Colossal flocks of blackbirds are a common wintertime phenomenon in Delaware

December 8, 2011 under CANR News

If your holiday shopping takes you to Christiana Mall, time your drive for a half hour before sunset. That’s when you’re most likely to see a massive flock of black birds winging its way to Churchmans Marsh.

This flock of several million birds forms a solid black carpet in the sky; if it was earlier in the day, when the sun is higher, the flock would blot it from view.  The mixed flock consists of true blackbirds (red-winged, specifically) but also common grackles, brown-headed cowbirds and starlings.

“It’s an amazing spectacle,” says Derek Stoner, past president of the Delmarva Ornithological Society. “The sky is filled with birds returning to roost in the marsh after a day of feeding. You get the very best views of this super flock around the intersection of Route 7 and Churchmans Road — as long as you time it right.”

A flock of blackbirds so colossal that they block the sun sounds like something straight out of Hitchcock’s thriller, The Birds, but it’s a common wintertime phenomenon in Delaware.

“The unique combination of Delaware’s marshes and the surrounding agricultural lands are what make the state an attractive winter residence for millions of blackbirds,” says Chris Williams, a University of Delaware associate professor of wildlife ecology. “You’ll also see this winter flock phenomenon in New Jersey, coastal Virginia and North Carolina, and other coastal regions in the South.”

The Churchmans flock is one of about a dozen winter flocks in Delaware, according to Williams. Each morning the flock splits up and disperses in search of food, including such things as corn stubble or seedy grass. Depending on food availability, the Churchmans flock may travel to Chester County, Pa., or as far as Lancaster before returning to its nightly roost in the marsh.

Blackbirds only form super flocks in winter, says Williams. By March, the flocks will disperse to set up nests and begin breeding. Some of the birds in the super flocks are year-long Delaware residents; others migrate here from Canada and other northern latitudes.

As to why a bird would decide to hang out with millions of other birds each winter, scientists have several theories, says Williams. One possible reason is that a flock provides better protection from predators. Each bird in a massive-size flock doesn’t have to be quite as vigilant as it would be if it was flying solo.

A large flock also creates the conditions for “predator confusion.” For the same reason that fish swim in schools, birds fly in flocks. It can be difficult for a predator to pick out individual prey in large groups. “All the birds massed together create sensory overload for the predator,” notes Williams.

In addition, the dilution effect occurs when there is a large flock. Simply put, this means that the mathematical odds that a bird will get eaten are smaller when the flock is larger.

A large flock also promotes greater feeding efficiency because the birds share information about food sources. “Blackbirds are known to be great communicators,” says Williams.

Although Williams is awed by the Churchmans flock as it wings its way over his Newark neighborhood, heading out for food, he dreads the inevitable February day when 20 or 30 birds will drop down from the flock and take up residency in his backyard.

“I keep feeders up all winter long and enjoy seeing a variety of birds at the feeders,” says Williams. “But all of sudden, in February, a small group of blackbirds will break off from the large flock overhead, descend on my feeders and eat all the seed in minutes.”

“Even if I take the feeders down, the birds stick around,” adds Williams. “Blackbirds in the backyard are a sure sign it’s mid-winter.”

Article by Margo McDonough

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Ducks in the dark

June 14, 2011 under CANR News

Orrin Jones is doing field work using night-vision riflescopes to study the behavior of the American black duck.

Chris Williams and his University of Delaware research team employ standard tools of the trade for waterfowl research – core drills for core sampling, binoculars for waterfowl viewing and lots of coffee for long stints in duck blinds. But Williams may be the first wildlife biologist to use apparatus more commonly seen on the battlefield – night-vision riflescopes.

Williams, associate professor of wildlife ecology in the College of Agriculture and Natural Resources, is studying the behavior of the American black duck to determine if there are adequate food resources on the Mid-Atlantic coast to support this dabbling duck, which has been identified as a “species of concern” by the U.S. Fish and Wildlife Service.

Although there’s lots of data on the daytime behaviors of the black duck, up until now no one had a good idea what it was up to at night.

“We were aware that the American black duck isn’t exclusively diurnal because of anecdotal knowledge about its nighttime calls,” says Williams. “But we didn’t know the extent of its nocturnal activities because we didn’t have the tools to study this.”

Until recently, night-vision technology wouldn’t have been up to the challenge of detecting subtle movements in the dark-colored (and aptly named) black duck, which is just 13 to 19 inches in height. But night-vision technology has improved dramatically since the military began using it extensively during the Iraq war. The latest devices can amplify light up to 50,000 times, producing clear images even on moonless nights.

It’s critical for Williams to know what black ducks do at night, as well as during the day, so he can accurately determine how much energy the birds expend. With this data, Williams and his research team will be able to establish an area’s “carrying capacity,” the number of birds a habitat can support.

“Habitat loss is a threat to the American black duck,” notes Williams. “Nationwide, black ducks have declined by as much as 60 percent. We need to understand the carrying capacity for the black duck so we can make appropriate land management decisions.”

Graduate student Orrin Jones led the field research for the project, which took place in Edwin B. Forsyth National Wildlife Refuge, six miles north of Atlantic City.  American black ducks overwinter on the Jersey shore, as well as refuges and open land on Delaware’s coast, from November through March.

Field work is never a piece of cake but the black duck project could have qualified for that old reality show America’s Toughest Jobs. Jones, graduate student Jeremiah Heise (who is studying the Atlantic brant but helped with the duck research) and four technicians divvied up round-the-clock shifts, five days a week.

Because it was important to study the duck’s behaviors in a variety of habitat, from high marsh to mud flats, some study sites were only reachable by boat. After 15-minute paddles in a canoe or hour-long motor boat rides, Jones would settle in for the 9 p.m. to 3 a.m. shift and painstakingly record each time a duck swam, flew or preened. Weather ran the gamut – the infrequent mild spell, but more often, cold, rain, snow or outright blizzard conditions.

“We only missed one day of observation, during the 2010 Super Bowl blizzard, because the snow was too deep even using our 4×4 work trucks,” he says.

But for Jones field work is a piece of cake compared to what this summer holds – hour after hour inside a climate-controlled laboratory, where Williams’ research team is cataloging how much energy was available in the marsh core samples.

Working in the laboratory as part of the black duck research are Zariel Johnson, Alexandra Joesten, Amanda Dunbar and Marissa Goldstein.

“I enjoy the challenges of rugged field work; it’s one of the reasons I got into avian research,” says Jones. “It’s going to be hard to be stuck inside.”

Hard but necessary. It takes about 64 hours in the lab to analyze data from each quadrant of marsh studied, estimates Williams. All told, that’s 8,000 hours of lab work for Williams’ research team.

“The American black duck was once one of the more abundant waterfowl species in eastern North America,” says Williams. “I hope this research gives us a much better understanding of the black duck’s habitat needs.”

Article by Margo McDonough

Photos by Danielle Quigley

View this article online on UDaily by clicking here.

 

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Study to quantify turbine impact on birds and bats

March 7, 2011 under CANR News

A study will quantify the impact of the wind turbine at UD's Hugh R. Sharp Campus in Lewes on birds and bats.

The University of Delaware’s 2-megawatt wind turbine is the site of new research that will help answer a common question about the alternative energy producers: How do they affect birds and bats?

The two-year project, which will assess the mortality risk of birds and bats around the turbine, is led by UD Department of Entomology and Wildlife Ecology researchers Jeffrey Buler and Gregory Shriver. It is funded by First State Marine Wind, a partnership between UD-owned Blue Hen Wind and turbine manufacturer Gamesa. The Delaware Department of Natural Resources and Environmental Control (DNREC) also committed funds to support the effort.

A complementary project at the wind turbine that focuses solely on bats is being conducted by an expert at Delaware State University and is funded by the Maryland Department of Natural Resources.

While a University-commissioned pre-construction study found that the turbine’s impacts on birds are likely to be minimal, that study also recommended that UD undertake post-construction monitoring. One motivating factor is the machine’s location at UD’s Hugh R. Sharp Campus in Lewes, which sits along an important international flyway stopover for migrating birds. UD and Gamesa thus placed a priority on this research once the turbine was up and running (it began producing power in summer 2010).

The research also fulfills UD obligations under the federal National Environmental Policy Act. UD has been working closely with U.S. Fish and Wildlife Service, DNREC and other stakeholders on the scope of the study.

“The results of the study will be useful for other coastal communities considering wind turbines and ought to provide some useful lessons for offshore wind energy projects,” said Jeremy Firestone, associate professor of marine policy. Firestone is a wind energy expert and faculty member in UD’s College of Earth, Ocean, and Environment (CEOE) and CEOE’s Center for Carbon-free Power Integration (CCPI).

The UD project began March 1, with spring and fall sampling periods focusing on birds and bats migrating through the area and summer and winter periods on resident bird and bat flight activity.

During each of the four seasons, the researchers will use a variety of techniques to collect data. Acoustic monitoring, visual surveys, radar, and thermal imaging will provide information on bird and bat traffic and flight patterns. Spring and fall carcass searches around the turbine will help determine the fatality rate.

Local and regional weather data, which will help researchers understand bird and bat movement, will be provided by a nearby meteorological tower and the National Weather Service.

“We want to monitor how much bird and bat activity there is in the vicinity of the turbine so we have a context for how much risk there may be for them to collide with the turbine,” said Buler, who specializes in using radar to track bird migration.

The scientists also want to know which birds and bats are moving through the area. Although the main focus is on migrating land birds and bats, other types of birds also occur near the turbine throughout the year. These include raptors, waterfowl, marsh birds, and shorebirds.

The team expects to have a final report of data and analysis completed by December 2013. They will present findings at technical meetings and publish them in scientific journals. The researchers also will share their bat data with Delaware State’s Kevina Vulinec, an expert on the winged mammals whose research looks to determine the type of bats around the turbine and their behavior.

“We are pleased by the collaboration with Delaware State University,” Firestone said. “These research projects are a prime example of how the UD wind turbine can serve as a platform for important research that will benefit society.”

Article by Elizabeth Boyle
Photo by Kathy F. Atkinson

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Wild animals cope with harsh winter weather

February 10, 2011 under CANR News

Humans may whine about the harsh weather but for most of us winter isn’t a matter of life or death. For many wild animals and birds, the stress of winter is life-threatening. Wild animals and birds must contend not only with extreme weather but with a lack of food and other resources, such as adequate shelter.

Winter adaptations vary by species. Some species migrate, some go into dormancy and some develop a thick skin and tough it out. The thick skin is literal — from the bushy cold-weather undercoat of the fox to the thick winter coat of the raccoon.

Many birds adapt to winter by getting the heck out of here. About half of Delaware’s common summer birds are migratory and depart for warmer climes each autumn, according to Chris Williams, a UD assistant professor of wildlife ecology in the College of Agriculture and Natural Resources.

The birds that do stick around Delaware often form flocks in the winter, comprised of members of the same species, or sometimes flocks of different species (known as mixed flocks). Common mixed flocks include small birds, like chickadees and titmice, which join larger birds, such as nuthatches and woodpeckers.

Flocking is a form of cooperative behavior that rarely occurs during spring and summer nesting season. Williams says that flocking can increase wintertime avian survival rates. Flocks have an easier time securing food since birds are foraging together. And when flocks roost together, heat loss is reduced. Flocking also can provide safety in numbers from predators.

Birds utilize a number of other survival strategies in winter, such as fluffing their plumage, which creates an insulating layer by trapping air. They cope with the cold by shivering, just like we do. And many species increase their metabolic rate to produce more body heat. The downside of this adaptation is that they need to eat more food, even though food supplies are limited.

A handful of species lower their metabolism, but only in the evening when food isn’t available. These birds enter a state called torpor, which causes lowered body temperature and decreased oxygen consumption.

Plenty of mammals also slow their metabolic rate in winter. Groundhogs that live in northerly climes are “true hibernators,” meaning they exist in a state of uninterrupted, deep sleep for six to seven months, with body temperatures so low their metabolisms are almost at a standstill.

However, Delaware’s groundhogs are “semi-hibernators,” says Derek Stoner, conservation coordinator at the Delaware Nature Society.

“In February and March, if it warms up to about 50 degrees, Delaware groundhogs will come out of their burrows,” says Stoner. “By St. Patrick’s Day, the males, in particular are very active on warm days. They visit other burrows in hopes of finding a mate.”

In the fall, Delaware’s groundhogs gained some 50 percent of their body weight to prepare for their long — if somewhat fitful — snooze. But they also stashed grass in their burrows for the occasional snack when they do awake. Chipmunks also are “semi-hibernators” at Delaware’s latitude.

Deer don’t hibernate in winter although they do move around less to conserve energy. In cold conditions, they gravitate to areas with good thermal cover, such as a patch of evergreen trees that’s protected from the wind and cold and thus a degree or two warmer than surrounding terrain.

In the Poconos and Adirondacks you can see herds of several hundred deer hanging out together in the woods. Here in Delaware, herds are smaller, usually about 40 deer. Stoner says that a herd has congregated on Coverdale Farm, near Way Road, for the past several weeks.

Like flocking behavior in birds, herding is a wintertime phenomenon that increases survival rates. Come spring, the herd breaks up and the deer will go their separate ways.

Unlike us, wild animals and birds don’t need to turn to the Weather Channel to know when a storm is brewing; they sense the shift in barometric pressure, says Stoner. While we make our pre-storm trip for milk, bread and eggs, they, too, make a mad dash for adequate provisions before the snow flies.

Article by Margo McDonough

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Center for Managed Ecosystems puts past urban forest research into new FRAME

June 8, 2010 under CANR News

Greg Shriver, assistant professor of wildlife ecology in the Department of Entomology and Wildlife Ecology and research scientist with the Center for Managed Ecosystems at the University of Delaware, is collaborating with the U.S. Forest Service to continue work on a project that focuses on assessing the conditions of urban forests and explores ways in which to improve those conditions.

The project is known as Forest Fragments in Managed Ecosystems, or FRAME, and it has its origins in a study titled “Wildlife Ecology and Urban Impact” conducted 45 years ago at UD by scientists in the Department of Entomology and Wildlife Ecology and the Forest Service.

The 1965 study was continued by Roland Roth, UD professor emeritus of wildlife ecology, beginning in 1972. Although Roth could not have known at the time, Shriver said that his work — conducted on the UD Farm — became the longest running study on the demographics of the wood thrush, a neotropical migratory bird.

Shriver, who subsequently picked up the mantle, called the wood thrush the “hallmark species” for this research and said FRAME builds on Roth’s earlier studies. The FRAME project was initiated as a collaborative effort between Shriver; Vincent D’Amico, a Forest Service scientist stationed at UD; Jake Bowman, associate professor of entomology and wildlife ecology; and Jeff Buler, assistant professor of entomology and wildlife ecology.

Shriver said FRAME is “a fairly large-scale forest fragmentation study aimed at assessing the condition of urban forest fragments to see if we can increase their quality.”

These forest patches dotting the developed landscape “are providing the some of the only remaining habitat for neotropical migratory birds, small mammals, and insects,” he said.

The group is currently establishing long-term plots and surveying the condition of Mid-Atlantic forest fragments.

After assessing the overall health of the forest fragments, Shriver said he and his colleagues will research ways to improve them. “The big picture is that these fragments are providing important ecosystem services — air, water, things required to make the area livable,” he said. “The goal of the FRAME project is to better understand the interactions between soil, water, plants and the animals dependent on them within urban and suburban environments.”

Shriver, who will be aided by graduate students, said the study will be multifaceted, with the first part focusing on multitrophic effects of soil acidification and biodiversity.

“There has been some concern that acidification in soils, especially here in the Northeast, could be limiting the availability of calcium-rich prey — such as snails and isopods — that birds need during the breeding season to make eggshells and feed their nestlings, because the nestlings’ growth rate is so fast and they need so much calcium,” Shriver said. “Studies have shown that if you have limited calcium availability, you have limited calcium-rich prey, which then limits the breeding density and reproductive success of some bird species.”

The FRAME study has broken the Newark area’s urban forest fragments into grids using GPS systems, starting with the original study patch from the Roth study and adding 19 other woodlots.

In each of the fragments, Shriver said he and his students plan to “estimate breeding bird territory density, nest survival, a measure of reproductive success, and species diversity. We’re also taking soil samples and then litter samples to see if we can link the soil pH to calcium-rich prey.”

Shriver explained that a low pH means that the soil has a high amount of acidification, and that “the acidification comes mostly from acid rain, which has been greatly reduced since the height of the Industrial Revolution, but the soils have likely not recovered. Once you push a soil into an acidic state, unless it has some buffering capacity, it is very hard to get it back.”

What happens with soil that has been pushed to an acidic state, he said, is a reduction in calcium-rich prey, which in turn limits food for breeding birds. The birds either have lowered reproductive success or leave that forest fragment.

The first two years of the FRAME study are dedicated to gathering the pre-data, showing the present condition of the soil. Shriver said the research team then plans to “lime the forest patches to see if we can increase their quality, which will raise the pH and release the calcium,” thereby improving biodiversity.

They plan to treat 10 sites with lime and leave another 10 sites untreated in order to compare differences in soil quality. He said he is confident that “changing the pH is going to change a lot to these forest fragments.”

The research team is partnering with the Newark Department of Parks and Recreation, New Castle County Parks, and Delaware State Parks. Shriver said that “without the cooperation and enthusiasm we’ve received from all the partners, this project would not be possible.”

Shriver received a bachelor of science degree in wildlife management from the University of Maine, a master’s degree in wildlife conservation from the University of Massachusetts and a doctorate in environmental forest biology from the State University of New York (SUNY). He joined the UD faculty in 2005.

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Native Delaware: Owl watchers can sometimes spot 8 species in state

January 25, 2010 under CANR News

We think of birds breeding in springtime, and while that’s prime time for songbirds and most other species, for owls, winter is the time to start breeding, says Chris Williams, a University of Delaware assistant professor of wildlife ecology. Read the full story at the News Journal.

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Cooperative Extension offers tips to attract birds to backyards

December 9, 2009 under CANR News, Cooperative Extension

Dot Abbott, a renewable resource agent for University of Delaware Cooperative Extension, trains Master Gardeners so they have the background knowledge to teach workshops about attracting birds and other wildlife to backyards. Read the full article on UDaily.

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