CIE Seminar Series – 2020: Resources, stress and fitness: how energy availability can mask trade-offs between survival and reproduction functions of mountain bluebird feathers

SPEAKER: Prof Creagh Breuner, Division of Biological Sciences, University of Montana (Organismal Biology, Ecology and Evolution, and The Wildlife Biology Program)

DATE & TIME: Friday, 1st May 2020 @ 12:00 noon

LOCATION: Seminar to be streamed via Zoom. Click HERE to connect.


Stress hormones are thought to benefit animals by redirecting energy from non-essential functions (reproduction) towards survival.

However, three separate hypotheses predict very different outcomes for glucocorticoid (stress hormone) effects on fitness. Field data testing between hypotheses has exploded over the last 11 years, but no clear concensus has emerged.

I propose the discrepancy in results may be due to variation in resource availability. In free-living animals, trade-offs between survival and reproduction may be masked by high resource availability in good years, but evident in poor years.

Current literature testing between these hypotheses rarely incorporates metrics of resource availability. In 1986 Van Noordwijk and de Jong proposed the acquisition/allocation model to explain positive vs. negative correlations between reproduction and survival across individuals. Their mode identifies resources as critical to evaluating individual allocation strategies (favoring reproduction vs survival), and therefore provides the ideal model for testing across the three hypotheses.

In this talk I will:

  1. Review the three hypotheses in light of the last 11 years of data;
  2. Review the relatively small subset of fitness/glucocorticoid papers that incorporate a resource perspective;
  3. Introduce the Van Noordwijk and de Jong framework as a model for fitness/glucocorticoid hypothesis testing, and;
  4. Discuss recent results testing the effects of resource limitation on tradeoffs between feather structure and color in mountain bluebirds (Sialia currucoides).


Creagh Breuner is a professor in both Ecology/Evolution and The Wildlife Biology programs at the University of Montana.

She has studied behavioral endocrinology within mechanistic, evolutionary, and conservation frameworks over the past 25 years, and now splits her time between research and heading the large UM Biology Division as Associate Dean.

For more info visit The Breuner Lab.

Video appointments with speaker may be made via

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Thanking you in advance!