There are 19 species of seabirds that breed along the Pacific coast of southeastern Alaska, British Columbia, and Washington (Table 1). Southeastern Alaska has the largest number (17) of species. Errors in species identification are most likely with the Larus gulls, particularly in southeastern Alaska where the herring gull (L. argentatus) and glaucous-winged gull (L. glaucescens) breed in mixed colonies (Patten and Weisbrod 1974). A similar situation exists in Washington where the western (L. occidentalis) and glaucous-winged gulls intergrade (Scott 1971). Brandt's (Phalacrocorax penicillatus) and double-crested cormorants (P. auritus) are often difficult to identify from the air. This would be a problem in Washington and the southwest coast of Vancouver Island, where the two species are locally sympatric.
Southeastern Alaska
The area under consideration is the 400-km-long Alexander Archipelago (Fig. 1). This complex pattern of islands, bays, and inlets is characterized by extremely high precipitation and typical cool marine temperatures. Average annual precipitation in the Sitka area is 245.4 cm (1931-60), and the average annual temperature is 6.3°C (U.S. Weather Bureau 1974). As a consequence of this cool, humid environment, most of the islands are densely covered with conifers, chiefly Sitka spruce (Picea sitkensis) and hemlock (Tsuga heterophylla), and an almost impenetrable shrub cover composed of salmonberry (Rubus spectabilis), elderberry (Sambucus callicaipa), devil's club (Echinopanax horridus), and three species of Vaccinium (Heath 1915).
Fig. 1. Map of southeastern Alaska showing major seabird breeding colonies: 1—North Marble Island; 2—Forrester Island.
There are 16 species of marine birds breeding in the Alexander Archipelago. The major seabird breeding colonies are located at Glacier Bay and at St. Lazaria, Hazy, and Forrester islands (Fig. 1; Table 2). Published surveys of these colonies are available only for St. Lazaria (Willett 1912) and Forrester islands (Heath 1915; Willett 1915). Several authors have reported on seabirds from surrounding areas (Grinnell 1897, 1898, 1909; Swarth 1911, 1922, 1936; Patten 1974). There have been no surveys of seabirds of southeastern Alaska since before the 1940's (J. G. King, Jr., personal communication). However, since census data are available for only two colonies, we discuss them in more detail.
| Bird species | St. Lazaria Island | Forrester Island | ||
|---|---|---|---|---|
| Number of pairs | Percent of total | Number of pairs | Percent of total | |
| Fork-tailed storm-petrel | 2,000 | 8.0 | 10,000 | 6.0 |
| Leach's storm-petrel | 20,000 | 80.0 | 50,000 | 30.0 |
| Pelagic cormorant | 150 | 0.6 | 150 | 0.0 |
| Black oystercatcher | 4 | 0.0 | 50 | 0.0 |
| Glaucous-winged gull | 300 | 1.2 | 8,000 | 4.8 |
| Herring gull | 220 | 0.0 | ||
| Common murre | 300 | 1.2 | 20,000 | 12.0 |
| Pigeon guillemot | 150 | 0.6 | 300 | 0.0 |
| Ancient murrelet | 20,000 | 12.0 | ||
| Cassin's auklet | 2,000 | 1.2 | ||
| Rhinoceros auklet | 75 | 0.0 | 20,000 | 12.0 |
| Horned puffin | 12 | 0.0 | 1,100 | 0.7 |
| Tufted puffin | 2,000 | 8.0 | 35,000 | 21.0 |
| Total | 24,991 | 166,820 | ||
The studies by Willett (1912, 1915) and Heath (1915) provide some base-line information on species composition and abundance with which future studies on St. Lazaria and Forrester islands can be compared (Table 2). The somewhat greater species diversity on Forrester Island is primarily due to its greater size and more suitable soil type for ancient murrelets (Synthliboramphus antiquus) and Cassin's auklets (Ptychoramphus aleutica), species that are absent on St. Lazaria. Storm-petrels (Oceanodroma spp.) are the most numerous species on both islands, but there are proportionately more storm-petrels (88%) on St. Lazaria than on Forrester (36%). On the other hand, there are many large, burrowing alcids on Forrester Island. Nearly a third of the birds on Forrester are rhinoceros auklets (Cerorhinca monocerata), tufted puffins (Lunda cirrhata), and horned puffins (Fratercula corniculata).
The species composition of seabirds breeding on other islands is similar to that found on Forrester and St. Lazaria islands but less abundant. In Glacier Bay, for example, the only population data available are those provided by Patten (1974) for North Marble Island: pelagic cormorants, Phalacrocorax pelagicus (30 pairs); black oystercatchers, Haematopus bachmani (8); herring gulls (7); glaucous-winged gulls (500); common murres, Uria aalge (18); pigeon guillemots, Cepphus columba (60); horned puffins (4); and tufted puffins (30).