A theoretical investigation of the effect of latitude on avian life histories

John M. McNamara, Zoltán Barta, Martin Wikelski, Alasdair I. Houston

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57 Citations (Scopus)

Abstract

Tropical birds lay smaller clutches than birds breeding in temperate regions and care for their young for longer. We develop a model in which birds choose when and how often to breed and their clutch size, depending on their foraging ability and the food availability. The food supply is density dependent. Seasonal environments necessarily have a high food peak in summer; in winter, food levels drop below those characteristic of constant environments. A bird that cannot balance its energy needs during a week dies of starvation. If adult predation is negligible, birds in low seasonal environments are constrained by low food during breeding seasons, whereas birds in high seasonal environments die during the winter. Low food seasonality selects for small clutch sizes, long parental care times, greater age at first breeding, and high juvenile survival. The inclusion of adult predation has no major effect on any life-history variables. However, increased nest predation reduces clutch size. The same trends with seasonality are also found in a version of the model that includes a condition variable. Our results show that seasonal changes in food supply are sufficient to explain the observed trends in clutch size, care times, and age at first breeding.

Original languageEnglish
Pages (from-to)331-345
Number of pages15
JournalAmerican Naturalist
Volume172
Issue number3
DOIs
Publication statusPublished - Sep 1 2008

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Keywords

  • Annual routine
  • Clutch size
  • Energy balance
  • Parental care

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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