Journal of Zoology (London) (in press)
Diving behaviour and foraging habitats of Brunnich's guillemots Uria lomvia breeding in the High-Arctic
Mehlum, F., Y. Watanuki & A. Takahashi
We studied the foraging behaviour of Brunnich's guillemots Uria lomvia in a high-arctic fjord system (Kongsfjorden) in western Spitsbergen. The physical oceanographic characteristics of the water change from the head of the fjord and westward into the Greenland Sea, and are reflected in the vertical profiles of water temperatures in different parts of the area. We instrumented nine chick-rearing Brunnich's guillemots with temperature-depth recorders, which generated vertical temperature profiles of the dives. These were compared to synoptic measurements of the water temperature characteristics of the region. This method was used to locate the foraging areas of the Brunnich's guillemots and to study the foraging site fidelity of individual birds. The results showed that only three of the nine birds foraged outside Kongsfjorden during the study period, and only 26 of the 186 dive bouts (14%) were conducted outside the fjord, 48-58 km from the colony. Most dives were probably made only a few kilometres from the colony. The data indicated that the birds showed strong fidelity to foraging areas at spatial scales of 1-20 kilometres. However, the birds sometimes moved between feeding areas characterised by different vertical temperature profiles. The guillemots made 2229 dives during the study period and spent ca. 10% of their time under water. The diving depth averaged 45 m, and the dive duration averaged 97 sec. The deepest dive recorded was 136 m and lasted 196 sec. We did not find any diel rhythm in the diving depths of the Brunnich's guillemots. Also, we found no diel pattern in diving frequency. These findings contradict the predominance of night-time diving observed in studies further south.
BD01-3
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