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Living on the Edge

A Day in the Life of a Hummingbird


Giovanni Casotti
Department of Biology
West Chester University


This case study describes the daily osmotic struggle for survival faced by hummingbirds. The narrative is written from the viewpoint of a human observer who sees an Anna's hummingbird feeding on flowers outside of her window.  She notices that the birds mostly feed early in the morning and again in the evening at dusk; midday encounters are rare.  The case raises questions about floral nectar production, how this correlates to feeding bouts, and how this in turn correlates to the daily osmotic challenges faced by these nectarivorous birds and their allies (sunbirds). Students will learn about renal adaptations for survival and how they operate. Finally, since hummingbirds have a high metabolic rate and cannot feed overnight they undergo torpor during this time, an energy saving physiologic state.  Students read journal articles to answer case questions, which should lead them to a better understanding of the related physiological processes of osmoregulation, metabolic rate and torpor.

  • Understand how the nephron operates in producing a concentrated urine.
  • Understand the osmotic challenges faced by aquatic and terrestrial animals.
  • Understand the daily osmotic challenges faced by nectarivorous birds such as hummingbirds.
  • Understand the mechanisms used by hummingbirds to cope with these osmotic challenges.
Keywords: hummingbird; osmoregulation; torpor; metabolism; osmosis; nectar; renal; renal system
Topical Area: N/A
Educational Level: Undergraduate upper division, Graduate
Formats: PDF, PowerPoint
Type/Method: Analysis (Issues), Journal Article
Language: English
Subject Headings: Biology (General)   Anatomy   Physiology   Science (General)  
Date Posted: 5/4/2017
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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Supplemental Materials

An optional PPT presentation on the physiology of osmoregulation is available to prepare students for the case study.

  hummingbird.ppt (~4MB)

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