Yellow-eyed Junco Junco phaeonotus

The Yellow-eyed Junco occurs in Transition and Boreal Zones in the mountains from the southwestern United States to Guatemala and is resident throughout much of its range. In southern Arizona and southwestern New Mexico, pairs maintain all-purpose breeding territories and then migrate to lower elevations and form winter flocks with the Dark-eyed Junco (Junco hyemalis). These relatively confiding birds forage on the ground and are easily seen, often frequenting campsites and picnic areas. In southern Arizona, pairs remain together throughout the breeding period, producing up to 3 successful broods per year. During the breeding period, males are often heard singing their multipart, warbler-like song from high atop conifers.

Yellow-eyed Junco is locally abundant, sedentary, and philopatric, and the species adapts well to captivity. These traits make it an exceptional species for behavioral studies, and its behavior and life history are reasonably well understood. Songs of the Yellow-eyed Junco, with their 2 to 3 parts and multiple trills, are highly variable within populations. This species was featured in classic studies on individual variation in song (1 Marler, P. and D. Isaac (1960). Song variation in a population of Brown Towhees. Condor 62:272-283. Close ) and song development (2 Konishi, M. (1964). Effects of deafening on song development in two species of junco. Condor 66:85-102. Close ). A series of studies on the effects of flock size on behavior and individual trade-offs among foraging, vigilance, and aggression were based on winter flocks of the Yellow-eyed Junco in southern Arizona (3 Caraco, T. (1979). Time budgeting and group size: a test of theory. Ecology 60:618-627. Close , 4 Caraco, T., S. Martindale and H. R. Pulliam (1980). Avian flocking in the presence of a predator. Nature 285:400-401. Close , 5 Caraco, T., S. Martindale and H. R. Pulliam (1980). Avian time budgets and distance to cover. Auk 97:872-875. Close , 6 Pulliam, H. R., G. H. Pyke and T. Caraco. (1982). The scanning behavior of juncos: a game theoretical approach. Journal of Theoretical Biology 95:89-103. Close ). Growth, energy expenditure, and time allocation are well understood in this species from studies conducted over the annual cycle in southern Arizona (7 Weathers, W. W., and K. A. Sullivan (1989) Juvenile foraging proficiency, parental effort, and avian reproductive success. Ecological Monographs 59: 223-246. Close , 8 Weathers, W. W. and K. A. Sullivan (1989). Nest attentiveness and egg temperature in the Yellow-eyed Junco. Condor 91:628-633. Close , 9 Weathers, W. W. and K. A. Sullivan (1991). Growth and energetics of nestling Yellow-eyed Juncos. Condor 93:138-146. Close , 10 Weathers, W. W. and K. A. Sullivan (1991). Foraging proficiency of parent Juncos and their young. Condor 93:346-353. Close , 11 Weathers, W. W. and K. A. Sullivan. (1993). Seasonal patterns of time and energy allocation by birds. Physiological Zoology 66:511-536. Close , 12 Sullivan, K. A. (1990). Daily time allocation among adult and immature Yellow-eyed Juncos over the breeding season. Animal Behaviour 39:380-387. Close , 13 Sullivan, K. A. and W. W. Weathers. (1992). Brood size and thermal environment influence field metabolism of nestling Yellow-eyed Juncos. Auk 109:112-118. Close ). In most passerine species, young birds are difficult to find once they leave the nest, and consequently little is known about fledgling and juvenile life history stages. Studies on mortality patterns, acquisition of foraging skills, energy expenditure, and time allocation of immatures has made a valuable contribution to our understanding of fledging and juvenile passerines (14 Sullivan, K. A. (1988). Age-specific profitability and prey choice. Animal Behaviour 36:613-615. Close , 15 Sullivan, K. A. (1988). Ontogeny of time budgets in Yellow-eyed Juncos: Adaptation to ecological constraints. Ecology 69:118-124. Close , 16 Sullivan, K. A. (1989). Predation and starvation: age-specific mortality in juvenile juncos (Junco phaeonotus). Journal of Animal Ecology 58:275-286. Close , 12 Sullivan, K. A. (1990). Daily time allocation among adult and immature Yellow-eyed Juncos over the breeding season. Animal Behaviour 39:380-387. Close , 7 Weathers, W. W., and K. A. Sullivan (1989) Juvenile foraging proficiency, parental effort, and avian reproductive success. Ecological Monographs 59: 223-246. Close , 9 Weathers, W. W. and K. A. Sullivan (1991). Growth and energetics of nestling Yellow-eyed Juncos. Condor 93:138-146. Close , 10 Weathers, W. W. and K. A. Sullivan (1991). Foraging proficiency of parent Juncos and their young. Condor 93:346-353. Close ). To date, most studies of behavior, ecology, and physiology of the Yellow-eyed Junco have been carried out in southern Arizona at the northern extent of its range. It is not known whether these populations are representative of populations throughout the range of the species.