I've known about pigeons being used for communications and even bottle-nose dolphins being used for clearing mines in WW2. But I'm just curious if they've ever attempted to use crows for reconnaissance or early warning systems. Especially for use at something like forward operating bases that are always prone to enemy ambushes. Or maybe even using crows to alert of enemy movements.

I watched a video earlier today on a YT channel I follow called Curious Droid. This episode went into how the U.S military had a hard time determining vietcong troop movements due to the thick jungle foilege. So DARPA developed this concept of electronic fenses, where the airforce would drop these sensor packages into the jungle. The package would have sesmic sensors and microphones to capture movement of enemy forces through the jungle. The problem was that this being the 1960s/70s - the batteries only lasted couple of weeks. Also data storage and tranmission rates weren't advance enough at the time to send that information to a centralize location far from the contested area. So they had to have an aircraft loitering above to collect this data and then fly the collected data to a processing facility in Thailand. By the time the data was classified and analyized, the intelligence collected wasn't really actionable for the commanders in the field.

Here is the video. https://www.youtube.com/watch?v=feDk6oaeVAY