The effect of ice conditions in northern Hudson Bay on breeding by Thick-billed Murres (Uria lomvia)

Abstract

We compared annual indices of breeding by Thick-billed Murres, Uria lomvia, at a colony in northern Hudson Bay with annual variation in the extent of sea-ice cover during May and June, the period when birds arrive and initiate breeding. Greater ice cover was associated with delayed breeding and lower attendance rates at the colony during the early incubation period (late June). We detected no effect on egg size, reproductive success, or adult body mass. The extent of ice cover in May was positively correlated with the proportion of Arctic cod fed to nestlings, and in June with the proportion of capelin in the rest of the diet. There was a positive correlation between the proportion of capelin in the chick diet and chick body mass at 14 days of age. We attribute the delay in laying during years of heavy ice cover to the reduced area available for foraging close to the colony. Prolonged persistence of ice, though delaying the onset of laying, may benefit the birds later in the season, as they forage preferentially in the vicinity of ice. We suggest that the strong relationships we observed between the extent of ice cover and aspects of the breeding biology of Thick-billed Murres may apply to other Arctic-nesting seabirds and may reflect conditions affecting the entire marine food web.

Trends in Forage Fish Populations in Northern Hudson Bay since 1981, as Determined from the Diet of Nestling Thick-billed Murres, <i>Uria lomvia</i>

“…As cod made up over 40% of diet items in eight of 19 years, and as this species appears to be a preferred diet item of thick-billed murres throughout much of their range in Canada (Gaston and Nettleship, 1981;Gaston and Bradstreet, 1993;Gaston and Hipfner, 2000), we also examined the representation of other taxa, once arctic cod had been removed (referred to as "sample minus cod"). Trends over years were tested for significant departure from random using the regression routine of STATISTICA (Statsoft Inc., 2001), with percentage data arcsin transformed.…”

“…Earlier sea-ice breakup has already been demonstrated to have caused earlier laying and higher colony attendance in thick-billed murres Uria lomvia (Gaston and Hipfner, 1998) in northern Hudson Bay, and it has caused deterioration in female body condition among polar bears Ursus maritimus in western Hudson Bay (Stirling et al, 1999).…”

“…The thick-billed murre is a circumpolar species that breeds only in the Arctic and Subarctic, wintering in the northernmost ice-free areas and feeding almost entirely in waters at less than 8˚C throughout the year (Tuck, 1961;Gaston and Hipfner, 2000). Thick-billed murres forage underwater to depths of 200 m (Croll et al, 1992;Falk et al, 2000), feeding on small fishes, squid, and large zooplankton (Gaston and Bradstreet, 1993;Gaston and Hipfner, 2000).…”

“…Thick-billed murres forage underwater to depths of 200 m (Croll et al, 1992;Falk et al, 2000), feeding on small fishes, squid, and large zooplankton (Gaston and Bradstreet, 1993;Gaston and Hipfner, 2000). Nestlings are fed by their parents at the breeding site for 15 -30 days before departing to sea.…”

Latitudinal gradients in sea ice and primary production determine Arctic seabird colony size in Greenland

“…In spring, thick-billed murres migrate up to several thousand kilometres from wintering grounds in Davis Strait, the Labrador Sea and Newfoundland to breeding sites in the high Arctic (Lyngs 2003). The energy cost of the migration is substantial and local feeding conditions at breeding sites before egg-laying are critical to survival and reproductive success (Gaston & Hipfner 1998;Hipfner et al 2005). Energetic theory predicts that any increased cost from distance migrated should be offset by benefits gained for long-term survival and reproductive success (Drent et al 2003).…”