One baby swan that was rescued with four others from the Charles River Esplanade Wednesday has died, officials said.
“Unfortunately, the one that had a foot injury did not make it,” said Zak Mertz, director of the New England Wildlife Centers’ Cape Cod branch, in a telephone interview Thursday afternoon.
The baby swans, or cygnets, were rescued after their parents were taken from the Esplanade Monday and euthanized after being suspected of bird flu.
The other four cygnets, Mertz said, are doing “reasonably well.” The cygnets were taken to the center by Boston Animal Control safely for assessment and care, officials said in a Facebook post Wednesday.
“Truthfully, when they came in, they were a little lethargic,” he said. “Losing a parent is hard. They were on their own for a little bit, and the stress of transport and getting to the facility can be hard.”
As of Thursday, the cygnets looked normal and were eating and alert, Mertz said.
“They were doing all the things they should be doing as little swans,” he said.
Mertz noted that caring for young waterfowl is challenging.
The cygnets were also tested for bird flu, and the preliminary results are negative, Mertz said. However, he said, they’ll still be isolated in a room away from other animals for an unknown amount of time.
“It’s important to note that wild swans can become debilitated for a number of reasons and we want to cover all our bases before drawing any conclusions,” the center said on Facebook.
The two adult swans, the cygnets’ parents, were taken from the Charles River Esplanade by an animal control officer Monday, who was aided by Boston firefighters, after multiple calls about the two sick swans, Mayor Michelle Wu’s office said in a statement Monday.
“Unfortunately the birds were quite ill, exhibiting symptoms consistent with Avian Influenza, and were humanely euthanized,” the office said in a statement.
In March, officials warned that bird flu had been detected in multiple parts of Massachusetts. The virus has become more of a concern recently amid an increase in reports of dead and dying seabirds, and officials suspect that highly pathogenic avian influenza is to blame. Hundreds of dead birds have recently been found on Martha’s Vineyard, for example.
Mertz said they’re still “cautiously optimistic” on the cygnets’ condition and will know more in the next couple of days.
“We’re proceeding with caution and we’ll be there every step of the way to help them along and try to get them back to the wild as soon as we can,” he said.
Material from prior Globe stories was used in this report. Emily Sweeney of the Globe staff contributed.