Hallazgo de dos nuevas colonias de Gaviota Cangrejera (Larus atlanticus) en el estuario de Bahía Blanca, provincia de Buenos Aires, Argentina

Aylen María de Prinzio; Rocío Mariano-Jelicich; Martín Sotelo; Leandro M. Marbán; Sofía Copello

doi:10.56178/eh.v41i1.1539

Short Communications Published 02 July 2026 https://doi.org/10.56178/eh.v41i1.1539

Discovery of Two New Colonies of Olrog’s Gull (Larus atlanticus) in the Bahía Blanca Estuary, Buenos Aires Province, Argentina

aerial census colony Bahía Blanca estuary Olrog’s Gull Larus atlanticus population size

Aylen María de Prinzio Instituto de Investigaciones Marinas y Costeras, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, (IIMyC, FCEyN, UNMdP, CONICET), Juan B. Justo 2550, CP 7600, Mar del Plata, Buenos Aires, Argentina

Rocío Mariano-Jelicich Instituto de Investigaciones Marinas y Costeras, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, (IIMyC, FCEyN, UNMdP, CONICET), Juan B. Justo 2550, CP 7600, Mar del Plata, Buenos Aires, Argentina

Martín Sotelo Dirección de Áreas Protegidas, Ministerio de Ambiente, La Plata, Buenos Aires, Argentina, Calle 7 Nro. 1076 entre 54 y 55, Piso 5to. CP 1900, La Plata, Argentina

Leandro M. Marbán Dirección de Áreas Protegidas, Ministerio de Ambiente, La Plata, Buenos Aires, Argentina, Calle 7 Nro. 1076 entre 54 y 55, Piso 5to. CP 1900, La Plata, Argentina

Sofía Copello Instituto de Investigaciones Marinas y Costeras, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, (IIMyC, FCEyN, UNMdP, CONICET), Juan B. Justo 2550, CP 7600, Mar del Plata, Buenos Aires, Argentina

Abstract

Olrog’s Gull (Larus atlanticus) is a larid species endemic to the South Atlantic coast and is considered Vulnerable in Argentina. Its breeding range is restricted to estuarine islands characterized by low elevation above sea level, sparse vegetation, and proximity to crab beds. Nearly the entire breeding population nests in protected areas with varying categories of conservation in Buenos Aires Province. During aerial censuses, conducted on 17 October 2025 to update population estimates, we recorded two new breeding sites of Olrog’s Gull in the Bahía Blanca estuary: one at the northeastern tip of Trinidad Island (39°05’S, 61°55’W) and the other at the northeastern tip of Ariadna Island (39°14’S, 61°58’W). Both sites are located within the Bahía Blanca, Bahía Falsa, Bahía Verde Nature Reserve. Apparently Occupied Nests, which provide an estimate of the number of breeding pairs, were counted yielding a total of 26 ± 2 (n = 7 photographs) and 22 ± 1 (n = 4 photographs), respectively. The colonies are located close to the tidal line and may therefore be vulnerable to substantial habitat alterations caused by severe storms or human activities such as dredging and recreational use. These sectors are currently outside the reserve’s strictly protected zone. As a result of this finding, they have been incorporated into the ongoing revision of the reserve’s zoning scheme to strengthen effective protection measures during this critical period for the species.

PDF (Spanish) PDF

References

Azpiroz AB, Caballero-Sadi D (2017) Gaviota cangrejera (Larus atlanticus). En: Azpiroz AB, Jiménez S, Alfaro M (eds) Libro Rojo de las Aves del Uruguay. Biología y conservación de las aves en peligro de extinción a nivel nacional: categorías ‘extinto a nivel regional’, ‘en peligro crítico’ y ‘en peligro’. DINAMA and DINARA, Uruguay. Pp. 155-164
BirdLife International (2025) Species factsheet: Olrog’s Gull Larus atlanticus. BirdLife DataZone. [URL: https://datazone.birdlife.org/species/factsheet/olrogs-gull-larus-atlanticus] (24/10/2025)
Borboroglu PG, Yorio P (2007) Breeding habitat requirements and selection by Olrog’s Gull (Larus atlanticus), a threatened species. The Auk 124(4):1201-1212. https://doi.org/10.1093/auk/124.4.1201
Delhey JKV, Carrete M, Martinez MM (2001a) Diet and feeding behaviour of Olrog’s Gull Larus atlanticus in Bahía Blanca, Argentina. Ardea 89(2):319-329
Delhey JKV, Petracci PF, Grassini CM (2001b) Hallazgo de una nueva colonia de la Gaviota de Olrog (Larus atlanticus) en la ría de Bahía Blanca, Argentina. Hornero 16(1):39-42. https://doi.org/10.56178/eh.v16i1.914
Devillers P (1977) Observations at a breeding colony of Larus (belcheri) atlanticus. Le Gerfaut 67:22-43
Dias MP, Martin R, Pearmain EJ, Burfield IJ, Small C, Phillips RA, Yates O, Lascelles B, Borboroglu PG, Croxall JP (2019) Threats to seabirds: a global assessment. Biological Conservation 237:525-537. https://doi.org/10.1016/j.biocon.2019.06.033
Fiori MS, Pratolongo PD (eds) (2021) The Bahía Blanca Estuary. Ecology and Biodiversity. Springer Cham, Switzerland. https://doi.org/10.1007/978-3-030-66486-2
Gregory RD, Gibbons DW, Donald PF (2004) Bird census and survey techniques. En: Sutherland WJ, Newton I, Green R (eds) Bird Ecology and Conservation: A Handbook of Techniques. Oxford University Press, Oxford, UK. Pp. 17-56. https://doi.org/10.1093/acprof:oso/9780198520863.003.0002
Herrera G, Punta G, Yorio P (2005) Diet specialization of Olrog’s Gull Larus atlanticus during the breeding season at Golfo San Jorge, Argentina. Bird Conservation International 15(1):89-97. https://doi.org/10.1017/S0959270905000079
La Sala LF, Perez A, Martorelli S, Smits J (2011) Breeding Biology of Olrog’s Gull in Bahía Blanca Estuary, Argentina. The Wilson Journal of Ornithology 123(2):243-250. https://doi.org/10.1676/10-156.1
Marbán LM, Zalba SM (2019) When the seeds go floating in: A salt marsh invasion. Estuarine, Coastal and Shelf Science 231:106442. https://doi.org/10.1016/j.ecss.2019.106442
Petracci PF, Sotelo, MR, Díaz LI (2008) Nuevo registro de nidificación de la Gaviota Cangrejera (Larus atlanticus) en la Reserva Natural Bahía Blanca, Bahía Falsa y Bahía Verde, Buenos Aires, Argentina. Hornero 23(1):37-40. https://doi.org/10.56178/eh.v23i1.748
Servicio de Hidrografía Naval (2025) Tablas de marea: Canal Principal a Bahía Blanca (Par 12 a 16), 17 de octubre de 2025. Ministerio de Defensa de la República Argentina. [URL: https://www.hidro.gov.ar/oceanografia/tmareas/form_tmareas.asp] (11/05/2026)
Suárez N, Retana MV, Yorio P (2011) Temporal changes in diet and prey selection in the threatened Olrog’s Gull Larus atlanticus breeding in southern Buenos Aires, Argentina. Ardeola 58(1):35-47. https://doi.org/10.13157/arla.58.1.2011.35
Yorio P, Rábano DE, Friedrich P (2001) Habitat and nest site characteristics of Olrog’s Gull Larus atlanticus breeding at Bahía San Blas, Argentina. Bird Conservation International 11(1):27-34. https://doi.org/10.1017/S0959270901001046
Yorio P, Bertellotti M, García Borboroglu P (2005) Estado poblacional y de conservación de gaviotas que se reproducen en el litoral marítimo argentino. Hornero 20(1):53-74. https://doi.org/10.56178/eh.v20i1.819
Yorio P, Petracci P, Borboroglu PG (2013) Current status of the threatened Olrog’s Gull Larus atlanticus: global population, breeding distribution and threats. Bird Conservation International 23(4):477-486. https://doi.org/10.1017/S0959270913000026

How to cite

Aylen María de Prinzio, Rocío Mariano-Jelicich, Martín Sotelo, Leandro M. Marbán, Sofía Copello (2026). Discovery of Two New Colonies of Olrog’s Gull (Larus atlanticus) in the Bahía Blanca Estuary, Buenos Aires Province, Argentina. El Hornero, Vol. 41 No. 1 (2026), 167-171. https://doi.org/10.56178/eh.v41i1.1539

Downloads

271Full-text views

2Formats

License: CC BY-NC 4.0

[1] Azpiroz AB, Caballero-Sadi D (2017) Gaviota cangrejera (Larus atlanticus). En: Azpiroz AB, Jiménez S, Alfaro M (eds) Libro Rojo de las Aves del Uruguay. Biología y conservación de las aves en peligro de extinción a nivel nacional: categorías ‘extinto a nivel regional’, ‘en peligro crítico’ y ‘en peligro’. DINAMA and DINARA, Uruguay. Pp. 155-164

[2] BirdLife International (2025) Species factsheet: Olrog’s Gull Larus atlanticus. BirdLife DataZone. [URL: https://datazone.birdlife.org/species/factsheet/olrogs-gull-larus-atlanticus] (24/10/2025)

[3] Borboroglu PG, Yorio P (2007) Breeding habitat requirements and selection by Olrog’s Gull (Larus atlanticus), a threatened species. The Auk 124(4):1201-1212. https://doi.org/10.1093/auk/124.4.1201

[4] Delhey JKV, Carrete M, Martinez MM (2001a) Diet and feeding behaviour of Olrog’s Gull Larus atlanticus in Bahía Blanca, Argentina. Ardea 89(2):319-329

[5] Delhey JKV, Petracci PF, Grassini CM (2001b) Hallazgo de una nueva colonia de la Gaviota de Olrog (Larus atlanticus) en la ría de Bahía Blanca, Argentina. Hornero 16(1):39-42. https://doi.org/10.56178/eh.v16i1.914

[6] Devillers P (1977) Observations at a breeding colony of Larus (belcheri) atlanticus. Le Gerfaut 67:22-43

[7] Dias MP, Martin R, Pearmain EJ, Burfield IJ, Small C, Phillips RA, Yates O, Lascelles B, Borboroglu PG, Croxall JP (2019) Threats to seabirds: a global assessment. Biological Conservation 237:525-537. https://doi.org/10.1016/j.biocon.2019.06.033

[8] Fiori MS, Pratolongo PD (eds) (2021) The Bahía Blanca Estuary. Ecology and Biodiversity. Springer Cham, Switzerland. https://doi.org/10.1007/978-3-030-66486-2

[9] Gregory RD, Gibbons DW, Donald PF (2004) Bird census and survey techniques. En: Sutherland WJ, Newton I, Green R (eds) Bird Ecology and Conservation: A Handbook of Techniques. Oxford University Press, Oxford, UK. Pp. 17-56. https://doi.org/10.1093/acprof:oso/9780198520863.003.0002

[10] Herrera G, Punta G, Yorio P (2005) Diet specialization of Olrog’s Gull Larus atlanticus during the breeding season at Golfo San Jorge, Argentina. Bird Conservation International 15(1):89-97. https://doi.org/10.1017/S0959270905000079

[11] La Sala LF, Perez A, Martorelli S, Smits J (2011) Breeding Biology of Olrog’s Gull in Bahía Blanca Estuary, Argentina. The Wilson Journal of Ornithology 123(2):243-250. https://doi.org/10.1676/10-156.1

[12] Marbán LM, Zalba SM (2019) When the seeds go floating in: A salt marsh invasion. Estuarine, Coastal and Shelf Science 231:106442. https://doi.org/10.1016/j.ecss.2019.106442

[13] Petracci PF, Sotelo, MR, Díaz LI (2008) Nuevo registro de nidificación de la Gaviota Cangrejera (Larus atlanticus) en la Reserva Natural Bahía Blanca, Bahía Falsa y Bahía Verde, Buenos Aires, Argentina. Hornero 23(1):37-40. https://doi.org/10.56178/eh.v23i1.748

[14] Servicio de Hidrografía Naval (2025) Tablas de marea: Canal Principal a Bahía Blanca (Par 12 a 16), 17 de octubre de 2025. Ministerio de Defensa de la República Argentina. [URL: https://www.hidro.gov.ar/oceanografia/tmareas/form_tmareas.asp] (11/05/2026)

[15] Suárez N, Retana MV, Yorio P (2011) Temporal changes in diet and prey selection in the threatened Olrog’s Gull Larus atlanticus breeding in southern Buenos Aires, Argentina. Ardeola 58(1):35-47. https://doi.org/10.13157/arla.58.1.2011.35

[16] Yorio P, Rábano DE, Friedrich P (2001) Habitat and nest site characteristics of Olrog’s Gull Larus atlanticus breeding at Bahía San Blas, Argentina. Bird Conservation International 11(1):27-34. https://doi.org/10.1017/S0959270901001046

[17] Yorio P, Bertellotti M, García Borboroglu P (2005) Estado poblacional y de conservación de gaviotas que se reproducen en el litoral marítimo argentino. Hornero 20(1):53-74. https://doi.org/10.56178/eh.v20i1.819

[18] Yorio P, Petracci P, Borboroglu PG (2013) Current status of the threatened Olrog’s Gull Larus atlanticus: global population, breeding distribution and threats. Bird Conservation International 23(4):477-486. https://doi.org/10.1017/S0959270913000026