Further Studies of the Genus Quiscalus

Abstract

IN my preceding 'Auk' papers' on the genus Quiscalus, I treated of the grackles of Louisiana and Mississippi. From those States, thanks chiefly to the cooperation of Mr. E. A. Mcllhenny, I have had a sufficient number of breeding males to warrant an attempt to define their ranges and relationships. Reviewing briefly the theories advanced and results obtained: early in the history of what is believed to be their post-glacial rangeextension from Florida and Texas respectively, Stone's and the Bronzed Grackles first met in southern Louisiana and completely merged by interbreeding. The area of intergradation in the State named now averages forty miles in width. North of this zone, which here trends east and west, only aeneus2 occurs; south of it, only stonei and the Florida form, from which it appears to have descended, are found. In the narrow band separating the two typical primary parental forms, complete intergradation occurs. Sometimes this phenomenon is found in a single colony. The relationships of the birds under these conditions seem clear. As we enter Mississippi the problem becomes more complicated. It will be found treated in the fourth of my 'Auk' papers. Here I wish merely to state that the first papers in this series treated of the birds concerned in the most southern area of their intergradation, while in the present paper I consider them in the most northern area of their intergradation. With the passage of time aeneus has extended its range northward through the interior to Slave Lake and from the upper Mississippi valley has swept eastward through New York on a front which now reaches from the lower Hudson valley eastward and northward; while stonei has ranged northward through Cis-Alleghenia to the northern limits of the Carolinian Fauna, including Long Island and the Connecticut valley. As we try to picture the original grackle invasion of this territory we must remember that by no means all of the newcomers were typical of either stonei or aeneus. The study of adequate material from Louisiana, and particularly Mississippi, has given us some conception of the character of the grackle population at the junction of the western with the eastern form. In this area of intergradation pure-blooded individuals are comparatively rare while intermediates