Inferring Movements and Staging Locations for Canvasbacks Using Light-Level Geolocators

Understanding the geographic extent and timing of wildlife movements enables resource managers to inform habitat needs of target species efficiently and effectively. We use light-level geolocators—which enable researchers to estimate individual locations from light-level data—to build a more complete understanding of the geography and timing of migratory movements for canvasback Aythya valisineria in the Pacific Flyway. During the springs of 2015–2017, we placed 151 geolocators on canvasbacks using two alternative attachment methods (leg-band vs. nasal-saddle mounts) during spring migration (February–March) near Reno, Nevada. Eight of these geolocators (five males and three females) were successfully retrieved, representing 10 near-complete annual migration cycles (two geolocators contained data for two migration years). Eight of the 10 estimated spring canvasback migrations (five male and three female) ended at breeding sites in the Prairie Pothole Region of southern Canada and northern United States (often via stopover sites in Utah and Montana), whereas one male and one female migrated to breeding sites in Alaska. Notably, one female settled on nesting grounds in southern Saskatchewan and then in central Alaska in successive years. During spring migration, canvasbacks made an average of 3.3 ± 0.5 stopovers, with an average duration of 14.8 ± 2.2 d. Three canvasbacks made a distinct molt migration after breeding. For fall migration, canvasback made an average of 2.7 ± 0.3 stopovers, lasting an average of 12.3 ± 2.5 d, on their way to wintering sites in California's Central Valley and coastal regions near San Francisco Bay. Retrieval rate for nasal-saddle-mounted geolocators was significantly lower than leg band-mounted devices because of failure of nasal-saddle attachment. This study demonstrates the value of geolocators for assessing year-round habitat use for waterfowl species that have negative behavioral reactions to traditional backpack devices. This information complements standard band-recovery approaches and enables waterfowl managers to ensure that the spatial and temporal distributions of individuals are identified so that habitat conservation efforts can reflect the full annual habitat use cycle.

Helmintos intestinales de algunas aves acuáticas en el estado de Hidalgo: estudio de caso, Lago de Tecocomulco

Como parte de un estudio de la calidad ambiental de Lago de Tecocomulco, Hidalgo, México, fueron colectados los helmintos intestinales de 70 aves de cinco especies: Anas americana, Anas discors, Aythya valisineria, Gallinula chloropus y Fulica americana. Los intestinos de las aves fueron donados por los cazadores locales, transportadas al laboratorio y los helmintos fueron colectados, fijados en AFA y conservados en alcohol etílico (70%) hasta su tinción y montaje. Ocho especies de dos taxa de helmintos fueron encontrados: Digenea-Echinostoma revolutum, Zygocotyle lunata, Echinoparyphium recurvatum, Notocotylus pacifer, Apatemon gracilis, Pseudoapatemon sp.; y Acanthocephala-Polymorphus trochus y Pseudocorynosoma constrictum. Echinostomum revolutum tuvo la mayor prevalencia, abundancia e intensidad promedio en las 36 aves de la Familia Anatidae; una prevalencia de 40% fue encontrada en cada especie de ave de esta familia. Sin embargo, en F. americana (Rallidae), P. trochus tuvo la mayor prevalencia (58.6%), una abundancia de 2.0 y N. pacifer tuvo mayor intensidad promedio (4.3). Echinostomum revolutum y Ps. Constrictum se registran por segunda ocasión en Hidalgo; Z. lunata, N. pacifer, A. gracilis y P. trochus son nuevos registros para las aves en Hidalgo y Pseudoapatemon sp. es un nuevo registro para México. Es importante monitorear los parásitos de las aves acuáticas migratorias en Lago de Tecocomulco ya que sirven como indicadores de la calidad ambiental del lago.

Spatial structure of a diving duck (Aythya, Oxyura) guild: how does habitat structure and competition influence diving duck habitat use within northern prairie wetlands?

What circumstances allow the coexistence of similar species is a common but complex question in community ecology. It is often assumed that sympatric species within the same guild must employ some mechanism of niche diversification to coexist. Diving duck (Anatidae: Aythya Boie, 1822 and Oxyura Bonaparte, 1828) competition is poorly understood and current evidence of coexistence mechanisms is contradictory. In the spring and summer of 2001 and 2002, we tested whether diving ducks foraging within prairie potholes segregate by depth to avoid competition. We sought to explain any segregation by sampling sediment particle size, compactness, and organic content; submergent vegetation; and benthic invertebrate densities in the foraging locations of each species. Our study was conducted at the wetland scale in southwestern Manitoba, Canada. We found that Redheads ( Aythya americana (Eyton, 1838)), Ruddy Ducks ( Oxyura jamaicensis (J.F. Gmelin, 1789)), Canvasbacks ( Aythya valisineria (Wilson, 1814)), and Ring-necked Ducks ( Aythya collaris (Donovan, 1809)) foraged most often at shallow depths (50–100 cm), while Lesser Scaups ( Aythya affinis (Eyton, 1838)) foraged at shallow to intermediate depths (50–150 cm). Thus, most divers did not segregate by depth. These results conflict with an earlier study that reported diving ducks segregated by depth to avoid competition. Diving ducks likely forage where prey abundance is greatest relative to the cost of diving to obtain that prey.

Winter Distribution and Survival of a High-Desert Breeding Population of Canvasbacks

The southernmost major breeding area of Canvasbacks (Aythya valisineria) is located at the Ruby Lake National Wildlife Refuge, Nevada, in the high desert of the western Great Basin. We determined winter distributions, recovery rates, and survival for Canvasbacks banded in Nevada from March to November, 1968–2000. Winter recovery distributions did not differ by sex or age, but differed between direct recoveries (same year as banding) and indirect recoveries (after year of banding), indicating variable site use between years. Of direct band returns (October–March), 92% were from the Pacific Flyway and 56% were from California alone. In California, recovery distributions shifted from southern California and the San Francisco Bay estuary in the 1970s to the Central Valley in the 1980s and 1990s. In the 1990s, there were no recoveries in San Francisco Bay, historically the major wintering area for Canvasbacks in the Pacific Flyway. Adult and juvenile survival decreased by 24% between the 1980s and 1990s. Ruby Lake Canvasbacks exhibited weaker fidelity to wintering sites than Canvasbacks wintering on the Atlantic and Gulf coasts. Moreover, no major concentrations occurred during fall migration, unlike patterns in eastern North America. Shifts in distribution and survival may correspond to effects of El Niño weather on habitat conditions in Nevada and San Francisco Bay, and to major improvements in water delivery and wetland restoration in the Central Valley. Canvasbacks that use widely distributed and variable habitats may be good indicators of the effects of changing climate and water-use practices on waterbirds throughout this arid region.Distribución Invernal y Supervivencia de una Población Reproductiva de Aythya valisineria en un Desierto de AlturaResumen. La principal área reproductiva más meridional de Aythya valisineria está localizada en el Refugio Nacional de Vida Silvestre de Lake Ruby, Nevada, en el desierto de altura de la gran depresión occidental. En este estudio, determinamos la distribución invernal, las tasas de recobramiento y la supervivencia para individuos de A. valisineria anillados en Nevada de marzo a noviembre entre 1968 y 2000. Las distribuciones de los recobramientos invernales no difirieron entre sexos ni edades, pero difirieron entre recobramientos directos (del mismo año de anillamiento) e indirectos (después del año de anillamiento), indicando que el uso de sitio era variable entre años. De los recobramientos directos de anillos (octubre–marzo), el 92% fueron del corredor de vuelo del Pacífico y el 56% fueron sólo de California. En California, la distribución de los recobramientos cambió del sur de California y el estuario de la bahía de San Francisco en los 1970s al Valle Central en los 1980s y 1990s. En los 1990s, no hubo recobramientos en la bahía de San Francisco, históricamente el área de invernada principal de A. valisineria en el corredor de vuelo del Pacífico. La supervivencia de adultos y juveniles disminuyó en un 24% entre los 1980s y 1990s. Los individuos de A. valisineria de Ruby Lake exhibieron una fidelidad más débil a sus sitios de invernada que aquellos que invernan en las costas Atlántica y del Golfo. Más aún, no se presentaron grandes concentraciones durante la migración de otoño, a diferencia de los patrones del este de Norte América. Los cambios en la distribución y la supervivencia podrían corresponder a los efectos del clima de El Niño sobre las condiciones del hábitat en Nevada y la bahía de San Francisco, y a grandes mejoras en el reparto de agua y la restauración de humedales en el Valle Central. Los patos A. valisineria, que utilizan hábitats ampliamente distribuidos y variables, podrían ser buenos indicadores de los efectos de los cambios climáticos y las prácticas de uso de agua sobre las aves acuáticas a través de esta región árida.