I recently purchased this Simmons Whitetail Trail Camera with Night Vision (4MP) to monitor the Screech Owls living in my front yard. It has great infrared capability but is not proving very adept at sensing these small owls as they go about their nightly activities.
For the price it is a great little gadget just keep in mind if it is small subjects you are trying to capture it will be hit and miss.
I opened it up to see if I could increase the sensitivity but could find no controls for such a purpose.