration varied with local demography in a sex‐specific way, stabilized population numbers and reduced extinction rates in the smallest populations.

Restoring avian island endemics: use of supplementary food by the endangered Pink Pigeon (Columba mayeri)

The wild population of Pink Pigeons (Columba mayeri) of Mauritius has recovered from ten individuals in 1990 to ~390 birds in 2008. Limited availability of native feeding habitat is a primary factor restricting further increases in population. Current management of the species includes provision of supplementary food (wheat) and restoration of native forest habitat. This study investigated dependence on supplementary food by examining patterns of supplementary food use and social interactions in two Pink Pigeon subpopulations. During 72 h of observations over a 10-week study period 99% of the birds visited supplementary feeding stations, and the combined duration of these visits per individual was 0–1.7% of the total observation period. Frequency of visits peaked in late afternoon and timing of feeding visits also varied between sexes in one subpopulation, where males fed for longer after daytime nest incubation (1600–1800 hours) than females, and females fed for longer than males throughout the middle of the day (1000–1300 hours). Younger birds (<1 year old) fed more frequently than older birds. Implications of these findings for the long-term management of this and other recovering avian populations are discussed.

Population variability in heat shock proteins among three Antarctic penguin species

Heat shock proteins (HSPs) are synthesised under stressful conditions such as exposure to elevated temperatures, contamination, free radicals, UV light or pathophysiological states resulting from parasites and/or pathogens. HSPs function to protect cells by means of modulation of protein folding. In Antarctica, these proteins have been studied in such organisms as protozoa and fishes, without attention to geographical variation. We studied the variation of HSP70 and HSP60 levels in Gentoo, Adelie and Chinstrap penguins among different populations along the Antarctic Peninsula from King George Island (62°15′S) to Avian Island (67°46′S). Our results show that the northern population of Gentoo penguin showed higher levels of HSP70 and HSP60 than the southern population. High temperature, human impact and immunity as a proxy for parasites and diseases in northern locations could explain such variation. Adelie penguin only showed significant geographical variation in HSP70, increasing north to south, a pattern perhaps related to increased UV radiation and decreased temperatures from north to south. Chinstrap penguin shows no population differences in the variation in neither HSP70 nor HSP60, although HSP70 showed marginally significant differences. Sexual differences in the level of these proteins are also discussed.

Geographic variation in the immunoglobulin levels in pygoscelid penguins

Antarctic organisms, including penguins, are susceptible to parasites and pathogens. Effects of infestation could differ in different locations along a geographical gradient from north to south consistent with conditions that affect the prevalence and virulence of parasites and pathogens. The immune system, including immunoglobulins as the main component of the humoral immune response, is the major way by which organisms confront infestation. We investigated the variation in immunoglobulin levels in three species of antarctic penguins (Pygoscelis antarctica, Pygoscelis papua, and Pygoscelis adeliae) along a geographical gradient from King George Island (62°15′S) to Avian Island (67°46′S). We found that immunoglobulin levels increased northwards in all the three species. This could indicate a higher impact of parasites and/or pathogens relative to the existing gradient in temperatures along this coast. Changing temperatures, consistent with global climate change, could be altering the ecology of parasite or pathogen infestation within the biota of northern Antarctica. We have also found marginal differences in immunoglobulin levels between sexes in both chinstrap and gentoo penguins.

Flight of the Dodo

Flight of the Dodo

Consequences of dispersal for the quantitative study of adaptation in small-scale plots: a case study of an avian island population

Consequences of dispersal for the quantitative study of adaptation in small-scale plots: a case study of an avian island population