A spike in lead poisoning deaths among Wellington's resurgent kaka population is being investigated by researchers.



"Lead is a highly toxic heavy metal that is reported to have a sweet taste - especially to parrots,'' Zealandia conservation manager Raewyn Empson said.



Zealandia, Massey University and Wellington Zoo are looking at the recent increase in cases of lead poisoning in urban kaka populations around the capital.



"Kaka are extremely intelligent birds and they are known for their inquisitive nature. They will often chew on lead nails and flashings that are common on the roof fixtures of older houses," Ms Empson said.



One way residents can reduce the number of lead poisoning cases is by not feeding the birds.



"We have heard of large flocks of kaka arriving in some backyards to wait for their evening feeds and this is when they're getting their fix,'' Ms Empson said.



People who feed kaka are being urged to make sure their roof fixtures are not lead-based.



"One family near the sanctuary has removed the lead nails in their roof and replaced them with something less appealing for the kaka to chew on," Zealandia chief executive Hilary Beaton said.



"Obviously we don't expect everyone to do this, but this family's actions are a great example of taking charge and adapting to a city with such a strong urban bird population."



Veterinary staff from Wellington Zoo visited Zealandia on Friday to take blood samples from nine chicks in the sanctuary. These have been rushed to Massey University where they will be tested for lead concentrations.



Results are expected within the next few days.



Similar studies have been done in the South Island with the kaka's close relative, kea. Kea's notoriously inquisitive and destructive nature has also brought them into contact with hazards such as lead-based roof fixtures.



These studies gave baseline information on lead concentrations within the kea population, which prompted the removal of lead-based roofing from DOC's back country huts throughout the South Island.



Kaka are classified as Nationally Vulnerable by the Department of Conservation with numbers declining throughout the country.



Kaka had disappeared as a breeding species from Wellington by the end of the 19th century.



They were first released in the Zealandia in 2002 and Wellington Zoo has also contributed to this population.



Wellington is thought to be home to between 200 and 250 birds, not including un-banded birds and chicks hatched outside of the sanctuary.

Meanwhile, new research has found kaka, pukeko and red-billed gulls are the native bird species most likely to cause problems in cities in the future.



Larger, denser populations could magnify a range of problems such as noise, fouling or nesting, exceeding residents' tolerance levels and conflict, the Victoria University of Wellington Centre for Biodiversity and Restoration Ecology study found.



It compared native birds in cities around the world and found species with a broad diet were the most likely to cause conflict in urban areas.



"A broad diet allows the birds to take advantage of the wide variety of often novel foods in the urban environment, leading to population growth," researcher Dr Wayne Linklater said.



"Traditionally native birds haven't been a problem in New Zealand cities because most of them live in our forests or by the sea, but ironically the success of nature restoration projects in urban areas may well raise the chances of conflict as more birds re-colonise our cities."



Kaka are already damaging property in Wellington, especially trees, and have been found to target the city's Botanic Gardens wwhere trees had been stripped in the native parrots unceasing search for sap.