General comment.—The exact relationship between molt and migration seems not to have been definitely established. The subject has received cursory attention in the literature and conflicting opinions have been expressed. Dwight (1900:126-128) believed that molt is completed or nearly completed before migration in nearly all passerine species that occur in New York save for certain swallows and flycatchers. Molt has since been found to precede migration of at least one of the flycatchers (Empidonax virescens) considered by Dwight to be an exception to this rule (Mengel, 1952). In Great Britain the subject of molt in migration was considered in some detail by Rintoul and Baxter (1914) and Ticehurst (1916), who arrived at conclusions similar to Dwight's. These workers also found certain swallows to be exceptions to the rule.

The above authors and others have shown that, at least among passerines, some body molt is frequently found in migrating individuals but that molt of tail feathers is much less often found and molt of remiges almost nonexistent. Baxter and Rintoul noted only four cases of molting wing feathers among hundreds of migrants. Among the diverse non-passerine orders the picture seems to be more complicated, as might be expected. We do not, however, comprehend the reasoning which led Meinertzhagen (1930:56) to summarize: "... on the whole it can be said that though birds seldom migrate when flight feathers are in quill, moult in general does not influence migration." This seems to us an obvious non sequitur. Meinertzhagen (loc. cit.) went on to say: "Males and females of one species are believed to moult simultaneously [see, however, Dwight, 1900:127], and there is no doubt that in some cases the two sexes migrate at slightly different times, and occasionally prefer different winter quarters. Birds of the year never moult their quills previous to their first autumn migration [Consultation of Dwight, 1900, who gives many examples of this, would have spared Meinertzhagen this error.], and yet they frequently follow adults on passage and sometimes precede them. There are no grounds for believing that adults have moulted their quills before birds of the year are prepared to migrate [but there are, in many cases; cf. Dwight, 1900:127], in the case where adults precede the latter. Neither is there any evidence to show that adults have not moulted their quills till after their offspring are ready for passage, in the case where they follow their offspring. It does not, therefore, appear that moult is an important factor."

Comments interpolated above show our feeling that this summary is inadequate and misleading. To us it seems that the extreme rarity in migration of birds with remiges in molt is strong evidence that molt does influence at least the time of migration. It is immaterial whether this molt occurs before or after migration, although in the majority of cases it seems to take place before. Much more needs to be known of the migration pattern and molt of each species before generalizations can safely be made.

Analysis of samples of migrants can show only the presence and nature or the absence of molt in birds actually migrating. In the present instance shortage of time and manpower for preserving some and processing all of the sample resulted in incomplete data being kept on molt. We include this section to emphasize uncertainties still prevalent and to stimulate further work.

Molt in the Topeka sample.—Our limited findings coincide with those of Rintoul and Baxter (1914). Body molt was noted in a number of individuals and species. When present, this molt almost invariably was in its final stages. One immature male Rose-breasted Grosbeak (October 1) was in heavy body molt. It is perhaps worthy of mention here that this grosbeak evidently migrates at times in extensive molt. An adult male (RMM 1102) taken by Mengel near Henderson, Kentucky, on September 9, 1949, was molting plumage of body, wings, and tail, no feather of the last being longer than one half inch. This remarkable specimen had only five primaries on one side and four on the other fully functional. The outermost on the left and two outermost on the right were from the previous plumage, not yet dropped; the three innermost of each wing were new and full-length.

In the present sample molt of remiges was noted in one specimen, an adult female Indigo Bunting (October 1) with outer primaries sheathed and with molt in progress in the body plumage. The one (immature) Yellow-breasted Chat in the sample (October 1) had all of its tail feathers nearly full-length but in quill, possibly as a result of accident, and two feathers were being replaced also in the tail of an immature Clay-colored Sparrow (October 6), which was also in body molt and had some, juvenal feathers on the belly and flanks.

Body molt near completion was further noted as follows: immature male Yellow-throated Vireo (October 1), adult male Blue-headed Vireo (October 1), immature female Leconte Sparrow (October 23), several Lincoln Sparrows (various dates).