Reproductive Behavior of the Yellow-Billed Loon, Gavia adamsii

S. Sjolander, G. Agren
1976 The Condor  
Little is known about the Yellow-billed Loon ( Gavia adamsii) . Its reproductive behavior has not been investigated apart from short observations by Kretzschmar and Leonowitsch ( 1965) and Sage ( 1971). We studied this species in Alaska as a part of an ethological study of the family Gaviidae. STUDY AREA AND METHODS The study was conducted in the Alaktak area of northern Alaska, about 80 km southeast of Point Barrow, from 1 July through 26 August 1972. This site was the only one found where the
more » ... one found where the species occurred, although the areas around the camps of the Naval Arctic Research Laboratory at Meade River, Peard Bay and Teshekpuk Lake were checked on foot and from the air. Of 33 pairs located, 10 were checked at least once a week throughout the study period, and four were followed closely (table 1). It was not possible to follow any one pair during the whole breeding cycle. Most pairs were already incubating when we first visited the area, and the young were only half-grown when we left in August. Data on courtship and copulation stem from two pairs attempting to renest and from one pair that never nested. Direct observations as well as still and motionpicture photographs were made from tent blinds and from natural concealment. Unfortunately, blinds are very conspicuous on the flat and open tundra; they obviously disturbed the birds, who avoided them. Although we do not believe that the presence of the blinds influenced the performance of displays, it may have affected their frequency and certainly the sites chosen for them. Observations were recorded for 231 h (table 1) at all times of day and night. Observation often was interrupted or disturbed by lengthy spells of fog and strong wind. The sex of the birds was determined by observing copulations and noting individual peculiarities in bill and plumage. Vocalizations were recorded on an Uher Report 4400 tape recorder with a Sennheiser MD 21 microphone and a 50 cm parabola. All birds recorded were breeding, and all recordings were made during the pre-hatching period. VOCALIZATIONS The vocalizations in this species were generally the same as those of G. immer (Sjolander and Agren 1972). All calls, however, were pitched about half an octave lower and were executed more slowly, at least the tremolo and the yodeling. Terminology follows that for G. immer (Olson and Marshall 1952, Sjiilander and Agren 1972). Audiospectrograms of most vocalizations are presented in figure 1. An analysis of the situations where different calls were heard is presented in table 2. Low Cull. A very weak, low-pitched, onenote call, heard only in calm weather from birds close to the observer ( < 50 m ). Per-14541 The Condor 78:454463, 1976 BEHAVIOR OF YELLOW-BILLED LOON 455
doi:10.2307/1367094 fatcat:6lpj2bppxva5rk2j4m24rtezhe