Thursday, January 20, 2022

High densities of water-birds at two New Zealand fresh-water urban lakes

TitleHigh densities of water-birds at two New Zealand fresh-water urban lakes
Publication TypeJournal Article
Year of Publication2018
AuthorsGill, BJ, West, RC
Type of ArticleFull article
Keywordsaquatic birds, biomass, density, Henley Lake, waterfowl, Western Springs Lake

We compared summer counts of water-birds (November–January, 2012–2016; mainly Anatidae, Phalacrocoracidae, Rallidae, Laridae) at 2 small, shallow, urban lakes set in parkland surroundings: Western Springs Lake (Auckland) and Henley Lake (Masterton), New Zealand. We recorded 25 species of water-birds; 17 at Western Springs Lake and 22 at Henley Lake, with 14 species in common. The average total densities (and biomasses) were 61 birds/ha (113 kg/ha) at Western Springs Lake, significantly higher than the 40 birds/ha (95 kg/ha) at Henley Lake. Ducks (Tadorninae, Anatinae) made the biggest single contribution to numbers at both lakes (40–60% of total water-bird density). Swans and geese (Anserinae) were less common than ducks but because they were heavier birds they accounted for 60–70% of total biomass, and were therefore the main consumers of food and producers of droppings. Introduced water-birds made up 60–70% of the density at both lakes, and 80–90% of the biomass, with no significant differences between lakes. The presence of some native species (in significantly greater total density and biomass at Western Springs Lake), and breeding of the endemic New Zealand scaup at both sites, illustrate the potential conservation value of New Zealand’s small urban lakes.

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