LWWWS recently had a report on swan numbers from Fish and Game manager Ian Hadland. Fish & Game Otago have been monitoring Black swan numbers at Lakes Waihola and Waipori for at least the last 20 years. The high summer aerial count is done in conjunction with the paradise shelduck moult count flight.
The data shows a highly variable population and this is largely explained by the fact that they are a transient bird which tends to use a number of lakes and estuaries across Otago and Southland. Due to the low number shot each hunting season (under 1000 Otago wide) it is not thought that hunter harvest of them has a big influence on their numbers. Even the organized hunt which took place in 1999 on Lake Waihola (where around 900 were shot) failed to have any long-term impact. The population seemingly bounced back and bubbled along somewhere between 1000 and 2500 birds. Variation aside, the data suggests a sustainable population and not one which is surging as some people suggest.
Black Swan do appear to be taking better advantage of nearby pastures though and that is making them more visible and is causing concern to landowners. Some may argue that sharing a lakeside property with a bit of wildlife comes with the territory. Others are less sympathetic and want to know why swan grazing habits have changed. One suggestion is that the swan, who’s main diet is lake weed, preys upon high quality pastures in the early spring when the aquatic vegetation has been eaten out. This may not be a swan numbers issue – it could be related to water quality or clarity. Whatever the reason, when the water temperatures warm up and the lake weed regrows, they do tend to return to lake grazing.
Posted in Biodiversity, Clutha District, Conservation, New Zealand, Otago, Waihola, Waipori, Wetlands
Tagged Biodiversity, Black Swans, Clutha District, Community Initiatives, Conservation, Fish and Game, Habitat restoration, LWWWS, New Zealand, Otago, Water Quality, Wetland