Comparison of bivalve communities between moulting and wintering areas used by Common Scoter Melanitta nigra in the German North Sea

• Published in: Estuarine, Coastal and Shelf Science
• Main Authors: Kottsieper, Johanna, Schückel, Ulrike, Schwemmer, Philipp, Fox, Anthony David, Garthe, Stefan
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Benthos; Environmental factors; Marine birds; Marine ecology; Seaduck diet; Melanitta nigra
• Online Access: https://pure.au.dk/portal/da/publications/comparison-of-bivalve-communities-between-moulting-and-wintering-areas-used-by-common-scoter-melanitta-nigra-in-the-german-north-sea(7c3b194b-3cf7-4760-95cd-73dda4c01e9b).html; https://doi.org/10.1016/j.ecss.2019.106398

The Common Scoter (Melanitta nigra) is a common sea duck, which predominantly feeds on sedentary benthic bivalve prey and occurs in large late-summer moulting concentrations in the German North Sea in areas which differ from those used by later wintering concentrations. Assuming scoters distribute in response to prey accessibility, abundance and profitability, we hypothesis that their contrasting distribution during moult compared to winter potentially reflects differences in prey type and distribution. We compared benthic bivalve community composition, abundance, ash-free dry mass and flesh-to-shell ratios between both areas to investigate factors influencing the seasonal difference in areas used by scoters. The American Razor Clam (Ensis leei) was the most common bivalve in the moulting area (mean abundance 1004 ± 1681 ind. m −2 , mean ± SD) with the highest flesh-to-shell ratio (0.341 g m −2 ± 0.729 g m −2 ), whereas the American Piddock (Petricolaria pholadiformis) showed the highest ash-free dry mass (0.635 g m −2 ± 0.392 g m −2 ). In the wintering area, the most common bivalve was the Bean-like Tellin (Fabulina fabula, 13 ± 17 ind. m −2 ), Spisula solida had the highest ash-free dry mass (1.639 g m −2 ± 1.262 g m −2 ) and F. fabula and Abra alba had the highest flesh-to-shell ratios. Overall benthic species community composition differed considerably between moulting and wintering areas, with fewer species and lower abundances in the wintering area. The high abundance and food quality (flesh-to-shell ratio) of E. leei (an invasive alien to the German North Sea since the 1980s) in the moulting area suggests its relative importance and potentially explains the seasonal differences of Common Scoter distributions.