ROOKERY: Counting their heron nests before the eggs hatch
With craned necks, the waders-wearing group scans their eyes across the perfectly blue sky.
“There, there’s the first nest,” says Mike Lott, manager of the Crow’s Nest Natural Area Preserve, pointing across the bare canopy toward Potomac Creek.
Easy to spot when trees are missing their leaves, the great blue heron nests could just be some of the biggest bird nests you’ve seen in this area.
Some trees carry dozens of nests—at least 25 were in one sycamore on this February morning.
And the birds, which feed along the area’s tidal creeks and rivers, return to their nesting areas year after year. They’ll be here later this month.
The heron rookery along the Potomac Creek is a decades-old breeding ground for the majestic slate-blue birds. They stand up to 5 feet tall, and group their nests into close colonies.
Over the years, colony numbers have fluctuated.
On this Friday morning, employees from Stafford County, the Northern Virginia Conservation Trust (which owns the rookery), and Lott from the Department of Conservation and Recreation, hiked through mud and briars to count the colonies.
The day’s tally was 246 nests, an increase from the year prior.
Limbs in some clumps of trees that supported the nests in years past were empty.
Others held more.
Herons are a species of concern, explained Assistant Planning and Zoning Director Kathy Baker. Their populations are easily disturbed. Employees from the county and NVCT have counted nests since 2007 to track their colonies.
Encroaching development, noise and construction can scare herons, leading them to abandon their nests, their eggs and their babies. Bald eagles and other prey are also of concern.
The 75-acre rookery is fairly protected and has little human disturbance—storms are perhaps the most damaging at this point.
The June 2012 derecho took down trees, including at least one that held some 20 nests high above. Lott noted the fledglings had at least already flown off; they weren’t as lucky during other storms.
“That’s one of the big things they’re dealing with is weather events,” Baker said.
A survey last fall said herons could be found in creeks and rivers across the area and most of the Chesapeake Bay, and the number of breeding colonies had grown dramatically since the early 1960s when the pesticide DDT decimated populations throughout the estuary.
The Center for Conservation Biology, based at the College of William & Mary in Williamsburg, also said that herons’ nesting colonies had been shrinking.
Herons should return to the rookery later this month, and claim old nests or build new ones. They’ll spend two days to two weeks picking up sticks, pine needles, reeds and moss to weave into a home for their two to six eggs.
Both males and females incubate the eggs and feed the young. They lay eggs in mid-March, and those hatch by the end of April. By July, most herons will have left the area. Where they go during the rest of the year isn’t clear.
At the rookery, colonies dot the edge of Potomac Creek, and birds often fly the 2 to 3 miles to the Rappahannock River to pick up fish for the babies.
Nests are typically built in sycamore trees, because of their large size, but the herons have also taken to building in tulip poplar, sweet gum and ash trees, Baker said, because that’s what’s available.
In 1993, a group said they saw 650 nests, but there’s no official record of that count.
In 2007, when Stafford first counted the colonies, they found 343 nests. The tally in 2013 was the lowest in eight years.
Katie Thisdell: 540/735-1975