In the absence of a recording, you want to try and be as descriptive as possible.
1. Were the notes short or long (measure in seconds)
2. How much space was between notes or sets of notes? (Again seconds)
3. Pitch? Can use a relative scale with other birds.
4. Tone. More subjective, but sweet, soft, sharp, scratchy, etc.
Fwiw I can't ID american birds, but the tips could still be useful!