Brainerd, Minn. – It's been more than a 15 years since I purchased my first trail camera.

Back then, my plan was to monitor animal activity on the 70 acres I own near Brainerd, not only for hunting and photography purposes but also as a way to measure the success or failure of various wildlife habitat management practices such as tree planting, wetlands restoration, wildlife food plots and mineral licks.

Now I continue to monitor my acreage using the latest digital surveillance cameras, and I still look forward to reviewing new images each day I go afield. I never know what creatures — rare or otherwise — may have passed since the last time I checked the cameras.

No wonder trail cameras are popular with deer hunters. These cameras are useful for monitoring activity at deer trails, rubs, scrapes, food plots and mineral licks. The cameras reveal important information about numbers of deer, their sizes, buck-to-doe ratios, and how many times each animal passes.

A trail camera is a weatherproof unit consisting of a digital camera that is triggered by an infrared heat-in-motion detector. Simply put, the camera is tripped when it detects any warm object in motion. Rain, snow and falling leaves or branches should not trigger the unit. The camera's functions are automatic, so focus and exposure are fully controlled. On most units, a flash is activated in lowlight conditions and at night, plus the time and date are printed on each image. Some units even display the current temperature, barometric pressure and moon phase. Many models feature a movie mode, allowing hunters to collect brief motion clips of their subjects.

On most trail cameras, there is a slight delay between the time an animal "trips the trigger" and when the image is actually taken. Some brands of cameras feature a delay of less than one second. A quick trigger speed assures that whatever walked past the camera — a deer, for instance — will be in the frame when the image is finally produced.

Over the years I've tried numerous brands of trail cameras. I've had a complaint or two about most. Delayed firing is a common problem, and so are false images produced when the sun, or even a sunbeam, triggers the camera. It's frustrating to find your digital card filled with images of nothing.

The best advice I can offer trail camera buyers is this: Be sure your dealer will allow you to return the merchandise for a refund if you are not happy. Also, test the functions of your new unit at home before placing it in the field. I suggest you read the instructions thoroughly, then place the camera on a tree in your yard and walk past the unit at varying angles, distances and speeds during both daylight and darkness. Then review the captured images to verify whether the unit functions to your satisfaction.

Bill Marchel, an outdoors writer and photographer, lives near Brainerd.