abstracts of oral and poster presentations - Pacific Seabird Group

chick-rearing constraints occur. After chick hatching, terns utilize the river less, except in high water level years
at the Reservoir, when fish availability is low. I will discuss how both constraints on foraging behavior affect
salmon predation by terns.
MECHANISMS THAT SHAPE SEABIRD DISTRIBUTION IN TIME AND SPACE: HYDROGRAPHY
AND SEABIRDS IN THE SOUTHEASTERN NORTH SEA
Nele Markones (markones@ftz-west.uni-kiel.de) and Stefan Garthe; Research and Technology Centre,
University of Kiel, GERMANY
Since 1990, seabird distribution in the southeastern North Sea has been recorded by German scientists
following the internationally standardised seabirds at-sea method. Meanwhile, the general distribution patterns
during the different seasons can be described for all common species. To reveal the mechanisms that shape and
control these distribution patterns, a suite of studies that took place during the non-breeding season was analysed
to investigate the relationships between seabird distribution and hydrography. For this purpose, we related the
distribution of all common species in the southeastern North Sea to horizontal and vertical profiles of different
hydrographic parameters. Analyses revealed that most of the common species showed a significant, or at least a
positive, correlation to a selection of different hydrographic structures. On the larger scale, these hydrographic
phenomena consisted of distinct water masses with differing salinity, temperature, and water transparency. At a
smaller scale, frontal structures, which were created e.g., by local upwellings or river-plume fronts, were
important. With the hydrographic situation in the southeastern North Sea being highly dynamic, we expect that
seabird distribution patterns also underlie a high variability due to their link to hydrographic features. By
analysing the exact nature of the relationship between seabird distribution and hydrography, it should be
possible to evaluate seabird distribution patterns and predict their variability.
XANTUS'S MURRELET MONITORING PROGRAM AT SANTA BARBARA ISLAND, CALIFORNIA,
1983–2003
Paige L. Martin (paige_martin@nps.gov) and Catherine A. Schwemm; Channel Islands National Park, Ventura,
CA USA
From 1983 to 2003, Channel Islands National Park (with assistance from other groups) monitored
samples of nests of Xantus's Murrelets (Synthliboramphus hypoleucus) at Santa Barbara Island, California, to
examine nesting phenology, occupancy, egg fate, and site productivity. Nesting phenology varied widely
between years, with egg-laying between February and July. Occupancy and annual productivity declined over
the study period, consistent with population declines reported for this colony by other studies. Annual
productivity ranged widely, from 0.39–1.21/nesting attempt. Although annual predation of eggs by deer mice
(Peromyscus maniculatus elusus) ranged widely (0.0–68.9%), we found no relationships between variation in
mouse density and levels of egg predation, hatching success, or site productivity. This monitoring program
should be improved and continued annually, in conjunction with long-term studies of murrelets, mammalian and
avian predators, prey resources, and other human impacts to assess and model population changes better at the
largest colony in California.
FORAGING BEHAVIOR OF STREAKED SHEARWATER IN JAPAN
Kei Matsumoto* 1 (Kei-mts01@av6.mopera.ne.jp), Nariko Oka 2 , Daisuke Ochi 1 , Yutaka Watanuki 1 , Fumihito
Mutou 3 , and Yoshiyuki Baba 4 ; 1 Graduate School of Fisheries Science, Hokkaido University, Hakodate JAPAN;
2 Research Division, Yamashina Institute for Ornithology, Chiba JAPAN; 3 Ocean Research Institute, The
University of Tokyo, Tokyo JAPAN; 4 Laboratory of Nature Conservation, SCS, Kyushu University, JAPAN
Maximal dive depths of several species of offshore albatrosses and petrels have been reported recently.
However, little is known about dive depth and daily foraging pattern of coastal feeding sheawaters. Streaked
Sheawaters are endemic in eastern Asia and are believed to feed in coastal waters during the breeding period.
We examined the diving behavior and diet of Streaked Shearwaters breeding on Mikura Island, southern Japan.
Basing on time-depth data collected using small data-loggers, sheawaters dived less than 7 m deep during
foraging trips of 1 to 13 days. Mean dive depth and duration were 1.5 ± SD 0.9 m and 4.6 ± SD 1.2 sec,
respectively. Most dives occurred in the daytime. During long trips (>5 days), birds fed in cold waters (