Reproduction 115 Dovekie response to Glaucous Gull behaviour and approach in North Greenland KURT K. BURNHAM and WILLIAM BURNHAM Abstract Dovekies Alle alle form breeding colonies of thousands of birds in North Greenland. One of their major predators, the Glaucous Gull Larus hyperboreus, attacks Dovekies while they attend their breeding colony. We found that Dovekies at the edge and at the center of the breeding colony responded similarly to gulls. Dovekies were sig- nificantly more likely to evacuate the colony when a gull approached low to medium in height (<60 m above colony) and flew with a steady wing beat or an irregular flight pattern. A gull that approached from inland was significantly more likely to cause the colony to evacuate than a gull that approached from the sea. Dovekies responded similarly to gulls in cloudy and clear conditions, but were significantly more likely to leave the colony when the weather was windy than when it was calm. Dovekies appear to evaluate the threat of gull predation based on the gull's behavior and its approach height. Our data suggest that Dovekies agree on the threat a gull poses as generally all birds evacu- ated the colony or remained. Partial evacuation of the colony was rare and occurred generally when gulls gave mixed signals such as flying high but irregularly. (Med et dansk resumé: Søkongernes reaktion på overflyvende Gråmåger i en nordgrønlandsk koloni) Introduction The Dovekie Alle alle is a small, 150 g planktivo- rous alcid that breeds in the Atlantic Arctic (Net- tleship 1996). Northwest Greenland has an excep- tionally large breeding population of Dovekies, es- timated at 33 million pairs (Egevang et al. 2003). They arrive at the breeding sites in north Green- land in mid-May and depart in late August (Sa- lomonsen 1950-51). A one-egg clutch is laid in a steep, rocky talus slope within several kilometers of the sea in late June and is incubated for 29 days (Evans 1981). Peak Dovekie hatching in the area is reported as about 20 July (Roby et al. 1981), and the semi-precocial chick leaves the nest after about 28 days (Evans 1981). The Glaucous Gull Larus hyperboreus, arctic fox Alopex lagopus, Gyrfalcon Falco rusticolus, and humans are the primary predators on Dovekies at the breeding colony (Salomonsen 1967, Stemp- niewicz 1983). Glaucous Gulls may have the great- est effect on Dovekies because they are numerous and frequently cause colonies to evacuate. Evacua- tion results in Dovekies expending more energy and interferes with breeding. Between 15 July and 3 August 1995, we inves- tigated how Dovekies in north Greenland respond to gull predation. We examined whether Dovekies evaluate the threat of aerial predators by quantify- ing gull flight and approach and the subsequent re- action of Dovekies to these gulls. We predicted that Dovekies on the edge of the colony would flush more often than those in the center because birds at the edge of breeding groups are believed to suffer from greater predation than those at the center (Birkhead 1985). Study area and methods The study site, located at 76º17' N, 69º03' W ap- proximately 30 km south of Thule Air Base (Pituffik), Greenland, was observed for 10 days. The sun is above the horizon 24 hours a day in Thule from 24 April through 21 August, and below the horizon from 22 November through 24 January. From 1951 through 1986, at Pituffik (elevation 76.5 m), mean monthly temperatures were -6ºC May, 2ºC June, 5ºC July, 4ºC August, and -2ºC September. De- spite the continued light and warmer temperatures, during the summer months weather can be harsh with frequent storms, high winds, and sea fog that may last for days, affecting Dovekies and their pred- ators. Ice-free land is limited to about 0-15 km from the sea and is bordered inland by the Greenland Ice Sheet. The topography is generally rolling hills and valleys with streams running from the ice sheet or glaciers. Most cliffs are adjacent to sea or glaciers and are used for nesting by gulls and fal- cons and may have extensive talus slopes below occupied by Dovekies. Vegetation is limited and very low to the ground. Plant species such as wil- low Salix and dwarf birch Betula are present at lower elevations, as well as some annuals, mosses, lichens, and fungi. Areas immediately below talus slopes with Dovekie colonies are usually covered by dense grass. Dansk Orn. Foren. Tidsskr. 99 (2005): 115-118