These birds were extremely aggressive with one bird evidently defending its nesting territory by hitting me on the head as I walked by on the roadside. The Arctic Tern is common in Svalbard breeding as single pairs or in colonies. This pair was displaying loudly, evidently establishing a territory. This species is famous for its annual migration from the Arctic to the Antarctic and back. Recent studies using radio tagging have confirmed its place as the world's record holder for long distance migration; 59,000 miles round trip. Note short, all red bill and legs, narrow dark primary tips and long shaft streak on p10 with white outer web extending to the tip. Canon PowerShot SX50 HS.
References:
Egevang, C., Stenhouse, I. J., Phillips, R. A., Petersen, A., Fox, J. W., & Silk, J. R. D. (2010). Tracking of Arctic terns Sterna paradisaea reveals longest animal migration. Proceedings of the National Academy of Sciences of the United States of America, 107(5), 2078–2081. http://doi.org/10.1073/pnas.0909493107
Fijn, R.C.; Hiemstra, D.; Phillips, R.A.; van der Winden, J. (2013). "Arctic Terns Sterna paradisaea from the Netherlands migrate record distances across three oceans to Wilkes Land, East Antarctica". Ardea. 101: 3–12. doi:10.5253/078.101.0102.
Gochfeld, M., Burger, J. & Garcia, E.F.J. (2018). Arctic Tern (Sterna paradisaea). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/54026 on 7 September 2018).
Hatch, Jeremy J.. (2002). Arctic Tern (Sterna paradisaea), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/arcter
Record-breaking bird migration revealed in new research. Newcastle University press release.