Behavioural studies of Great Northern Divers Gavia immer wintering on the coast of Jæren, SW Norway in 1996–2010, revealed interspecific aggression by divers against several species of waterbirds. Aggression was shown against two species of cormorants, five species of diving ducks, two species of grebes, one species of diver, one species of alcid, one species of merganser, and against Shelduck Tadorna tadorna. In relation to their occurrence in the vicinity of individual Great Northern Divers, piscivorous birds were significantly more often subject to aggression than other waterbirds. Aggression towards piscivorous species was in accordance with predictions from a food competition hypothesis, but possible benefits from threatening and attacking non-piscivorous ducks seem unclear. No support was found for hypotheses related to sexual selection or predation.
Byrkjedal, I. 2011a. Social behaviour of wintering Great Northern Divers Gavia immer in relation to age categories. Ornis Norvegica 34: 10–16.
Byrkjedal, I. 2011b. Kleptoparasitism of wintering Great Northern Divers Gavia immer by gulls. Ornis Norvegica 34: 17–18.
Byrkjedal, I. & Eldøy, S. 1984. Høst- og vinterbestanden av vannfugl på Jæren 1983/84 og noen oppsummeringer for perioden 1979/80-83/84. Falco 13: 159–173.
Byrkjedal, I. & Eldøy, S., Grundetjern, S. & Løyning, M.K. 1997. Feeding associations between Red-necked Grebes Podiceps griseigena and Velvet Scoters Melanitta fusca in winter. Ibis 139: 45–50.
Cramp, S. & Simmons, K.E.L. (eds.) 1977. The birds of the Western Palearctic. Vol 1. Oxford University Press, Oxford.
Evers, D.C., Paruk, J.D., McIntyre, J.W. & Barr, J.F. 2010. Common Loon (Gavia immer). The Birds of North
America Online (A. Poole, ed.) Ithaca: Cornell Lab of ornithology (http:bna.birds.cornell.edu/bna/ species/313).
Follestad, A., Gjershaug, J.O. & Stokke, B.G. 2016. Ferdselsrelaterte forstyrrelser på fugl i Jærstrendene
landskapsvernområde. NINA Rapport 1243: 1–112.
Ford, T.B. & Gieg, J.A. 1995. Winter behavior of the Common Loon. Journal of Field Ornithology 66: 22–29.
Henderson, P. 2014. Identification guide to the inshore fishes of the British Isles. Pisces Conservation Ltd.,
Kirkham, I.R. & Johnson, S.R. 1988. Interspecific aggression in loons. Journal of Field Ornithology 59: 3–6.
Rummel, L. & Goetzinger, C. 1978. Aggressive display in the Common Loon. Auk 95: 183–186.
Sperry, M.L. 1987. Common Loon attacks on waterfowl. Journal of Field Ornithology 58: 201–205.
Sjölander, S. & Ågren, G. 1972. Reproductive behaviour of the Common Loon. The Wilson Bulletin 84: 296–308.
Tozer, R. 1993. Interspecific aggression by Common Loons. Ontario Birds 11: 2–5.
Tysse, T. 1981.Vinterbestanden av lom og dykkere i Rogaland. Falco 10: 4–24.