A Breeding Biology Study of the Verdin, Auriparus flaviceps (Sundevall) in Arizona

The breeding biology of the verdin, Auriparus flaviceps (Sundevall), was studied from February 1965 through January 1967 in a Larrea-Franseria-Cercidium association, 9 miles NE of Mesa, Maricopa Co., Arizona. Behavioral data were obtained principally from studying 12 banded nesting pairs. Ninety-three verdins (36 adults, 26 immatures, fledglings that had not completed the postjuvenal molt, and 31 nestlings) were marked. The solitary verdin was resident in the study area and appeared to occupy a large home range. Breeding home ranges of six pairs in 1965 averaged 23.7 acres. Only the area near the nest was defended by both sexes. Vocal activity appeared to be extremely important in pair-formation and in integrating the verdin's activities. Eight different notes were distinguished; functions of these are discussed. Two kinds of nests were constructed: -breeding nests built by the pair and utilized for rearing the young; roosting nests built by either the male, female or lst-year verdins for roosting. Two types of roosting nests were distinguished: small nests built in late summer and larger structures, similar to breeding nests, built in autumn and winter. Roosting nests had less lining material, the entrance was more centered and the nest cup, was not deep compared to the breeding nest. Both roosting and breeding nests were composed of three distinct layers. The verdin entered the roost for the night earlier than most desert birds, and was one of the latest to arise in the morning. In 1965 eggs were found from 6 March to 8 June; in 1966, from 16 March to 29 May. Eggs were laid singly on consecutive days. Mean clutch size for 28 clutches was 3.82 eggs. Modal clutch size was four eggs. Second broods were common. Only the female incubated; the male did not develop an incubation patch. The incubation period ranged from 14 to 17 days in five nests. The mean diurnal attentive period was 11.9 min and the mean inattentive period was 9.6 min. The female incubated throughout the night. During the 1st week of the nestling period, only the female was observed to feed the young. Thereafter, the male fed the nestlings as frequently or more frequently than the female. No evidence of regurgitation feeding was found. The nestling period was 17 to 19 days. Hatching weights of the young ranged from 0.7 to 1.0 g. Fledglings received care for about 18 days; typically the male assumed this task and it was he who usually took the fledglings to the nest to roost. Fledglings were dependent upon their parents for food during the 1st week. Hatching success for 25 breeding nests was 48.8%; fledgling success was 29.1%. In 20 completed clutches, hatching success was 54.5%; fledgling success 32.4%. 1 Present address: Department of Biology, Florida Technological University, Orlando 32816