Yellow-eyed Junco Junco phaeonotus

This junco of the Transition and Boreal Zones of mountains in the southwestern United States, Mexico, and parts of Central America 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 Dark-eyed Juncos (Junco hyemalis). These relatively tame birds forage on the ground and are easily seen, often frequenting campsites and picnic areas. In s. Arizona, pairs remain together throughout the breeding season, producing up to 3 successful broods per season. During the breeding season, males are often heard singing their multipart, warblerlike song from high atop conifers.

Yellow-eyed Juncos are locally abundant, sedentary, and philopatric, and they adapt well to captivity. These traits make this 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 (Marler and Isaac 1960c Marler, P. and D. Isaac (1960). Song variation in a population of Brown Towhees. Condor 62:272-283. Close ) and song development (Konishi 1964a 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 Yellow-eyed Juncos in southern Arizona (Caraco Caraco 1979 Caraco, T. (1979). Time budgeting and group size: a test of theory. Ecology 60:618-627. Close , Caraco 1979 Caraco, T. (1979). Time budgeting and group size: a test of theory. Ecology 60:618-627. Close , Caraco et al. Caraco et al. 1980a Caraco, T., S. Martindale and H. R. Pulliam (1980). Avian flocking in the presence of a predator. Nature 285:400-401. Close , Caraco et al. 1980b Caraco, T., S. Martindale and H. R. Pulliam (1980). Avian time budgets and distance to cover. Auk 97:872-875. Close , Pulliam et al. 1982 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 (Weathers and Sullivan Weathers and Sullivan 1989a Weathers, W. W., and K. A. Sullivan (1989) Juvenile foraging proficiency, parental effort, and avian reproductive success. Ecological Monographs 59: 223-246. Close , Weathers and Sullivan 1989b Weathers, W. W. and K. A. Sullivan (1989). Nest attentiveness and egg temperature in the Yellow-eyed Junco. Condor 91:628-633. Close , Weathers and Sullivan 1991b Weathers, W. W. and K. A. Sullivan (1991). Growth and energetics of nestling Yellow-eyed Juncos. Condor 93:138-146. Close , Weathers and Sullivan 1991a Weathers, W. W. and K. A. Sullivan (1991). Foraging proficiency of parent Juncos and their young. Condor 93:346-353. Close , Weathers and Sullivan 1993 Weathers, W. W. and K. A. Sullivan. (1993). Seasonal patterns of time and energy allocation by birds. Physiological Zoology 66:511-536. Close , Sullivan 1990 Sullivan, K. A. (1990). Daily time allocation among adult and immature Yellow-eyed Juncos over the breeding season. Animal Behaviour 39:380-387. Close , Sullivan and Weathers 1992 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 among immature Yellow-eyed Juncos have made a valuable contribution to our understanding of fledging and juvenile passerines (Sullivan Sullivan 1988a Sullivan, K. A. (1988). Age-specific profitability and prey choice. Animal Behaviour 36:613-615. Close , Sullivan 1988b Sullivan, K. A. (1988). Ontogeny of time budgets in Yellow-eyed Juncos: Adaptation to ecological constraints. Ecology 69:118-124. Close , Sullivan 1989 Sullivan, K. A. (1989). Predation and starvation: age-specific mortality in juvenile juncos (Junco phaeonotus). Journal of Animal Ecology 58:275-286. Close , Sullivan 1990 Sullivan, K. A. (1990). Daily time allocation among adult and immature Yellow-eyed Juncos over the breeding season. Animal Behaviour 39:380-387. Close , Weathers and Sullivan Weathers and Sullivan 1989a Weathers, W. W., and K. A. Sullivan (1989) Juvenile foraging proficiency, parental effort, and avian reproductive success. Ecological Monographs 59: 223-246. Close , Weathers and Sullivan 1991b Weathers, W. W. and K. A. Sullivan (1991). Growth and energetics of nestling Yellow-eyed Juncos. Condor 93:138-146. Close , Weathers and Sullivan 1991a Weathers, W. W. and K. A. Sullivan (1991). Foraging proficiency of parent Juncos and their young. Condor 93:346-353. Close ). Since most studies to date on this species have been conducted at the northern exent of its range, it would be worthwhile to investigate the behavior and population dynamics of other populations of Yellow-eyed Juncos.