This is currently a work in progress, but I wanted to begin tinkering with Google Calendar's embed function before the calendar is finished. There are still some errors in the calendar to correct, and the following groups still haven't been inputted: Polioptilidae, Fringillidae, Icteridae, Acciptridae, and Charadriiformes.
Another issue is that the colors I've attached to each species to indicate frequency don't show up in the embedded widget, so you will have to subscribe to the calendar to see those (for now). Regardless, the list below is the majority of species you can see today; if you click on each species and then click "More Details", you will be able to see the color code.
Here's the description from of the calendar, with a key to the color coding:
"A calendar meant to notify and inform when all regular species of birds found in Northeast Illinois (Lake, McHenry, Cook, and DuPage counties) can be found. Notes on where to look and links to eBird Data will eventually be added. All date ranges and average peak dates are based on eBird frequency.
Gray - Cosmic Mind-bender
Red - Occasional
Yellow - Rare
Blue - Uncommon
Green - Common
eBird Data: http://goo.gl/b9e96Y"