Interrupted incubation: How dabbling ducks respond when flushed from the nest

Area of Science:

• Wildlife ecology
• Avian biology
• Behavioral ecology

Background:

• Nesting birds balance egg incubation with self-maintenance needs.
• Uniparental incubation often involves periodic recesses for foraging.
• Disturbances like predators or human activity can interrupt natural incubation patterns.

Purpose of the Study:

• To characterize incubating mallard (Anas platyrhynchos) and gadwall (Mareca strepera) hens' responses to flushing by predators and investigators.
• To compare the duration and habitat use during natural and disturbance-initiated incubation recesses.

Main Methods:

• Observing and recording incubation recess behavior of mallard and gadwall hens in Suisun Marsh, California.
• Comparing recess durations initiated by investigators versus natural hen-initiated recesses.
• Analyzing hen movement patterns and habitat selection (wetland vs. upland) during different recess types.
• Assessing the impact of repeated nest visits and transmitter attachment on recess behavior.

Main Results:

• Investigator-initiated diurnal recesses were 63% longer than natural diurnal recesses.
• Nocturnal recesses (likely predator-induced) were shorter than natural diurnal recesses.
• Hens moved further from the nest during diurnal recesses than nocturnal ones, with varied wetland/upland habitat use.
• Investigator-initiated recesses did not influence subsequent natural recess duration unless hens were fitted with GPS-GSM transmitters, which increased recess duration by 26%.

Conclusions:

• Incubation interruptions by investigators and predators have measurable, specific effects on hen behavior.
• Hens may not fully meet physiological needs during investigator-initiated recesses.
• The attachment of GPS-GSM transmitters significantly impacts incubation recess behavior, suggesting a need for careful consideration in wildlife studies.