Diversity and abundance of water birds in a subarctic lake during three decades

Abstract

Klemetsen A and Knudsen R. 2013. Diversity and abundance of water birds in a subarctic lake during three decades. Fauna norvegica 33: 21-27.The numbers of divers, ducks, gulls, terns and waders in the 15 km 2 oligotrophic lake Takvatn, North Norway, were estimated six times during 1983-2012. Systematic mapping surveys were done by boat within the first week after the ice-break in June. Twenty-one species were observed over the years and 12 were regarded as breeding on the lake. Red-breasted merganser Mergus serrator was the dominant diving bird, with the estimated minimum number of breeding pairs varying from 15 to 39 among the years. Black-throated diver Gavia arctica (1-3 pairs), tufted duck Aythya fuligula (2-15 pairs) and common scoter Melanitta nigra (1-5 pairs) bred regularly, while velvet scoter Melanitta fusca (1-2) and goldeneye Bucephala clangula (2-4) were found in some years and mallard Anas platyrhynchos (1 pair) and wigeon Anas penelope (1 pair) in one year. Common gull Larus canus (6-30 pairs) and arctic tern Sterna paradisaea (2-35 pairs) bred in all years. Common sandpiper Tringa hypoleucos (3-9 pairs) and redshank Tringa totanus (1-4 pairs) were regular waders. Density variations of mergansers, gulls and terns are possibly related to density variations of threespine stickleback Gasterosteus aculeatus, their dominant fish prey. As predators and parasite hosts, the water birds are important links in the food web of the lake.

High parasite diversity in the amphipodGammarus lacustrisin a subarctic lake

“…The persistently high abundance and prevalence of Plagiorchis sp. (Table 1) are likely related to the relatively rich and stable aquatic bird community (Klemetsen & Knudsen, 2013), the putative final hosts for Plagiorchis sp. in Takvatn, and also the high abundance of its first intermediate snail host R. balthica (Klemetsen & Elliott, 2010), as final host diversity and abundance can drive abundance and diversity in larval trematode communities in intermediate host snails (Hechinger & Lafferty, 2005).…”

“…4–8°C). To obtain a broader range of parasite diversity in G. lacustris in the lake, gammarids were collected from five sites (L1‐L5), including two in the vicinity of an important nesting area for birds (L4 and L5; Klemetsen & Knudsen, 2013). Sampling was carried out over three years during different times of the ice‐free period (August and October 2012, June and September 2013, and August 2015).…”

Fish culling reduces tapeworm burden in Arctic charr by increasing parasite mortality rather than by reducing density‐dependent transmission

“…This parasite might have been able to persist by infecting sticklebacks (Kuhn et al, 2015). Red-breasted mergansers, the final hosts of D. ditremus, tripled in abundance from 1983 to 1992, probably in response to increases in stickleback numbers (Klemetsen & Knudsen, 2013;Klemetsen et al, 2002) that red-breasted mergansers prefer to eat (Gardarsson & Einarsson, 2002). The unexpected initial increase in D. ditremus per charr could also have been caused by increased consumption rates on copepods or sticklebacks in the remaining charr (Amundsen, 1989(Amundsen, , 1994Amundsen et al, 2007).…”

Effects of fish species composition on Diphyllobothrium spp. infections in brown trout – is three‐spined stickleback a key species?

“…This probably also applies to the potential final bird hosts of Diphyllobothrium spp. that commonly occur in northern Norwegian lakes (Klemetsen & Knudsen ). The occurrence and abundance of sticklebacks may suggestively influence the presence of fish‐eating birds at a lake (Klemetsen & Knudsen ).…”

“…that commonly occur in northern Norwegian lakes (Klemetsen & Knudsen ). The occurrence and abundance of sticklebacks may suggestively influence the presence of fish‐eating birds at a lake (Klemetsen & Knudsen ). Fish‐foraging by birds will therefore assumedly take place more frequently in lakes where sticklebacks are present, which may cause an overall increase in the occurrence of Diphyllobothrium spp.…”