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Failure to Fly

Osprey chick population at a record low

You can see the tag on the left leg of the unfledged male osprey.

May on the Patuxent River — Weeks of harsh weather and rain hammer a lonely tower, resolute like a final soldier in battle. A mother osprey braces in her nest, doing everything she can to protect her offspring. Little does she know, it is too late. No chicks will hatch in her nest this year, and she and her mate will have a ­lonely summer on the river.

This season has not been kind to osprey, but at first glance, you wouldn’t know it.

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When I accompanied Greg Kearns on an osprey-tagging trip, nothing about the sunny July day seemed amiss.

Jetting about the Patuxent River in a motorboat with a makeshift osprey research sign duct-taped to the side, I joined a team of eight researchers, checking every osprey tower within a 10-mile radius of Brooms Island.

From our boat, it was difficult to see the near full-grown osprey chicks, flat in their nests above the water. Harder still, as we’d come to find, because nest after nest was empty.

“This is unusual,” said Kearns, naturalist and environmental educator at Patuxent River Park. “Normally we’re tagging dozens of chicks in a day.”

That day, after eight hours on the river, we checked more than 100 nests — and tagged only 18 chicks.

Tagging the birds was surprisingly easy. Armed with a ladder, tagging equipment and an eager crew, we approached the nests over the water. Kearns steered the boat as close as he could, and using a line, we tied the boat to the posts.

One of the researchers climbed the ladder, reached into the tire-sized nest and grabbed the chicks by the talons. With careful hands, he passed them down to us for tagging and weighing.

It was a windy day, and at times the boat rocked perilously side to side. But we couldn’t wait for better weather to tag these birds. As Kearns explains, osprey follow a seasonal pattern that makes timing crucial.

Parents lay their eggs in the early spring. Hatching begins around May. Newly hatched chicks fit easily in the palm of your hand. At six weeks, they are big fluffy birds almost the size of their parents. At eight weeks, they can fly.

Kearns tags the chicks just before they are mature enough to fly away. That way, the tags, like metal bracelets, fit easily around the birds’ feet without sliding over the claws. Go out too early, and the tags won’t fit. Wait too long, and the birds will fly away.

At six weeks, the unfledged chicks lay flat in their nest, playing dead as we advanced. Ferocious as they look head-on, here they are helpless. Despite their deadly talons, they will not attack.

Protecting the Species

Folks on the river get defensive about osprey. More than once, residents approached us from their docks to watch. Some were hostile, but their attitudes changed when they saw what we were doing.

Mostly, people wanted to know why Kearns tags the birds.

“I’m leaving behind a very detailed collection of data showing a long-term print — more than 40 years,” he said.

Kearns has been in charge of the project for most of those 40 years, having taken over after the founder, Steve Cardano, retired.

“Tagging birds is going to leave behind a legacy of information for researchers,” Kearns says. “Ten years from now, if the population keeps going down, they’ll be able to look back and see when it began.”

But Kearns hopes the population will rebound. There’s no telling whether this year will be an outlier or the start of a devastating trend.

Kearns is not even sure what caused so many nests to fail, but he has a hunch.

 

“My belief is that it coincides with the weather,” he says. “In May, during critical hatch time, we had a long period of cold and rainy weather. If a mother gets agitated and gets off her nest, her eggs are ruined.”

Other possibilities are predation, disease and declining food supply. While the nests, in towers over the water, are safe from raccoons and other land predators, they still must contend with aerial foes.

Great horned owls pose the biggest threat to osprey, plucking chicks from their nests like apples from a barrel. Kearns says between 10 and 15 percent of chicks fall prey to owls each year.

Kearns speculates that increased boat traffic might also have been a factor in the ospreys’ poor luck. Any disturbance might cause a mother to temporarily flee her nest, leaving the eggs exposed.

Interestingly, the osprey fared worst in the more open parts of the river. In Jug Bay and other narrow parks downstream, the birds’ success rates were higher.

Still, when Kearns is used to seeing 75 percent or more of nests with healthy chicks in the summer, the 50 percent success rate of Jug Bay seems like failure.

In total, 107 chicks have been accounted for this year. In previous years, that number exceeded 200.

Time will tell if the numbers will rise again. Next year, you can join the osprey saga. Every June and July, Kearns takes up to 450 citizens out on the water to see the beloved birds up close.

“I try to accommodate everyone,” he says. “It’s important to get people excited about nature. When they’re out there getting their hands on a bird, it’s a totally unique experience.”

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Throughout August, the newly fledged chicks will soar over the waters of the Chesapeake and its rivers, practicing independence. Some time during these weeks, their parents will wean them. After six weeks or so flying and fishing, their migratory clocks will go off, urging them on an overland and water-journey of thousands of miles. These chicks are the hope of the species.

While there seems to be a lack of chicks in the Brooms Island area, here in the Sparrows Point area (North Point Peninsula), I am seeing quite a surplus. I have been watching 9 nests within a 5-6 square mile area and almost all of the nests have an average of 2 chicks each (one has a single chick, most have two chicks, and I believe that one has three chicks). I've been excited to watch these nests prosper this year. I had reported on the success of three nests last year to the Chesapeake Conservancy, and am thrilled that their numbers appear to be growing in this area.