One may well assume that almost all the Nearctic species of mammalian fleas have probably been discovered. Concentrated collecting and study of mammals and their parasites for more than half a century has not only yielded a largely complete roster of the flea species present but has also elucidated the geographical distributions and host associations of many of them. However, this can hardly be said for the bird flea, which have been relatively neglected. The distributions and ecology of the known species are imperfectly understood and interesting records and new species can still be found, especially in the western and northern parts of the region, if one takes the trouble to search. For example, recent collections from birds' nests in Alaska, made by Dr. Robert Rausch, have yielded a number of distributional surprises (e.g., Ceratophyllus gallinae (Schrank), formerly believed to be confined to eastern North America) and examination of the nests of a mere six species of birds by the writer and J. E. H. Martin of the Entomology Research Institute during a brief collecting trip on the Alaska Highway in August, 1959, revealed five species of fleas, all belonging to the genus Ceratophyllus Curtis, and including two of special interest. One of these is new to science. The second, identified here as Ceratophyllus balati Rosicky, a species recorded in the literature only from Czechoslovakia, is redescribed here for the convenience of North American students, and also to supplement the original description. In addition to describing these, the writer wishes, in this paper, to emphasize the paucity of our knowledge of bird fleas in the hope that ornithologists and others who may find opportunities to collect and examine birds' nests (after the fledglings have left) will search for fleas.