Wildlife

Ring of Fire
Bogoslof Birds

Seabirds Respond to Volcano’s Changing Habitat

Nesting habitat for birds on volcanic Bogoslof Island (54^oN, 168^oW), Alaska, has changed constantly since this island emerged from the sea starting in 1796. Bird populations have fluctuated with those changes.

Rock cliffs formed, eroded into boulders, and then broke down into soil which supported vegetation. During the period of greatest recorded land mass (late 1800s), cliff-nesting habitat was at least 17 times greater at Bogoslof and 25 times greater at Fire Island than in the 1973 when censuses were again taken on this one-mile-long island.

Murres increased the most after cliff formation, reaching peak numbers by the late 1800s. The 1899 Harriman Expedition stopped on Bogoslof Island and C. Hart Merriam described the murres as darkening the sky when flushed off their cliffs.

With later cliff reduction, the murre population decreased proportionally, reaching a low of less than 100,000 by 1935.

Cliff-nesting black-legged kittiwakes and cormorants may have followed a similar pattern. Without another eruption, cliff nesting habitat will continue to decrease. Cliffs along the edges of Bogoslof’s plateau are eroding at a more rapid rate than at adjacent Castle Rock, Kenyon Dome, and Fire Island.

Boulder-strewn beaches have periodically provided potential nesting habitat for pigeon guillemots and horned puffins at Bogoslof, but the light pumice-like boulders soon eroded into sand, making this habitat available only briefly. Boulder habitat could be created again on Bogoslof only by another eruption.

Kenyon Dome, composed primarily of basalt columns, is a relatively stable structure which should provide long-term habitat for crevice nesters such as horned puffins.

The erosion of volcanic rocks into soil helped to form habitat for burrow-nesting birds. Formation of the plateau in the early 1900s was the first habitat of this sort on Bogoslof. The two burrowing species that now breed on Bogoslof (fork-tailed storm-petrel and tufted puffin) have only been found breeding here since the 1930s.

The increase in tufted puffins has been phenomenal - from 60 to 5,000 birds in 27 years. Only since 1950 has the cover of vegetation stabilized the soil enough to prevent burrows from easily collapsing. The formation of a vegetated slope (Puffin Slope) has been key to the tufted puffin increase.

The increase in vegetation also is correlated with the presence of glaucous-winged gulls, winter wrens and song sparrows. All of these birds require plants for nest material.

The changes in the composition and abundance of birds on Bogoslof Island provide a ongoing example of the colonization by seabirds of a recently-formed volcano.

NOTE: In 1909 President Theodore Roosevelt dedicated Bogoslof and Fire islands as a sanctuary for sea lions and nesting marine birds. They are now part of the Alaska Maritime National Wildlife Refuge. The islands were added to the National Wilderness Preservation System in 1970.

Learn More about Wildlife on Bogoslof Island

Radio Interview Transcript, contrasting red-legged kittiwakes of Bogoslof and Pribilof islands (includes link to audio)

Effects of Food Stress on reproductive performance of seabirds at Pribilofs and Bogoslof Islands, Bering Sea(includes photos)

Last updated:September 8, 2008