LOGTAIL DUCM PATCH

The largest wintering concentration of arctic- and subarctic-breeding sea ducks on the U.S. Winter prey resources provide energy to build body reserves that fuel migration and reproduction (Lovvorn etВ al. However, there is little information on how oceanic prey resources influence wintering sea duck distributions on the Atlantic United States, outside of bays and harbors. eastern seaboard sustain a large proportion of its wintering sea ducks (family: Anatidae tribe: Mergini White etВ al. This interaction will be important to the designation of marine protected areas.ДЄ small number of critical feeding areas on the U.S. As supported by our generalized additive models, we propose that the positive spatial associations among these species are at least partly explained by local enhancement or facilitation, whereby each species of duck derives foraging benefit from noting the location of aggregations of the other. Enhanced concentrations of prey within a relatively narrow zone on Nantucket Shoals provide a predictable food resource to wintering sea ducks whose populations are in decline.

LOGTAIL DUCM PATCH

These multi-scalar nested associations suggest that the sea ducks foraged within a hierarchical patch system structured by the tidal regime, and concentrated in areas of spatially anchored recurring prey, with highest densities in southwest areas. Both long-tailed ducks and white-winged scoters associated with amphipod and clam aggregations at similar scales, and tracked amphipod and clam concentrations at larger spatial scales, up to ~30В km. Long-tailed ducks and white-winged scoters were counted during systematic low-level aerial surveys. Gammarid amphipods were collected seasonally by bongo tows over 39В yr (1977вЂ“2016), and Atlantic surf clams and ocean quahogs were collected by hydraulic dredge over a 34-yr timescale (1982вЂ“2016). Despite the difference in diet, the two duck species overlap in spatial distribution in relation to a prominent tidal front on the west side of Nantucket Shoals where nested swarms of pelagic amphipods and massive clam beds occur in persistent broadscale concentrations. We examine the long-term co-occurrence of long-tailed ducks ( Clangula hyemalis) and white-winged scoters ( Melanitta fusca) wintering at the Nantucket Shoals off Massachusetts, USA, and ask: (1) What oceanographic features attract these aggregations? (2) How are distributions of prey and sea ducks related to one another? and (3) What is the explanation for the spatial association between these two species? A winter concentration of long-tailed ducks on the order of 3В Г—В 10 5 birds have been present near Nantucket Island and the Nantucket Shoals since the 1970s, and there is evidence of some concentration there since the late 1800s.

Logtail ducm