Yves Aubry

MIGRATORY CONNECTIVITY IN BICKNELL'S THRUSH: LOCATING MISSING POPULATIONS WITH HYDROGEN ISOTOPES

Abstract The measurement of the abundance of naturally occurring deuterium (δD) in feathers grown in North America can provide geographical information on location where the feather was grown. Previously, we used this technique to link populations of Bicknells Thrush (Catharus bicknelli) breeding in northeastern North America (to 46°N) with wintering grounds in the Dominican Republic. That study indicated the presence of a subpopulation of wintering birds with more depleted feather δD values than those measured on their known breeding grounds. This suggested either a more northerly or a higher altitude breeding source population than previously measured. We located two populations of Bicknells Thrush in Quebec, Canada, at Mine Madeleine (49°N) and at Mont Gosford (45°N). The Mine Madeleine birds had feather δD values overlapping those of the unidentified subpopulation found wintering in the Dominican Republic. At Mont Gosford, hatch-year birds were more depleted in their feather δD values than after-second-year birds suggesting their more northerly origins and capture during the early fall migration period. Our study demonstrates how the stable-isotope approach can be used to document connectivity between breeding and wintering populations of migratory birds. Conectividad Migratoria en Catharus bicknelli: Localización de Poblaciones Perdidas con Isótopos de Hidrógeno Resumen. La medición de la abundancia de deuterio en estado natural (δD) en las plumas formadas en América del Norte puede brindar información geográ fica sobre la localización en donde se formó la pluma. Anteriormente usamos esta técnica para relacionar las poblaciones de Catharus bicknelli que se reproducen en el noreste de América del Norte (hasta 46°N) con las áreas de invernada en República Dominicana. Ese estudio indicó la presencia de una subpoblación de aves invernantes con valores de δD en las plumas por debajo de los valores medidos de los sitios conocidos de cría. Esto sugirió la presencia de una población reproductiva proveedora de individuos localizada más al norte o a mayor elevación que las registradas anteriormente. Localizamos dos poblaciones de C. bicknelli en Québec, Canadá, una en Mine Madeleine (49°N) y otra en Mont Gosford (45°N). Las aves de Mine Madeleine tuvieron valores de δD en las plumas que se superpusieron con aquellos de la subpoblación no identificada encontrada invernando en República Dominicana. En Mont Gosford, las aves del primer año de edad presentaron valores más bajos de δD en las plumas que aquellos encontrados en aves del segundo año de edad o mayores, sugiriendo un origen más boreal y que fueron capturadas durante el inicio del período de migración otoñal. Nuestro estudio demuestra como el mé todo de isótopos estables puede ser usado para documentar conectividad entre poblaciones reproductivas e invernales de aves migratorias.

The Motus Wildlife Tracking System: a collaborative research network to enhance the understanding of wildlife movement

We describe a new collaborative network, the Motus Wildlife Tracking System (Motus; https://motus.org), which is an international network of researchers using coordinated automated radio-telemetry arrays to study movements of small flying organisms including birds, bats, and insects, at local, regional, and hemispheric scales. Radio-telemetry has been a cornerstone of tracking studies for over 50 years, and because of current limitations of geographic positioning systems (GPS) and satellite transmitters, has remained the primary means to track movements of small animals with high temporal and spatial precision. Automated receivers, along with recent miniaturization and digital coding of tags, have further improved the utility of radio-telemetry by allowing many individuals to be tracked continuously and simultaneously across broad landscapes. Motus is novel among automated arrays in that collaborators employ a single radio frequency across receiving stations over a broad geographic scale, allowing individuals to be detected at sites maintained by others. Motus also coordinates, disseminates, and archives detections and associated metadata in a central repository. Combined with the ability to track many individuals simultaneously, Motus has expanded the scope and spatial scale of research questions that can be addressed using radio-telemetry from local to regional and even hemispheric scales. Since its inception in 2012, more than 9000 individuals of over 87 species of birds, bats, and insects have been tracked, resulting in more than 250 million detections. This rich and comprehensive dataset includes detections of individuals during all phases of the annual cycle (breeding, migration, and nonbreeding), and at a variety of spatial scales, resulting in novel insights into the movement behavior of small flying animals. The value of the Motus network will grow as spatial coverage of stations and number of partners and collaborators increases. With continued expansion and support, Motus can provide a framework for global collaboration, and a coordinated approach to solving some of the most complex problems in movement biology and ecology.

Population Trends in Semipalmated Sandpipers from Migration Counts

Abstract. Although Semipalmated Sandpipers are one of the most common shorebirds in North America, analyses of migration trends using data from the Maritimes, International and Ontario Shorebird Surveys, as well as the Quebec Checklist, collected between 1974–1998, consistently showed negative trends. An additional eleven years of data was assessed to determine if declines were ongoing. Analysis (Pearson correlation) of the Quebec Checklist data indicated a significant decline overall, from 1976 to 2008, and the percentage of checklists reporting flocks of >1,000 birds has decreased significantly since the 1970s. New analyses of population trends with migration monitoring data from eastern and central North America were conducted for the 35-year period from 1974 to 2009, using program ESTEQNINDEXE. Trends, although generally negative, were not statistically significant. In the North Atlantic region, where survey sites had the highest counts of Semipalmated Sandpipers, average abundance indices showed a pronounced decrease between 1985 and 1999 and an increase since then. Although the trend was not statistically significant, declines in Ontario amounted to an estimated 8% per year from 1974 to 2009. Counts were variable for Semipalmated Sandpipers in the Midcontinent region, although average abundance indices appeared lower in the second half of the analysis period (1989–2009). Thus, the population status of Semipalmated Sandpipers in North America may have improved since the 1990s, at least in the east.

A winter distribution model for Bicknell's Thrush (Catharus bicknelli), a conservation tool for a threatened migratory songbird.

Conservation planning and implementation require identifying pertinent habitats and locations where protection and management may improve viability of targeted species. The winter range of Bicknell’s Thrush (Catharus bicknelli), a threatened Nearctic-Neotropical migratory songbird, is restricted to the Greater Antilles. We analyzed winter records from the mid-1970s to 2009 to quantitatively evaluate winter distribution and habitat selection. Additionally, we conducted targeted surveys in Jamaica (n = 433), Cuba (n = 363), Dominican Republic (n = 1,000), Haiti (n = 131) and Puerto Rico (n = 242) yielding 179 sites with thrush presence. We modeled Bicknell’s Thrush winter habitat selection and distribution in the Greater Antilles in Maxent version 3.3.1. using environmental predictors represented in 30 arc second study area rasters. These included nine landform, land cover and climatic variables that were thought a priori to have potentially high predictive power. We used the average training gain from ten model runs to select the best subset of predictors. Total winter precipitation, aspect and land cover, particularly broadleaf forests, emerged as important variables. A five-variable model that contained land cover, winter precipitation, aspect, slope, and elevation was the most parsimonious and not significantly different than the models with more variables. We used the best fitting model to depict potential winter habitat. Using the 10 percentile threshold (>0.25), we estimated winter habitat to cover 33,170 km2, nearly 10% of the study area. The Dominican Republic contained half of all potential habitat (51%), followed by Cuba (15.1%), Jamaica (13.5%), Haiti (10.6%), and Puerto Rico (9.9%). Nearly one-third of the range was found to be in protected areas. By providing the first detailed predictive map of Bicknell’s Thrush winter distribution, our study provides a useful tool to prioritize and direct conservation planning for this and other wet, broadleaf forest specialists in the Greater Antilles.