Environmental group Forest and Bird say the effects of the oil spill from a grounded container ship off Tauranga are reaching bird colonies as far north as Whangarei.
Beaches in the Bay of Plenty including Papamoa and Mount Maunganui have been closed as experts continue to clean up toxic oil that has washed ashore since Monday.
Some 500 birds have died from the spill, while 70 birds including 13 rare dotterels and four seals are being treated at the wildlife recovery centre in Tauranga, Maritime New Zealand says.
However, a spokesperson for Forest and Bird says the list of wildlife being treated is growing by the day.
Al Fleming says breeds of birds that visit the Whangarei area from hundreds of kilometres away, including types of albatross, are known to have become victims of the oil pollution.
Mr Fleming says Buller's shearwaters, which only breed on the Poor Knights Islands near Whanagrei, have also been affected.
Maritime New Zealand says people should report dead birds, so a wildlife team can collect and examine them.
