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1 January 2016 Annual Variation in Breeding Numbers of Two Gull Species in Response to Regional Stock Size and Local Availability of Japanese Sand Lance on Rishiri Island, Northern Japan
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Abstract

Breeding population abundance such as colony size of seabirds is not generally considered to be particularly sensitive to the annual dynamics of the food conditions because of the long life-span and high adult survival rate. However, in seabird species in which adults decide to breed or not depending on the food conditions, population abundance can respond sensitively to the annual variation in the food conditions. Here, we examine the effects of the regional annual stock abundance of Japanese Sand Lance Ammodytes personatus, and their local temporal availability during the egg-laying period on the size of a Black-tailed Gull Larus crassirostris and Slaty-backed Gull L. schistisagus, breeding colony over 12 years on Rishiri Island, northern Japan. The total number of nests of both gull species increased significantly with the regional annual stock abundance, but not with the local temporal availability of the sand lance. The number of Black-tailed Gull nests without eggs was significantly higher in the year with lower local temporal availability indicating that more Black-tailed Gull parents gave up egg-laying after nest building. Colony size in these species can be a useful indicator reflecting local food conditions.

© The Ornithological Society of Japan 2016
Kentaro Kazama, Masahiko Sato, and Kazuki Kosugi "Annual Variation in Breeding Numbers of Two Gull Species in Response to Regional Stock Size and Local Availability of Japanese Sand Lance on Rishiri Island, Northern Japan," Ornithological Science 15(1), 85-94, (1 January 2016). https://doi.org/10.2326/osj.15.85
Received: 10 April 2015; Accepted: 27 June 2015; Published: 1 January 2016
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