Effect of altitude on male parental expenditure in Mountain Bluebirds (Sialia currucoides): Are higher-altitude males more attentive fathers?

L. Scott Johnson, Jessica L. Brubaker, Emilene Ostlind, Susan L. Balenger

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Male investment of time and energy in caring for offspring varies substantially both between and within bird species. Explaining this variation is of long-standing interest to ornithologists. One factor that may affect male care is breeding site altitude, through its effects on climate. The harsher, less predictable abiotic conditions at higher altitudes are hypothesized to favour increased male investment of time and energy in offspring care. We tested this hypothesis by comparing male parental behaviour in Mountain Bluebirds (Sialia currucoides) nesting at 1500 and 2500 m a.s.l. in the Bighorn Mountains of Wyoming, USA. We compared rates of prey delivery to nestlings at these two altitudes at two times: 1-2 days after hatching, when females spend much of their time brooding young, and 12-13 days later, when brooding has ended and nestling energy demands are peaking. High-altitude males fed nestlings 18 and 28% more often than low-altitude males early and later in the nestling stage, respectively, but only the difference in late-stage feeding rates were significant. Like males, females at the high site also fed nestlings significantly more often than females at the low site later in the nestling stage (45% difference in feeding rates). Consequently, the proportion of all feeding trips made by males at the high site (40%) did not differ significantly from that at the low site (44%). Parents at the high altitude may feed nestlings more often to compensate for their greater thermoregulatory costs. Parents may also be attempting to assist nestlings in storing fat and/or attaining a large size and effective homeothermy as quickly as possible to enhance nestling ability to survive bouts of severe weather which are common at high altitudes.

Original languageEnglish (US)
Pages (from-to)9-16
Number of pages8
JournalJournal of Ornithology
Volume148
Issue number1
DOIs
StatePublished - Jan 2007
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgments Beatrice Beuf, Robert Berry and the Gar-ber family granted permission to work on their property. Dick Newman, the Powderhorn Bluebird Club and Bob Berry allowed us access to their nest boxes at the low-elevation site. Harald Golden of the U.S. Forest Service allowed us access to nest boxes at our high-elevation site and provided logistical support. Beatrice Beuf provided living accommodations at the low-altitude site and much moral support. Roberta Young and the staff of Bear Lodge Resort provided accommodations at the high-altitude site. Jerry Eastman built many of the nest boxes used in this study. Bonnie Johnson and Nell MacCarty assisted in the field. We benefited from extensive discussions with Alex Badyaev regarding his work in Russia. Anne Balogh, Clint Otto, Don Forester, Quent Lupton and two anonymous reviewers provided comments, which improved the manuscript considerably. Financial support came through grants from Towson University’s Faculty Development and Research Committee and Undergraduate Research Committee and from the National Science Foundation (grants DBI-9732442 and IBN-0316541). To all we are grateful. This research complies with the laws of the United States of America.

Keywords

  • Altitude
  • Elevation
  • Mountain Bluebird
  • Parental care
  • Sialia currucoides

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