Many smartphones have a pre-loaded voice recorder app which can be used in the field to record singing birds but for nocmig you’re better downloading an app that allows recordings to be saved in WAV format (default MP3 may lose quality). Røde Rec offers lots of flexibility but appears to be available only for Apple.
As you’ll be recording continuously from dawn to dusk you’ll need plenty of in-built memory, or a large memory card to hold all the recordings. Plus you’ll need to have the phone plugged in to the mains so it doesn’t run out of juice half way through the night.
Many of the recommendations in this article on recording bird song with a smartphone also apply to recording nocmig.