Corticosterone predicts double-brooding in female savannah sparrows (Passerculus sandwichensis)

Area of Science:

• Avian ecology
• Endocrinology
• Behavioral ecology

Background:

• Double-brooding can increase reproductive success, but not all females in multi-brooded populations achieve this.
• The Quality Hypothesis suggests only high-quality females can afford the energetic costs of double-brooding.
• Glucocorticoids, like corticosterone, are key in energy regulation and may indicate female quality.

Purpose of the Study:

• To investigate if baseline corticosterone concentrations correlate with female Savannah sparrow quality (body condition, fat score).
• To determine if baseline corticosterone predicts the likelihood of attempting a second brood.
• To explore the role of breeding stage in corticosterone assessment.

Main Methods:

• Analysis of 12 years of reproductive data from migratory Savannah sparrows (Passerculus sandwichensis).
• Measurement of baseline corticosterone concentrations in relation to female quality metrics.
• Statistical modeling to link corticosterone levels to double-brooding probability across breeding stages.

Main Results:

• Strong negative correlation between baseline corticosterone and female fat score.
• Weak negative correlation between baseline corticosterone and body condition.
• Moderate evidence that higher baseline corticosterone during the first brood nestling stage negatively predicts double-brooding.

Conclusions:

• Baseline corticosterone levels in Savannah sparrows can reflect female physiological condition.
• Corticosterone may play a role in the decision-making process for attempting a second brood.
• Breeding stage is crucial when measuring corticosterone to understand its relationship with parental quality and reproductive strategies.