Crow's Nest Great Blue Heron Nest Count - Through the Years.

Another year, another successful heron count! This year marks 21 years of nest surveys at Crow’s Nest Natural Area Preserve in Stafford. For even longer, Great Blue Herons have called Crow’s Nest home, their rookery ranking among the largest Great Blue Heron nesting sites in the Chesapeake Bay watershed. When the Heron Rookery was acquired by NVCT in 1997, it spanned 70 acres. Through persistent work to protect additional land for inclusion in Crow’s Nest Natural Area Preserve, NVCT expanded the rookery to 113 acres. Now, the rookery is a part of Crow’s Nest Natural Preserve and under the stewardship of both NVCT and the Virginia Department of Conservation and Recreation (DCR). Each year on the same day that land stewards go out to complete their yearly survey of the property, we gather conservationists and partners to count and monitor heron nests!  

What has changed over the years we have tracked Great Blue Heron nests?  

setting up drone

Our count methods have, for the most part, remained the same, with a few upgrades—like the ability to capture and utilize drone footage. The rookery is divided into six sections where trees with nests are heavily concentrated. Trees that have recorded nests within the past five years are tagged so surveyors can identify them and record how many nests they hold. If a tree goes more than 3 years without a nest, it is removed from the list and added back only when nests reappear. We split into two groups: one covering the marshland and the other taking a slightly less mucky path. Surveyors wade through streams and push through thick bramble to get a clear view of the nests.  

As early as February, herons begin laying clutches of two to six eggs. By March and early May, chicks start hatching. Herons and their nesting success are extremely sensitive to disturbance, which is why counts typically occur in late January to early February before most eggs are laid, or in late June, when chicks are tall and awkward-looking but sturdier. Over time, surveys shifted to the cooler month of January to avoid rising early-summer temperatures. However, as the climate swings to extremes on both ends of the spectrum, the return of heavy snow to Northern Virginia winters has created new challenges. Last year, we managed to complete the survey while sliding across frozen marshes and trudging down snowy hills. This year, significant snowfall forced us to reschedule, but we were able to find a date after the snow had melted to complete our count! 

(Left to right: Photos by John Hopewell (2016 summer survey, heron hatchling),

Over the past ten years, our counts have averaged between 200 and 300 nests. Losing a few nests here and there does not necessarily signal trouble for our beloved Great Blue Herons. Some years, strong windstorms or unexpected snow cause nests to tumble from treetops. Natural predation and shifts in preferred nesting trees, such as sycamores, also occur. During the 2013 survey, we recorded a significant decline, likely due to the powerful June 2012 derecho that swept through Northern Virginia. More than 140 nests were blown from their perches, and the count dropped from 296 nests to 153. However, herons are resilient. The following year, numbers rebounded to expected averages.  

(left to right: nest map, 30 nests in one tree, fallen nest)

This year’s nest total, unfortunately, did not deliver the results we hoped for. The nest count total was 158, a drop of 43 nests from the previous year’s count.  Approximately 75 percent of the drop was tied to 30 nests being lost from one tree. We aren’t sure what caused the loss of nests in a tree that hosted 30 nests last year, but recent snowstorms are most likely to blame. However, creeping development in Stafford and drastic shifts in climate, as well as more dramatic weather events, can’t be overlooked as possible influences. A significantly smaller total is never easy to report, but it reminds us that our work is far from finished. Herons have come back from worse, and our commitment to expanding Crow’s Nest is fueled by the need to provide better conditions for these remarkable birds to breed, nest, and thrive. 

2022 Heron count

Great Blue Herons themselves are a significant conservation success story. During the 1960s and early 1970s, the widespread use of DDT led to eggshell thinning and major reproductive failures in many wading birds, including Great Blue Herons. After DDT was banned in 1972, heron populations gradually rebounded. In the Chesapeake Bay region, improved water quality and stronger environmental protections have helped Great Blue Herons recover and even expand in some areas. This proof that dedicated conservation efforts can and do make a difference is what fuels our work, especially at Crow’s Nest. Our dedication to expanding Crow’s Nest Natural Area Preserve over the past 30 years is fueled by our vision of fortified natural resources to withstand the impacts of changing land use and the climate crisis.  

2022 Heron Nest Count

Protecting this landscape protects far more than herons—it safeguards an entire community of wildlife. As we look ahead to future counts, we remain hopeful and committed, knowing that with continued stewardship, the skies above Crow’s Nest will stay filled with the steady wingbeats of Great Blue Herons for generations to come.