W. Douglas Robinson

Opportunistic surveys, such as those archived by citizen science biodiversity inventory programs, can provide species observations over large spans of space and time. Like most biodiversity data, opportunistic reports suffer from imperfect detection of organisms, which can distort species distribution models used for science and natural resource management. Occupancy models and their variants account for imperfect detection, but opportunistic surveys are usually not collected using the sampling protocols required for occupancy modelling. The Site Clustering Problem addresses this issue by formulating the construction of sites from unstructured observations as a clustering task. We developed and evaluated a workflow for building occupancy models from opportunistic data, comprised of steps to cluster observations, form site geometries and fit models. We compared eight clustering approaches as potential solutions to the Site Clustering Problem on 31 avian species in Oregon, USA. We evaluated the clustering approaches based on predictive performance of the downstream occupancy models and analysed the impact of species traits such as home range size and habitat type on the results. In simulation studies, we measured the difference between estimated parameters and true data‐generating parameters. Our evaluation revealed several insights. Clustering methods from machine learning that accounted for similarity in both environmental and geographic space allowed observations from nearby geospatial coordinates in similar environments to be grouped together, and some of these methods were top performers. That said, the simple approach of grouping two to ten co‐located observations as sites was also competitive. This study explored a set of options for bridging the gap between large databases of opportunistic biodiversity surveys and the sampling frameworks underlying models that correct for imperfect detection of organisms. Our results provide preliminary guidance for modellers seeking to create sites for occupancy models as well as directions for future work. In particular, we expect that the development of clustering approaches that can consider species‐specific spatial constraints will improve solutions to the Site Clustering Problem.

Accurate density estimates are fundamental to conservation planning and biodiversity monitoring. In distance sampling, the half-normal detection function is commonly used to model the relationship between perceptibility and distance, but its fixed geometric form may not adequately represent species-specific detection processes. We evaluated how the choice of detection function influences density estimates using both simulated and empirical data. In simulations, we generated point count data under varying perceptibility scenarios and compared density estimates from half-normal, hazard rate, and negative exponential detection functions against known true values, alternating each function as the data-generating process and fitting correctly specified and misspecified models. Empirically, we implemented these detection functions within an integrated distance sampling (IDS) framework that integrates professional survey data and eBird observations to estimate density for 66 bird species. Simulation results showed that when the half-normal function represented the true detection process, it produced the most accurate density estimates. When the hazard rate function represented the true detection process, hazard rate models yielded slightly less biased estimates but performed comparably to half-normal models. Negative exponential models consistently showed the greatest negative bias. Empirically, 42 (64%) species were better supported by detection functions other than half-normal, and 18 species exhibited significantly higher median density estimates under these alternative IDS models. These findings indicate that reliance on a default half-normal function may overlook species-specific detection processes. Selecting best-fit detection functions (i.e., half-normal or hazard rate) can improve estimates, though hazard rate models may overestimate density when detections are highly overdispersed.

Purple Finch ( Haemorhous purpureus ) populations in eastern and western North America differ in morphological traits and genetic characteristics, yet their vocal divergence has not been quantified. We analyzed flight-call structure in Eastern and Western birds using measurements of frequency and call duration. Multivariate analyses revealed strong acoustic differentiation between subspecies, driven primarily by differences in maximum frequency, minimum frequency, and frequency span. Duration was not significantly different. Variation among subspecies in flight call characteristics was much greater than variation within individuals or within subspecies. Discriminant function analyses correctly identified calls in 93% of samples that were originally identified by the recordist or by assignment based on known geographic ranges. The five misclassified birds were all recorded in the West, had been assigned subspecies status based on range, were detected only outside the typical breeding season and were statistically Easterns. After re-assignment, the chance of misclassifying a bird to the incorrect subspecies was near zero. Only one bird in our sample, recorded in the putative zone of overlap in the Pacific Northwest, was marginally intermediate in its frequency characteristics. The reliable identification of flight calls is useful because Eastern and Western Purple Finches are highly distinctive genetically and may warrant full species status. In addition, the growing popularity of public archives for bird sound recordings increases the possibilities to track movements of infraspecifically diverse taxa like Purple Finches that are highly vocal but whose plumage variation is subtle. Finally, the existence of structurally divergent calls suggests the possibility of broader ecological and evolutionary differentiation.

Community-sourced biodiversity imagery has expanded rapidly in the past decade, facilitating analyses of ecology on unprecedented spatial scales. Proliferation of these databases has also helped to reveal understudied or previously overlooked aspects of many species’ basic biology. The Evening Grosbeak (Hesperiphona vespertina) is considered to be a species of conservation concern, and many aspects of its diet have yet to be investigated, including how its diet varies seasonally and across its large North American range. The Evening Grosbeak’s striking plumage, frequent occurrences at bird feeders, and nomadic behavior all make them popular targets of bird photographers and a prime species for study using large community-sourced archives. We reviewed more than 50,000 photographs of Evening Grosbeaks archived in the Macaulay Library, a large public database, to gain a more detailed understanding of the diet of this species. While most Evening Grosbeak images found in the Macaulay Library depicted birds foraging at bird feeders, 1075 images were found to be of birds consuming natural (non-feeder) food items. We mapped the location of these natural dietary items to four distinct regions within the Evening Grosbeak’s geographical range and found a diet consisting of at least 96 species of plants from 25 families, 1 species of insect, and 2 species of lichen from 1 family. Despite the high diversity of dietary items we identified, richness estimators suggest even greater diversity of dietary foods exists, especially in the Pacific Northwest. Using these data and published literature on the Evening Grosbeak’s diet, we discuss the characteristics of preferred Evening Grosbeak dietary items, as well as the advantages and limitations of using community-science data for such analyses. To our knowledge, this is the first range-wide, descriptive study of a songbird species’ diet using photographs made publicly available in a community-sourced archive.

Accurate assessments of changes in breeding bird populations require regular, structured surveys or, alternatively, carefully documented benchmarks that can be precisely repeated. We re-surveyed a historic benchmark of forest bird communities in Western Oregon, USA, originally conducted by Stanley Anderson between 1968-1970. Anderson’s thesis uniquely preserves detailed plot locations, species density estimates, vegetation structure summaries and methodological descriptions — an uncommon level of documentation for the time. To facilitate accurate comparisons and future re-surveys, we explain how we aligned our methods with Anderson’s and incorporated modern bird counting techniques. We also provide our raw data, metadata and methodological details to ensure transparency and reproducibility. Anderson’s work presents unusually old and detailed datasets of forest bird communities preserved from the Pacific Northwest, USA. It provides a unique opportunity to examine long-term changes in breeding bird communities within these forested landscapes affected by anthropogenic influence. The data and methods presented here are well-documented, ensuring that this benchmark can be effectively used for precisely repeatable re-surveys and comparative studies.

El Darién de Panamá, es uno de los últimos bosques fronteras del mundo. los Pueblos Indígenas desempeñan un papel fundamental como administradores de bosques intactos y Darién no es una excepción. Aquí utilizamos grabadoras de sonido para documentar la comunidad de aves. La identificación de aves fue realizada por Euclides Campos, panameño y guía de aves, así como Doug Robinson, ornitólogo conocedor de la avifauna de Panamá. Retuvimos solo las especies reportadas por ambos coautores. El análisis de los cantos de las aves fue complementado con observaciones hechas por técnicos Emberá en transectos de 1Km. El análisis de los cantos de las aves permitió identificar sonidos de especies. Esto a su vez nos permitió calcular la riqueza de especies. Las curvas de acumulación de especies se generaron agrupando todas las grabadoras, separando las estaciones seca y húmeda. Se agruparon las especies de aves según sus preferencias alimenticias. Se realizó un análisis de correspondencia en las comunidades de aves por sitio para determinar si las comunidades de aves diferían en el paisaje muestreado. La lista de aves obtenidas sirvió para estimular el debate en torno a los poseedores del conocimiento tradicional Emberá sobre aves. La información sobre conocimientos tradicionales de aves fue validada en una reunión con autoridades tradicionales de la región de Balsa (Cacique regional, el presidente del Congreso y los seis Nokos) y hombres y mujeres (40 personas). Una motivación de los Emberá al unir fuerzas con nosotros es documentar y mostrar su éxito en la conservación del bosque. Mientras el mundo enfrenta una sexta crisis de extinción masiva, el pueblo Emberá del río Balsa convive con el bosque de una manera pacífica.

Abundances of breeding forest birds have apparently declined in North America during the last five decades, possibly influenced by anthropogenic effects. We re-surveyed breeding birds in coniferous woodland plots initially surveyed in the late 1960s in western Oregon, USA. We aligned methods with those originally used and incorporated modern methods to estimate densities. To relate local results to regional trends, we compared them with Breeding Bird Survey (BBS) data. We assessed potential drivers of change for species exhibiting strong differences by relating bird density to changes in habitat and landscape composition. Eighty percent of species had densities similar to 50 years ago. Five of sixty-four species declined statistically significantly. Declines were poorly explained by changes in vegetation structure or landscape cover composition. Thirty-one species were apparently stable on plots but declined in the region. For a few species, comparisons of estimates should be viewed with caution as density estimates based on the original method were unusually high or low. Our modern estimates typically had measurement errors encompassing the 1960s estimates of density. We conclude that this Pacific Northwest bird community has remained similar through time despite 50 years of intensive forest management, indicating resilience to this level of anthropogenic activity.

Nest predation rates critically influence avian biodiversity and evolution. In the north temperate zone, increased nest failure along edges of forest fragments is hypothesized to play a major role in the disappearance of bird species from disturbed landscapes. However, we lack comprehensive syntheses from tropical latitudes, where biodiversity is highest and increasingly threatened by habitat fragmentation and disturbance. We assembled data from five decades of field studies across the global tropics (1,112 populations of 661 species) and used phylogenetic models to evaluate proposed predictors of nest success. We found significant effects of several traits, including adult body mass and nest architecture. Contrary to results from many temperate locations, anthropogenic habitat disruption did not consistently reduce nest success; in fact, raw nest success rates were lower in large tracts of primary forest than in disturbed or fragmented landscapes. Follow-up analyses within species, using a subset of 76 species for which we had estimates of nest survival in habitats with different levels of disruption, confirmed that neither disturbance nor fragmentation significantly influenced nest success. These results suggest that nest predation alone cannot explain observed declines in avian biodiversity in tropical forest fragments, raising new questions about the demographic processes that drive extinction in the tropics.