Second North American Sea Duck Conference - Patuxent Wildlife ...

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SECOND NORTH AMERICAN SEA DUCK CONFERENCE Diana V. Solovieva ARTIFICIAL NEST CONSTRUCTION FOR THE SCALY-SIDED, CHINESE, MERGANSER Wrangel Island State Reserve, Obrucheva Str., 38, Pevek, 689400; Diana@DS3902.spb.edu The scaly-sided merganser (Mergus squamatus) is among the rarest sea ducks in the world with a declining population estimated at 4,500 individuals (BirdLife International 2000) in 1990. The species is listed as “Endangered” by IUCN and is listed in the national Red Data Books of Russia, China, and South Korea. Most of the population breeds in the Far East of Russia. Known reasons of decline include habitat loss due to logging of the flood-plain forests, mortality from gill-net fishing, and shooting. Recent surveys indicated slight increase in breeding number probably up to 10,000 individuals in the world (Shohrin & Solovieva 2003). An artificial nest program for this species has been started in Primorye, Far East, Russia in 2000. We compared two different types of artificial nests for their occupancy by the scaly-sided merganser. First type was a 90 cm long eight-angle wooden tube open from above and the second type was wooden box with square flow and front entrance. Box sizes were adapted to the scaly-sided merganser: height 65 cm, flow side 30 cm, oval entrance 10x8 cm. Tube nest construction was suggested after observation over natural nests of the particular cavity nesting occupation rate is significant (p
SECOND NORTH AMERICAN SEA DUCK CONFERENCE THE COSTS OF MATE GUARDING TO MALE COMMON EIDERS Ben Steele, Aleksi Lehikoinen, Markus Öst, and Mikael Kilpi. Colby-Sawyer College; bsteele@colby-sawyer.edu Male Common Eiders (Somateria mollissima) are known to guard their mates against interference or copulations by other males during the laying period. This activity is accentuated in the archipelago of southwest Finland where the male biased sex ratio (about 56% males) means many single males approach paired ducks. We hypothesized that guarding involves a cost to mated males in less time available for foraging during this energetically stressful time of year. Unmated males may be adopting an alternative mating strategy, in which their survival is increased by feeding more and their reproductive success may benefit from occasional extra pair copulations. Scan sampling of 96 males in 2003 and 71 in 2004 showed that unmated males foraged more in 2003, but not in 2004. The number of dives per hour showed a similar pattern: in 2003, unmated males dove more than mated males. Unmated males participated in more aggressive encounters per hour than mated males, during preincubation, but spent a lower proportion of their time in aggression, suggesting that their aggressive encounters were shorter than that of mated males. In both years, mated males were clearly dominant over unmated ones, winning most aggressive encounters. These results suggest that there is no consistent feeding advantage of not being mated, and that unmated males may just be subordinate, perhaps younger males, excluded from breeding. Scan sampling omits “harassment groups” consisting of 5 to 60 unmated males that chase a mated pair for up to two hours. During this time, no foraging takes place and it appears as if large amounts of energy are expended by the mated male defending the female. The number of males participating in these harassment groups increases during the breeding season as some females leave to incubate, thereby increasing the male bias of the sex ratio. These groups may constitute an occasional, but intense cost to mated males. NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA 119
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