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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5278

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Methods

Nesting distributions were determined for the more common ground-nesting bird species in Glacier Bay, including Arctic Tern, Black Oystercatcher, Mew Gull, and Glaucous-winged Gull. Observations of less abundant ground-nesting marine bird species were recorded, including Herring Gull (Larus argentatus), Red-throated Loon (Gavia stellata), Canada Goose (Branta canadensis), Willow Ptarmigan (Lagopus lagopus), Semipalmated Plover (Charadrius semipalmatus), Spotted Sandpiper (Actitis macularia), Least Sandpiper (Calidris minutilla), Parasitic Jaeger (Stercorarius parasiticus), and Aleutian Tern (Sterna aleutica).

The study area included shoreline within Glacier Bay proper, a recently deglaciated estuarine fjord within Glacier Bay National Park and Preserve (fig. 1). Ground-nesting marine birds and their associated nests were surveyed from June 4 through July 15, 2003; May 17 through July 1, 2004; and May 20 through June 26, 2005 (table 1). About 353, 692, and 158 km of shoreline was surveyed in 2003, 2004, and 2005, respectively (table 1 and fig. 2).

The focus of the survey areas differed during each year of the project. Areas of high visitor use were surveyed in 2003. These areas were defined on the basis of data from the National Park Service (unpub. data, 2004) as shoreline sites having 30 or more overnight visits between 1995 and 2002. Owing to relatively low nesting activity observed at sites surveyed in 2003, the survey was expanded in 2004 to include the entire shoreline except the Beardslee Islands. In 2005, the survey focused on areas where nesting activity was identified in 2003–04 and included wildlife closures and egg-collection sites historically used by Alaska Native peoples (fig. 3; Hunn and others, 2002). In 2004 and 2005, areas with higher nesting concentrations and the potential for disturbance from visitor use were revisited. These sites included the islet at the entrance to Scidmore Bay, the north spit at McBride Glacier, Sealers Island, the islet at Tlingit Point, and the west entrance to Reid Inlet (fig. 1). The number of nests and territorial pairs present were noted during each visit to these sites.

Surveys were conducted in a way to maximize the detection of birds. All areas classified as high visitor use were surveyed using a land-based approach, where observers walked the length of the beach. In areas classified as low visitor use (< 30 overnight visits in 7 years), the shoreline was surveyed from a distance of 3–15 m using a skiff in motorized waters, or a kayak in non-motorized waters. When potential nesting behavior was observed (including concentrations of birds on shore, defensive behavior by one or more birds, the presence of paired birds, or birds sitting in an incubation posture), the vessel was brought ashore and the survey was continued by walking the length of the beach. At all survey locations, the site and nest positions were recorded by using hand-held Garmin eTrex Venture Global Positioning System (GPS) units, and nest contents (eggs, chicks) also were recorded. Adult behavior, general habitat characteristics, and evidence of human disturbance also were noted.

Potential nest sites were identified by noting the location of territorial pairs. These sites were areas where defensive adults were present and nesting was likely to occur but clutches had not been initiated or found. Territorial pairs exhibited defensive behavior that included wing displays, piping or “alarm call” vocalizations, circling overhead or “dive bomb” aerial displays, and reluctance to flush from an area. When defensive behavior was observed but a clutch was not found, the location was marked as containing a territorial adult or pair.

Surveys of closed areas were conducted by tallying all birds and marine mammals on the water and on land. One or two observers went ashore to count all visible nests and note nest contents. Efforts were made to minimize disturbance and, owing to the high density of nests at these sites, GPS waypoints were not recorded at each nest.

In 2004–05, Black Oystercatcher and Arctic Tern nesting data were obtained from a concurrent study on Black Oystercatchers conducted in the Beardslee Islands region (Tessler and Garding, 2006). These nesting locations were included to describe bay-wide distribution in this report.

Data from Sharman and others (2005) were used to define nesting habitats used by nesting birds in Glacier Bay. These data, collected between 1997 and 2003 during Glacier Bay’s Coastal Resources Inventory and Mapping Project, included segment class and sediment type. Shoreline segments (generally 50–1,000 m in length) within Glacier Bay proper were classified as typical, complex, and glacial outwash. Typical segments generally were consistent in geomorphic attributes throughout the horizontal boundaries of the segment, whereas complex segments lacked consistent topographic qualities, such as slope or ratio of shoreline length to vegetation boundary length. Examples of complex segments include extensive estuarine habitats near stream mouths, rocky spits, and embayments with sinuous shorelines. Glacial outwash segments were extensive hydrologically dynamic outwashes near glacier termini. Primary sediment types were qualified as bedrock, a continuous rock surface; boulder, > 256 mm in diameter; cobbles, 64–256 mm; pebbles, 4–64 mm; granules, 2–4 mm; coarse sand, 1–2 mm; fine sand, 0.06–1 mm; and silt, < 0.06 mm or mud. A geographic information system was used to locate the shoreline segment that contained each active nest and the segment’s classification and primary substrate type was used to determine the type of habitat used for nesting by common species. More information on the methodology for the Coastal Resources Inventory and Mapping Project is available at http://www.nps.gov/archive/glba/InDepth/learn/preserve/projects/coastal/index.htm (accessed April 20, 2007).

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