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Migratory & Wintering Shorebird Monitoring

Piping plover (Charadrius melodus), photograph by MDF, 2008
Piping plover (Charadrius melodus), photograph by MDF, 2008.

Migratory & Wintering Shorebird
Monitoring Reports & Briefs

Migratory & Wintering Shorebird Sampling Protocols & Procedures

For more information contact: Michael W. Byrne


Monitoring Objectives

  • Determine the status and trends in normalized observations of migratory and wintering shorebirds.
  • Determine the trends in normalized observations of migratory and wintering shorebirds in areas open and closed to vehicles.
  • Determine the habitat types used by migratory and wintering shorebirds and whether these patterns change over time.


Shorebirds play a vital role in the trophic dynamics of our coastal ecosystems (Moreira 1997, Leguerrier et al 2003) and are indicators of the conditions of those systems (Morrison 1986). Because many shorebird species are highly specialized predators, the diversity of species present and their duration of stay in a location is often a good indication of the condition of that location.

Shorebirds also contribute to many people's general enjoyment of the outdoors, are the focus for many wildlife watchers, and consequently, have a significant positive impact on state and local economies (Leonard 2008). In a recent study of the economic impact of wildlife watching, Florida ranked 2nd, North Carolina ranked 8th, and Georgia 17th in the number of people involved in wildlife-watching activities, with 4.2, 2,6, and 1.9 million documented participants, respectively (Leonard 2008). Of these states, Florida ranked 2nd, Georgia 4th, and North Carolina 14th in total annual salaries, wages, and business income to the state resulting from wildlifewatching activities, at just under two billion, one billion, and a half a billion dollars, respectively (Leonard 2008).

Despite this quantifiable interest, and subsequent positive financial impact, many shorebird populations have exhibited substantial population declines (Donaldson et al. 2000, Brown et al. 2001). Approximately half of all shorebird species are considered at risk (Brown et al 2001), many of which use the National Parks in Southeast Coast Network (SECN) at some time during the year. Among these species are piping plover (Charadrius melodus), red knot (Calidris canutus), American oystercatcher (Haematopus palliates), and Wilson's plover (Charadrius wilsonia), which are considered focal species as a part of this monitoring protocol.

The National Park Service strives to understand, maintain, restore, and protect the natural resources, processes, systems, and values of the parks while providing meaningful and appropriate opportunities to enjoy them. This protocol is designed to inform park managers of the distribution of wintering and migratory shorebirds throughout park units, the habitats in which shorebirds are commonly observed, the times of day/year in which those observations occur, and the presence or absence of local and system drivers that are known or expected to affect shorebirds. However, consistently and systematically collected data on trends in presence,
timing, and habitat use for do not exist for wintering and migratory shorebirds that occur in SECN parks.

Specifically, park managers need information regarding areas of active and consistent shorebird use to guide multiple management decisions. The ability to predict areas of use by shorebirds, many of which are protected through one or more statutes or regulations, will allow NPS managers to make decisions regarding seasonal access restrictions and the type and intensity of visitor access. Identification and inventories of habitat types are critical to park managers for managing designated critical habitat, essential habitat, and recovery areas to maintain and enhance their value for the recovery of threatened and endangered species (NPS Natural Resource Management Policies and

Monitoring Approach

Field Sampling Methods

Field sampling is conducted following the methods in the SECN's migratory and wintering shorebird monitoring protocol (Byrne et al. 2009). The technique for quantifying focal-shorebird observations consists of time-constrained transect-based surveys with distance sampling of all habitat types within each park mile (Anderson et al 1979, Buckland et al. 2001). Each transect is one-mile in length and surveyed for 30 minutes. When a focal shorebird is observed, the habitat type in which it was observed, general activity (i.e., moving, flying, sedentary), and distance from the observer is recorded. The azimuth of the transect and azimuth to the focal shorebird is also recorded. General weather conditions, tidal stage, and potential sources of disturbance (i.e., vehicles, people, dogs) are also recorded within each sampling unit. The sampling units are also surveyed for beached shorebirds. When a beached or moribund shorebird is detected, the species, condition, and any obvious possible causes of death were recorded. Methods followed those developed by Byrne et al. (2009).

Data Analysis

Normalized counts (i.e., number of observations / unit of effort) are used for all calculations and most summaries, as a means to control for effort since effort varied across sampling units. Power analysis was conducted for piping plover, American oystercatcher, and red knot in accreted areas (i.e., high-intensity sampling units) and in accreted areas and beachfront areas combined (i.e., across sampling regimes). Our sampling objective is to secure 90% assurance (i.e., power) that we could detect an annual change of 20% in the mean of normalized counts (i.e., minimum detectable change) with a 5% chance of a false-change error (i.e., detecting a change when one does not actually exist). The power to detect annual and monthly trend was calculated with an equation for permanent plots without the finite population factor (Elzinga et al. 1998).

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Parks Where Protocol Will Be Implemented

CAHA - Cape Hatteras National Seashore

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  • Anderson, D.R., Laake, J.L., Crain, B.R., and Burnham, K.P. 1979. Guidelines for line transect sampling of biological populations. Journal of Wildlife Management 43:70-78.
  • Brown, S., C. Hickey, B. Harrington, and R. Gill. 2001. The United States shorebird conservation plan, 2nd ed. Manomet Center for Conservation Sciences. Manomet, Massachusetts, USA.
  • Buckland, S.T., D.R. Anderson, K.P. Burnham, J.L. Laake, D.L. Borchers, and L. Thomas. 2001. Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press. 432 pp.
  • Byrne, M.W., J.M. Maxfield, and J.C. DeVivo. 2009. Migratory and wintering shorebird monitoring at Southeast Coast Network Parks. National Park Service, Fort Collins, Colorado.
  • Donaldson, G. M., C. Hyslop, R. I. G. Morrison, H. L. Dickson, and I. Davidson. 2000. Canadian Shorebird Conservation Plan. Canadian Wildlife Service, Ottawa, Canada.
  • Elzinga, C.L., D.W. Salzer, and J.W. Willoughby. 1998. Measuring and monitoring plant populations. BLM Technical Reference 1730-1, Denver, CO, USA.
  • Leguerrier, D., N. Niquil, N. Boileau, J. Rzeznik-Orignac, P. G. Sauriau, O. Le Moine, and C. Bacher. 2003. Numerical analysis of the food web of an intertidal mudflat ecosystem on the Atlantic coast of France. Marine Ecology Progress Series 246:17-37.
  • Leonard, J. 2008. Wildlife watching in the U.S.: The economic impacts on state and national economies in 2006. Addendum to the 2006 national survey of fishing, hunting, and wildlife associated recreation. Report no. 2006-1. U.S. Fish and Wildlife Service, Arlington, Virginia, USA.
  • Moreira, F. 1997. The importance of shorebirds to energy fluxes in a food web of a south European estuary. Estuary, Coastal and Shelf Ecology 41:67-78.
  • Morrison, M. 1986. Birds as indicators of environmental change. Current Ornithology 3:485-490.

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