Retirement investment theory explains patterns in songbird nest-site choice

Proceedings of the Royal Society B: Biological Sciences
By: , and 



When opposing evolutionary selection pressures act on a behavioural trait, the result is often stabilizing selection for an intermediate optimal phenotype, with deviations from the predicted optimum attributed to tracking a moving target, development of behavioural syndromes or shifts in riskiness over an individual's lifetime. We investigated nest-site choice by female golden-winged warblers, and the selection pressures acting on that choice by two fitness components, nest success and fledgling survival. We observed strong and consistent opposing selection pressures on nest-site choice for maximizing these two fitness components, and an abrupt, within-season switch in the fitness component birds prioritize via nest-site choice, dependent on the time remaining for additional nesting attempts. We found that females consistently deviated from the predicted optimal behaviour when choosing nest sites because they can make multiple attempts at one fitness component, nest success, but only one attempt at the subsequent component, fledgling survival. Our results demonstrate a unique natural strategy for balancing opposing selection pressures to maximize total fitness. This time-dependent switch from high to low risk tolerance in nest-site choice maximizes songbird fitness in the same way a well-timed switch in human investor risk tolerance can maximize one's nest egg at retirement. Our results also provide strong evidence for the adaptive nature of songbird nest-site choice, which we suggest has been elusive primarily due to a lack of consideration for fledgling survival.

Publication type Article
Publication Subtype Journal Article
Title Retirement investment theory explains patterns in songbird nest-site choice
Series title Proceedings of the Royal Society B: Biological Sciences
DOI 10.1098/rspb.2013.1834
Volume 281
Issue 1777
Year Published 2014
Language English
Publisher The Royal Society Publishing
Contributing office(s) Coop Res Unit Leetown
Description Article 20131834; 8 p.
Country Canada, United States
State Manitoba, Minnesota
Other Geospatial Rice Lake National Wildlife Refuge, Sandilands Provincial Forest, Tamarac National Wildlife Refuge
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