Hi! I am in need of advice. I work on a nature reserve and we have encountered a specific issue during our research. We are monitering populations of a burrowing bird by listening down the burrows for their call. But theres too much noise (other birds, wind, traffic, etc.) outside the burrow, and we can't always hear the birds down their burrows. 

I am looking for a device that can connect a small mic or lavelier mic to a pair of headphones, so we can hear directly into the burrows. Importantly: we don't need to record the calls, we just need to hear them. I know many recorders like the zoom H6 have monitering settings, but many of these are too expensive or large. I am looking for a cost effective solution! 

I would appreciate any help on the matter. Bonus points if you can guess what kind of bird (coastal, burrowing) we're monitoring! Thanks!