Syracuse.com - What's the real reason bald eagles congregate now on Onondaga Lake's south end?

[HuntingNY-News]

Actually, it's because of the large numbers of gizzard shad - a baitfish found in Onondaga Lake that reaches lengths of 10 to 14 inches as an adult.

The eye-opening number of bald eagles gathering at the south end of Onondaga Lake has attracted a lot of attention in recent weeks.

The majestic birds, sometimes more than two dozen at a time, sit in trees overlooking an area of open water that doesn't freeze over because of warm water being discharged into the lake by a pipe from the nearby Metropolitan Sewage Treatment plant.

The open water attracts other migrating waterfowl, including ducks and geese that feed on aquatic vegetation and other small aquatic creatures. During the late hunting season each year, the area attracts duck hunters - and more recently wildlife photographers.

But why are the eagles there in the first place? Is it because of the ducks and the geese? Do they depend on eating these migrating waterfowl to survive?

Actually, it's because of the large numbers of gizzard shad - a baitfish found in Onondaga Lake that reaches lengths of 10 to 14 inches as an adult.

David Lemon, regional fisheries manager for the state Department of Environmental Conservation's Cortland office, noted Onondaga Lake has large numbers of gizzard shad. He said Onondaga Lake, Oneida Lake and other local waterways are in "the northernmost extent of the fish's range."

Each winter, he said, the species experiences a large die-off, particularly the younger, more fragile fish. Onondaga Lake's gizzard shad are attracted to the warm, open water around the sewage discharge pipe because they're trying to survive.

Matt Frackelton, of Baldwinsville, a duck hunter and environmental scientist who frequents Onondaga Lake, said he often hunts the lake's south end. He said when the lake's water turns cold he's notices huge, thick schools "from the top of the surface to the bottom" of gizzard shad in the water around the discharge pipe area

He said whenever he drives his 14-foot duck hunting boat through that area during the cold months, "I actually hit them with the boat and my motor." He added that he doesn't hunt by the sewage discharge pipe.

Frackelton said he's noticed the eagles frequently feeding on the gizzard shad. But what about the ducks and geese?

"Eagles are opportunistic feeders. They will go after a duck that's hurt, or sick or that's been shot by a hunter and not retrieved fast enough," he said. "It's much easier for them to catch the shad, which are schooled up and stressed from the low temperature than it is to catch a healthy duck that can fly and dive to escape."

Frackelton's observation make perfect sense, said Lemon and Randy Jackson, senior research associate, and associate director at Cornell's Biological Field Station on Oneida Lake in Bridgeport.

"I've seen a lot of eagles on Oneida Lake," Jackson said. "Anytime I've seen one, the bird has had a fish in its mouth."

Lemon said he saw bald eagles gather around a water discharge pipe during the cold months of a utility company on the Susquehanna River near Johnson City, and also at a location on the lower Susquehanna in Maryland.

"Same thing. The warm water attracted the gizzard shad. I saw the eagles feeding on them left and right," he said.

Frackelton and others wonder if the gizzard shad are picking up excessive amounts of mercury and other contaminants from the lake - and thus poisoning the unsuspecting eagles that feed on them.

Gordon Patterson, a SUNY ESF professor whose expertise includes environmental and aquatic toxicology, said that's unikely, particularly with mercury. He said gizzard shad feed lower in the food chain with a diet that consists primarily of small aquatic invertebrates known as zooplankton.

"Consequently, they are less susceptible to the food web effects that tend to increase mercury bioaccumulation up the food web," he said. "Gizzard shad also tend to grow quite quickly, which can help dilute the extent of mercury accumulated in their tissues."

View the full article on The Syracuse Outdoors Blog