The diet of Olrog's Gull (Larus atlanticus) reveals an association with fisheries during the non-breeding season
María Paula Berón A B , Juan Pablo Seco Pon A , Germán O. García A , Carla A. Paterlini A , Rocío Mariano-Jelicich A and Marco Favero A
+ Author Affiliations
- Author Affiliations
A Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICET – Universidad Nacional de Mar del Plata, Funes 3250 (B7602AYJ), Mar del Plata, Argentina.
B Corresponding author. Email: mpberon@mdp.edu.ar, mpb03@yahoo.com.ar
Emu 113(1) 69-76 https://doi.org/10.1071/MU11100
Submitted: 12 December 2011 Accepted: 1 November 2012 Published: 22 February 2013
Abstract
In this study, we used stable-isotope analysis to determine the importance of different food resources in the diet of an endemic gull species of the Atlantic coast of southern South America during the non-breeding period. We compared the isotopes 15N and 13C in the blood of Olrog’s Gulls (Larus atlanticus) of different ages with those in potential prey of the Gulls. We also determined the abundance of Olrog’s Gull in their wintering areas and attending coastal fisheries operations in a small region of Argentina. An isotope-mixing model showed differences in the isotopic signatures of adult, subadult and juvenile Gulls. Although the isotope-mixing model showed crabs as the main prey, it also showed that demersal and pelagic fish may be important in the diet. We speculate that the demersal and pelagic fish in the diet, shown by their isotopic signatures in the Gulls, may be taken in association with coastal fisheries, particularly bottom otter-paired trawling. At-sea observations showed that Olrog’s Gulls were one of the most-common birds attending fishing operations of the Argentine coastal fishing fleet, taking advantage of fish mostly made available through hauling operations.
Additional keywords: crabs, dietary habits, foraging, stable-isotopes.
References
Abraham, E. R., Pierre, J. P., Middleton, D. A. J., Cleal, J., Walker, N. A., and Waugh, S. M. (2009). Effectiveness of fish waste management strategies in reducing seabird attendance at a trawl vessel. Fisheries Research 95, 210–219.| Effectiveness of fish waste management strategies in reducing seabird attendance at a trawl vessel.Crossref | GoogleScholarGoogle Scholar |
Anderson, O. R. J., Small, C. J., Croxall, J. P., Dunn, E. K., Sullivan, B. J., Yates, O., and Black, A. (2011). Global seabird bycatch in longline fisheries. Endangered Species Research 14, 91–106.
| Global seabird bycatch in longline fisheries.Crossref | GoogleScholarGoogle Scholar |
Barrett, R. T., Camphuysen, K. C. J., Anker-Nilssen, T., Chardine, J. W., Furness, R. W., Garthe, S., Huppop, O., Leopold, M. F., Montevecchi, W. A., and Veit, R. R. (2007). Diet studies of seabirds: a review and recommendations. ICES Journal of Marine Science 64, 1675–1691.
| Diet studies of seabirds: a review and recommendations.Crossref | GoogleScholarGoogle Scholar |
Bearhop, S., Waldron, S., Votier, S. C., and Furness, R. W. (2002). Factors that influence assimilation rates and fractionation of nitrogen and carbon stable isotopes in avian blood and feathers. Physiological and Biochemical Zoology 75, 451–458.
| Factors that influence assimilation rates and fractionation of nitrogen and carbon stable isotopes in avian blood and feathers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhsFygt7w%3D&md5=a2620194213579f7e6005af683ed8f30CAS |
Bearhop, S., Phillips, R. A., McGill, R., Cherel, Y., Dawson, D. A., and Croxall, J. P. (2006). Stable isotopes indicate sex-specific and long-term individual foraging specialisation in diving seabirds. Marine Ecology Progress Series 311, 157–164.
| Stable isotopes indicate sex-specific and long-term individual foraging specialisation in diving seabirds.Crossref | GoogleScholarGoogle Scholar |
Berón, M. P. (2003). Dieta de juveniles de Gaviota Cangrejera (Larus atlanticus) en estuarios de la Provincia de Buenos Aires. El Hornero 18, 113–117.
Berón, M. P., and Favero, M. (2009). Mortality and injuries of Olrog’s Gull Larus atlanticus individuals associated with sport fishing activities in Mar Chiquita Coastal Lagoon, Buenos Aires Province. El Hornero 24, 99–102.
Berón, M. P., and Favero, M. (2010). Monitoreo de la dieta de la Gaviota de Olrog (Larus atlanticus) en la Laguna Mar Chiquita (Buenos Aires, Argentina) durante el período no reproductivo. Ornitologia Neotropical 21, 215–224.
Berón, M. P., Favero, M., and Gómez Laich, A. (2007). Use of natural and anthropogenic resources by the Olrog’s Gull Larus atlanticus: implications for the conservation of the species in non-breeding habitats. Bird Conservation International 17, 351–357.
| Use of natural and anthropogenic resources by the Olrog’s Gull Larus atlanticus: implications for the conservation of the species in non-breeding habitats.Crossref | GoogleScholarGoogle Scholar |
Berón, M. P., García, G. O., Luppi, T. A., and Favero, M. (2011). Age-related prey selectivity and foraging efficiency in Olrog’s Gulls Larus atlanticus feeding on crabs in their non-breeding grounds. Emu 111, 172–178.
| Age-related prey selectivity and foraging efficiency in Olrog’s Gulls Larus atlanticus feeding on crabs in their non-breeding grounds.Crossref | GoogleScholarGoogle Scholar |
Bibby, C. J., Burgess, N. D., and Hill, D. A. (1997). ‘Bird Census Techniques.’ (Academic Press: London, UK.)
BirdLife International (2012). Olrog’s Gull Larus atlanticus. (BirdLife International: Cambridge, UK.) Available at http://www.birdlife.org/datazone/speciesfactsheet.php?id=3210 [Verified 22 May 2012].
Blom, P. H. (1987). Capturing and handling raptors. In ‘Raptor Management Techniques Manual’. (Eds B. A. G. Pendleton, B. A. Millsap, K. W. Cline and D. M. Bird.) pp. 99–123. (National Wildlife Federation: Washington, DC.)
Botto, F., and Iribarne, O. (2000). Contrasting effects of two burrowing crabs (Chasmagnathus granulata and Uca uruguayensis) on sediment composition and transport in estuarine environments. Estuarine, Coastal and Shelf Science 51, 141–151.
| Contrasting effects of two burrowing crabs (Chasmagnathus granulata and Uca uruguayensis) on sediment composition and transport in estuarine environments.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXmsFemtrc%3D&md5=fbfefcec394e48fd4ed72568c5ad11a1CAS |
Botto, F., Valiela, I., Iribarne, O., Martinetto, P., and Alberti, J. (2005). Impact of burrowing crabs on C and N sources, control, and transformations in sediments and food webs of SW Atlantic estuaries. Marine Ecology Progress Series 293, 155–164.
| Impact of burrowing crabs on C and N sources, control, and transformations in sediments and food webs of SW Atlantic estuaries.Crossref | GoogleScholarGoogle Scholar |
Botto, F., Gaitán, E., Mianzan, H., Acha, M., Giberto, D., Schiariti, A., and Iribarne, O. (2011). Origin of resources and trophic pathways in a large SW Atlantic estuary: an evaluation using stable isotopes. Estuarine, Coastal and Shelf Science 92, 70–77.
| Origin of resources and trophic pathways in a large SW Atlantic estuary: an evaluation using stable isotopes.Crossref | GoogleScholarGoogle Scholar |
Brooke, M. (2004). ‘Albatrosses and Petrels Across the World.’ (Oxford University Press: Oxford, UK.)
Bugoni, L., McGill, R. A. R., and Furness, R. W. (2008). Effects of preservation methods on stable isotope signatures in bird tissues. Rapid Communications in Mass Spectrometry 22, 2457–2462.
| Effects of preservation methods on stable isotope signatures in bird tissues.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXhtVehtbjP&md5=73ab0ed11a07a701bc1d31c66c6d462aCAS |
Burger, J., and Gochfeld, M. (1996). Family Laridae (Gulls). In ’Handbook of the Birds of the World. Vol. 3: Hoatzin to Auks’. (Eds J. del Hoyo, A. Elliot and J. Sargatal.) pp. 572–623. (Lynx Edicions: Barcelona.)
Caut, S., Angulo, E., and Courchamp, F. (2008). Dietary shift of an invasive predator: rats, seabirds and sea turtles. Journal of Applied Ecology 45, 428–437.
| Dietary shift of an invasive predator: rats, seabirds and sea turtles.Crossref | GoogleScholarGoogle Scholar |
Cherel, Y., Hobson, K. A., and Hassani, S. (2005). Isotopic discrimination between food and blood and feathers of captive penguins: implications for dietary studies in the wild. Physiological and Biochemical Zoology 78, 106–115.
| Isotopic discrimination between food and blood and feathers of captive penguins: implications for dietary studies in the wild.Crossref | GoogleScholarGoogle Scholar |
Cherel, Y., Phillips, R. A., Hobson, K. A., and McGill, R. (2006). Stable isotope evidence of diverse species-specific and individual wintering strategies in seabirds. Biology Letters 2, 301–303.
| Stable isotope evidence of diverse species-specific and individual wintering strategies in seabirds.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD28jhtVOktQ%3D%3D&md5=a0af0d68dac2d30cdb74b473736af9e5CAS |
Cherel, Y., Hobson, K. A., Guinet, C., and Vanpe, C. (2007). Stable isotopes document seasonal changes in trophic niches and winter foraging individual specialization in diving predators from the Southern Ocean. Journal of Animal Ecology 76, 826–836.
| Stable isotopes document seasonal changes in trophic niches and winter foraging individual specialization in diving predators from the Southern Ocean.Crossref | GoogleScholarGoogle Scholar |
Ciancio, J. E., Pascual, M. A., and Beauchamp, D. A. (2007). Energy density of Patagonian aquatic organisms and empirical predictions based on water content. Transactions of the American Fisheries Society 136, 1415–1422.
| Energy density of Patagonian aquatic organisms and empirical predictions based on water content.Crossref | GoogleScholarGoogle Scholar |
Consejo Federal Pesquero (2006). Resolución N_ 15/2006 Medidas de manejo del ‘variado costero’. Available at http://www.cfp.gob.ar/index.php?inc¼resoluciones&anio¼2006&lang¼es [Verified 10 May 12].
Copello, S., and Favero, M. (2001). Foraging ecology of Olrog’s Gull Larus atlanticus in Mar Chiquita Lagoon (Buenos Aires, Argentina): are there age-related differences? Bird Conservation International 11, 175–188.
| Foraging ecology of Olrog’s Gull Larus atlanticus in Mar Chiquita Lagoon (Buenos Aires, Argentina): are there age-related differences?Crossref | GoogleScholarGoogle Scholar |
Corder, G. W., and Foreman, D. I. (2009). ‘Nonparametric Statistics for Non-Statisticians: A Step-by-Step Approach.’ (Wiley: New York.)
Cousseau, M. B., and Perrota, R. G. (2004). ‘Peces Marinos de Argentina: Biología, Distribución, Pesca.’ 3rd edn (Tercera edición). (Publicaciones especiales INIDEP: Mar del Plata, Argentina.)
Crawford, R. J. M. (2007). Food, fishing and seabirds in the Benguela upwelling system. Journal of Ornithology 148, 253–260.
| Food, fishing and seabirds in the Benguela upwelling system.Crossref | GoogleScholarGoogle Scholar |
Duffy, D. C. (1983). The foraging ecology of Peruvian seabirds. Auk 100, 800–810.
Dulvy, N. K., Sadovy, Y., and Reynolds, J. D. (2003). Extinction vulnerability in marine populations. Fish and Fisheries 4, 25–64.
| Extinction vulnerability in marine populations.Crossref | GoogleScholarGoogle Scholar |
Errazti, E., and Bertolotti, M. I. (1998). Flota costera: descripción de las principales características en la región bonaerense. Frente Marítimo 17, 63–70.
Forero, M. G., Bortolotti, G. R., Hobson, K. A., Donazar, J. A., Bertelloti, M., and Blanco, G. (2004). High trophic overlap within the seabird community of Argentinean Patagonia: a multiscale approach. Journal of Animal Ecology 73, 789–801.
| High trophic overlap within the seabird community of Argentinean Patagonia: a multiscale approach.Crossref | GoogleScholarGoogle Scholar |
Gannes, L. Z., del Rio, C. M., and Koch, P. (1998). Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology. Comparative Biochemistry and Physiology Part A 119, 725–737.
| Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK1czksFKmtw%3D%3D&md5=10f1b2449d6a66fe70e5883802a23b16CAS |
García-Borboroglu, P., and Yorio, P. (2007). Comparative habitat use by syntopic Kelp Gulls (Larus dominicanus) and Olrog’s Gulls (Larus atlanticus) in coastal Patagonia. Emu 107, 321–326.
| Comparative habitat use by syntopic Kelp Gulls (Larus dominicanus) and Olrog’s Gulls (Larus atlanticus) in coastal Patagonia.Crossref | GoogleScholarGoogle Scholar |
Garthe, S., and Huppop, O. (1994). Distribution of ship-following seabirds and their utilization of discards in the North Sea in summer. Marine Ecology Progress Series 106, 1–9.
| Distribution of ship-following seabirds and their utilization of discards in the North Sea in summer.Crossref | GoogleScholarGoogle Scholar |
Harrison, P. (1983). ‘Seabirds: An Identification Guide.’ (Houghton Mifflin: Boston, MA.)
Hobson, K. A., and Clark, R. G. (1992). Assessing avian diets using stable isotopes II: Factors influencing diet-tissue fractionation. Condor 94, 189–197.
| Assessing avian diets using stable isotopes II: Factors influencing diet-tissue fractionation.Crossref | GoogleScholarGoogle Scholar |
Hobson, K. A., and Welch, H. E. (1992). Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis. Marine Ecology Progress Series 84, 9–18.
| Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3sXitFGitQ%3D%3D&md5=659621177f2e8e8e9384f8e414a4e69eCAS |
Hobson, K. A., Gibbs, H. L., and Gloutney, M. L. (1997). Preservation of blood and tissue samples for stable-carbon and stable-nitrogen isotope analyses. Canadian Journal of Zoology 75, 1720–1723.
| Preservation of blood and tissue samples for stable-carbon and stable-nitrogen isotope analyses.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2sXntlOisbk%3D&md5=87296e7a14d2adc08133d2e7d04a6556CAS |
Hodum, P. J., and Hobson, K. A. (2000). Trophic relationships among Antarctic fulmarine petrels: insights into dietary overlap and chick provisioning strategies inferred from stable-isotope (δ15N and δ13C) analyses. Marine Ecology Progress Series 198, 273–281.
| Trophic relationships among Antarctic fulmarine petrels: insights into dietary overlap and chick provisioning strategies inferred from stable-isotope (δ15N and δ13C) analyses.Crossref | GoogleScholarGoogle Scholar |
Hudson, A. V., and Furness, R. W. (1989). The behaviour of seabirds foraging at fishing boats around Shetland. Ibis 131, 225–237.
| The behaviour of seabirds foraging at fishing boats around Shetland.Crossref | GoogleScholarGoogle Scholar |
Inger, R., and Bearhop, S. (2008). Applications of stable isotope analyses to avian ecology. Ibis 150, 447–461.
| Applications of stable isotope analyses to avian ecology.Crossref | GoogleScholarGoogle Scholar |
Jackson, A., Inger, R., Bearhop, S., and Parnell, A. (2009). Erroneous behaviour of MixSIR, a recently published Bayesian isotope mixing model: a discussion of Moore & Semmens (2008). Ecology Letters 12, E1–E5.
| Erroneous behaviour of MixSIR, a recently published Bayesian isotope mixing model: a discussion of Moore & Semmens (2008).Crossref | GoogleScholarGoogle Scholar |
Kelly, B., Dempson, J. B., and Power, M. (2006). The effects of preservation on fish tissue stable isotope signatures. Journal of Fish Biology 69, 1595–1611.
| The effects of preservation on fish tissue stable isotope signatures.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXht1GjsLw%3D&md5=2581a1e93c6b86f55f70f4b3a0618fa4CAS |
Lasta, C. A., Ruarte, C. O., and Carozza, C. R. (2001). Flota costera argentina: antecedentes y situación actual. In ‘El Mar Argentino y sus Recursos Pesqueros 3: Evolución de la Flota Pesquera Argentina, Artes de Pesca y Dispositivos Selectivos’. (Eds M. I. Bertolotti, G. A. Verazay and R. Akselman.) pp. 89–106. (Publicaciones especiales INIDEP: Mar del Plata, Argentina.)
Lewis, S., Sherratt, T. N., Hamer, K. C., and Wanless, S. (2001). Evidence of intraspecific competition for food in a pelagic seabird. Nature 412, 816–819.
| Evidence of intraspecific competition for food in a pelagic seabird.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXms1artLc%3D&md5=9e879252a538b86ab9df697c3abee98fCAS |
Logan, J. M., Jardine, T. D., Miller, T. J., Bunn, S. E., Cunjak, R. A., and Lutcavage, M. E. (2008). Lipid corrections in carbon and nitrogen stable isotope analyses: comparison of chemical extraction and modeling methods. Journal of Animal Ecology 77, 838–846.
| Lipid corrections in carbon and nitrogen stable isotope analyses: comparison of chemical extraction and modeling methods.Crossref | GoogleScholarGoogle Scholar |
Mariano-Jelicich, R., Botto, F., Martinetto, P., Iribarne, O., and Favero, M. (2008). Trophic segregation between sexes in the Black Skimmer revealed through the analysis of stable isotopes. Marine Biology 155, 443–450.
| Trophic segregation between sexes in the Black Skimmer revealed through the analysis of stable isotopes.Crossref | GoogleScholarGoogle Scholar |
Martínez, M. M., Isacch, J. P., and Rojas, M. (2000). Olrog’s Gull Larus atlanticus: specialist or generalist? Bird Conservation International 10, 89–92.
| Olrog’s Gull Larus atlanticus: specialist or generalist?Crossref | GoogleScholarGoogle Scholar |
Moreno, R., Jover, L., Munilla, I., Velando, A., and Sanpera, C. (2010). A three-isotope approach to disentangling the diet of a generalist consumer: the Yellow-legged Gull in northwest Spain. Marine Biology 157, 545–553.
| A three-isotope approach to disentangling the diet of a generalist consumer: the Yellow-legged Gull in northwest Spain.Crossref | GoogleScholarGoogle Scholar |
Navarro, J., Louzao, M., Igual, J. M., Oro, D., Delgado, A., Arcos, J. M., Genovart, M., Hobson, K. A., and Forero, M. G. (2009). Seasonal changes in the diet of a critically endangered seabird and the importance of trawling discards. Marine Biology 156, 2571–2578.
| Seasonal changes in the diet of a critically endangered seabird and the importance of trawling discards.Crossref | GoogleScholarGoogle Scholar |
Parnell, A., Inger, R., Bearhop, S., and Jackson, A. L. (2008). SIAR: Stable Isotope Analysis in R. (The Comprehensive R Archive Network) Available at http://cran.r-project.org/web/packages/siar/index.html [Verified 15 July 2012].
Pauly, D., Christensen, V., Dalsgaard, J., Froese, R., and Torres, F. (1998). Fishing down marine food webs. Science 279, 860–863.
| Fishing down marine food webs.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1cXhtVOjtro%3D&md5=7d47cbf564a308f1c834d20b04eb32a2CAS |
Pierre, J. P., Abraham, E. R., Middleton, D. A. J., Cleal, J., Bird, R., Walker, N. A., and Waugh, S. M. (2010). Reducing interactions between seabirds and trawl fisheries: responses to foraging patches provided by fish waste batches. Biological Conservation 143, 2779–2788.
| Reducing interactions between seabirds and trawl fisheries: responses to foraging patches provided by fish waste batches.Crossref | GoogleScholarGoogle Scholar |
R Development Core Team (2011). ‘R: a Language and Environment for Statistical Computing.’ (R Foundation for Statistical Computing: Vienna, Austria.) Available at http://www.R-project.org [Verified 22 July 2012].
Ramos, R., Ramírez, F., Sanpera, C., Jover, L., and Ruiz, X. (2009). Feeding ecology of Yellow-legged Gulls (Larus michahellis) in the western Mediterranean: a comparative assessment using conventional and isotopic methods. Marine Ecology Progress Series 377, 289–297.
| Feeding ecology of Yellow-legged Gulls (Larus michahellis) in the western Mediterranean: a comparative assessment using conventional and isotopic methods.Crossref | GoogleScholarGoogle Scholar |
Rubenstein, D. R., and Hobson, K. A. (2004). From birds to butterfly: animal movement patterns and stable isotopes. Trends in Ecology & Evolution 19, 256–263.
| From birds to butterfly: animal movement patterns and stable isotopes.Crossref | GoogleScholarGoogle Scholar |
Santora, J. A., Dietrich, K. S., and Lombard, D. (2009). Fishing activity and seabird vessel attendance near the northern Antarctic Peninsula. Marine Ornithology 37, 241–244.
Seco Pon, J. P., and Favero, M. (in press). Olrog’s Gull Larus atlanticus attending high-seas trawlers during the breeding season. El Hornero , .
Seco Pon, J. P., García, G., Copello, S., Moretinni, A., Lértora, H. P., Mauco, L., Pedrana, J., and Favero, M. (2012). Seabird and marine mammal attendance in the Chub Mackerel Scomber japonicus semi-industrial Argentinian purse seine fishery. Ocean and Coastal Management 64, 56–66.
| Seabird and marine mammal attendance in the Chub Mackerel Scomber japonicus semi-industrial Argentinian purse seine fishery.Crossref | GoogleScholarGoogle Scholar |
Tavecchia, G., Pradel, R., Genovart, M., and Oro, D. (2007). Density-dependent parameters and demographic equilibrium in open populations. Oikos 116, 1481–1492.
| Density-dependent parameters and demographic equilibrium in open populations.Crossref | GoogleScholarGoogle Scholar |
Tieszen, L. L., Boutton, T. W., Tesdahl, K. G., and Slade, N. A. (1983). Fractionation and turnover of stable carbon isotopes in animal tissues: implications for δ13C analysis of diet. Oecologia 57, 32–37.
| Fractionation and turnover of stable carbon isotopes in animal tissues: implications for δ13C analysis of diet.Crossref | GoogleScholarGoogle Scholar |
van Gils, J. A., Piersma, T., Dekinga, A., Spaans, B., and Kraan, C. (2006). Shellfish dredging pushes a flexible avian top predator out of a marine protected area. PLoS Biology 4, e376.
| Shellfish dredging pushes a flexible avian top predator out of a marine protected area.Crossref | GoogleScholarGoogle Scholar |
Votier, S. C., Bearhop, S., Witt, M., Inger, R., Thompson, D., and Newton, J. (2010). Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems. Journal of Applied Ecology 47, 487–497.
| Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems.Crossref | GoogleScholarGoogle Scholar |
Wickliffe, L. C., and Jodice, P. G. R. (2010). Seabird attendance at shrimp trawlers in nearshore waters of South Carolina. Marine Ornithology 38, 31–39.
Yorio, P., Bertellotti, M., and García Borboroglu, P. (2005). Estado poblacional y de conservación de gaviotas que se reproducen en el Litoral marítimo Argentino. El Hornero 20, 53–74.
Yorio, P., Petracci, P., Magnanelli, M., Sotelo, M., Suárez, N., Carrizo, M., Delhey, V., Sarria, R., Amado, R. O., Jensen, O. H., Agüero, M. L., García Borboroglu, P. (2012). Actualización del estado de la población reproductora de la Gaviota de Olrog (Larus atlanticus). Technical report, Centro Nacional Patagónico (CENPAT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Wildlife Conservation Society (WCS).
Zar, J. H. (1999). ‘Biostatistical Analysis’. 4th edn. (Prentice-Hall: Englewood Cliffs, NJ.)