Red-throated Loon Gavia stellata Scientific name definitions

"...the wild call of the Red-throated Diver is enough to make one's flesh creep: it resembles the cry of a little child in pain, but is more akin maybe to the wail of a lost spirit, echoing and re-echoing round the lonely hills." E. L. Turner, 1913 (1 Turner, E. L. (1913). The Red-throated Diver in its breeding haunts. British Birds 12:150–159. Close )

Loons typically evoke images of broad, picturesque lakes, striking black and white breeding plumage, and melodic territorial yodels. The Red-throated Loon does not fit this archetype. Instead, this smallest member of the family Gaviidae breeds in small arctic and boreal lakes, bears relatively plain gray plumage, save for its namesake throat patch, and utters a call during breeding that is generously described as cacophonous. In further contrast to congeners, the Red-throated Loon does not feed within its territorial breeding lake, but instead behaves as a central-place forager, flying between separate breeding and foraging areas, often inshore marine habitat, to feed and to provision its young. Rather than molting flight feathers during winter, as do other loon species, the Red-throated Loon molts during fall, often at sites intermediate to breeding and wintering sites. Smaller body size allows it to take flight over a much shorter distance, perhaps an adaptation to an earlier period in its evolutionary history when most ice-free lakes available for breeding were small and shallow.

With a circumpolar distribution, the Red-throated Loon breeds in tundra and boreal landscapes, up to high latitudes. During winter, it primarily resides along both Atlantic and Pacific coasts of North America and Eurasia, the Great Lakes, and Black, Caspian and Mediterranean Seas. In North America, it breeds mainly on small ponds in remote coastal tundra habitat, so it is not often encountered while in its breeding plumage. In contrast, the Red-throated “Diver” is better known in Eurasia, where it breeds in more populated regions, including Scotland and Scandinavia. In the most northern parts of its range, above 75°N, it has only 2–3 months to nest and raise its young to fledging.

One of the earliest publications on avian behavior, and the first major work on any loon species, was J. S. Huxley's (2 Huxley, J. S. (1923). Courtship activities in the Red-throated Diver (Colymbus stellatus) with a discussion of the evolution of courtship in birds. Zoological Journal of the Linnean Society 35:253–292. Close ) landmark treatise on Red-throated Loon behavior and the evolution of courtship in birds. For decades, the species has been the subject of considerable field research to monitor reproductive success in Sweden (3 Lokki, J., and K. Eklöf (1984). Breeding success of the Red-throated Diver (Gavia stellata) in southern Finland. Annales Zoologici Fennici 21:417–419. Close , 4 Dahlén, B., and M. O. G. Eriksson (2002). Breeding biology of the Red-throated Loon Gavia stellata in the core area of the Swedish population. Ornis Svecica 12:1–33. Close , 5 Eriksson, M. O. G., and M. Åhlund (2013). Dynamics of breeding site choice of Red-throated Loon (Gavia stellata)—abandonments, new establishments and re-occupations. Ornis Svecica 23 (3-4):130-142. Close , 6 Dahlén, B., and M. Eriksson (2016). Does breeding performance differ between solitary and colonial breeding Red-throated Loon (Gavia stellata) in the core area of the Swedish population? Ornis Svecica 26 (3-4): 135-148. Close ) and the United Kingdom (7 Gomersall, C. H. (1986). Breeding performance of the Red-throated Diver, Gavia stellata, in Shetland. Holarctic Ecology 9:277-284. Close , 8 Okill, J. D., and S. Wanless (1990). Breeding success and chick growth of Red-throated Divers Gavia stellata in Shetland 1979-88. Ringing & Migration 11:65-72. Close , 9 Booth, C. J. 1999. Breeding success of Red-throated Divers on Orkney Mainland, 1973–1998. Scottish Birds 20:94–97. Close ). Individuals banded during these efforts have provided information on dispersal, migration routes, and survival rates ( 10 Okill, J. D. (1992). Natal dispersal and breeding site fidelity of Red-throated Divers (Gavia stellata) in Shetland. Ringing & Migration 13:57-58. Close , 11 Hemmingsson, E., and M. O. G. Eriksson (2002). Ringing of Red-throated Diver Gavia stellata and Black-throated Diver Gavia arctica in Sweden. Wetlands International Diver/Loon Specialist Group Newsletter 4:8–13. Close ). Foraging behavior, chick diet, and characteristics of boreal breeding habitat have been quantified (12 Norberg, R. Å., and U. M. Norberg (1976). Size of fish carried by flying Red-throated Divers Gavia stellata (Pont.) to nearly fledged young in nesting tarn. Ornis Fennica 53:92–95. Close , 13 Eriksson, M. O. G., D. Blomqvist, M. Hake, and O. C. Johansson (1990). Parental feeding in the Red-throated Diver Gavia stellata. Ibis 132:1–13. Close , 14 Skyllberg, U., J. Lessmann, and P. Hansson (1999). Importance of lake and nesting site characteristics for the breeding success of sea-foraging Red-throated Divers Gavia stellata in Västerbotten, Sweden. Ornis Svecica 9:107–120. Close ), specifically in relation to lake acidification by airborne contaminants from fossil-fuel-burning power plants (15 Eriksson, M. O. G., and P. Sundberg (1991). The choice of fishing lakes by the Red-throated Diver Gavia stellata and Black-throated Diver G. arctica during the breeding season in southwest Sweden. Bird Study 38:135-144. Close , 16 Eriksson, M. O. G. (1994). Susceptibility to freshwater acidification by two species of loon: Red-throated Loon (Gavia stellata) and Arctic Loon (Gavia arctica) in southwest Sweden. In Aquatic Birds in the Trophic Web of Lakes (J. J. Kerekes and J. B. Pollard, Editors), Hydrobiologia 279/280: 439-444. Close , 17 Eriksson, M. O. G. (2006). Breeding success of the Red-throated Diver Gavia stellata in relation to water chemistry and composition of the fish stocks in different fishing lakes. Ornis Svecica 16:211–231. Close , 18 Eriksson, M. O. G., and H. Paltto (2010). Water chemistry and the composition of fish stocks in the breeding lakes of Black-throated Diver Gavia arctica, and a comparison with the fishing lakes of Red-throated Diver Gavia stellata. Ornis Svecica 20:3-30. Close ) and the consequent degradation of breeding habitat (16 Eriksson, M. O. G. (1994). Susceptibility to freshwater acidification by two species of loon: Red-throated Loon (Gavia stellata) and Arctic Loon (Gavia arctica) in southwest Sweden. In Aquatic Birds in the Trophic Web of Lakes (J. J. Kerekes and J. B. Pollard, Editors), Hydrobiologia 279/280: 439-444. Close ) and contamination of eggs (19 Eriksson, M. O. G., I. Johansson, and C. G. Ahlgren (1992). Levels of mercury in eggs of Red-throated Diver Gavia stellata and Black-throated Diver G. arctica in Southwest Sweden. Ornis Svecica 2:29-36. Close , 20 Eriksson, M. O. G., and P. Lindberg (2005). Mercury exposure to Red-throated Divers Gavia stellata and Black-throated Divers Gavia arctica in Sweden. Ornis Svecica 15:1-12. Close ).

In North America, Red-throated Loon populations have varied widely in several parts of the breeding range, perhaps due to variations in ocean conditions, such as water temperature and its effects on marine fish communities (21 Anderson, P. J., and J. F. Piatt (1999). Community reorganization in the Gulf of Alaska following ocean climate regime shift. Marine Ecology Progress Series 189:117-123. Close , 22 Schmutz, J. A. (2014). Survival of adult Red-throated Loons (Gavia stellata) may be linked to marine conditions. Waterbirds 37(sp1):118–124. Close ). This population variation has stimulated an increase in research since 2000 in North America, where aspects of its breeding biology have been investigated at sites from Alaska (23 Ball, J. R. (2004). Effects of parental provisioning and attendance on growth and survival of Red-throated Loon pre-fledglings: A potential mechanism linking marine regime shifts to population change. M.S. thesis, Simon Fraser University, Burnaby, BC, Canada. Close , 24 Rizzolo, D. J., J. A. Schmutz, S. E. McCloskey, and T. F. Fondell (2014). Factors influencing nest survival and productivity of Red-throated Loons (Gavia stellata) in Alaska. Condor 116(4): 574-587. Close , 25 Rizzolo, D. J., J. A. Schmutz, and J. R. Speakman (2015). Fast and efficient: Postnatal growth and energy expenditure in an arctic-breeding waterbird, the Red-throated Loon (Gavia stellata). Auk 132: 657-670. Close , 26 Uher-Koch, B. D., J. C. Koch, K. G. Wright, and J. A. Schmutz (2018). Comparative nest survival of three sympatric loon species breeding in the Arctic. Journal of Avian Biology 49:e01671. Close ), across the Canadian Arctic (27 Eberl, C. (1993). Effect of food, predation and climate on selection of breeding location by Red-throated Loons (Gavia stellata) in the high Arctic. Unpublished M.S. thesis, University of Ottawa, Ottawa, ON, Canada. Close , 28 Eberl, C., and J. Picman (1993). Effect of nest-site location on reproductive success of Red-throated Loons (Gavia stellata). Auk 110:436-444. Close , 29 Dickson, D. L. (1993). Breeding biology of Red-throated Loons in the Canadian Beaufort Sea region. Arctic 46:1-7. Close , 30 Dickson, D. L. (1994). Nesting habitat of the Red-throated Loon, Gavia stellata, at Toker Point, NWT. Canadian Field-Naturalist 108:10-16. Close , 31 Dickson, D. L., and J. Beaubier (2011). Red-throated monitoring in the southeast Beaufort Sea region: 2007-2008 update. Canadian Wildlife Service Technical Report Series Volume 517: 1-38. Close ), and towards the southern extent of its range on Haida Gwaii in British Columbia (32 Douglas, S. D., and T. E. Reimchen (1988). Habitat characteristics and population estimate of breeding Red-throated Loons, Gavia stellata, on the Queen Charlotte Islands. British Columbia Canadian Field-Naturalist 102:679–684. Close , 33 Douglas, S. D., and T. E. Reimchen (1988). Reproductive phenology and early survivorship in Red-throated Loons, Gavia stellata. Canadian Field-Naturalist 102:701-704. Close ), often in comparison to sympatric Pacific Loon (Gavia pacifica; 34 Davis, R. A. (1972). A comparative study of the use of habitat by Arctic and Red-throated loons. Ph.D. dissertation, University of Western Ontario, London, ON, Canada. Close , 35 Petersen, M. R. (1976). Breeding biology of Arctic and Red-throated Loons. M.S. thesis, University of California, Davis, CA, USA. Close , 36 Bergman, R. D., and D. V. Derksen (1977). Observations on Arctic and Red-throated loons at Storkersen Point, Alaska. Arctic 30:41-51. Close , 37 Rizzolo, D. J. (2017). Contrasting diet, growth, and energy provisioning in loons breeding sympatrically in the Arctic. Ph.D. dissertation, University of Alaska, Fairbanks, AK. 159 pp. Close ). Satellite telemetry has provided valuable information on migratory movements of breeders from Alaska (38 McCloskey, S. E., B. D. Uher-Koch, J. A. Schmutz, and T. F. Fondell (2018). International migration patterns of Red-throated Loons (Gavia stellata) from four breeding populations in Alaska. PLoS ONE 13: 1–15. Close ), and movements and marine habitat selection of loons wintering along the mid-Atlantic coast (39 Gray, C. E., A. T. Gilbert, I. J. Stenhouse, and A. M. Berlin (2017). Occurrence patterns and migratory pathways of Red-throated Loons wintering in the offshore Mid-Atlantic U.S., 2012–2016. In Determining Fine-Scale Use and Movement Patterns of Diving Bird Species in Federal Waters of the Mid-Atlantic United States Using Satellite Telemetry, U.S. Department of the Interior, Bureau of Ocean Energy Management, OCS Study BOEM 2017-069, Sterling, VA, USA. pp. 60–102. Close ). Its dispersed distribution across large, remote terrestrial and marine habitats has made quantifying demographic parameters, other than the fate of eggs, challenging; there is only one study that has estimated adult survival in North America (22 Schmutz, J. A. (2014). Survival of adult Red-throated Loons (Gavia stellata) may be linked to marine conditions. Waterbirds 37(sp1):118–124. Close ), and key parameters, such as juvenile survival and age of first breeding, are unknown.

Because of its sensitivity to disturbance, broad distribution in coastal tundra habitat, and reliance on the marine environment during breeding, the Red-throated Loon has been identified as an indicator species for environmental change on its breeding habitat (36 Bergman, R. D., and D. V. Derksen (1977). Observations on Arctic and Red-throated loons at Storkersen Point, Alaska. Arctic 30:41-51. Close , 40 Dickson, D. L. (1992). The Red-throated Loon as an indicator of environmental quality. Canadian Wildlife Service Occasional Paper 73. Close , 16 Eriksson, M. O. G. (1994). Susceptibility to freshwater acidification by two species of loon: Red-throated Loon (Gavia stellata) and Arctic Loon (Gavia arctica) in southwest Sweden. In Aquatic Birds in the Trophic Web of Lakes (J. J. Kerekes and J. B. Pollard, Editors), Hydrobiologia 279/280: 439-444. Close ). This role is likely to become more important given the unprecedented changes occurring in both coastal tundra and inshore marine habitats as the average global temperature rises in response to anthropogenic greenhouse gas emissions.