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Newton swan takes wing after lead poisoning

The New England Wildlife Center
The Newton swan was relocated to the Foundry Water Reservoir in Hingham, where it seems to get along with its feathered peers.

A sickly swan rescued in Newton is back on its webbed feet after weeks of being treated for lead poisoning.

The swan was spotted on the Charles River near California Avenue in late November, acting oddly lethargic. A call from a passerby led the Animal Rescue League of Boston to capture it and send it to the New England Wildlife Center in South Weymouth for treatment.

“The fact that an animal is able to be caught in the first place is a sign that it’s not doing well,” said Dr. Gregory Mertz, chief executive officer of the wildlife center. “This swan had dangerous levels of lead in its system when it came in.”

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A lead level above 10 micrograms per deciliter of blood is considered toxic, Mertz said. The Newton swan had a reading of 13 micrograms per deciliter. A normal level is zero.

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The Newton swan was finally released Feb. 1, but three others — from Quincy, Marblehead, and Framingham — are also being treated at the center. Although only one has been diagnosed with toxic levels of lead, all three had lead in their systems.

Some animals come in with lead levels as high as 65 micrograms per deciliter. It’s a problem that Mertz said is becoming increasingly common among local waterfowl.

Hundreds of years of hunting with lead bullets and fishing with lead weights has caused lead to build up in the sediment of ponds and other waterways in the Boston area.

Water birds that look for food at the bottom of ponds ingest particles of lead, which eventually gets into their bloodstreams. The toxin builds up and causes negative neurological and physical effects.

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The Newton swan was suffering from kidney problems and weight loss due to lead poisoning when it was brought into the wildlife center. It also had trouble balancing and flying.

“There’s not a pond you can go to in this area that you don’t see ducks or geese or swans. I would estimate that over the past 25 years the swan population alone has increased to almost 20,000” in the southern New England area, Mertz said. “Of those animals, I would say 50 percent are suffering from lead poisoning.”

The Newton swan was diagnosed quickly after a blood sample was taken to determine its level of lead exposure. The swan was then given calcium EDTA to draw the lead out of its system.

This process can be harsh on a swan’s already damaged kidneys, so the center also provides fluids and vitamins for nutritional support. Afterward, the gastrointestinal tract needs to be repopulated with good bacteria to help with digestion.

Dozens of lead poisoned animals undergo this process every year, but it is time consuming and expensive, and about half of the animals are saved.According to the center, 50 to 75 percent of the waterfowl they treat annually have some level of lead poisoning.

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The center diagnoses lead poisoning using CDC guidelines for humans, but because tolerance for lead exposure can vary among species, the veterinarians always consider physical symptoms such as weakness, seizures, vomiting, and weight loss in addition to blood tests and radiographs.

Luckily, the Newton swan was able to recover and has been returned to the wild. Typically the center releases swans back to where they came from to reunited them with their mates, but the Newton swan had been attacked by a larger, territorial swan at its old home.

Instead, it has been relocated to the Foundry Water Reservoir in Hingham.

“This is a good swan habitat. The water wasn’t frozen over and it wasn’t already occupied by other swans,” Mertz said. “It took the swan took some time to rehabilitate, but releasing it has been successful.”

Zipporah Osei can be reached at zipporah.osei@globe.com