March through May, 2009 - New Jersey Audubon Society

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In 1986, the New Jersey Division of Fish and Wildlife’s Endangered and Nongame Species Program began an annual survey of spring migrating shorebirds on Delaware Bay beaches to determine their distribution and trends. This annual shorebird survey documented significant numbers of spring shorebirds in Delaware Bay by the end of its initial seven years of operation (Clark et al. 1993). Since then, Delaware Bay has become widely recognized for the “shorebird-horseshoe crab phenomenon” that has attracted eco-tourists and galvanized conservation action to prevent its loss. In this paper we present data from the long-term aerial survey of shorebirds, 1986 through 2008. Figure 1. The Delaware Bay study area and the route of the aerial shorebird survey conducted once per week for six weeks each spring, 1986-2008. 86 — March through May, 2009
Study Area Delaware Bay is situated in the mid-Atlantic region of the United States, and is bounded by the lands of New Jersey and Delaware (Fig. 1). Tidal amplitude in the bay is approximately 2.5 m. The lower bay shoreline consists almost entirely of sandy beach, with very little adjacent tidal marsh (Spartina spp.). The upper bay shoreline is a mixture of sod and sand, with extensive adjacent tidal marsh. The upper regions of the bay also contain large river outflows that form sandy deltas. There is sparse development of residential buildings and bulkheads on both shores, although generally more development in the lower bay. Methods We surveyed approximately 80 km of shoreline in New Jersey and 80 km of shoreline in Delaware. Survey flights were made once per week for six weeks, from the first week of May to the second week of June, in a Cessna high-wing airplane. We began our flights on the New Jersey side at the Cape May Canal (approximately 2 km north of the bay entrance) and continued north to the Cohansey River, then crossed the bay into Delaware and flew south from Woodland Beach to Cape Henlopen (Fig. 1). All flights were conducted on the falling tide, 3-4 hours after high tide, a period when birds are usually feeding on beaches. The aircraft was flown at an altitude of approximately 25 m, 30 m offshore and a speed of 110 km/hr. The plane temporarily flushed birds off the beaches as it passed, which facilitated counting and identification. Each survey was completed in approximately two hours. The survey crew included one biologist who counted birds in each flock, one who estimated the species composition of the flock, and a third person who recorded the information on U.S.G.S. topographic maps. The same count observer (K. Clark) participated in all 23 years of surveys. The species observer in 1986-1988 was P. Dunne (who also conducted the 1981-1983 surveys by NJ Audubon) and J. Dowdell for most of the remaining years (1989-2005). R. Porter participated in other aerial surveys, and took over the species observer position in 2006-2008. There were many different survey recorders over the years, generally all with familiarity with the bay’s topographic features. The survey method was changed beginning in 2009, so we report only data between 1986 and 2008. The majority of shorebirds were identified to species; small birds of the genus Calidris were classified as “peep” when species could not be determined. For each year we completed six counts of shorebirds at one week intervals, except 1987 and 1988 when we missed two surveys each year because of inclement weather, and 1995 and 1996 when we missed one and two surveys, respectively. Results The most abundant species in our surveys were Semipalmated Sandpiper, followed by Ruddy Turnstone, Red Knot and Sanderling (Table 1). These four species accounted for 92% of shorebirds counted, while Dunlin and dowitchers accounted for about 8%. While the number of total shorebirds counted in one two-hour survey averaged nearly 180,000 birds, it ranged from a high over 425,000 in 1986 to a low of 105,000 in 1990 (Table 1). Annual variation was often substantial, both in the total shorebirds counted on one day, and in the peak counts of individual species that could occur on days other than the peak count of total birds. The peak count of total birds usually occurred on the fourth week of surveys between 24 and 30 May; in 23 years only four (17%) season-peaks fell outside those dates (Fig. 2). Counts of nearly all six species of shorebirds varied significantly over the 23-year study period (Fig. 3). A regression analysis plotted on annual peak counts by species showed significant declines in Red Knot and Ruddy Turnstone (P
Page 1 and 2: Birds March through May, 2009 — V
Page 3 and 4: the location; all records involve a
Page 5 and 6: Red-necked Stint Calidris ruficolli
Page 7 and 8: Ash-throated Flycatcher has become
Page 9 and 10: Western Tanager Piranga ludoviciana
Page 11: Co. 2 birds. D. Brill*. Tagged Onta
Page 15 and 16: proximity of sandy New Jersey Atlan
Page 17 and 18: Status and Trends. The peak counts
Page 19 and 20: Format of the Regional Reports Spec
Page 21 and 22: Denmark 29 Apr (RR), and another wa
Page 23 and 24: Arboretum in Morristown 5 Apr (KC).
Page 25 and 26: An Eared Grebe on Newark Bay was a
Page 27 and 28: This Thayer’s Gull, left, at Sout
Page 29 and 30: Twp; IBSP is Island Beach State Par
Page 31 and 32: Nine Black-billed Cuckoos were foun
Page 33 and 34: Lower Delaware Valley, including Bu
Page 35 and 36: Up to 5 Brewer’s Blackbirds (3 ma
Page 37 and 38: The impoundment at Heislerville, Cu
Page 39 and 40: Fifty Years Ago — Spring 1959 com

March through May, 2009 - New Jersey Audubon Society

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