Page:Condor15(1).djvu/31

 Jin., 1913 OUTLOOK FOR CONSERVING THE BAND-TAILED PIGEON 31 In structure the nests are mere platforms of coarse 'twigs. 'One now in the Museum of Vertebrate Zoology was obtained at Fuller's Mill, in the San Jacinto Mountains, at about 590o feet altitude. The nest rested oh a large limb of a black oak, about five feet froin the main trunk, and was partly supported on one side by a small dead limb. The nest is a frail structure, made mostly of dead twigs from pine and oak trees. These twigs are laid crosswise so that there is a great amount of interstitial space. The diameter of the mass is about 220 milli- meters (83 inches), though several straggling twigs extend far beyond this limit: the depth is about :[oo millimeters (4 inches). The single egg rested at one side f the center of this rude platform. As remarked by Gilman (:[903, p. :[34) of two nests found by him in the San Jacinto Mountains at 6500 feet altitude, it is a marvel how the egg can be kept warm enough to hatch, resting on such an airy structure at that cool altitude. It is believed that both birds take part in incubation. Bendire (:[892, p. :[27) states the period of incubation to be from :[8 to 2o days. He states further that the youngleave the nest about one month after hatching. If we allow one week for the selection of nesting site and construction of nest, a total of Very close to two months is thus devoted to a single rearing. RA?E OF INCREASE In our present study, in which we are seeking for facts upon which to base recommendations relative to the proper treatment of the Band-tailed Pigeon so as to make it of greatest value to the sportman's interests, perhaps the most im- portant thing to determine is the rate of reproduction of the bird. Unfortunately the published information in regard to the number of eggs laid or young reared consists largely of general statements. At the north;in Ore- gon and Washington, there is no doubt but that two eggs not infrequently com- pose one setting. We have definite information that in the Willamette Valley three nests were found each of which contained two eggs (Bendire, :[892, p. I23). On the other hand, Dawson (I9O9, p. 553) says explicitly: eggs usually one, sometimes two. Another report, from Beaverton, Oregon, gives one as the com- plement (Woodcock, :[9o2, p. 28). In Arizona, all reports agree that but a single egg is laid. Three specific cases are on record of one egg being found in each nest. This is true also of Colorado. In California we have heard frequent reports to the effect that two eggs are commonly laid. As shown from the accompanying table, so far as definite ac- counts are available, but a single egg was the full nest complement in all cases but one. If two eggs are laid it can thus only be in exceptional instances, so rare as to be ignored in deductions concerning rate of increase. The occasional ex- ira egg might well be considered as offset by .desertions of nests, or disasters from other causes. In no case has more than one squab been found in a nest, though the data is confessedly limited. The egg-laying season of the pigeon is restricted at all latitudes to the sum- mer months. This, as shown on previous pages, is probably correlated with the fact that the bird repairs to the Transition life zone for the breeding season, which, whether at sea level in the north or on mountain ranges at the south, pre- sents inhospitable climatic conditions at other seasons. In fact, the birds them- selves undergo an annual migration, latitudinal at the north, vertical at the south. In the state of Washington, according to Dawson (:[9o9, p. 555) the pigeons arrive at the latitude of the Columbia River in April and depart in October or November; they arrive at Blaine, near the British boundary, the first week in May