From Courtney Thompson, Regional Park Ranger, Environment Canterbury
At the last update, I reported on a colony of around 1500 black-billed gulls that had set up behind McLeans Island. Unfortunately, this colony has now almost completely dispersed and we can fairly confidently say this was due to southern black-backed gull predation and harassment (the video below was taken by Steve Attwood Saturday 21 November – see his report).
I reported last time on a second colony that was forming near The Sanctuary wetland a little further downstream. This colony continued to grow and was at around 1000 adult birds at our last count, but unfortunately, the river came up at the end of last week and washed out roughly half the colony plus a group of white-fronted terns nesting nearby. We will continue to monitor this colony and trap predators along the adjacent riverbank as long as there are birds present.
This leaves our current main colony of several hundred black-billed gulls out from the end of Haul Road (see map).
There are also a good number of black-fronted terns nesting in close proximity. We have placed multiple signs as well as placing logs at the river access point in an attempt to funnel people naturally downstream and away from the colony. This colony was untouched by the recent rise in river levels, but with nor-west winds predicted to continue this week, we will keep monitoring the situation as the river is likely to come up slightly again. It may turn out that the black-billed gulls washed out from The Sanctuary join in with the Haul Road colony.
Southern black-backed gull control is on-going and we have a few operations planned for the next week or two to try and keep numbers under control, especially around the native breeding colonies.