This Moose Jaw swan, and mate, must stay the summer at Regina's Wascana Lake, because of their territorial behaviour. (CBC)

Two swans that spend their winters in Regina will not be returning to their familiar summer nest in Moose Jaw's Crescent Park this summer.

Park authorities in Moose Jaw said the birds were becoming a problem and, since a small creek in the park needed maintenance anyway, the city decided to leave the swans in Regina for the season.

The problem with the swans, according to Moose Jaw Mayor Dale McBain, is that they could be aggressive toward other birds.

"There had been some calls from folks that had been down with their kids, wanting to feed the ducks and ... having the swans come in and interfere," McBain explained to CBC News on Thursday.

"They get a little territorial during mating season and when they have some cygnets, their little ones," McBain added. "So, this year we're not bringing them back."

McBain said the swans might even enjoy the summer in Regina, which has a larger body of water for them: Wascana Lake.

"We're giving them a time-out," McBain said. "And being in Regina and Wascana, it's a bigger lake, and it's more likely that they'll be away from other birds."

In Moose Jaw, the swans regularly nested in a spot near the Serpentine, a small creek that runs through Crescent Park.

That water is not there, this year, McBain explained.

"This year, we drained the water. We're doing some repairs on the lines that feed the Serpentine."

McBain said the swans could yet return.

"They may be back next year. We'll just have to evaluate that as we go along."

Moose Jaw parks officials told CBC News that the birds have had their wings clipped and are transported to and from Regina by city staff.