This is called 'false positive'. In general, this is caused by environmental factors such as wind (moving branches), solar radiation, precipitation, but also (overflying) insects. However, it is also possible that the detection field is wider than the field of view or that you are dealing with a slow detection time, so that an animal is detected by the sensor but is not visible on the image. Some trailcameras offer the possibility to adjust the sensitivity. A high sensitivity maximises the detection capability of the PIR sensor and most small, moving temperature differences with the environment are detected. This may be ideal for capturing smaller mammals that excrete less heat, but generally also leads to many false positives. With a lower sensitivity, you avoid getting unnecessary images. This is particularly useful when capturing larger mammals.

Tips:

• Take the position of the sun into account. A northern position ensures that the trailcamera is not directly affected by sunlight.
• Make sure that the detection area is free from distracting objects, such as high vegetation, branches and leaves.
• Be aware of the size of the detection and field of view of the camera trap.
• When determining the sensitivity, take into account (environmental) factors (animal species, season, weather forecast, landscape etc.) that influence the detectability of the sensor.