Cooperative Research Units
Education, Research And Technical Assistance For Managing Our Natural Resources
Home | Intranet | Digital Measures | Help

Are long lives of south temperate songbirds explained by reduced energy expenditure of parents compared with north temperate species?


April 2016 - April 2017


Songbirds in the tropics and southern hemisphere commonly have long lives and small clutch sizes compared with north temperate species. Yet, understanding of the causes underlying demographic strategies in southern regions remains poor. Causes of variation in longevity, in particular, have long intrigued and mystified scientists. The rate of living hypothesis postulates that long-lived species express lower metabolism to reduce physiological costs affecting longevity. Similarly, the cost of reproduction hypothesis suggests that reduced parental energy expended to raise offspring allows longer lives. Parental energy expenditure varies differently than basal metabolism across species, making tests of both hypotheses important. Indirect evidence provides some potential support for each hypothesis, but direct tests based on measurement of metabolism, reproductive energy expenditure, and adult survival in the same populations of long-lived species are needed. Tests are particularly needed because some evidence raises questions about each hypothesis. For example, body mass is a major determinant of metabolic rates, but does not explain broad variation in adult survival of songbirds. Parents of long-lived south temperate species feed their young at similar rates as north temperate species, which may indicate that long-lived species are expending as much energy as shorter-lived north temperate species during reproduction. I propose to measure daily energy expenditure and resting metabolism during the nestling period among long-lived species at my South Africa site. I am already measuring these traits for short-lived species at my north temperate site to provide a unique opportunity to address long-standing questions of global patterns.


Current Staff

Federal Staff: 95

Masters Students: 239

Phd Students: 142

Post Docs: 53

University Staff: 240

5 Year Summary

Students graduated: 701

Scientific Publications: 1936

Presentations: 4260



Funding Agencies

  • National Geographic Society


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey