These small, fast flying seabirds are unique among alcids in North America in their use of coastal coniferous forests, primarily old-growth trees, as nesting habitat. Their solitary nests are usually concealed within the forest canopy, and breeding birds are cryptic and primarily crepuscular at nest sites.
Because of their secretive behavior and elusive nests, Marbled murrelets were considered the "enigma of the Pacific" and were one of the last ornithological mysteries in North America, as the first nest was not discovered until 1974.
Distribution at inland nesting sites is fragmented, as birds occur only in areas where suitable habitat remains. It visits inland breeding sites at all times of the year except during the prebasic molt in early fall.