|
|
|
|
Results of the 2010 Dyke Marsh Breeding Bird Survey
The 2010 Dyke Marsh Breeding Bird Survey was conducted as part of a continuing biological inventory of the tidal wetland. The breeding status of each species was determined by means of behavioral criteria. Species were placed into one of 4 categories: confirmed breeder, probable breeder, possible breeder, and present. The official survey was conducted between Saturday, May 22 and Sunday, July 4, but any data collected outside of this period that confirmed a breeding species was entered into the database. This permitted us to weed out most migrants that do not use the marsh to breed. I also included information provided from the Sunday morning walks to supplement data reported by the survey teams. The survey tract encompassed the Belle Haven picnic area, the marina, the open marsh, the Potomac River shoreline, and the surrounding woodland from the mouth of Hunting Creek to Morningside Lane. The volunteers documented 80 species at Dyke Marsh during the 2010 survey. By the time data collection was completed, they had collectively confirmed 37 species as breeders, recorded 7 species as probable breeders, and reported 24 species as possible breeders. An additional 12 species were present in the survey tract during the official reporting period, but were considered not to be in suitable breeding habitat. Ospreys have a large and very visible presence at Dyke Marsh, so I was surprised when the data showed a reduced breeding success during the 2010 breeding season. Last year Ospreys occupied 13 nests and most of them produced fledged young. At least 5 of the rootball nests were washed away by flooding following the February 2010 snowstorm, and in the case of the 2 rootball nests lying off the north end of the picnic area, the fallen-over trees supporting the nests also were washed away. By April 9 a Canada Goose occupied the long-established nest at Pipeline Bay, presumably to incubate her own eggs. In some cases destroyed or abandoned nests were replaced after Osprey breeding pairs began arriving in early March. The Osprey pair nesting between the islands off the Haul Road peninsula rebuilt their nest on a neighboring rootball and the Pipeline Bay nest was replaced by new construction near the southern shoreline of Pipeline Bay, a location we unofficially refer to as Barge Point. The survey volunteers documented 10 active Osprey nests. Surprisingly, only 4 of these nests produced nestlings: the platform nest across from Hunting Creek, the pilings nest in the channel, the well-known marina nest, and the newly-constructed nest at Barge Point. The marina breeding pair also suffered nestling mortality, losing 1 of 3 original nestlings. I am hard pressed to explain the low success rate. Surely the destruction of several nests in post-snowstorm flooding did not play a role. Although the foundations remained intact, even the successful nests on the pilings and the marina had to be rebuilt from scratch. Problems with the prey base? The marina pair appeared to have no problems catching and bringing in fish. There could be several explanations for the loss of 1 nestling besides starvation. A host of first-time breeders? There is little way to prove this without an identifying band on each bird. We will have to wait and see the results of the 2011 survey and speculate that this was a temporary, if unexplainable situation. The Bald Eagle nest near Morningside Lane was successful for the second straight year. The single nestling was last documented in the nest on June 13 and a canoe team later reported it perched in the company of its parents near the nest site on June 27. In contrast to the successful breeding effort at Morningside Lane, the bald Eagles occupying the golf course nest failed again. I received reports in March of problems between the original breeding pair followed by speculation that the male had been replaced. By April 10 an Osprey was perched in the nest. Soon thereafter the nest appeared to be abandoned. Least Bitterns initially confounded me. In the Big Gut, one week's survey results produced no birds only to be followed the next week by a report of a half dozen individuals. This persisted for the entire survey. Least Bitterns appeared scarcer in the marsh vegetation around Haul Road. By Independence Day the volunteers had documented only a single individual in this location. Then on July 11, members of the Sunday morning walk reported a fledgling flying over the marsh accompanied by its parents and a canoe team photographed a Least Bittern nest with a female standing nearby. Marsh Wrens were far easier to find, but the population showed no evidence of increasing. Only about 12 males established territories in the marsh vegetation along the Haul Road peninsula and adjacent Hog Island and a single songster was present just south of the Little Gut. Yet by the end of the survey observers reported football-shaped Marsh Wren nests dotting the channel separating the peninsula from Hog Island. At least the first decade of the 21st Century ended with Marsh Wrens maintaining a presence at Dyke Marsh.
I received photographs of a Northern Parula, a Prothonotary Warbler, and a Cedar Waxwing with nesting material snug in their beaks, confirming all 3 species as breeders. These photographs were followed by an observation of a Cedar Waxwing engaged in nest building on May 23rd and a bird sitting on the nest the following week. A Prothonotary Warbler was documented on June 20 carrying food to an unlocated nest at Pipeline Bay. Volunteers documented territorial Warbling Vireos throughout appropriate habitat during the 2010 survey, but it was in the north picnic area on June 5 that a bird was seen carrying nesting material, thus confirming this species once again as a breeder. Great Crested Flycatchers were reported in small numbers, primarily from the wooded area next to the south picnic area and the marina, and it was from here that an observer reported a breeding pair tending to 3 fledged youngsters on July 11. Acadian Flycatchers and Red-eyed Vireos concentrated their breeding efforts along the parkway south of the Big Gut footbridge. An Acadian Flycatcher was sitting on a nest located at the end of the branch of a Red Maple approximately 10 feet above the paved trail just south of the Tulane Drive parking lot during a June 13 survey. The following week volunteers observed a Red-eyed Vireo feeding a fledged youngster near the same location. Barn, Tree, and Northern Rough-winged Swallows were again confirmed as breeders during the 2010 survey. Observing fledgling Northern Rough-winged Swallows perched on a snag off Dead Beaver Beach waiting to be fed by busy parents has just about become a yearly tradition. What can you say about Eastern Kingbirds? Just one thing. They continue to be prolific. Rounding out the list of notable breeders are Orchard and Baltimore Orioles. Despite an initial outbreak of anthracnose in the Sycamores, a condition that appeared to disrupt oriole breeding success in 1998, both species successfully produced fledglings in 2010.
Honorable mention for the 2010 breeding bird survey goes to Eastern Towhee and Green Heron. I received a report of an independent juvenile Eastern Towhee along Haul Road on June 20 in an area where an adult had been observed on May 16. A canoe team observed a presumably independent juvenile Green Heron on Independence Day. The kicker is that an adult also was reported, but at a distance so that the juvenile appeared to be neither dependent nor even associated with this individual. Breeders or dispersed birds? I'd like to conclude with a mention of breeding waterfowl at Dyke Marsh. Canada Geese and Mallards have been common breeders for the nearly 2 decades that I have been compiler. They continue to be so, but I have noticed a change in the pattern of Mallard breeding. In previous years the tendency was to see Mallards breeding early in the season with a hen accompanied by up to a dozen nearly grown youngsters by mid to late June. Observing small ducklings after this time was unusual. This year I received a number of reports of Mallard hens with recently hatched ducklings well into late July or August. What is occurring here? Is it possible that Mallards are double or even triple clutching because of high rates of nest failure early in the season? Why also the trend toward smaller clutches? Could it be a high rate of depredation of eggs and ducklings or perhaps high egg infertility rates or even embryonic mortality? This is something I will be watching in 2011. Finally, you may notice that the confirmed category for 2010 is missing a familiar, and until this year, consistent breeder at Dyke Marsh: the ever popular Wood Duck. I sincerely hope that in 2011 we will again enjoy the sight of Wood Duck youngsters in the care of their mother. I wish to thank all the volunteers for their participation in the 2010 Dyke Marsh BBS. In alphabetical order: Dave Boltz, Ed Eder, Myriam Eder, Sandy Farkas, Kurt Gaskill, Susan Haskew, Phil Kenny, Elizabeth Ketz-Robinson, Glenn Koppel, Dorothy McManus, Ginny McNair, Larry Meade, Roger Miller, Elton Morel, David "Nick" Nichols, Marc Ribaudo, Rich Rieger, Don Robinson, Peter Ross, Molly Ross, Trish Simmons, Ned Stone, Paula Sullivan, Melina Tye, Rob Tye, Margaret Wohler, Frances Zorn. The 2010 Breeding Bird Survey results are as follows:
Definition of Categories: Larry Cartwright
|
|||||||||||||||||||||
|
Home
Friends of Dyke Marsh, Inc. is a
non-profit 501(c)(3) organization.
|
