This auklet apparently once bred in great numbers on islands in or near the Sanak Group where Chase Littlejohn (Bendire 1895) found them to be twice as numerous as the ancient murrelets. Murie (1959) did not find them there.
Littlejohn began encountering Cassin's auklets at sea some 290 km southeast of Unga, Shumagin Islands. Murie (1959) encountered them near the Shumagins in May 1937. During the FWS 1973 reconnaissance survey of the Alaska Peninsula, these auklets were not encountered (or at least not identified) until we reached the vicinity of Unga Strait where we saw a few in mixed flocks with other murrelets and auklets. They were most numerous in East Nagai Strait. We encountered them only twice in a situation which indicated they might be breeding—on Hall and Herendeen islands on the north end of Little Koniuji Island.
Murie (1959) considered Cassin's auklet to be no longer common west of Kodiak. In Gabrielson's many voyages through the northern and western Gulf of Alaska he encountered them only twice, once off Cape Spencer and once in the Chiswell Islands.
Thoresen (1964) commented that throughout the northern part of its range the Cassin's auklet has become gradually less frequent. Although there are no data to dispute this, I believe, as do Isleib and Kessel (1973), that they are more numerous than observations would indicate, and I would apply this to the entire area. There are certainly colonies remaining in the Shumagin Islands, and quite probably along the south coast of the Kenai Peninsula. When it is possible to fully explore the Sandman Reefs there is a good probability that they will be found there.
We can only guess at the reasons for their decline. Bendire (1895) and Murie (1959) have described some contributing factors.
Parakeet Auklet (Cyclorrhyncus psittacula)
Gabrielson and Lincoln (1959) described the parakeet auklet as the least colonial of any of the Alaskan auklets. They also considered the Aleutian Islands to be its principal nesting grounds. There are old records of breeding parakeet auklets from Kodiak (Friedmann 1935) and Little Koniuji (Bean 1882). Grinnell (1910) reported two that were seen on Green Island, Prince William Sound, and several more that were seen near Knight Island.
Murie (1959) did not see any parakeet auklets near Kodiak and Afognak islands which he considered to be the eastern part of their range. He did not think they were abundant anywhere along the Alaska Peninsula. He found a few near Sutwik Island in May 1936 and then noted that they were fairly common near the Shumagins in May 1937.
Gabrielson found this species to be quite numerous on the north side of Chowiet Island in the Semidi Islands in 1945 (Gabrielson and Lincoln 1959). He also saw numerous individuals in Marmot Strait and saw one in the Chiswell Islands during the same year. David Roseneau (Isleib and Kessel 1973) found hundreds close to East Amatuli Island in the Barren Islands in 1965.
During FWS colony surveys, parakeet auklets have been found in close proximity to six seabird colonies in Prince William Sound. During the July-August 1972 surveys, they were estimated to number about 3,000 in the Sound. They have also been found closely associated with Chisik Island (David Snarski, personal communication), the Chiswell Islands, Nord and Sud islands in the Barrens, Sea Otter Island, and Central and Long islands along the Alaska Peninsula. They were most numerous in the Shumagin Islands, where they were found near Castle Rock, Hall (9,000), Herendeen (3,000), Atkins (more than 5,000), and Little Koniuju islands. They were again encountered south and west of Cold Bay at High, Fawn, Let, Amagat, Umga, and Patton islands. Many of these islands are in the north half of the Sandman Reefs, the only portion where any attempt has been made to survey seabird colonies.