Here are some great beginner resources for learning about Northern American birds:
The Cornell Lab of Ornithology’s All About Birds
The Cornell Lab of Ornithology’s Birds of North America (only the Introductions for each entry are free)
Nation Audubon Society’s Bird Guide
Westchester County-related:
Saw Mill River Audubon’s (SMRA) Westchester County Checklist (PDF of printable checklist)
Hudson River Audubon Society’s (HRAS) Westchester County Checklist
For fun:
The Cornell Lab’s Ontario Feederwatch Cam (for the grosbeaks and the grouse!)
The Cornell Lab’s Bird Song Hero
Lang Elliot’s YouTube Page (excellent videos of individual birds singing)