Behavioral Ecology and Sociobiology

, Volume 33, Issue 5, pp 305–312

Exploitative compensation by subordinate age-sex classes of migrant rufous hummingbirds

  • F. Lynn Carpenter
  • Mark A. Hixon
  • Ethan J. Temeles
  • Robert W. Russell
  • David C. Paton
Article
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Summary

The three age-sex classes of rufous hummingbirds (Selasphorus rufus) that directly interact on southward migratory stopovers in our California study system differ in territorial ability and resource use. Immature males are behaviorally dominant to adult and immature females and defend the richest territories. Here, we test the hypothesis that the territorially subordinate age-sex classes compensate exploitatively for their exclusion from rich resources. Our results show that females were able to accumulate energy stores at rates comparable to males despite their subordinate territorial status. Territorial females gained body mass at the same rate and in the same pattern as males, and resumed migration at the same body masses. Moreover, during periods when birds were nonterritorial and used dispersed resources, adult and immature females maintained or gained body mass, whereas immature males lost mass. We suggest that females may be energetically compensated by (1) lower costs of flight incurred during foraging and defense, resulting from their lower wing disc loading, and (2) greater success at robbing nectar from rich male territories, resulting from duller coloration (immature females), experience (adult females), and, possibly, hormonal differences. In the future, experiments will be necessary to distinguish the various hypotheses about the mechanisms involved in compensation.

Key words

Intraspecific dominance Foraging ecology Migration Stopovers Hummingbirds 

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • F. Lynn Carpenter
    • 1
  • Mark A. Hixon
    • 2
  • Ethan J. Temeles
    • 3
  • Robert W. Russell
    • 1
  • David C. Paton
    • 4
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of CaliforniaIrvineUSA
  2. 2.Department of ZoologyOregon State UniversityCorvallisUSA
  3. 3.National Zoological ParkSmithsonian InstitutionWashingtonUSA
  4. 4.Department of ZoologyUniversity of AdelaideAdelaideAustralia

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