Toronto police are bringing reinforcements in an ongoing battle to rid their boathouse of winged invaders they say pose a threat to officers' — and possibly the public's — safety.

For years, the force's marine unit has struggled to deal with an infestation of barn swallows, which nest in the boathouse and leave it covered in droppings.

The birds are a protected species and cannot be disturbed during nesting season. Moving their nests requires permission from the provincial Ministry of Natural Resources.

In a letter to city officials last year, the Toronto Police Services Board called for prompt action on what it called an issue with "potential impacts on operational resources and public safety, as well as on the health and safety of members of the Marine Unit."

The infestation "necessitates costly cleaning operations and utilizes the resources of the unit unnecessarily," the letter said.

"It can also have an adverse effect on public safety as it can at times impede emergency response due to the need to remove bird feces from boats and equipment."

The droppings can also increase the risk of exposure to some diseases, it said.

Birds slated to stay for one more season

A new three-year project set to begin this month aims to find the birds a new home and discourage them from returning to their current nesting grounds, a spokeswoman for the city said.

Officers will have to deal with their unwelcome guests at least another season, however: the first year of the project consists mainly of consulting with experts and surveying the barn swallow population, Natasha Hinds Fitzsimmins said in an email.

Next year, an alternate nesting site will be set up within a kilometre of the boathouse, as laid out in the ministry's
requirements, she said.

Existing nests will also be removed and additional measures taken to deter the birds from returning, she said.

The last year will be spent surveying the birds to see how they respond to the change.

"The modifications to the nesting situation will need to be monitored year after year to determine the success of the nesting relocation and barn swallow population," Hinds Fitzsimmins said.

Closing the doors? That didn't work

In the meantime, she said, "the best course of action to reduce the chance of bird infestation has been and continues to be to keep the doors closed, especially during periods of bird migration."

Robert Duncan, a program co-ordinator for the Toronto police occupational health and safety unit, said that was "the first thing they looked at" but it didn't work.

"They're quite small birds and unfortunately because the water levels fluctuate the birds were just getting underneath the doors even when they're fully dropped," he said.

"The other problem, of course, is that because they're an emergency response unit, having the doors closed can slow down the response to an emergency call, so that's a public safety consideration we had to make."

He said police don't want to harm the birds, just evict them.