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Scientific Investigations Report 2007–5278

Scientific Investigations Report 2007–5278

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Distribution of Ground-Nesting Marine Birds

Ground-nesting marine birds were widely distributed throughout the bay, and nesting was documented for the first time at some sites. The largest previously undocumented breeding habitat was found in the recently deglaciated area along the north shore of Muir Inlet, where nesting was highly dispersed in outwashes and along the hillsides. Notable concentrations of ground-nesting birds at previously undocumented locations also were found on the Grand Pacific Glacier moraine, the Adams Glacier outwash, and at the small unnamed islet at Tlingit Point.

Overall, 252 active nests and 52 territorial pairs were mapped in 2003, 402 active nests and 158 territorial pairs were mapped in 2004, and 941 active nests and 49 territorial pairs were mapped in 2005 (table 2). The difference in nest and territorial pair counts among years reflects differences in the shoreline covered and the areas of focus for a given year. Summaries of nest counts and contents at different locations are provided for the more common ground-nesting species.

Life history traits of the common species, including solitary versus colonial nesting habits, determined the bay-wide distribution patterns observed. Black Oystercatchers, a solitary nesting species, were abundant and widely distributed within Glacier Bay. Mew Gulls nested either solitarily or sometimes in mixed colonies with other species and were more widely distributed than other colonial species. In contrast, Arctic Terns and Glaucous-winged Gulls were relatively abundant; however, they occurred in fewer areas of Glacier Bay within more concentrated colonies.

In this section, findings are presented for the four common species and for several less common species. Observations are then described for nesting at specific sites within the bay, including three sites with current high visitor use, six sites with current low visitor use, at wildlife closures, and at historic egg-collection sites. The section concludes with a discussion of shoreline habitat availability and use by ground-nesting birds in Glacier Bay.

Arctic Tern

Nesting distribution for Arctic Terns was largely restricted to the upper arms of the bay and a few treeless islets in the lower bay (fig. 4). The largest Arctic Tern colonies were found near the moraine of the Grand Pacific Glacier, on Sealers Island, and on the islet at Tlingit Point. Smaller nesting concentrations were located in Adams Inlet and on an islet at the entrance to Scidmore Bay (table 8, at back of report). Additionally, 10 nests containing eggs were found at Topeka outwash by NPS researchers conducting unrelated research on June 15, 2004; however, all nests were gone by June 30 (Tania Lewis, National Park Service, oral commun., 2004), and no nesting activity was observed during the survey of that outwash on July 1, 2004. Nesting attempts also were observed at Reid Inlet in 2004 and at McBride Inlet in 2004 and 2005 (see section, “Areas of Concern”). Arctic Terns commonly nested in mixed colonies with Mew Gulls, Glaucous-winged Gulls, and Aleutian Terns (at one site).

Black Oystercatcher

Breeding Black Oystercatchers were widely distributed in Glacier Bay (figs. 5 and 6). Notable concentrations of breeding birds were found on Leland Islands, the islet at Tlingit Point, on several islands in the Beardslee Islands in 2005 (Tessler and Garding, 2006), and on Sturgess Island (table 9, at back of report). Black Oystercatchers nested solitarily or near nesting Mew Gulls, Arctic Terns, or Glaucous-winged Gulls. Black Oystercatcher nests commonly were found near old (indicated by vegetation overgrowth) empty scrapes, indicating that one or more pairs had nested nearby previously (within the same season or in past years).

Mew Gull

Mew Gulls nested throughout the upper bay in Geikie Inlet and in Fingers and Berg Bays (figs. 7and 8). Higher concentrations of nests were found at the head of Queen Inlet and along the north shore of Muir Inlet between Riggs and Muir Glaciers (table 10, at back of report). Mew Gulls also were found nesting on the largest unnamed closed island near Russell Island. In some areas, they nested in mixed colonies with Arctic Terns, Glaucous-winged Gulls, and other species, whereas they were solitary nesters in other areas.

Glaucous-Winged Gull

Most Glaucous-winged Gull nests were found at islands that generally were closed to public visitation (so called wildlife closures) in the central and lower bay (fig. 9 and table 11, at back of report). Glaucous-winged Gulls generally nested in concentrated colonies, such as those found at South Marble Island, Lone Island, Geikie Rock, and Boulder Island. At these sites, they nested in close proximity to one another with nests commonly hidden in ryegrass (Elymus arenarius) or built on bedrock. An exception to the concentrated colonies was along the north shore of Muir Inlet, where nests were dispersed along a 10-km stretch of early successional habitat between Riggs and Muir Glaciers. Although most nests along the north shore of Muir Inlet colony were found close to the shore, one nest was located nearly 400 m inland on the top of a hill.

Herring Gull

Herring Gull nests were found near the head of Muir Inlet, on a cliff in Johns Hopkins Inlet, on Geikie Rock, and on the islet at Tlingit Point (fig. 10). This species nested in mixed colonies with Glaucous-winged Gulls, Mew Gulls, and Arctic Terns. Herring Gull nests were considerably less abundant than those of Glaucous-winged Gulls. Evidence of hybridization between Herring and Glaucous-winged Gulls was observed. Three gull nests could not be identified as either species because the nests were high on a cliff and the incubating adult could not be identified. In one case, an individual from each species was attending the same nest. Copulation between a Herring Gull and a Glaucous-winged Gull was observed at the mixed gull colony along the north shore of Muir Inlet, and adults with blackish-grey wing-tips, an intermediate characteristic between the two species, were observed at the same location.

Other Species

In addition to the abundant ground-nesting species, several other less abundant species also were observed nesting on beaches in Glacier Bay. These species are solitary nesters and have well camouflaged nests. Because of these cryptic nesting habits, the survey methods did not adequately detect breeding activity for the species and nests were only found incidental to searching on land for other nests. Thus, our results represent a minimum estimate of pairs and nests for these species. Because of low sample size, average clutch size for these species was not calculated.

Red-Throated Loon

A Red-throated Loon nest containing one egg and attended by one adult was located at a small pond along the northern shore of Muir Inlet (fig. 11). Another adult was observed at an adjacent pond, but no nest was found.

Canada Goose

One Canada Goose nest was found near the entrance to Scidmore Bay (fig. 11).

Willow Ptarmigan

One Willow Ptarmigan nest was located in Reid Inlet (fig. 11). Willow Ptarmigan were observed at the alluvial fan near Russell Cut, but no nest was found there.

Semipalmated Plover

Semipalmated Plovers were found nesting at several locations throughout the bay, with notable concentrations at the north spit of McBride Inlet, at Reid Inlet, and at the Adams Glacier outwash (fig. 12). They were found nesting near low vegetation on flat, sand and gravel shorelines and mostly up-bay, where early successional habitat is abundant.

Spotted Sandpiper

Surveys located two active Spotted Sandpiper nests in 2003 and six active nests in 2004. In addition, nine territorial pairs were located in 2004 (fig. 11). Their nests commonly were found near freshwater runoff within dense vegetation.

Least Sandpiper

Two Least Sandpiper nests were found that contained eggs: one at Reid Inlet and one at McBride Inlet (fig. 11).

Parasitic Jaeger

Parasitic Jaeger nests were found near Reid Glacier and in Adams Inlet (fig. 11). Pairs of Parasitic Jaeger were observed flying at the east glacier face in Reid Inlet and over Forest Creek in Muir Inlet in 2004.

Aleutian Tern

Four Aleutian Tern nests and one territorial pair were found in Adams Inlet (fig. 11). There were 37 adult Aleutian Terns at this site on June 14, 2005. In addition, one adult Aleutian Tern, behaving in a moderately defensive manner (alarm calling, circling overhead) was observed at the alluvial fan near Russell Cut on May 21, 2004. All observations of Aleutian Terns were within Arctic Tern nesting colonies. In flight, the Aleutian Terns could be distinguished most easily from the Arctic Terns by their call. The four nests were made on top of vegetation (including yellow mountain avens, Dryas drummondii) adjacent to sparse Sitka Alder (Alnus viridis subsp. sinuata) shrubs. The Arctic Terns nesting in the same outwash were nesting closer to shore on bare sand and were separate from the Aleutian Tern nests.

Areas of Concern Open to Public Access

Sites that met either of the following criteria were defined as areas of concern:

  1. Shorelines currently receiving high visitor use (> 30 overnight visits) that contain concentrated nesting activities.
  2. Shorelines currently receiving low visitor use (< 30 overnight visits) that contain concentrated nesting activities in areas where visitor use may increase in the future because of changing camper drop-off locations and small islands where camping may seem attractive to visitors who want to avoid bear encounters.

We identified areas of concern in three high visitor use areas and six low visitor use areas (fig. 13 and table 3).

High Visitor Use

Sealers Island

The high visitor use area at Sealers Island supports nesting Arctic Terns, Black Oystercatchers, Mew Gulls, and Glaucous-winged Gulls (table 3). In 2003, the survey found 16 Arctic Tern nests at this site. During the survey in 2004, recently depredated Arctic Tern eggshells and 8–10 defensive adults were noted at this site on May 28. Nesting had not been successfully reinitiated by June 16. In 2005, Sealers Island was visited three times: May 29, June 6, and June 26. During these visits, surveys found 46 nests with 75 adults present, 14 nests with 45 adults present, and 13 nests with 55 adults present, respectively (table 4).

Survey observations suggest that predation of Arctic Tern nests, by either bears that frequented the colony or by Northwestern Crows (Corvus caurinus) that nest in the center of the island, was a factor in the reduced nesting activity on the island during the 2005 breeding season. Predated eggshells were observed on the second and third visits in 2005. Furthermore, on the second visit, there was recent bear scat on the far edge of the nesting area, indicating that at least one bear walked through the colony. At least five Northwestern Crow nests were observed in the center of the island in 2003, and one pair nested in the Arctic Tern colony area in 2004.

North Spit at McBride Glacier

In the past, Arctic Terns have nested in fairly low concentrations at the spit in front of McBride Glacier (Greg Streveler and Bruce Paige, retired, National Park Service, oral commun., 2005). Nesting Arctic Terns were absent from the McBride Glacier area during the survey in 2003 for this study. Only 3–8 nests were found in 2004 and 2005. In all years of the survey, terns were observed flying in the area and feeding offshore. Mew Gulls, Black Oystercatchers, and Semipalmated Plovers also nested within the high visitor use area on the north spit (table 3).

West Entrance to Reid Inlet

Arctic Terns also have used the spit at the entrance to Reid Inlet for nesting in the past (Wik, 1968; Bruce Paige, retired, National Park Service, oral commun., 2005). Arctic Terns were absent from Reid Inlet during the survey in 2003; however, 15 nests were found in 2004 between May 27 and June 6. By June 26, 2004, all Arctic Tern nests had disappeared. One of those nests was trampled by a visitor on June 20, 2004. This was the only observation of direct human impact on beach-nesting birds during the study. No Arctic Terns were observed nesting at this site during four visits between May 21 and June 18, 2005 (table 4). Black Oystercatcher, Mew Gull, and Semipalmated Plover nests also were found on the west spit at the entrance to Reid Inlet during all years of the study.

Low Visitor Use

North Shore of Muir Inlet

The low visitor use area on the north shore between Riggs and Muir Glaciers had more nests than any other area open to visitors in the bay; surveys found 69 nests in 2004 and 63 nests in 2005. There also were at least 21 nests in this area in 2003; however, not all nests on this shoreline were mapped during the survey. The poor weather prompted the survey team to minimize egg exposure time while adults were off the nest. In general, nesting was spread out over a large area of early successional, sparsely vegetated hillside.

Adams Glacier Outwash

The large outwash on the southwest shore of Adams Inlet had at least 30 and 54 active nests from several species in 2004 and 2005, respectively. At this site, about 500 Arctic Terns were noted in 2004 and 357 Arctic Terns were noted in 2005 (table 3). Most of the adult Arctic Terns were feeding in the nearshore area at this site. The survey also found nesting Black Oystercatchers, Mew Gulls, Semipalmated Plovers, Parasitic Jaegers, and Aleutian Terns. Nests were highly dispersed within this large cobble outwash, and it is possible that the number of nests was underestimated owing to the cryptic nature of nests.

Moraine at Grand Pacific Glacier

The moraine at the base of Grand Pacific Glacier is notable because the Arctic Tern bird count and nesting activities were the highest in the bay. A total of 64 Arctic Tern nests and 3 Mew Gull nests were found at this site on June 13, 2005. In addition, there were about 200 adult Arctic Terns, 11 Mew Gulls, and 2 Parasitic Jaegers flying over this area (table 3).

Unnamed Islet Northwest of Eider Island

The unnamed islet northwest of Eider Island had 13 Arctic Tern and 4 Black Oystercatcher active nests, and some 300 Arctic Tern adults on May 27, 2004. Fifteen Arctic Tern nests contained eggs on June 20, 2005. Fifteen Black Oystercatcher nests were initiated over the course of the summer (Alaska Department of Fish and Game, 2006).

Islet at the Entrance to Scidmore Bay

On June 30, 2004, a total of 23 nests of Black Oystercatchers, Mew Gulls, and Arctic Terns were found on the islet at the entrance to Scidmore Bay (table 3). A Canada Goose nest containing six eggs was found on June 17, 2005. Arctic Terns were not found on this islet in 2003 or 2005.

Islet at Tlingit Point

Nesting concentration was relatively high at the islet at Tlingit Point during all 3 years of this study, with 11 nests and 3 territorial pairs in 2003, 18 nests and 3 territorial pairs in 2004, and 36 nests and 1 territorial pair in 2005. Arctic Terns, Black Oystercatchers, Mew Gulls, Glaucous-winged Gulls, and Herring Gulls nest on this small island (table 3). This island is close to a regular camper dropoff at Sebree Island and therefore has a high potential for camping.

Wildlife Closures

Areas that have been historically closed to foot traffic because of concerns about disturbance to wildlife were surveyed in 2003 and 2005 to assess the current status of nesting birds.

Unnamed Islands East of Russell Island

The four unnamed islands east of Russell Island were surveyed on July 2, 2003, and the largest island was surveyed again on June 18, 2005 (table 5). Arctic Terns, Black Oystercatchers, and Mew Gulls were nesting on the group of three small islands to the east of the largest island in 2003. The largest and westernmost island in this group is an important nesting area for these species. Most of the nesting activity was limited to the west point of the island. In 2003, surveys observed nesting Arctic Terns, Black Oystercatchers, and Mew Gulls; 1 Arctic Tern egg was hatching and 1 Black Oystercatcher chick and 13 Mew Gull chicks were at the water’s edge. In 2005, surveys located two Black Oystercatcher nests and two territorial pairs, and nine Mew Gull nests. Arctic Terns were not nesting on the island during the 2005 survey, although two adults were present.

Lone Island

On July 15, 2003, there were nine harbor seals (Phoca vitulina) and three Steller’s sea lions (Eumetopias jubatus) hauled out on Lone Island; therefore, observations were made from the boat to minimize disturbance. There were 44 empty Black-legged Kittiwake (Rissa tridactyla) nests, and adults were stomping on nesting material or standing in pairs on nests; however, no chicks were observed nor any eggs in the nests. The Northwestern Crows were concentrated in alder where they may have been nesting. One Tufted Puffin (Fratercula cirrhata) was seen flying from a burrow on the northeast side of the island. In 2003, survey members did not go ashore because the NPS waiver to conduct research in a closed area was issued after the incubation period and it was not possible to quantify nests at the time of the survey.

The survey team circumnavigated Lone Island and landed ashore to count nests on June 12, 2005. A total of 125 active nests were found and 115 of these were Glaucous-winged Gull nests (table 5). Most Glaucous-winged Gull nests were in the grassy meadow near the center of the island; average clutch size was 2.4 eggs/nest (n = 115). Of the 47 Black-legged Kittiwake nest bowls observed, 15 were being incubated by an adult. Eight of those were active nests, 5 contained two eggs, and 3 contained a single egg. From the water, the survey also observed four Herring Gulls sitting on nests, although it was unsafe to check the contents of these cliff nests while the survey members were on land. Two Black Oystercatcher nests and one territorial pair were found during the survey on land.

Geikie Rock

Geikie Rock was surveyed from a skiff on July 15, 2003. Five Glaucous-winged Gull chicks were at the shoreline, and fish-holding behavior was observed in Arctic Terns and Pigeon Guillemots (Cepphus columba), which suggests they also were nesting in the area. Of the 250 Black-legged Kittiwakes on the rock, about 90 percent were immature. The survey team stayed offshore to minimize disturbance to the colony during chick rearing.

On June 12, 2005, a total of 52 active nests were found at Geikie Rock (table 5). The survey located 3 Black Oystercatcher nests and 2 territorial pairs, 48 Glaucous-winged Gull nests, and 1 Herring Gull nest. The average Glaucous-winged Gull clutch size was 2.52 eggs/nest (n = 48).

Leland Islands

Leland Islands were surveyed by foot on July 7, 2003. Eight Black Oystercatcher nests, all containing eggs, were found on the northern part of the island. On June 23, 2005, the survey found 24 active nests. Nine Arctic Tern and 2 Black Oystercatcher nests were mapped on the southern part of the island, and 13 Black Oystercatcher nests were mapped on the northern part of island.

Boulder Island

Boulder Island was surveyed by foot on July 12, 2003. A total of 41 active Glaucous-winged Gull nests were found with an average clutch size of 2.58 eggs/nest (n = 40). One nest had one chick and one hatching chick. Two active Black Oystercatcher nests also were found on this island.

Flapjack Island

Flapjack Island was surveyed from land on June 26, 2003. The survey found 26 active Glaucous-winged Gull nests concentrated on the north end of the island. Average clutch size was 1.68 eggs/nest (n = 25). Twenty-five Glaucous-winged Gull nests contained eggs, and one nest had a single chick. One Black Oystercatcher nest with eggs and one territorial Black Oystercatcher pair also were found on the island. This island appears to be an important roosting area for birds. A group of 43 non-breeding Black Oystercatchers, about 225 adult and more than 900 subadult Black-legged Kittiwakes, 200 mostly subadult Glaucous-winged Gulls, and about 300 Red-breasted Mergansers (Mergus serrator) were found on the beach (table 5).

South Marble Island

South Marble Island was surveyed on June 10, 2005. The survey noted 311 Black-legged Kittiwake nests, 34 of which were being incubated. Three potential Tufted Puffin nests were identified from adults flying from crevices, and 85 Glaucous-winged Gull adults were sitting on nests on cliffs viewed from the water. Five additional Glaucous-winged Gull nests were viewed from land and they had incubating adults and therefore unknown nests contents. There were an additional 200 Glaucous-winged Gull nests visible from land, and the average clutch size was 2.4 eggs/nest (n = 200). Three Black Oystercatcher nests also were located on the island.

Efforts were made to minimize disturbance to marine birds and mammals on the island; however, most of the Steller’s sea lions that were hauled out were flushed from the island when the survey team landed. About 305 Steller’s sea lions were noted on the island during our survey: 120 were on the southern islet, 85 were near the center of the island facing east, and 100 were on the north end of the island.

Eider Island

Eider Island was surveyed on June 26, 2005. Two active Black Oystercatcher nests and one territorial pair were found on the island.

Egg-Collection Sites Historically Used by Alaska Native People

There were five sites identified in Hunn and others (2002) that contained more than 25 Glaucous-winged Gull nests: Flapjack Island, Boulder Island, South Marble Island, Lone Island, and Geikie Rock. Five sites had zero nests of any bird species and eight sites had less than 10 nests (table 6). Many of the historical native egg-collection sites do not support nesting populations of marine birds, owing to the succession of terrestrial vegetation after glacial retreat. For example, Willoughby Island was once a large nesting colony for gulls with little vegetation or soil along the western slope (Bailey, 1927). During our surveys, only a single nesting pair of Black Oystercatchers was found on Willoughby Island and the western slope of the island was covered in woody vegetation.


Shoreline habitat in Glacier Bay varies in complexity and substrate type (Sharman and others, 2005; fig. 14). Primary substrate for complex shoreline segments consisted largely of pebbles, fine sand, and silt. Glacial outwash shoreline segments were dominated by fine sand and silt, whereas the more typical shoreline segments consisted mostly of pebbles, fine sand, and silt. Typical shoreline segments also contained more bedrock, boulder, and cobbles as primary substrate than other segment types. Overall, there is more shoreline classified as typical than as complex or glacial outwash.

Habitat used for nesting varied by species (fig. 15). Arctic Tern nests were found more often in fine-sand habitats than in other habitat types. Black Oystercatcher nests were usually found along shorelines with pebbles as the primary substrate, whereas most Glaucous-winged Gulls nested on bedrock. Mew Gulls nested in a variety of substrate types. Frequency of occurrence for Arctic Tern nests in glacial outwash shoreline types was higher than the frequency for other shoreline types. Nests of Black Oystercatchers, Mew Gulls, and Glaucous-winged Gulls were usually found on typical shoreline types (table 7).

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