CH3 - Hormones and Neurobiology

Who Conducted Bird Stressor Experiment

Lynn Martin

What species was the bird stressor experiment conducted on

House sparrows (Passer Domesticus)

Why were house sparrows used for the bird stressor experiment

• Had one of the boradest distributions due to their ability to invade new habitats

• They were first introduced in Mombasa, Kenya and expended North/West over 6 decades

Corticosterone

• Measured in the bird stressor experiment

• it’s a glucocorticoid hormone linked to stress response

Hypothesis of the bird stressor experiment

Birds on the edge of expansion would show the strongest corticosterone surge when exposed to stressors, due to encountering the most novel environments.

Methods of the bird stressor experiment

• Collection: Birds were captured at varied distances from Mombasa

• Stress Exposure: They were placed in a cloth sack for 30 mins

• Sampling: Blood samples were taken before and after stress

Results of the bird stressor experiment

• During the breeding season, the change in corticosterone increased with distance from Mombasa

• Distribution of stress hormone receptors facilitated the strongest repsonse in birds furthest from Mombasa

Working Hypothesis (hasn’t been tested yet) of the bird stressor experiment

• Inc in corticosterone leads to a better memory of stressors

• In new environments, the benefit of remembering stressors in greatest in leading-edge populations

Bird Stressor Experiment Graph - KNOW AXES

Stress Hormones and invasion where the stress response in house sparrows increased as a function of distance from original site.

Proximate Analysis

• Questions framed as “how is it that” or “what is it that”

• Focuses on mechanisms WITHIN an organism

  • Ex. looking at a voice box to answer why birds sing

• Not evolutionary in nature

  • But it’s still useful to understand the evolutionary forces

  • Proximate is just as important regardless

• Key feature: Factors that operate within the lifetime of an organism rather than inferences of historical evolutionary forces

Ultimate Analysis

• “Why is it that”

• Focuses on evolutionary explanations

  • Natural selection

  • Phylogeny

Links with Proximate and Ultimate

• Ultimate knowledge can help design better proximate studies and vice versa

  • Ex. Studying male aggression

  • Understanding evolutionary pressures can guide how proximate mechanisms are analyzed

• Proximate knowledge can inform the ultimate understanding

  • Hormones influencing male aggression may lower a disease resistance, which may have incorporated into NS models

Who did the plumage experiment?

Geoff Hill

What species were examined in the plumage experiment?