Optimizing sampling design to deal with mist-net avoidance in Amazonian birds and bats

Area of Science:

• Wildlife ecology
• Conservation biology
• Bioacoustics

Background:

• Mist netting is a common method for sampling bird and bat populations.
• Animals can develop net shyness, leading to decreased capture rates over time.

Purpose of the Study:

• To quantify the decline in mist net captures due to net avoidance in Amazonian birds and bats.
• To evaluate how different survey designs, including moving nets, affect sampling efficiency.

Main Methods:

• Mist nets were set in the same location for four consecutive days to measure capture decline.
• Resampling techniques were used to simulate different logistic scenarios and assess survey efficiency.
• Capture rates and species detection were analyzed for both birds and bats.

Main Results:

• Net avoidance significantly reduced captures, with a 28% decline in birds and 47% in bats between the first and second days.
• Moving nets daily increased captures by 30% for birds and 70% for bats.
• The benefits of moving nets diminished if it resulted in lost netting time.

Conclusions:

• Net avoidance is a critical factor affecting mist netting efficiency, particularly for bats and commoner species.
• Adjusting survey designs, such as daily net relocation, can mitigate avoidance effects and improve sampling.
• Strategic decisions on moving nets should consider the primary survey objective (e.g., individual captures vs. species detection) and logistical constraints.