A Plan for Monitoring Shorebirds During the Non-breeding Season in Bird Monitoring Region Virginia – BCR 30 and 27
Prepared by: Shiloh Schulte and Sandy Chan
Version *.*
2003
Updated 2008
Table of Contents
Introduction 3
Methods 5
Results – Shorebirds 7
Site Descriptions 8
Chincoteague National Wildlife Refuge 8
Virginia Coast Reserve 10
Back Bay National Wildlife Refuge and False Cape State Park 16
References 19
Introduction
The bird conservation initiatives - waterbirds, waterfowl, shorebirds and landbirds - are cooperating to design a comprehensive “integrated bird monitoring” (IBM) program for Canada and the United States. The conceptual framework for IBM (Fig. 1) includes strong emphasis on detecting species at risk and helping to protect them. These broad goals are achieved by estimating population trends and defining requirements for viable populations. These objectives in turn are accomplished by population modeling based on population levels, demographic rates and habitat information. Population trends are estimated by surveying breeding populations whenever possible, and by surveying the species for which this is not feasible at other times of year. Surveys of all species are made throughout the year to help identify and monitor use of suitable habitat.
Figure 1. Conceptual framework for integrated bird monitoring.
Most surveys in upland habitats are designed at a large spatial scale (e.g., southern Canada and the United States) and do not require detailed information at the local level. Surveys of wetland habitats, in contrast, must be carefully designed to insure that the habitat is well covered, and different methods may be needed in different environments. A series of “regional assessments” is thus being prepared to help design the wetland surveys. Regions were formed by intersecting a Bird Conservation Region (BCR) map with a Province and State map, deleting small polygons and smoothing the borders (Fig. 2). The resulting “Bird Monitoring Regions” can be used to scale up results to either BCRs or Provinces and States.
Figure 2. Shorebird Planning and Bird Conservation Regions in Canada and the United States.
Adapted from: USFWS-U.S. Shorebird Plan and CWS-Canadian Shorebird Conservation Plan
The regional assessments summarize current information about wetland bird distribution, abundance, habitat relationships and timing of use within the Region and identify information needed to design reliable monitoring programs. These “needed pilot studies” are then prioritized by people concerned with monitoring birds in the region and a plan is developed to carry out the work. Carrying out the pilot studies is expected to take 1-3 years. Long-term surveys will then be implemented. Additional details are provided in “Managers Monitoring Manual” available at http://www.pwrc.usgs.gov/monmanual/techniques/shorebirdsnonbreedingsites.htm. More information on regional progress can be found at the U.S. Shorebird Plan’s Regional Conservation Plan website (http://www.fws.gov/shorebirdplan/RegionalShorebird.htm).
Methods
Focal wetland species of shorebirds were first identified. The initial list included all wetland species of shorebirds that are common or abundant at any time of year within the Region, according to Brian Harrington and based largely upon data from the International Shorebird Surveys (ISS). Sites in which any of the focal species are common or abundant at any time of year were then identified using a list prepared for this project and supplemented by information provided by birding guides, ornithologists and birders knowledgeable of the Region. Most sites were single areas, such as a National Wildlife Refuge, but dispersed sites, such as “lakes >10 ha”, could also be identified.
Figure 3. PRISM sites in BCR 13, 14, 30, 27, and 31.
The International Shorebird Survey (ISS) provided species numbers for some of the identified sites. The ISS is a volunteer based survey initiated in 1974 by Brian Harrington. Volunteers select their survey sites and are given guidelines on census frequency and data collection for spring and fall migration. The ISS guidelines ask volunteers to survey once every 10 days from April 1st to June 10th for spring migration, and once every 10 days from July 11th to October 31st for fall migration. ISS records provided the maximum counts recorded for species where the identified site is also an ISS site.
Survey methods for sites include appropriate tide levels for surveys, if that information is available. Tide levels for surveys are based on the advice of biologists and birders with knowledge about the sites. Due to the different geography of the sites, different tide levels
are recommended to concentrate the birds for a survey. While high tide at one site may bring in birds that are spread out over an expansive area at low tide, high tide at another site may completely cover the habitat or food resources and scatter the birds elsewhere. Therefore, different tide levels may be recommended for different sites.
Additional site information may also include information about visibility. Excellent/good visibility simply means that the birds can be seen without obstruction clearly enough to identify to species, either by physically getting close enough or with a good scope or binoculars.
Maps showing land ownership, roads and wetlands were prepared for the region. Maps of each site were also prepared and information useful in designing surveys for the focal species was presented. The survey objective was assumed to be estimating the average number of birds of each focal species present within the site during a specified interval. Up to three types of habitat were described for each focal species: Type 1 habitat, outlined in purple on the maps, included regularly-used areas that should be sampled using a well-defined sampling plan. Type 2 habitat, which was outlined in red, included areas used sparingly by the focal species. Type 2 habitat is not surveyed as often or with rigorously defined methods, but is surveyed less formally every few years to document continued low use by the focal species. Type 3 habitat receives virtually no use by the focal species during the study period and is not surveyed as part of the monitoring program. Requests, however, are circulated for any records of the focal species occurring in substantial numbers in these areas.
A description of each site was prepared with the following headings:
Boundaries and ownership
Focal species using the site and timing of use
Location of type 1 and 2 habitat within the site
Access to the type 1 and 2 habitat and visibility of the birds
Past and current surveys
Potential survey methods
Description
Selection bias
Measurement error and bias
Needed pilot studies
We assume for any survey that the study area and study period (within years) have been defined. The goal of the survey was assumed to be estimating the trend, across several years, in the average number of birds present during the study period. Bias means a long-term trend in the ratio (number recorded)/(average number present). Selection bias ensues when some portion of Type 1 habitat has zero chance of being surveyed, usually due to access problems, and there is a long-term trend in the proportion of birds using the non-sampled portion. Exclusion of some Type 1 habitat does not necessarily cause selection bias because trends in the sampled areas might be the same as trends in the non-sampled areas. Anytime some portion of Type 1 habitat could not be included in the sampled areas, the potential for selection bias and ways to reduce it were discussed. Measurement error means not detecting all birds present in the surveyed area at the time of the survey. Measurement bias is a long term trend in the proportion of birds present at the time of the survey that are detected on the survey. Measurement error does not necessarily cause measurement bias because the proportion of birds detected might not change through time. Anytime measurement error was probable, its magnitude and probable stability through time were discussed along with ways to reduce the proportion of birds missed on the surveys.
Results – Shorebirds
Table 1. Focal shorebird species for BCR 30
CODE / SPECIESBBPL / Black-bellied Plover
SEPL / Semipalmated Plover
AMOY / American Oystercatcher
GRYE / Greater Yellowlegs
LEYE / Lesser Yellowlegs
SOSA / Solitary Sandpiper
SPSA / Spotted Sandpiper
WHIM / Whimbrel
RUTU / Ruddy Turnstone
REKN / Red Knot
SAND / Sanderling
SESA / Semipalmated Sandpiper
LESA / Least Sandpiper
WRSA / White-rumped Sandpiper
DUNL / Dunlin
SBDO / Short-billed Dowitcher
Site Descriptions
Chincoteague National Wildlife Refuge
Description: Most of Chincoteague National Wildlife Refuge is located on the Virginia side of Assateague Island; 418 acres of it are on the Maryland side. In Virginia, 427 acres are found on Morris Island and 546 acres comprise Wildcat Marsh on the northern tip of Chincoteague Island.Additionally, Chincoteague NWR boundaries extend south to encompass all or part of the following barrier islands (not shown in the map above): Assawoman,Metompkin, and Cedar.
Chincoteague NWR includes more than 14,000 acres ofbeach, dunes, marsh and maritime forest. The beach extends from the intertidal zone into the dunes along the entire east and south sides of the island.The salt marsh can normally be found to the west of the barrier islands that comprise the refuge. The refuge also contains 14 freshwater impoundments covering over 2,623 acres. The impoundments are drawn down in the spring to create mud flat habitat for shorebirds and then raised in the fall with rainwater.
The most productive areas for shorebirds according to Paul and Ann Smith, the refuge’s shorebird surveyors, are the Wash Flats located toward the north half of the refuge and the Assateague Bay/Channel area. Shorebird use at the other impoundments is variable depending on the water levels. Chincoteague NWR biologist, Tom Penn, provided the maximum population estimates from the shorebird surveys. The following are the most abundant species with the maximum estimate for each species from the spring and fall migration periods of 1998-2002:
April – June: BBPL (89), SEPL (2,890), PIPL (18), KILL (15), AMOY (36), GRYE (83), LEYE (17), SPSA (24), WILL (136), WHIM (284), RUTU (136), REKN (543), SAND (1,930), SESA (7,651), LESA (1,253), SBDO (5,964), DUNL (6,663);
July – October: BBPL (194), SEPL (1,460), PIPL (44), KILL (57), AMOY (35), GRYE (158), LEYE (288), SPSA (41), WRSA (13), WILL (248), WHIM (118), RUTU (86), REKN (88), SAND (5,348), SESA (9001), LESA (972), SBDO (340), and DUNL (674).
Survey Method: Ground surveys by truck around impoundments and beaches. Paul and Ann Smith have been conducting shorebird surveys for the refuge for the past 13 years. They survey the refuge by vehicle once a week during migration and once every other week the rest of the year. They follow a 35-36 mile survey route from Toms Cove Hook to the Old Fields Impoundment on Tuesdays beginning at about 7:30am. The length of time to complete the survey depends on the number of birds present.
Selection Bias: None.
Measurement error: *
Measurement bias: *
Pilot Studies: None needed.
Local Contacts: Tom Penn, Biologist, Chincoteague NWR
Paul and Ann Smith, Refuge Shorebird Survey Team
Virginia Coast Reserve
Description: The Virginia Coast Reserve encompasses most of the Virginia’s eastern shore, which stretches from the Maryland border to the Chesapeake Bay. Barrier islands running parallel to the coastline along much of the Atlantic shore comprise a large part of the coastal habitat. The Nature Conservancy (TNC) owns all or part of 14 of the 18 barrier islands and manages them as the Virginia Coast Reserve. The Reserve has extensive salt marshes, mudflats, bays and sandy beaches. This region is very important for shorebirds, particularly in the spring when, according to Barry Truitt of TNC, up to 500,000 may move through.
During peak migration, shorebirds can be found throughout the Reserve. REKN, DUNL, SESA and BBPL are found in the greatest numbers along the barrier islands, particularly at inlets. According to Barry Truitt, high-use areas include (but are not limited to) the south tip of Metompkin Island, the beaches on Paramore, and the inlets at North Cobb and North Myrtle Islands. The mudflats of the inner bays between Ramshorn and Metompkin are heavily used by shorebirds, especially WHIM, SBDO and peeps.
Access: The Reserve is accessible only by boat or aircraft. State biologist Ruth Boettcher is working to establish three survey routes for regular boat access in the Virginia Coast Reserve. Survey points along these routes are located at high tide roost sites, shell rakes and oyster flats. (See areas outlined in the map below for route locations in the upper, middle and lower seaside of the Reserve.)
Survey Method: Sites on the outer beaches should be surveyed on the falling tide. The inner bay mudflats should be surveyed near low tide. Sites along the three survey routes being tested by Ruth Boettcher should be surveyed at high tide and preferably mornings, when wind and water are calmer for boat surveys. High tide roosts with birds should be approached by boat from above so that observers can cut the engine and drift down onto birds as quietly as possible. An image stabilizer for optics is strongly recommended to help minimize error due to wave action and boat vibration.
Selection Bias: Unknown.
Measurement error: Unknown.
Measurement bias: Unknown.
Pilot Studies: The immensity of the Reserve and the difficulty of access make surveys of this region problematic. Regular boat and ground surveys at select locations combined with periodic aerial surveys of the entire Eastern Shore will be necessary to complete surveys of this region. Ruth Boettcher of the VA Dept of Game and Inland Fisheries (Wildlife Diversity Program) has selected three survey routes that can be surveyed by boat on a regular basis. She conducted surveys along them in Fall 2004, Spring 2005 and will continue in Fall 2005.
Local Contacts: Ruth Boettcher, VA Dept of Game and Inland Fisheries (Wildlife Diversity Program); Barry Truitt, TNC.
Seaside shorebird survey routes on the Virginia Shore
Wachapreague Survey Route