Correlation between Zebra Mussel <i>Dreissena polymorpha</i> biomass and biomass of all other food taxa in the digestive tracts of 32 Greater Scaup <i>Aythya marila</i> from the Odra River Estuary during the non-breeding seasons in the years 2008–2013.

<p>Each point represents a single bird.</p

Estimated smoothing functions modeling Greater Scaup <i>Aythya marila</i> abundance in relation to the area of occurrence of Zebra Mussel <i>Dreissena polymorpha</i> (km², left-hand panel– 5A) and Zebra Mussel density (tons per 1 km², right-hand panel– 5B) from the best-supported model.

<p>Shaded areas denote 95% confidence intervals around the smoothing functions.</p

Spatial distribution and abundance of Greater Scaup <i>Aythya marila</i>–mean number of individuals per 1 km² based on censuses in the non-breeding period (October to April, 2002–2014), see also Table 2.

<p>(A). Spatial distribution and biomass of Zebra Mussel <i>Dreissena polymorpha</i> on the 2x2 km modeling grid (B).</p

The study area—the Odra River Estuary, NW Poland, bordered by a bold line.

<p>The study area—the Odra River Estuary, NW Poland, bordered by a bold line.</p

Greater Scaup <i>Aythya marila</i> and its flocks in the Odra River Estuary.

<p>A—Scaup flock in the Miroszewo (MI) subarea, 16.10.2013, photo by D. Marchowski. B and E—part of a line of Scaup directly above the Zebra Mussel aggregation in the Miroszewo (MI) subarea, B—16.10.2013, E—09.10.2013, photo by D. Marchowski. C—adult male of Scaup, Pomeranian Bay near Świnoujście, 16.02.2014, photo by D. Kilon. D—Scaup females in the Pomeranian Bay near Świnoujście, 16.02.2014, photo by D. Kilon. F—part of a 30 000-strong flock of Scaup directly above the Zebra Mussel aggregation in the Krzecki Wyskok (KW) subarea, 16.10.2013, photo by D. Marchowski.</p