Excellent question, Bernice (in Chicago).
Here's some solution options to consider:
1. First, based on teaching "bird by ear" classes for more than 25 years, I believe every birder progresses different to identify birds by ear.
That’s why I offer 10 diverse hints in my Top Ten Tips To Improving Your Birding By Ear handout that’s free at my web site: warblerwatch.com
There, first click on “Birding Links,” and when the next screen shows a menu of files, click on Top Ten Tips To Improving Your Birding By Ear to access it and/or print it.
As a prequel to what you’ll read, here’s one tip among the 10:
#5. “Draw” bird vocalizations using your own “short-hand” notation marks, ala the chapter in Sibley’s Birding Basics (i.e., a quasi-sonogram shorthand method that he introduces). After your birding foray and when you’re out of the field, use these written notation marks while listening to songs/calls on media (e.g., CDs) to ID the species you heard and/or better learn their song/call patterns.
2. I suggest you consider perusing the web site:
It's excellent and Nathan Pieplow's two ear birding guides are fine resources:
The Field Guide to Eastern Bird Songs of North America....and The Field Guide to Western Bird Songs of North America.
The introduction to both of these field guides hosts valuable information from which the vigilant reader will immediately benefit.