Bruce Mahalski, of Owhiro Bay, asks :-
Why have I found so many dead black-backed gulls (both adult and juvenile) on the beach at Owhiro Bay over the last two summer/autumn periods? The beach is well inside the local marine reserve. Last year I found about 20 dead birds and a similar number this year. What is killing these birds?
Graeme Taylor, a zoologist with the Department of Conservation, and Elizabeth Bell, an ecologist with Wildlife Management International Ltd, replied.
This species of gull is not protected under the Wildlife Act. These could be young birds that were reared in the local colonies and this is part of the normal post-breeding season attrition that happens in seabirds, especially after a successful breeding season. Some young seabirds fail to thrive and locate suitable food resources. These weaker birds end up dying and many wash up on local beaches.
Another possibility is these birds could be part of a gull management project carried out for various reasons. At times, some birds are poisoned to reduce numbers to manageable levels. That would include adult birds.
In one example of control needed on safety grounds, Wildlife Management International Ltd (WMIL) completes an annual contract for Wellington airport to control black-backed gull numbers near the airport to reduce the incidence of aircraft strikes.
WMIL monitors a number of sites (Wellington City and Petone shorelines, Miramar Peninsula, Palliser Spit, Pencarrow/Baring Head, Tapu-te-ranga and Siren Rocks) each year for the airport control, counting black-backed gull nests, breeding pairs and roosting or loafing adults, sub-adults or juveniles.
They have not been culling black-backed gulls for a number of years. The last culling operation on behalf of the airport was in 2003 (around Miramar Peninsula) and more specifically for Tapu-te-ranga was in 1998. Since then, on Tapu-te-ranga and Siren Rocks the black-backed gull nests have been counted and all eggs are pricked or more recently oiled, to reduce productivity.
It is possible that other agencies or individuals may be undertaking some level of black-backed gull control using poison at other locations for nuisance reasons.