Birds use individually consistent temperature cues to time their migration departure

Area of Science:

• Ecology
• Animal Behavior
• Physiology

Background:

• Bird migration timing is crucial for fitness, influenced by internal rhythms and external cues.
• Variable environments pose challenges for migration timing, potentially leading to arrival mismatches.
• The role of environmental cues in individual departure decisions remains under-investigated.

Purpose of the Study:

• To investigate how individual birds make departure decisions for migration.
• To determine the influence of environmental cues (temperature, photoperiod, wind) on migration timing.
• To assess if individual departure decisions can lead to population-level phenological adjustments.

Main Methods:

• Satellite tracking of 48 Asian houbara (Chlamydotis macqueenii) over multiple years.
• Analysis of individual departure timing in relation to temperature, photoperiod, and wind data.
• Comparison of individual repeatability for different environmental cues.

Main Results:

• Spring departure timing was most consistently linked to individual temperature conditions, showing higher repeatability than photoperiod or wind.
• Birds departed at lower temperatures from more northerly wintering sites.
• Individual departure decisions led to earlier population-level migration in warmer springs, with individuals arriving at consistent temperatures.
• Autumn departures were also temperature-repeatable but less distinct, with wind used as a supplementary cue.

Conclusions:

• Individual departure decisions, informed by local temperatures, enable population-level phenological adaptation to variable spring temperatures.
• This mechanism allows for pre-adaptation to changing environmental conditions without genetic shifts in reaction thresholds.
• Asian houbara demonstrate a flexible migration strategy influenced by individual environmental assessments.