Status and productivity of Common Eiders in relation to Great Black-backedGulls and Herring Gulls in the southern Bay of Fundy and the northern Gulfof Maine

The breeding population of Common Eiders (Somateria mollissima) in the Bay of Fundy has remained stable over the last decade, ranging from 8,000 to 10 ,000 breeding pairs. However, the number of ducklings surviving to fledging in the Bay of Fundy decreased from >14% of the adult breeding population p rior to 1991 to <10% between 1995 and 1998. Although the breeding populatio n in the Grand Manan Archipelago decreased over the decade, these colonies produced more ducklings that survived to fledgling in the Bay of Fundy betw een 1995 and 1998 and represented an important source of potential recruits (44-87%) to the eider population. Higher duckling production in the Grand Manan Archipelago cannot be attributed to higher hatch success, but may ref lect lower predation rates by Great Black-backed Gulls (Larus marinus). The number of ducklings observed during aerial surveys was not correlated with commercial catches of herring (Clupea harengus), an alternative food sourc e for predatory gulls. Duckling survival to fledgling was higher for a loca l breeding population in the Gulf of Maine (12%) than in the Bay of Fundy ( 6%). The relatively large number of ducklings associated with a two-island archipelago within the Petit Manan National Wildlife Refuge accounted for a large proportion of the surviving ducklings and may reflect lower predatio n rates by Great Black-backed Gulls as a result of gull control measures. T he current populations of Herring Gulls (L. argentatus) and Great Black-bac ked Gulls breeding in the Bay of Fundy in New Brunswick are estimated at 5, 367 pairs (5,011-7,282: 95% CI) and 1,771 pairs (1,685-1,868: 95% CI) respe ctively. Assuming that the age structure of gulls in this region is similar to that of the expanding New England population, the total number of indiv idual gulls in the Bay of Fundy probably exceeded 56,393 (54,173-62,289: 95 % CI) in 1998.