Foraging habitat selection by gull–billed tern (Gelochelidon nilotica) in Central Spain (Castilla–La Mancha)

Abstract

Foraging habitat selection by gull-billed tern (Gelochelidon nilotica) in Central Spain (Castilla-La Mancha). The gull-billed tern breeds in temporary lakes in Castilla-La Mancha in Central Spain but depends on surrounding land habitats to feed its chicks. It is therefore vital to know the type of environments it selects to capture prey to feed nestlings. The aim of this study was to evaluate the use of habitats for hunting by adult gull-billed tern. Of 66 lakes monitored between 1996 and 2016, we found the gull-billed tern used 12 for breeding. Each lake was used during this period for 1-14 breeding seasons. We selected circular areas around the three wetlands where the species bred in 2013 and 2014. Within these circles, we sampled a total of 60 random points and recorded 125 gull-billed tern contacts (including between 1 and 39 birds). We estimated the same environmental variables at contact and random points, including land use and the distance to the nearest wetland, the nearest colony and to several types of anthropic uses (paved roads, houses, and cities). To evaluate habitat selection we calculated the Manly selection index for soil use variables, and fitted linear mixed models to evaluate differences in the distance variables. Land uses selected for foraging by the gull-billed tern were mainly cereal crops, whereas vineyards were avoided. The birds foraged on average up to 2 km from the colonies and tended to avoid proximity of towns and paved roads, suggesting that the species is sensitive to human disturbance. Vineyards are the main land use in this region and the intensity is increasing. Our results suggest vineyards should be limited in areas around these wetlands so that gull-billed terns may forage in their preferred sites.

Plastic Debris in Nests of Two Water Bird Species Breeding on Inland Saline Lakes in a Mediterranean Biosphere Reserve

“…Moreover, a lack of information about the plastic debris availability in the biosphere reserve and its surroundings can make the identification of possible selection patterns difficult. However, given the foraging ranges of the gull-billed terns [ 38 , 49 ], the plastic items in their nests might originate from distant and heterogenous sources. Ecologically different species can act as differential “plastic importers” to inland lakes by increasing the presence of this pollutant at certain points, such as roost areas and protected breeding colonies.…”

“…Although most of the lakes are temporary, the natural regime of some is altered by wastewater input, which prolongs the hydroperiod [ 34 , 35 ]. The biosphere reserve wetlands host 26 wader species [ 36 ] and are also a wintering ground for cranes ( Grus grus ) [ 37 ] and the breeding habitat for other birds such as the gull-billed tern ( Gelochelidon nilotica ) [ 38 ], the black-winged stilt ( Himantopus himantopus ), and the greater flamingo ( Phoenicopterus roseus ) [ 39 ].…”

“…According to the most recent available information [ 42 ], the species is categorized as “Least Concern” on the European Red List of Birds, with a “Stable” status and an estimated population of 16,100–19,700 mature individuals. In our study area, agricultural intensification could be related to a decrease in suitable feeding habitats for this species [ 43 ] because it hunts insects in land areas near the wetlands to feed chicks [ 38 ]. These colonial breeders build their nests on the ground on islets with clayey bottoms and high vegetation cover that are surrounded by shallow water [ 44 , 45 ] and use sticks, algae, stones, and other debris as material ( Figure 1 D).…”

Presencia y reproducción de la pagaza piconegra (Gelochelidon nilotica), en la provincia de Albacete (Castilla-La Mancha)

“…No obstante, si consideramos que en La Mancha las aves de las colonias se trasladan entre 0,3 y 6,2 km para alimentarse (Britto et al, 2018), las citas en el entorno de Albacete ciudad (la gran mayoría en los meses de abril y mayo), podrían atribuirse al paso migratorio debido a su localización lejana (decenas de kilómetros), de las zonas de reproducción.…”

“…La aparente preferencia de las zonas agrícolas manchegas alrededor de la ciudad de Albacete para alimentarse, en relación con otras zonas de cultivo cercanas a la colonia de Pétrola, podría deberse a un sesgo en las observaciones, a falta de estudios concretos. Sobre todo considerando que en La Mancha las aves tienden a evitar la cercanía de pueblos y ciudades cuando se alimentan (Britto et al, 2018).…”