If you want to spot your quarry whilst being totally covert, there's no better way than with a thermal imaging spotter. Basically, if it's out there, you will see it because it detects the body heat and shape of an animal in detail. It can also be used during the day, for spotting animals and finding quarry that has been shot.
Pulsar are the worldwide market leader in thermal imaging technology, their thermal spotters are second to none. Using the latest 640x480 17µm <25mK NETD thermal sensors in their top models you can expect nothing but incredible clarity in the field.