Roosts are important sites for shorebirds in non‐breeding areas at night and during high tides. How the spatial configuration of food and risk of predation and disturbance influence roost site use in tropical locations remains poorly known. We analysed the locations of nocturnal roosts of Whimbrel Numenius phaeopus in mangroves of Sanquianga National Park, Colombia, with respect to variation in spatial variables related to food resources and risk of predation and disturbance. We contrasted characteristics of all 13 known nocturnal roost locations with those of all other mangrove islands (n = 209) within the limits of the park. We estimated the distance from roosts and other mangrove islands to foraging sites, and sources of predators and human disturbance. Larger areas of feeding habitat surrounded nocturnal roosts than other mangrove islands, and the average distance to individual feeding patches was shorter. Roosts were also more isolated than other islands, but proximity to sources of human disturbance did not differ. We conclude that Whimbrel roost site use in Sanquianga was best explained by a combination of access to feeding territories and isolation from potential sources of mainland predators, but not by avoidance of human disturbance. Beyond identifying factors influencing roost site selection, the large aggregations of individuals in single locations may suggest that presence of conspecifics itself also plays a role in the formation of Whimbrel roosts. We highlight the interaction of food and risk landscapes with intraspecific attraction on the roost site selection by Whimbrels and the importance of mangroves as roosting sites in tropical regions.

11 % de las aves playeras del corredor migratorio del Pacífico americano están disminuyendo y otro 46 % no cuenta con información para estimar su estado poblacional. Para entender la magnitud y las causas de estos cambios, se requiere información de sitios de concentración como la bocana de Iscuandé (IS) y el Parque Nacional Natural Sanquianga (PNNS). Para caracterizar la composición de las comunidades de aves playeras en estos sitios, se analizaron diez años de conteo. A partir de la abundancia proporcional, la prevalencia y la densidad media de cada localidad, se evaluó si existían diferencias entre sitios con diferente influencia marina y del río Patía. IS aportó el 63 % de la abundancia promedio, siendo el 80 % aves playeras pequeñas. En PNNS, la abundancia se repartió 40-60 % entre aves grandes y pequeñas, y la contribución de cada bocana fue proporcional al área muestreada. Estos resultados muestran que los dos sitios tienen comunidades diferentes de aves playeras. Esta heterogeneidad espacial tiene importantes implicaciones ecológicas y de conservación. El recambio en la composición taxonómica y por grupos de tamaño de aves playeras sugiere diferencias en el hábitat intermareal y en los organismos que lo habitan, lo que ofrece alternativas para la conservación de diferentes especies.

Conservation planning for marine-coastal environments requires updated and detailed maps; the aim of this work is to generate detailed maps for two mudflats in the Iscuandé River Delta (Bocana de Iscuandé) in the Colombian Pacific Coast (Department of Nariño). These are important areas for fauna, especially migratory shorebirds. To address this problem, this study investigated the use of unmanned aerial vehicles (UAVs) as an alternative for collecting detailed mapping information in areas of difficult access using photogrammetric methodsand a geographic information system (GIS). UAV images were used to generate maps with a high level of detail at a scale of 1:10,000 that include detailed information about environments such as mudflats and mangroves which had not been mapped before. UAVs are a practical tool for mapping places where weather and access conditions hinder the use of satellite images or conventional aerial photography. They are also useful for mapping areas with high temporal and spatial variability, such as mudflats, where other platforms may not reveal their short-term dynamics. Our results show that this technique has a high potential for mapping such environments, and reveal that the Iscuandé mudflats aremaintained by a relative equilibrium between the ebb and flow of waves and tides, and are also influenced by the local climate. This type of application provides critical data for conservation and management strategies of areas with great ecological importance.

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