Breeding Bird Survey





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Results of the 2014 Dyke Marsh Breeding Bird Survey

Larry Cartwright Marks 20 Years at Breeding Bird Survey

The Friends of Dyke Marsh honored Larry Cartwright at the quarterly meeting on May 16, 2012, with a certificate of appreciation on this his twentieth year as the Coordinator of the Breeding Bird Survey. This activity, a continuing biological inventory of the Dyke Marsh Wildlife Preserve, has provided trend information on the Marsh since the 1960's. The Friends also gave Larry a portrait of his beloved Prothonotary Warbler. President Glenda Booth presided.

Larry Cartwright

FODM President Glenda Booth awards a certificate of appreciation to Larry Cartwright.  Photo by Dorothy McManus.

The 2014 Dyke Marsh Breeding Bird Survey was conducted as part of a continuing biological inventory of the tidal wetlands. The breeding status of each species was determined by means of behavioral criteria. Species were placed into one of four categories: confirmed breeder, probable breeder, possible breeder, and present.

    The 2014 survey was conducted between Saturday, May 24 and Sunday, July 6, 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 and reliable individuals 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 from the shoreline to the channel, and the surrounding woodland from the mouth of Hunting Creek to Morningside Lane. Volunteers found 84 species at Dyke Marsh during the survey. By the completion of data collection, 44 species had been confirmed as breeders, six species were listed as probable breeders, and 17 species as possible breeders. An additional 17 species were identified in the survey tract during the reporting period, but were considered not to be in suitable breeding habitat.

American goldfinch

A female American Goldfinch works at a half-finished nest.  Photo by Ed Eder.

    The analyzed data indicates both good news and areas of continuing concern. Breeding woodpeckers seemed to do quite well in 2014 and volunteers observed Red-bellied, Downy, and Hairy Woodpeckers, and Northern Flickers all with fledged young. As in previous years, we discovered breeding Eastern Kingbirds, and Orchard and Baltimore Orioles everywhere that there were trees to host a nest. Territorial Warbling Vireos were singing from every possible location too, but it wasnít until July 6 that the survey documented its first, and only, evidence confirming breeding, a nest near the boardwalk entrance. Observers reported possibly two Great Crested Flycatcher family groups in the south picnic area.

Yellow Warbler

A female Yellow Warbler is gathering spider silk for nesting material.   Photo by Ed Eder.

    Survey teams did quite well on confirming the warblers. Prothonotary Warblers, Common Yellowthroats, Northern Parulas, and Yellow Warblers all were tallied as confirmed breeders. These warbler species are fairly common in the survey tract during the breeding season, but it can be exceedingly difficult to confirm all four of them. Brown Thrashers, not always easy to find or even present at Dyke Marsh during the survey, were reported from several locations in 2014. I was delighted to find a Brown Thrasher pair near the Haul Road wooden bridge on June 18 followed by a report on July 8 of a ground foraging Brown Thrasher fledgling in the company of an adult near the boardwalk entrance.

    Several confirmation misses are worthy of note. A Willow Flycatcher reported by multiple observers near the boardwalk from mid-May to early June apparently departed without attempting to breed. The now famous Eastern Screech-Owl pair put on quite a show in early March, copulating and giving every indication of preparing to breed, but we could not quite positively identify the nest cavity or locate young. A June 1 report of a Red-tailed Hawk pair near an empty nest in the south marsh was exciting news, but subsequent survey teams could not locate the pair or determine that the nest actually belonged to the hawks. Too bad, because Red-tailed Hawk has not been confirmed as a breeder in the 22 years that I have been compiler.

    Ospreys had a highly successful breeding season in 2014. Survey teams discovered 10 Osprey nests and eight of these eventually contained nestlings. Of the successful endeavors, the platform nest near Porto Vecchio was the most productive, fledging four youngsters. That may be a new record for the Dyke Marsh breeding bird survey. Another observer reported a nest with four nestlings near the island in Pipeline Bay, but Iím not sure that all of them fledged.

Osprey nest

This marina tilted nest with adults and nestlings was a success last season.  Photo by Bill Young.

    The breeding Osprey pair at the marina nest perhaps had the most difficult time fledging their two youngsters. During the winter, pressure from moving ice pushed the pole supporting the nest platform to a precarious 45 degree angle. We were amazed as we watched the Ospreys build the nest, adding more sticks to one side of the platform than the other to compensate for the lean. We held our breath as the two nestlings grew, hoping that the pole would not collapse or the nestlings slide out of the nest into the water. But fledge they did, and kudos to the Osprey breeding pair that made it happen!

    There is a corollary to the marina Osprey nest story. A group of Purple Martins nested at the base of the platform of the marina nest during the 2012 and 2013 breeding season. On April 6, 2014 observers during a Sunday morning walk saw four Purple Martins flying around inspecting the platform, but the birds apparently decided that the lean was too great to try to nest there for a third year. So several found an alternative according to one report. They apparently nested in the masts of some of the inactive sailboats in the marina, and with some success. An adult was found feeding a fledged youngster in mid-July at the boardwalk. More fledglings were sighting in the following weeks.

White-breasted Nuthatch

A White-breasted Nuthatch female carrying nesting material.  Photo by Ed Eder.

    A new eagle nest along the tree line just west of the Little Gut was first reported under construction on December 21, 2013. Several observers noted some dark smudging in the tail of the smaller male eagle, indicating that he was probably only four or five years old, and likely a first time breeder. We watched the nest with much anticipation and everything seemed to be doing well until late March. On March 26 crows and Blue Jays were at the rim of the nest with no adult eagles in sight, not a good sign. Several of us assessed that it was the excessive cold our area experienced in late March that likely killed young nestlings and caused nest abandonment, and not just the presumed inexperience of the Bald Eagle breeding pair. On a happier note, the Morningside Lane Bald Eagle nest once again was successful, with the breeding pair fledging its single nestling by mid-June.

    There remains much concern about the future of the Marsh Wren breeding population at Dyke Marsh. As in previous years, Marsh Wrens in the northern portion of Dyke Marsh were concentrated in the marsh vegetation on the north side of the Haul Road peninsula and the larger of the adjacent islands. By late June a canoe team could clearly see perhaps a half dozen nests in the Narrow-leaf Cattails as the surveyors transited the channel separating the peninsula from the island. By plotting locations of singing Marsh Wrens, I calculated that there was a minimum of 16 males on territory at this location.

Marsh Wren

The Marsh Wren breeding population status is a concern.  Photo by Ed Eder.

    Unfortunately, there were no Marsh Wrens in the portion of the southern marsh that we refer to as the Big Gut in 2014. Indeed, there has been no reliable presence of Marsh Wrens in the Big Gut since 2000 when the breeding population throughout Dyke Marsh gave initial indications of a decline. After an absence of several years, a few Marsh Wrens occupied a tributary of the Big Gut in 2011 followed by a few more in 2012. By 2013 one survey team reported the presence of approximately a half dozen singing males and a minimum of four nests. One observer even documented a nest containing youngsters. Hope stirred that the Big Gut would host an even larger Marsh Wren presence in 2014. It didnít. Iím confident Marsh Wrens will be at their usual location in the north marsh in 2015, but unwilling to make any prediction of what will happen in the Big Gut. The last decade and a half suggests it could go either way.

    The pattern and concentration of the Least Bittern population at Dyke Marsh increasingly seems to parallel that of the Marsh Wren. I assess that Least Bitterns are starting to focus their breeding efforts on the marsh vegetation around the Haul Road peninsula, to include the Little Gut. A canoe team tallied five Least Bitterns within five minutes of entering a tributary of the Little Gut on a June 7 survey. That includes a definite breeding pair. Another breeding pair was found near the north end of the boardwalk and at least a territorial male maintained a constant presence at the southern tip of the peninsula just off the boardwalk. In contrast, Least Bitterns south of the Little Gut seemed to be found primarily in the extreme upper portion of the Big Gut. Survey teams in the Big Gut reported no definite breeding pairs. Sightings or heard vocalizations were all of single birds. It may be that the rapid erosion in the lower portion of the Big Gut is making the habitat unsuitable for Least Bitterns.

    Unfortunately we were not able to confirm Least Bittern as a breeder anywhere in Dyke Marsh. Several light colored birds seen in flight along Haul Road towards the end of the survey could have passed as either adult females or fledged young. So Least Bittern went into the probable breeder category for 2014.

    This survey would not be possible without the hard work and dedication of so many volunteers who collected breeding bird data in 2014 as part of a Dyke Marsh survey team or who provided information as leader of a Sunday morning bird walk. I want to thank all those who contributed to the survey. In alphabetical order, they are: Bob Beard, Dave Boltz, Ed Eder, Myriam Eder, Sandy Farkas, Kurt Gaskill, Susan Haskew, Gerry Hawkins, Ellen Kabat, Elizabeth Ketz-Robinson, Dorothy McManus, Ginny McNair, Larry Meade, Roger Miller, Nick Nichols, Patrice Nielson, Marc Ribaudo, Rich Rieger, Don Robinson, Peter Ross, Molly Ross, Trish Simmons, Ned Stone, Jessie Strother, Paula Sullivan, John Symington, Maggie Symington, Bill Whitacre, Margaret Wohler, Katherine Wychulis.

    The 2014 Breeding Bird Survey Results:

    Confirmed - 44 Species: Canada Goose, Wood Duck, Mallard, Osprey, Bald Eagle, Mourning Dove, Red-bellied Woodpecker, Downy Woodpecker, Hairy Woodpecker, Northern Flicker, Great Crested Flycatcher, Eastern Kingbird, Warbling Vireo, Blue Jay, Fish Crow, Northern Rough-winged Swallow, Purple Martin, Tree Swallow, Barn Swallow, Carolina Chickadee, Tufted Titmouse, White-breasted Nuthatch, Marsh Wren, Carolina Wren, Blue-gray Gnatcatcher, American Robin, Gray Catbird, Brown Thrasher, European Starling, Cedar Waxwing, Prothonotary Warbler, Common Yellowthroat, Northern Parula, Yellow Warbler, Song Sparrow, Northern Cardinal, Red-winged Blackbird, Common Grackle, Brown-headed Cowbird, Orchard Oriole, Baltimore Oriole, House Finch, American Goldfinck, House Sparrow.
    Probable - 6 Species: Least Bittern, Red-tailed Hawk, Eastern Screech-Owl, Acadian Flycatcher, Red-eyed Vireo, Indigo Bunting.
    Possible - 17 Species: Pied-billed Grebe, Black-crowned Night-Heron, Mississippi Kite, Cooper's Hawk, Killdeer, Spotted Sandpiper, Yellow-billed Cuckoo, Chimney Swift, Belted Kingfisher, Pileated Woodpecker, Eastern Wood-Pewee, Willow Flycatcher, American Crow, House Wren, Northern Mockingbird, American Redstart, Chipping Sparrow.
    Present - 17 Species: American Wigeon, Ruddy Duck, Common Loon, Horned Grebe, Double-crested Cormorant, Great Blue Heron, Great Egret, Black Vulture, Turkey Vulture, Greater Yellowlegs, Ring-billed Gull, Caspian Tern, Rock Pigeon, Black-billed Cuckoo, Alder Flycatcher, Mourning Warbler, Blackpoll Warbler.

Definition of Categories:
Confirmed Breeder: Any species for which there is at minimum evidence of a nest. A species need not successfully fledge young to be placed in the confirmed category.
Probable Breeder: Any species engaged in pre-nesting activity, such as a male on territory, courtship behavior, or even the presence of a pair, but for which there is no evidence of a nest. Since birds can and do sing and display to females during migration, this category cannot be used until the safe dates are reached.
Possible Breeder: Any species, male or female, observed in suitable habitat, but giving no hard evidence of breeding. Unless actively breeding, all birds in suitable habitat before the start of the safe date are placed in this category.
Present: Any species observed that is not in suitable habitat or out of its breeding range.
Definition of Safe Dates: We use safe dates as a means of deciding if a bird can be considered a breeder or a migrant. Safe dates are simply defined as a period of time beginning when all members of a given species have ceased to migrate in the spring and ending when they begin to migrate in the fall. Unless a bird is engaged in behavior that confirms breeding, it will be placed no higher than in the possible breeder category if it is observed outside the safe dates assigned to that species.

Larry Cartwright
Dyke Marsh Breeding Bird Survey Coordinator

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Last Revised: May 29, 2015