Current status of the threatened Olrog’s GullLarus atlanticus: global population, breeding distribution and threats

Abstract

SummaryOlrog’s Gull Larus atlanticus breeds only in Argentina and is currently categorized as “Vulnerable”. Knowledge of the location of colonies and an updated understanding of human activities that may impact their breeding populations are crucial to the development of adequate conservation and management actions. In this paper we update the breeding distribution and abundance of Olrog’s Gull, using information from three aerial surveys (2004, 2007 and 2009) in its main breeding area, Buenos Aires Province, complemented by additional nest counts in southern Chubut Province, covering its entire breeding range. We also provide an updated and more detailed account of threats faced by Olrog’s Gulls at their nesting grounds, and summarise progress made towards their protection. The number of breeding sites was 7–12 per year, with locations differing among years. Five previously unrecorded breeding locations were identified. Colony size ranged from 5 to 3,540 breeding pairs, with the total breeding population 4,860–7,790 pairs, 98% of which nest in southern Buenos Aires Province. The main threats faced by breeding Olrog’s Gulls include coastal development, pollution, sport fishing and unregulated tourism and recreational activities. Recent strengthening of the protected area system in Argentina has resulted in all known breeding sites, with the exception of Isla Brightman, falling within protected areas. We need comprehensive, simultaneous surveys to track global population trends. Despite enhanced protection of Olrog’s Gull breeding populations, efforts are still needed to ensure that guidelines for their protection are included in management plans and that these are implemented effectively.

Foraging areas of Orlog’s gulls in an estuarine ecosystem of Argentina: are they underprotected?

“…In this area there are three protected areas: the Reserva Natural de Usos Múltiples Bahía Blanca, Bahía Falsa, Bahía Verde (2600 km 2 ), Reserva Natural Municipal Costera Bahía Blanca (3.1 km 2 ), and Reserva Natural Islote de la Gaviota Cangrejera/Isla del Puerto (16.1 km 2 ). Every year, the latter concentrates the largest known breeding colony of Olrog's Gulls (38° 49' S, 62° 16' W), which comprises ~ 3,500 pairs distributed in subcolonies adjacent to the intertidal area (Yorio et al 2013). In the study area, Olrog's Gulls start laying their eggs in early September, eggs start hatching between late September and early October, and chicks are fully edged by late December (La Sala et al 2011a).…”

“…Seabird foraging ranges can be used to identify candidate locations for protection (Thaxter et al 2012), and protecting these areas could bene t whole ecosystems (Hooker and Gerber 2004). The Olrog's Gull (Larus atlanticus) is a near threatened species (BirdLife International 2018) endemic to the Atlantic coast of Argentina, Uruguay and southern Brazil (Yorio et al 2013). Few Olrog's Gull breeding sites have been identi ed, and all of them are located in Argentina (Yorio et al 2013).…”

“…The Olrog's Gull (Larus atlanticus) is a near threatened species (BirdLife International 2018) endemic to the Atlantic coast of Argentina, Uruguay and southern Brazil (Yorio et al 2013). Few Olrog's Gull breeding sites have been identi ed, and all of them are located in Argentina (Yorio et al 2013). Most of the breeding population concentrates in the Bahía Blanca Estuary (BBE), Buenos Aires province (Petracci and Sotelo 2013), with the largest colony known to this date located in Isla del Puerto (Delhey et al 2001a).…”

Foraging areas of Orlog's gull in an estuarine ecosystem of Argentina: are they underprotected?

“…The Olrog's Gull (Larus atlanticus) is a near threatened species (BirdLife International 2018) endemic to the Atlantic coast of Argentina, Uruguay and southern Brazil (Yorio et al 2013). Few Olrog's Gull breeding sites have been identi ed, and all of them are located in Argentina (Yorio et al 2013). Most of the breeding population concentrates in the Bahía Blanca Estuary (BBE), Buenos Aires province (Petracci and Sotelo 2013), with the largest colony known to this date located in Isla del Puerto (Delhey et al 2001a).…”

Use of winter habitat at an early age: spatial ecology and association with human activities of juvenile Olrog’s GullLarus atlanticus

“…Its breeding range is restricted to only two nesting areas along 2,500 km of the central Argentinian coast. The number of breeding sites varied between seven and 12 per year, with locations differing among years and the global breeding population was estimated at 8,000 pairs (Yorio et al 2013). The breeding season starts at the end of October and hatching usually occurs in early November-December.…”