Seasonal acclimatization to temperature in monk parakeets

Area of Science:

• Avian physiology
• Ecological energetics
• Thermoregulation

Background:

• Understanding seasonal adaptations in bird physiology is crucial for predicting responses to environmental changes.
• Monk parakeets (Myiopsitta monachus) exhibit distinct behaviors and habitat use across seasons, suggesting physiological adjustments.

Purpose of the Study:

• To determine the summer metabolism and insulation of monk parakeets.
• To compare summer physiological values with previously reported winter data.
• To investigate the relationship between body size and seasonal changes in fasting metabolic rate (FMR).

Main Methods:

• Measurements of fasting metabolism and evaporative water loss in summer.
• Comparison of summer data with existing winter data for monk parakeets.
• Analysis of thermal conductance and dry heat transfer coefficients.
• Literature review to establish relationships between body mass and seasonal FMR variation.

Main Results:

• Nighttime fasting metabolism was significantly lower in winter (6.11 Wkg^-1) compared to summer (8.20 Wkg^-1).
• Winter birds exhibited significantly lower evaporative water loss (2.24 mg H₂O g^-1 h^-1) than summer birds (3.05 mg H₂O g^-1 h^-1) at 20-30° C.
• No significant seasonal differences were found in overall body insulation or dry heat transfer coefficients.
• A derived equation (winter FMR/summer FMR = 1.49 Mb^-0.077) shows that smaller birds have higher winter FMR, while larger birds (>200 g) have higher summer FMR.

Conclusions:

• Monk parakeets exhibit seasonal physiological adjustments, particularly in nighttime metabolism and water loss, but not in overall insulation.
• Body size is a critical factor determining the direction of seasonal fasting metabolic rate changes in birds.
• These findings contribute to understanding avian adaptation to varying thermal environments.