Wellington birds are showing their true colours after the airport has had them painted in a project to monitor birdstrike.

Hundreds of gulls painted in shades or orange, blue and green are now flying above Wellington.

Wellington Airport organised for the black-backed gulls found in the region's landfills to be painted so they could be tracked to see how they contributed to birdstrike.

Head of operations Matt Palliser said the favourable weather enabled the birds to be spray-painted at the Southern, Spicer (Porirua) and Silverstream landfills.

"If it's applied correctly and we've got the right conditions, they will be bright blue, bright apple green and bright orange."

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KEVIN STENT/STUFF Southern Landfill operations manager Darren Hoskins sends the orange paint out into the sky.

At Spicer and Silverstream, they had already painted about 400-600 birds, and at the Southern Landfill about 200, he said.

Painting started on Monday and may continue until next week.

To prepare the birds for their new, coloured finery, gulls at the landfills had been sprayed with water.

The food grade-quality dye used was not harmful to the birds or the environment and is designed to wash off after two to four weeks.

Members of the public have been asked to contribute to the study by reporting sightings of the coloured gulls on Wellington Airport's website.

KEVIN STENT/STUFF The food grade-quality dye used is not harmful to the birds or the environment and is designed to wash off after two to four weeks.

The study, believed to be the first of its kind in New Zealand, will also help track birds' nesting and migrating movement patterns, subsequently tracked by GPS.

Southern black-backed gulls - one of only two native bird species not protected by the Wildlife Act - are known for posing a threat to aircraft taking off and landing.

KENVIN STENT/STUFF At the Southern Landfill orange paint is being used, apple green at Spicer in Porirua and blue at Silverstream.