Distribution and abundance of Marbled Murrelets in Alaska

Most seabirds breed in colonies on offshore islands, but throughout most of their range from California to Alaska Marbled Murrelets (Brachyramphus marmoratus) fly inland to nest on trees in old-growth coniferous forests. Some fraction of the murrelet population nests on the ground in Alaska. The relative distribution and abundance of murrelets in forested and treeless areas of Alaska is poorly known. We analyzed data on seabird abundance at sea and on colonies in Alaska that were obtained under the Outer Continental Shelf Environmental Assessment Program during the 1970s and 1980s. Whereas most seabirds may be censused at breeding colonies, murrelet populations must be estimated from surveys at sea. We compared colony and pelagic population estimates for 13 colonial seabird species in Alaska and found that they were strongly correlated (r² = 0.94). We therefore used at-sea censuses to estimate that at least 160,000 murrelets reside in Alaska. Most (97%) Marbled Murrelets are concentrated offshore of large tracts of coastal coniferous forests in southeast Alaska (Alexander Archipelago), Prince William Sound, and the Kodiak Archipelago.