Some Americans dread winter and, if they have the time and the means, will travel to warmer parts of the country to wait it out. Others enjoy the cold temperatures and can’t wait for the first snow. Most just adapt to the season, adding layers to keep them warm or staying indoors in front of a warm fire. Birds, it turns out, face the winter season similarly.

Many birds, about 340 species, do leave North America to winter in the tropical regions of Mexico, Central America, South America and the Caribbean. But plenty of birds remain here year round.

Look outside on a blustery winter day and you’ll still see songbirds flitting at feeders and ducks swimming in icy creeks. Nearly one million waterfowl fly to the Chesapeake region from northern breeding grounds each year. They find that the winters here suit them just fine. How do they do it?

Birds, like mammals, are warm-blooded, meaning they must maintain a constant body temperature as the temperature around them changes. To do this, they spend much of their time feeding so they can generate enough heat.

Meat-eating birds, like hawks and owls, may stay put if enough prey is available.

Birds that can switch from a primarily insect diet to a seed diet can stay put throughout the winter. And many people love to help them out. In fact, the 2011 National Survey of Fishing, Hunting and Wildlife-Associated Recreation found that more than 50 million Americans reported feeding wild birds around their home, making it the most popular wildlife watching activity.

But the available food is not enough. To survive severe weather, birds have developed adaptations.

One feature that sets birds apart from other animals is feathers. Birds’ bodies are covered with an outer layer of fairly stiff but flexible contour feathers and an under layer of fluffy down feathers. The contour feathers provide protection against wind, rain and snow. The down feathers act as a layer of insulation.

Tightly knit together and overlapping, feathers protect the skin and hold a layer of air over the bird’s body. Because birds control the position of their feathers through muscular movements, they are able to “puff” themselves up. By adjusting their feathers, birds create and trap larger pockets of warm air near their skin, enhancing insulation.

Many birds have an oil gland located at the base of their tail. Secreted oil is rubbed over the feathers with the beak or bill. This is known as preening. Preening creates a shield that helps block wind and repel water. Ducks, geese and swans can survive in water that is close to freezing because the amount of oil in their feathers makes them waterproof.

Waterfowl and other waterbirds also have a layer of fat that keeps them warm.

Anyone who has ever gone outside on a cold, windy day without a hat knows that uncovered body parts lose heat quickly. The same is true for birds. But they can adjust to this in several ways. Often birds will stand on one leg, tucking the other up among their feathers. Birds are also observed with their beaks tucked under their feathers. Smaller birds often drop on the ground to cover both legs with their fluffed up bodies.

To minimize heat loss from legs, the arteries and veins in legs of many birds lie in contact with each other and function to retain heat. Arterial blood leaves a bird’s core at body temperature while venous blood in the feet is cool. Heat is conducted from the warmer arteries to cooler veins.

Waterfowl have fleshy feet with little blood circulation so they are less sensitive to cold. Constricting blood vessels reduces the amount of blood flow to the feet at low temperatures. Thus the core temperature of a duck or gull standing on ice may be 104 degrees Fahrenheit but the temperature of their feet may be just above freezing.

Winter songbirds, waterbirds and waterfowl are often the only types of wildlife easily seen (and enjoyed) this time of year. Just imagine how the dull the landscape would be without these bright and hardy souls.

By Kathy Reshetiloff
Bay Journal News Service

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis. Distributed by Bay Journal News Service.

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Many Bay tributaries saw their weakest shad runs in years — perhaps ever — this spring as the silvery fish continues to struggle to make a comeback around the Chesapeake and along the East Coast.

Data show the James, York and Susquehanna rivers had their worst American shad spawning runs in recent history, and biologists say the cold winter, cool spring and a sudden warmup in the middle of the spawning run may have contributed to the poor showing.

“Catches, in general, were extremely low,” said Brian Watkins, a biologist with the Virginia Institute of Marine Science, which annually surveys the state’s major rivers. “What we kept hearing all up and down the coast was the same thing — poor. It wasn’t just a Chesapeake Bay thing.”

There were exceptions. The Potomac’s shad population continued its upward trajectory. And shad numbers in the adjacent Rappahannock River also showed hints of recovery.

But on the Susquehanna River — once the largest shad spawning river on the East Coast — the 8,341 shad lifted over the Conowingo Dam were the fewest since the multimillion dollar fish elevator began operating in 1997. That continued a steady decline in shad numbers since it reached a peak of 193,574 in 2001.

“It is like we are continuing to find a new bottom here,” said Josh Tryninewski, of the Pennsylvania Fish and Boat Commission’s anadromous fish restoration unit. “It is concerning.”

The James and York rivers had their lowest catch indices since 1998, when VIMS researchers began monitoring.

The preliminary James index, which estimates relative shad abundance, was 1.33 this year, well below the average of 6.4. The preliminary York index was 1.93 compared with the average of 5.74.

Neither the James nor the York have shown a long-term trend in the monitoring.

The story is better on the Rappahannock. Its preliminary index of 5.08 was the lowest since 2009, but above its average of 3.83 since 1998. “The Rappahannock has been showing a glimmer of hope over the years,” Watkins said.

The best news in the Bay continues to be in the Potomac, which has shown a steady increase in shad abundance since the late 1990s.This year, shad abundance continued to increase, hitting 133.1 percent of the restoration target, according to data collected by the Potomac River Fisheries Commission.

The river met its recovery goal in 2011, with shad returning to numbers not seen since the early 1950s — making it one of the few bright spots for American shad along the East Coast, where overall abundance is near an all-time low.

It’s unclear why the Potomac has fared so well. Jim Cummins, living resources director for the Interstate Commission on the Potomac River Basin, said several factors may have contributed.

A fish passage completed 15 years ago at Little Falls Dam near the District of Columbia opened about 10 miles of the river before Great Falls forms a natural barrier to upstream migration. That area might be especially important for spawning success, Cummins said, because it has a smaller population of minnows, which are major predators of shad eggs, than downstream areas.

Also, a return of underwater grass beds in the tidal fresh areas of the river may have helped by providing a refuge for young shad, Cummins said. And water quality in the river has generally improved.

“These recoveries are not caused by one thing,” Cummins said. “It is a combination of factors.”

Whatever the reason for the comeback, Martin Gary, director of the Potomac River Fisheries Commission, said there are no plans to open the river to harvests beyond current rules that allow fishermen to keep some shad caught as bycatch in the striped bass fishery. Gary said he would like to see clearer evidence of a Baywide recovery before that happens.

“As a manager, I don’t see this as a Potomac-specific issue,” he said. “I see it more as a Bay issue.”

Neither Maryland nor Delaware have programs to assess the spring shad run.

The poor shad run in most areas, coupled with unfavorable weather, also hurt shad stocking efforts. The late spring followed by a rapid warmup provided a narrow window to catch shad, and biologists said eggs from fish caught toward the end of that period, as the water warmed, were in poor condition.

“We had such cold weather, and then it heated up real fast,” said Chuck Stence, of the Maryland Department of Natural Resources anadromous fish program. “It doesn’t give you a whole lot of time to go out and catch your broodstock.”

The number of shad larvae stocked in the Choptank was low: 635,000. But that was offset in part by good survival in ponds at the hatchery where biologists rear larger shad, which have higher survival rates when stocked. They were able to stock 456,000 early juvenile shad, which were 30–45 days old, and 38,000 late juveniles, which were about 90 days old. Both of those numbers were similar to recent years.

In Delaware, 447,000 larvae were stocked in four locations on the Nanticoke and its tributaries, a bit less than their 500,000 average, said Johnny Moore, a fisheries biologist with the Delaware Department of Natural Resources and Environmental Control’s Division of Fisheries.

Just less than 2 million were stocked in the Susquehanna by the Pennsylvania Fish and Boat Commission, the fewest of any recent year. As many as 4.7 million had been stocked in the Bay’s largest tributary as recently as 2010.

The U.S. Fish and Wildlife Service and the Virginia Department of Game and Inland Fisheries stocked 3.5 million shad larvae in the James River, fewer than the river’s 5 million target.

Things were worse for the Pamunkey Indians, whose hatchery stocked less than 300,000 larvae on the Pamunkey River, a tributary to the York. Last year, it produced more than 2.1 million.

“It took us two weeks of fishing before we started even catching any shad,” said Glen Miles, who operates the tribe’s hatchery. “My dad was one of the fishermen. He said he hadn’t seen it this bad in 40 years.”

Still, even in a generally poor year, there were splashes of good news, even for stocking efforts. This was the third, and final, year of stocking river herring on Baltimore’s Patapsco River, and biologists said it was their best for stocking the fish.

Of the two river herring species, the DNR stocked 543,000 alewife larvae and 60,000 early juveniles, as well as 200,000 blueback herring larvae and 90,000 early juveniles. It also stocked more than 1 million hickory shad and 300,000 American shad into the urban waterway.

In addition, monitoring by the U.S. Fish and Wildlife Service found evidence of natural reproduction by blueback herring this spring. “My preconceived notion of the Patapsco was that it was too impaired from storm drain runoff and all the insults that it sees,” said Steve Minkkinen, who heads the USFWS Maryland Fisheries Resource Office. “It is nice to see that some anadromous species can still survive there.”

Shad and river herring are anadromous fish that spend most of their lives swimming along the coast but return to their native rivers to spawn. Once their numbers were staggering — stories from colonial times tell of migrations so dense that fish would be crushed by wagons crossing streams. For much of the 20th century, shad supported the most valuable commercial fishery in the Bay.

Decades of overfishing, dam construction, habitat destruction and pollution have reduced their numbers to a fraction of historic levels. Efforts around the Bay have sought to rebuild populations through stocking; the removal of dams and construction of other fish passages; and improved water quality, but populations have remained low.

Fishing for American shad and river herring is banned in most areas along the East Coast, and other conservation efforts have been ramped up in recent years.

In August, the U.S. Fish and Wildlife Service filed new comments seeking greater action by Exelon Corp., owner of the Conowingo Dam, to improve fish passage at the dam. Exelon is seeking a new multi-decade operating license for the 100-foot-high Susquehanna River dam from the Federal Energy Regulatory Commission.

Efforts are also under way to curb the bycatch of shad in other fisheries along the Atlantic coast. In June, the Mid-Atlantic Fishery Council, which regulates catches in waters more than 3 miles offshore, reduced the allowable shad and river bycatch from 89 metric tons to 82 metric tons in the Atlantic mackerel fishery.

By Karl Blankenship
Bay Journal News Service

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