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 Sept., 1918 EVIDENCE THAT MANY BIRDS REMAIN MATED FOR LIFE 169 Among the woodpeckers, one of the best evidences that the same pair re- mains together year after year is the series of nesting cavities excavated up and down a single dead tree or branch. A pair of Cabanis Woodpeckers (Dryobates v. hyloscopus) had nested for several seasons in the dead top of a tall pine. One winter, this broke off and lodged in the top of an adjoining pine. Even with their nest site in this apparently insecure position the woodpeckers were unwill- ing to leave it, and their new nest was found dug in the same old tree top in its inverted position. Along the San Pedro River the Cactus Woodpecker (Dryo- bates s. cactophilus) is the only one nesting at all commonly. In the lines of wil- lows bordering the irrigation ditches and in the small groups found along the river banks, I had quite a list of pairs whose nests I could count upon finding within certain circumscribed areas. They exhibited individual characteristics. One pair never dug its nest lower than twenty feet from the ground and usually selected a site that overhung the water. Another liked short stubs not over five or six feet tall. Another was partial to fence posts. While these selections were not invariably followed they were so usual that I always began my search by ex- am.ining all the available sites of that character before looking at others and was usually successful in my first search. In the giant cactus around Tucson, the Gilded Flicker (Colaptes chrysoides) and the Gila Woodpecker (Centurus uro- pygialis) were very common and I have a long list of pairs of these two species with specified groups of cactus where they are to be found. Of the doves, the Inca Dove (Scardafella inca) and Mexican Ground Dove (Uhaemepclia p. pallescens) illustrate my point the best. Qne pair of Inca Doves in Tombstone nested either in an elderberry tree on a certain corner, or in a mulberry tree some seventy-five yards farther down and across .the street. Even repeatedly losing their eggs failed to disturb them. One pair of Mexican Ground Doves always nested in a certain clump of willow brush or an adjacen large willow tree. I believe the other two nesting doves, the White-winged Dove (Melopelia asiatica) and Mourning Dove (Zenaidura m. carolinensis) would of- rer as good examples were it not that the locality where I most regularly collected them, along the San Pedro River near Fairbanks, was a favorite hunting ground or the sportsmen of that region and that the pairs were constantly being broken up by one or the other of the birds being shot. The Canyon Towhee (Pipilo f. mesoleucus) and Abert Towhee (Pipilo aberti) could both be relied upon to nest regularly in given spots. A pair of Can- yon Towhees had their first nest of the season always in the vines growing on our house. Their second nest was in a nearby umbrella tree. Their third nest was either in this same tree or ih a small cottonwood just outside the fence. In this case the marked similarity of the eggs each year was very good evidence that the same bird laid them, and as the two birds were resident and hung around the house all the year it seems almost an assured fact that she had the same mate each time. Along the San Pedro River I had a series of pairs of the Abert Towhee located from which I could secure sets whenever I chose, during the season. As many of these birds built in situations where I could collect nothing but the nests (i. e., without the supporting branches) they frequently used exactly the same site year after year. I could multiply the illustrations used and make them include the Anthony Green Heron (Butorides v. anthonyi), Western Yellowthroat (Geothlypis t. oc- cidcntalis), Cooper Tanager ( Piranga r. cooperi), Western Blue Grosbeak ( Gui- raca c. lazula), Arizona Pyrrhuloxia ( Pyrrhuloxia s. sinuata), Cassin and Vest-