Two kayakers scared hundreds of migratory birds at Yukon's Swan Haven on Saturday as they paddled down the middle of the bird sanctuary and set up a campfire.
Many birds flew away, while others retreated to the lake ice.
That's concerning to biologists.
Scott Cameron, wildlife viewing technician with Environment Yukon, says the birds rely on the the ice-free water of M'Clintock Bay in Marsh Lake as a place to feed and rest.
"A lot of these birds have migrated from southern British Columbia or even Washington State or California. They've migrated a long way; they're tired. Their fat reserves have been depleted."
Trumpeter swans can migrate more than 3,000 kilometres.
Cameron says each bird typically stops a few days at Swan Haven before flying towards breeding grounds in northern Yukon and Alaska.
About 1,200 birds were at the haven over the weekend, before the kayakers arrived.
"When people disturb them, they stop feeding. They also burn additional energy by flying around. By burning extra energy and not feeding, it's putting additional stress on the birds. They still need to migrate north and successfully breed. The more we stress and disturb them, the lesser the chances of that happening successfully," Cameron said.
Trumpeter swans are considered "specially protected" under Yukon's Wildlife Act.
North American swan populations were almost decimated in the late 1800s due to overhunting and international demand for swan feathers. Wildlife conservation and reintroduction efforts since then have helped bring the population back to about 50,000 birds in recent decades.
CBC Yukon contacted conservation officers to find out if they are considering charges against the kayakers, but has not heard back.
Paddlers required help from RCMP
The two kayakers stayed near the swans for about five hours. They were about one kilometre from the interpretive site and viewing platform which welcomes tourists to watch the birds at a distance.
After a few hours the men tried to leave, but they appeared to be having some troubles.
"The two people had returned to their kayaks and our contractor who operates the facilities on the weekends noticed them having some trouble," Cameron said.
"They seemed to be in some distress. Given the time of year and water temperatures, we decided to call 911 and report that."
Local RCMP helped the men get back to shore .
Cameron doesn't know if the men live in Yukon or were visiting.
Signage there, but not everyone abides
It's not the first time people have disturbed the birds at the haven. Environment Yukon has installed signs at rest stops along the Alaska Highway asking people not to approach birds during April.
"The message has been really constant. Unfortunately not everyone gets it or maybe not everyone adheres to it," Cameron said.