Page:Auk Volume 37-1920.djvu/154

 84 Grinnell, Sequestration Notes. Uau. 5 soon passed and the rest of the month was rather even weather, with not a low temperature. On March 25 I found that Piping Plovers had arrived on the beach, but I saw neither Sanderlings nor Red-backs. April 1 was warm, sunny and springlike. "Many Geese are going over the beach and I find that the numbers of Piping Plovers have increased since March 25. Saw two Sanderlings whch may or may not have been the birds of last winter." 52 Cedar St., Maiden, Mass. SEQUESTRATION NOTES. BY JOSEPH GRINNELL. There is every reason to believe that the voices of birds have been subject to a process of evolution which has led from the sim- plest beginnings to a condition which is rather complicated in the higher present-day species. The first sounds uttered by primitive birds were doubtless entirely of an incidental nature, due to expul- sion of air under stress of pain or fear, or simply of physical impact. According to one theory (Witchell, 'The Evolution of Bird -Song,' London, 1896) the first specialization accompanied combat and involved a meaning of defiance or intimidation; from this it was an easy step to notes conveying the idea of alarm to other indi- viduals of the same species. Whatever the course in the early development of bird voices, it is obvious to any field student that in the higher existing birds an often very elaborate system of cries or calls obtains, with an associated wide range of meaning; as witness the Titmouses and Ruby-crowned Kinglets. Some of the meanings, in certain species, have been demonstrated beyond all question of doubt. The less obvious meanings will have to be worked out by slow process, and exceeding care be taken to avoid mere guess-work.