Postnuptial Molt in Harris' Sparrows

deGraw, William A.; Kern, Michael D.

doi:10.2307/1368718

Cited by 7 publications

(11 citation statements)

References 17 publications

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“…We have not been able to find information about the exact time when these two categories of feathers are shed during the prenuptial moult of Pied Flycatchers, but body moult commonly occurs while the flight feathers are replaced in songbirds. In the few cases where body tracts have been examined individually, greater wing coverts and tertials moult at the same time (King 1972, De Graw & Kern 1990).…”

Section: Discussionmentioning

confidence: 99%

Ptilochronology proves unreliable in studies of nestling Pied Flycatchers

Kern

Cowie

2002

Ibis

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Ptilochronology does not appear to be a reliable measure of the daily growth rate of contour feathers or the nutritional state of nestling Pied Flycatchers Ficedula hypoleuca. Growth bars on primary remiges, which according to ptilochronology represent a day’s increment of feather growth, are only about half as wide as the actual daily increase in the length of these feathers while they are growing. The average width of the growth bars on primaries was also uncorrelated with other commonly used measures of growth or nutritional status (increase in body mass or in the size of the wing or tarsus), although these were highly correlated with each other. In adult flycatchers, the average width of the growth bars on tertials was unrelated to the average bar width on greater coverts, although both feathers are replaced during the winter (prenuptial) moult. This suggests that the growth bars either do not reflect the nutritional status of adults during normal periods of moult or that contour feathers in different tracts vary in their sensitivity to the nutritional status of the moulting bird. To our knowledge, this is the first time that anyone has attempted to apply ptilochronology to nestlings. It is noteworthy that a method of measuring growth and nutritional state that has shown promise when applied to induced feathers of adult birds seems to be unreliable when applied to the developing plumage of nestlings, and perhaps the normal (not‐induced) replacement plumage of adults.

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Section: Discussionmentioning

confidence: 99%

Ptilochronology proves unreliable in studies of nestling Pied Flycatchers

Kern

Cowie

2002

Ibis

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“…I examined molt in birds captured in Potter traps or mist nets, or collected for stomach content analysis, between their arrival on the breeding grounds and 20 July, by which time all known nesting pairs had fledged young (Norment 1992). For comparative purposes, I scored molt using the system used by DeGraw and Kern (1990) for Harris' Sparrows, with each molting primary feather, secondary feather, or rectrix assigned a score of one point. Body and crown molt were assigned one to three points, depending on the intensity of molt.…”

Section: Study Site and Methodsmentioning

confidence: 99%

“…They studied prebasic molt using caged birds captured during fall migration near Omaha, Nebraska, and exposed to photoperiods comparable to those found on their breeding grounds (ca. 60°N) beginning in mid-May (DeGraw and Kern 1990). Prebasic molt lasted about 82 days in individual Harris' Sparrows, and the timing of molt initiation in captive birds suggested overlap between breeding activities and prebasic molt in wild Harris' Sparrow populations (DeGraw and Kern 1990).…”

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“…gambelii until after young have fledged, and molt is restricted to the period between the end of reproductive activities and the beginning of fall migration (King et al 1965: DeWolfe 1967: Morton et al 1969. However, DeGraw and Kern (1990) reported a diferent pattern of prebasic molt in Harris' Sparrows (Zonotrichia querula), which breed in the forest tundra-transition zone of northern Canada, from about 57°N to 69°N (Godfrey 1986). They studied prebasic molt using caged birds captured during fall migration near Omaha, Nebraska, and exposed to photoperiods comparable to those found on their breeding grounds (ca.…”

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confidence: 99%

“…60°N) beginning in mid-May (DeGraw and Kern 1990). Prebasic molt lasted about 82 days in individual Harris' Sparrows, and the timing of molt initiation in captive birds suggested overlap between breeding activities and prebasic molt in wild Harris' Sparrow populations (DeGraw and Kern 1990). Given the difference between molt patterns found in captive Harris' Sparrows and in Z. leucophrys breeding at high latitudes, observations on prebasic molt in free-ranging Harris' Sparrows should be of interest.…”

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confidence: 99%

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Prebasic (postnuptial) molt in free-ranging Harris' Sparrows, Zonotrichia querula, in the Northwest Territories, Canada

Norment

1995

The Canadian Field-Naturalist

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Harris' Sparrows (Zonotrichia querula) in the Northwest Territories, Canada, in 1989-1991, were single-brooded, although they occasionally replaced a clutch if the loss occured prior to hatching. Harris' Sparrow breeding chronology is highly synchronized, and the fledging period for first nests was 3-14 July. Of 21 adult Harris' Sparrows captured on or after 3 July, no bird captured prior to 13 July was molting: estimated dates for prebasic molt initiation in 10 birds captured after beginning molt ranged from 13 to 18 July. The almost complete separation of the nestling phase and molt initiation support the idea that most Harris' Sparrows at my study site did not begin prebasic molt until after their young fledged. This is similar to most passerines breeding at high latitudes, including White-crowned Sparrows (Zonotrichia leucophrys). However, my results contradict results of previous workers who found that caged Harris' Sparrows exposed to natural photoperiods found on their breeding grounds initiated prebasic molt at the time when breeding Harris' Sparrows should be feeding nestlings. This difference may be attributed to earlier use of birds which had not participated in the reproductive cycle.

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