Long-Distance Homing by Nonmigratory Dark-Eyed Juncos

Nolan, Val; Ketterson, Ellen D.; Wolf, Licia

doi:10.2307/1368291

Cited by 9 publications

(3 citation statements)

References 11 publications

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“…Our study site is the Mountain Lake Biological Station in Giles County, Virginia (described in Nolan et al 1986, Wolf 1987. In juncos that breed at high elevations in the southern Allegheny Mountains ("Carolina" juncos), some individuals move short distances downslope in autumn or early winter, but some, usually adult males (i.e., more than one year old), remain on the breeding ground (Nolan et al 1986, Ketterson et al 199 1 b).…”

Section: Study Populationmentioning

confidence: 99%

Testosterone and Avian Life Histories: Effects of Experimentally Elevated Testosterone on Prebasic Molt and Survival in Male Dark-Eyed Juncos

et al. 1992

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Male Dark-eyed Juncos (Junco hyemalis) that breed in Virginia begin their prebasic molt after breeding has ended, usually in August. Almost all males caught in late October have completed the molt. In 1989, we obtained anecdotal evidence that males whose testosterone (T) we maintained at artificially elevated levels beyond the end of the breeding season postponed or suppressed prebasic molt. To test the effect of T experimentally, in spring 1990 we implanted some males (T-males) with testosterone and others (Cmales) with empty implants, and we released both groups to breed. We caught some members of both treatment groups in October and removed their implants. The T-males had delayed their prebasic molt, while the C-males were molting on schedule. Other implanted T-and C-males were not caught; these carried their implants into winter. Next spring we examined surviving males whose implants we had removed in October as well as males whose T-and C-implants had not been removed. T-males whose implants we had removed had molted completely, despite their delayed start, whereas T-males whose implants we had not removed had not molted. Still-implanted C-males had molted. We compared the minimum overwinter survival (i.e., return rates in spring) of the treatment groups. T-and C-males whose implants we had removed in October returned at the same rate, but among males whose implants we had not removed, significantly fewer T-males than C-males returned. The transition between reproduction and molt of male juncos apparently can be blocked by preventing the normal seasonal decline in T. This suggests a physiological basis for a possible trade-off between time allocated to reproduction and time allocated to molt. Our results indicate that males could maintain high T and prolong breeding, possibly into October, and still molt completely with no adverse effects. We consider why such a modification of schedule has not occurred. However, postponement of molt beyond some date in autumn, possibly late October, suppresses it altogether, as indicated by the failure to molt of the returning T-males whose implants we did not remove. This treatment group apparently suffered higher overwinter mortality, and we consider possible reasons.

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Section: Study Populationmentioning

confidence: 99%

Testosterone and Avian Life Histories: Effects of Experimentally Elevated Testosterone on Prebasic Molt and Survival in Male Dark-Eyed Juncos

et al. 1992

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“…The Dark-eyed Junco in eastern North America breeds primarily in Canada and winters in southern Ontario and in the United States almost to the Gulf of Mexico (Bent 1968). (An essentially sedentary population [Nolan et al 1986] that inhabits the southern Appalachian Mountains is not relevant to this paper.) The breeding and non breeding ranges overlap very little, and probably all or almost all individuals migrate.…”

Section: Dominance and Winter Distributionmentioning

confidence: 99%

Timing of Autumn Migration and Its Relation to Winter Distribution in Dark‐Eyed Juncos

Nolan¹,

Ketterson²

1990

Ecology

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Migratory Dark—eyed Juncos in eastern North America migrate southward in autumn and tend to segregate in the winter range according to sex and age. North to south, the most abundant classes are young males, adults males, young females, and adult females. Because adults tend to dominate young at winter feeding sites, this distribution appears at first to conflict with the view that dominance interactions are responsible for differential avian migrations and that dominant individuals remain nearest the breeding range. However, if young juncos establish winter residency at earlier dates than adults, a prior residence effect might make them dominant. This hypothesis requires that young arrive at wintering sites earlier than adults and that residents of all classes arrive earlier than their transient counterparts. We tested these predictions by comparing first—capture dates of juncos at Bloomington, Indiana, which is north of the latitudianal midline of the junco's winter range. During 13 autumns, individuals were classed as local residents or an transients and were sexed and aged. Contrary to predictions were not caught earlier than transients. Further, adults were caught earlier, not later, than young among transiets and probably also among residents. Thus, settlement of the winter range does not proceed from north to south, and dominance established through prior residence cannot account for the concentration of 1st—yr males in the northern part of the winter range. The fact that some sex—age classes tend to winter south of others predicts that at a northern capture site the classes that migrate farthest should be commoner among transients than among residents. This expectation was fulfilled. In addition, the median capture dates of the sex—age classes were arranged approximately according to the north—to—south order of their distribution, indicating that classes with the farthest to travel passed through (transients) or settled (residents) earliest in autumn. We conclude that comparison of autumn migration schedules of transiet and resident passerine birds at a single location can yield considerable information about the dynamics of settlement of the entire winter range, including possible information about differences in destination of subsets of transients.

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“…observ.) and are sedentary or make short altitudinal migrations (Nolan et al 1986). During the breeding season, males are territorial; pairs form in March or April and some remain together until October or possibly later (pers.…”

Section: Species and Study Areamentioning

confidence: 99%

Effect of Sex, Stage of Reproduction, Season, and Mate Removal on Prolactin in Dark-Eyed Juncos

et al. 1990

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Prolactin has been associated with incubation and brooding in passerine birds, but its possible association with other parental behaviors remains unclear. We measured plasma concentrations of prolactin (prl) in Dark-eyed Juncos (Bunco hyemalis), a species in which only females incubate and brood but both sexes feed nestlings. Breeding males and females were bled at the time their eggs hatched, and half the males were taken from their territories. Females and the remaining males were bled again when their young left the nest. Removed males were quickly replaced by new males, some of which we caught and bled. Replacement males courted the females but rarely fed their predecessors' young. Removed males were held in an aviary and bled again in late summer. Prl concentrations were higher in females than males, both at hatching and at nest leaving. Female prl was higher at hatching than at nest leaving and did not vary seasonally. Male prl was higher at hatching than at nest leaving and higher earlier in the season than later. Rearing young alone had no detectable effect on prl in females. Prl of replacement males was lower than that of fathers at hatching but not at nest leaving. Prl in removed males in the aviary was lower than in fathers at hatching but not at nest leaving. These patterns of prl secretion resemble those in other species that raise more than one brood per season and in which females provide the bulk of parental care. In addition, prl may be associated with male parental behavior in juncos.

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Long-Distance Homing by Nonmigratory Dark-Eyed Juncos

Abstract: Sexual behaviour and seasonal changes in the gonads and adrenals of the mallard. Proc. Zool. Sot. Lond. 117:28 l-304. HOUSTON, D. C. 1976. Breeding of the White-backed and Ruppell' s Griffon Vultures, Gv~s africanus and G. ruep&llii. Ibis 1 l&14-40. __ "

Cited by 9 publications

References 11 publications

Testosterone and Avian Life Histories: Effects of Experimentally Elevated Testosterone on Prebasic Molt and Survival in Male Dark-Eyed Juncos

Testosterone and Avian Life Histories: Effects of Experimentally Elevated Testosterone on Prebasic Molt and Survival in Male Dark-Eyed Juncos

Timing of Autumn Migration and Its Relation to Winter Distribution in Dark‐Eyed Juncos

Effect of Sex, Stage of Reproduction, Season, and Mate Removal on Prolactin in Dark-Eyed Juncos

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