Snowpack and variation in reproductive ecology of a montane ground-nesting passerine, Junco hyemalis

Ornis Scandinavica
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Abstract

Effects of snow depth and rate of snowmelt on reproduction of a montane ground-nesting passerine were examined in a 5-year study of Dark-eyed Juncos Junco hyemalis in northern Utah, USA. Distribution of clucth sizes differed significantly among years. Although most clutches contained four eggs, 3-egg clutches, due primarily to second nestings, were more common during a year of early snowmelt and 5-egg clutches were most common during two years of late snowmelt. Average clutch size was lowest in an early snowmelt year and average clutch size and date at which meadows became snow-free were significantly positively correlated. Average hatching date of 4-egg clutches was also significantly positively correlated with date at which meadows became snow-free demonstrating that most birds tracked the pattern of snowmelt. Early snowmelt may allow more pairs to attempt second nesting, but late-lying snow causes breeding to be delayed, allowing time for only one nesting attempt. During this delay, female juncos continue to feed and some may gain enough reserves to produce larger clutches, accounting for the increase in average clutch size in years of late snowmelt. Three female juncos examined in June 1982, a period of late snowmelt, had significantly more lipid reserves than did six males collected at the same time, suggesting that females are not physiologically stressed while awaiting snowmelt. By tracking snowmelt patterns, juncos synchronize production of young with peak summer insect abundance and potentially decrease risk of predation. Snow depth and rate of snowmelt are thus proximate environmental factors that may influence the reproductive ecology of ground-nesting passerines.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Snowpack and variation in reproductive ecology of a montane ground-nesting passerine, Junco hyemalis
Series title Ornis Scandinavica
DOI 10.2307/3676568
Volume 16
Issue 1
Year Published 1985
Language English
Publisher Scandinavian Ornithologists' Union
Publisher location Oslo
Description 6 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ornis Scandinavica
First page 8
Last page 13
Country United States
State Utah