Distribution, Abundance and Reaction to Aerial Surveys of Post-breeding King Eiders (Somateria spectabilis) in Western Greenland

Moulting and post-breeding king eiders in western Greenland were surveyed in late August and early September of 1993, 1994, and 1995. We counted all eiders observed during fixed-winged aircraft flights along coastlines and offshore transects. The coastline in the survey area is roughly 13 400 km long, and our flightlines totalled approximately 16 500 km. The areas optimal for the birds were covered fully several times; in less suitable areas, only a fraction of the coastline was covered. Using the largest count for coastlines covered more than once, we counted a total of 22 980 king eiders. Large numbers of king eiders were observed at a number of remote localities on the west coast of Disko Island and in southern Upernavik. At localities considered to have frequent disturbance, few birds were observed. Highest densities were found along coasts with sandy or muddy areas at the shorelines. Overall we estimate that 30 000 to 40 000 king eiders reside in the coastal zone of western Greenland in late August. Even allowing for a high turnover rate, as different individuals may occupy the moulting areas during the extended period from July to October, this figure can account for only half of a 1950s estimate that 200 000 males and immatures were moulting in western Greenland.Fin août et début septembre en 1993, 1994 et 1995, on a dénombré les eiders à tête grise durant la mue et après la reproduction dans l'ouest du Groenland. On a compté tous les eiders aperçus durant des vols effectués par des aéronefs à voilure fixe le long de transects longeant la côte et au large. La côte de la zone étudiée fait en gros 13 400 km de long et nos vols ont couvert une distance d'environ 16 500 km. Les meilleures zones pour les oiseaux ont été complètement couvertes plusieurs fois; dans les zones leur convenant moins bien, on n'a couvert qu'une partie de la côte. En se basant sur les plus grands nombres dans le cas des lignes côtières couvertes plus d'une fois, on a compté un total de 22 980 eiders à tête grise. On a observé de grands nombres d'eiders à tête grise dans plusieurs localités reculées, sur la côte occidentale de l'île Disko et dans l'Upernavik méridional. On a observé peu d'oiseaux dans les localités considérées comme subissant des perturbations anthropiques fréquentes. Les densités les plus fortes se trouvaient sur les côtes possédant des zones sableuses ou boueuses le long du rivage. On estime que, dans l'ensemble, de 30 000 à 40 000 eiders à tête grise résident dans la zone côtière du Groenland occidental à la fin du mois d'août. Même en tenant compte du haut taux de renouvellement, car différents individus peuvent occuper les mêmes zones de mue durant la période prolongée de juillet à octobre, ce chiffre ne représente que la moitié de celui des années 1950, alors qu'on estimait à 200 000 le nombre d'oiseaux mâles et immatures qui muaient dans le Groenland occidental

Transect width and missed observations in counting muskoxen (Ovibos moschatus) from fixed-wing aircraft

While conductioning muskox-censuses (Ovibos moschatus) in winter in Jameson Land, NE Greenland, from a fixed-wing aircraft, we examined the width of transects covered. We used a laser range-finder binocular for measuring the distance to observed groups. We found that 1000 m was a reasonable limit for observing a high proportion of the muskoxen present even though it was possible to observe muskoxen from 4000 m or even more. Using two observers on the right side of the aircraft each speaking into a tape recorder with an automatic time signal, we recorded observations and performed a double-observer experiment. By matching the group sizes and perpendicular distances with times of observation we could compare observations of the two observers. We found that both observers missed up to 25% of muskoxen within a 2000 m transect width. The main reasons for missing animals is difficulty in obtaining reference points in snow covered landscape and fatigue of the observers. Calibration of estimated distances using read-outs from the laser-range finder is an adequate method of obtaining distance data for line transect calculations. Our double-observer experiment demonstrated that even groups close to the transect are easily missed

Population demography of the muskoxen in Jameson Land, 1982-1990

Studies of the Jameson Land muskox population in Northeast Greenland were conducted 1982-1990 in conjunction with an oil exploration. A population monitoring program consisted of one yearly aerial survey in late winter and a ground survey for population composition in August. The estimated unadjusted minimum average population size was approximately 4000 with a maximum size of 4700 and a minimum of 2800 muskoxen. The monitoring program was adequate to detect an annual change of about 10%. Population composition data proved to be essential. The only indication of a negative impact from oil exploration was detected in the fraction of yearlings. The average calf proportion was roughly 18% and about half of the calves died during their first year. The population density and composition was similar to the Banks Island muskox population in Canada and to the West Greenland population although the latter population had a higher productivity. Seismic operations and/or climatic conditions may have had a negative impact on the calf survival during 1986-1989, when fractions of yearlings were significantly lower than before and after the exploration