Submission by Guardians of Pāuatahanui Inlet 26 July 2018
Greater Wellington Regional Council Proposed Pest Management Plan 2018
We endorse and support the list of proposed pests and the related methods set out in the proposed Strategy.
We submit that there should be two further additions to the Strategy:
1: Canada Geese; and
2: Agapanthus
Our reasons for these proposals are:
Canada Geese
Canada Geese have been a pest in the Pāuatahanui Inlet for some time. Their presence recurs every year and the numbers vary. But it’s not unusual to see 50 to 80 birds in the Inlet. Their diet includes short pasture grasses and herbaceous saltmarsh, together with sea grass. Their feeding habits strip plants. They are crowding out other, native birds. They roost in large numbers on the shoreline of the Inlet. They also produce large volumes of waste – up to half a kilo per bird per day which gets deposited on shoreline and near shore areas, as well as farmland.
In terms of management options, it seems that interfering with eggs and nests is only partially successful. Culling the birds seems to be a necessary option.
Proposal
We therefore consider that Canada Geese should be listed in the Pest Management Strategy and that the method of management should be sustained control including egg and nest interference and culling.
Supporting Information
The following 2013 commentary by Robin Chesterfield and Wanda Tate from the Pāuatahanui Reserve Committee sets out the problems affecting the Wildlife Reserve at the Eastern End of the Pāuatahanui Inlet:
“What exactly is the problem with Canada Geese?
Firstly, the food. The preferred food of Canada geese is short pasture grasses and herbaceous wetland plants. ‘The geese feed ravenously on the herbaceous saltmarsh plants that fringe the tidal area and just strip them,’ says Mrs Tate. ‘At times during the year we’ve seen groups of 20 to 30 birds on one of the Reserve tidal basins. We’re particularly concerned with their impact on a rare native plant called Mimulus repens or Maori musk.’
The voracious feeding habits of the Canada geese also seriously affect the food available for the Inlet’s native birds. The tidal basins are the feeding spots for waders including pied stilts, and their numbers are actively threatened by the loss of their food source. Kingfishers and herons are also affected, as they are unable to feed at prime locations when Canada geese are roosting in large numbers on the shorelines of the Pāuatahanui stream mouth.
The problem gets worse at the start of the breeding seasons when pairs are seeking safe nesting sites.
The key characteristics of a good nesting site are a plentiful food supply for the adult birds and quick easy access to a reliable waterway, since water is the safest environment for newly hatched goslings to escape to. Such sites are essential until the goslings fledge and then throughout the summer until the moult is over and the adult birds can fly again.
Suitable breeding and moulting sites are often quite limited in area and several pairs of geese will nest around the same site, with an average nest containing anything up to nine eggs. Bird expert and Chairman of Forest and Bird’s Pāuatahanui Wildlife Reserve Committee Robin Chesterfield notes that when the geese first nested in the Wildlife Reserve there were seven adult birds and 26 goslings roosting along about 15 metres of grassed track, feeding there and in the adjacent pond.
For the last few years a particular tidal basin in the Reserve has been the preferred nesting site for up to six Canada geese breeding pairs. Unfortunately this tidal basin is not only the main feeding ground for the native pied stilt but also its chief nesting site. The Canada geese are using the shell islands where the stilts normally nest as lookout posts and pushing the native birds out. ‘Their presence is endangering an important southern North Island pied stilt breeding colony,’ says Robin Chesterfield.
And finally, that awkward question of poo. Canada geese are large birds that eat a lot and produce a lot of waste – up to half a kilo per day per bird goes into the Inlet. It doesn’t take many birds concentrated into such a small area for 4-6 weeks to do a lot of damage. Public access tracks are fouled to the point where they become unusable, but it’s the muddying and fouling of the habitat used by the native birds that causes the most concern. ‘Herons, pied stilts, shovellers – they’re all being affected,’ says Wanda Tate.
So much for the problems. What about solutions? Research has been done into how best to control geese numbers, including into the effectiveness of intervening at the hatching stage. That has already been tried at the Reserve. ‘We had hoped that population control could be achieved by finding the nests and preventing the eggs from hatching but that hasn’t worked,’ says Wanda Tate. ‘We were quite optimistic when no goslings were hatched in the Reserve in 2013, but unfortunately late in the breeding season three pairs of geese that had raised clutches further afield brought their goslings into the Reserve so our efforts at controlling numbers at a specific vulnerable site were largely ineffective.’
In Canada and USA, where Canada geese are increasingly entering the ‘peri-urban’ (as opposed to wild) environment in damaging numbers, experience seems to indicate that interfering with breeding by addling or oiling eggs is not enough to offset the effect of the 20-30 year life expectancy of the geese.
An increase in total numbers of birds in the wider area will put even more pressure on current nesting and moulting sites. More destruction of the saltmarsh plants, more fouling of the Inlet and its edges and further intrusion into the habitat of the native birds would be inevitable. ‘Here at Forest and Bird Pāuatahanui we are conservationists, but conservation of our native bird and plant life requires immediate control of Canada geese numbers. We can’t let numbers just go on increasing. Future generations would never forgive us,’ says Wanda Tate.”
Agapanthus
Agapanthus is a weed plant that forms dense and expansive mats that are hard to eradicate. It has been bred because of its looks and flowers, but it tends to overpower and has led to the exclusion of other species, including native vegetation. It occupies increasing areas of land around the Porirua Harbour and adjacent to roads, reserves and walkways. It is also now invading and thriving on seashore areas around the Pāuatahanui Inlet.
Proposal
Agapanthus should be eradicated on all public areas (such as road berms, reserves and walkways), and the harbour foreshore. Its propagation and sale should be banned from garden centres. Information should be provided to property owners on the pest status of agapanthus and how to control it.
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