Status and trends of Gull-billed Tern Gelochelidon nilotica in Europe and Africa

Abstract

Gull-billed Tern Gelochelidon nilotica is classed as Endangered in Europe (Tucker and Heath 1994, Hagemeijer and Blair, 1997), but there have been no detailed studies of the trends in the different populations occurring in Europe and Africa. Here we study the status and trends of the species in Europe and north and north-east Africa. We estimate the total population at 10,500–12,900 breeding pairs, and recognize two biogeographical populations in this region. The western population, comprising colonies in northern Europe (Denmark, Netherlands, Germany), France, Italy, Spain, and north and north-east Africa, consists of at most 6,200 pairs, 1,800 of which are in African colonies. The eastern population, comprising colonies in the Balkan Peninsula, Greece, shores of the Black Sea and Sea of Azov, and Turkey, consists of at most 6,800 pairs. Two trends were observed: a first phase from 1900 up to the mid-1970s in which the northern European populations practically disappeared; and a second phase of stabilization, or even increase, in some of the western colonies, while the eastern population continued to decline. There is a marked concentration of the species in just a few localities in the countries of the Mediterranean basin.

Satellite Telemetry Reveals Strong Fidelity to Migration Routes and Wintering Grounds for the Gull-Billed Tern (Gelochelidon nilotica)

“…Terns deployed with a PTT lasting longer than 12 months exhibited a return to San Diego in the spring the following breeding season, and all terns that were tracked longer than 18 months returned to the same winter locations that were used the previous year, suggesting that there is a strong degree of fidelity to both breeding and winter locations within the San Diego breeding population. Breeding location fidelity has been reported to be low to moderate in Gull-billed Terns along the Atlantic coast (Erwin et al 1998;Miller et al 2013;Gochfeld et al 2019), but it is noted as varying widely between nesting locations in Europe (Møller 1982;Sánchez et al 2004). We are unaware of any other research focused upon Gull-billed Tern wintering site fidelity.…”

“…2019). In Eastern Europe, the Gull-billed Tern is listed as endangered with a suspected population decline of 30% throughout the European range while populations in Asia and Australia appear to be stable (Sánchez et al 2004). The North American breeding population is estimated to be 4,160 to 5,200 breeding pairs (Molina and Erwin 2006;Molina et al 2014).…”

Predictors of Gull-billed tern (Gelochelidon nilotica) nest survival in artificial coastal saltpans, Bohai Bay, China

“…Nest predation was rarely recorded during our study where the breeding sites of Gull-billed tern were isolated, which may have served as protection against terrestrial mammalian predators, such as dogs, foxes, and rats, as observed in other studies (e.g., Nelson, 1979;Hamer, Schreiber & Burger, 2002). Although the eggs and chicks of Gull-billed tern have been reported to be prey for other bird species such as Great horned owl (Bubo virginianus), Barn owl (Tyto alba), Short-eared owl (Asio flammeus), Yellow-legged gull (Larus cachinans) and Black-headed gull (L. ridibundus) (Sánchez & Blasco, 1986;Sánchez et al, 2004), we suspect that the effect of avian predators in our study was somewhat minimal because only a Peregrine falcon (Falco peregrinus) was observed on a single occasion during our surveys.…”

“…The species occupies a variety of habitats that include inland freshwater or saltwater lakes, rivers, and marshes ( Snow & Perrins, 1998 ; Zhao, 2001 ), although it remains poorly studied across much of its range and may have experienced population declines ( Erwin et al, 1999 ; Molina & Erwin, 2006 ). Consequently it is currently listed as conservation concern in Europe, Africa and North America ( Kushlan et al, 2002 ; Sánchez et al, 2004 ; Molina & Erwin, 2006 ; Staneva & Burfield, 2017 ). Gull-billed tern is an opportunistic dietary generalist that uses both terrestrial and aquatic resources in wetland mosaics that mainly includes lizards, flying insects, estuarine fish, and both marine and estuarine crab species ( Bogliani et al, 1990 ; Stienen, Brenninkmeijer & Klaassen, 2008 ; Albano et al, 2011 ; Goodenough, 2013 ).…”

Effects of Diet on Growth-Related Patterns of Energy and Macronutrient Assimilation Efficiency in a Semi-Precocial Bird, the Gull-Billed TernGelochelidon nilotica

“…Cramp 1985, Dunn & Agro 1995. The Gull-billed Tern Gelochelidon nilotica is a particularly opportunistic species which takes a wide spectrum of different sizes and types of prey, including insects, in its breeding habitats (Sánchez et al 1991, Sánchez et al 2004a, Dies et al 2005.…”