This video from the USA says about itself:
Be a Better Birder: Warbler Identification
10 July 2018
Warblers are a favorite among birders of all skill levels because they’re so rewarding. With their bright colors and globe-trotting habits, warblers add excitement to spring birding. But they often flit by quickly and can be tricky to identify.
We know that it can feel overwhelming at first. Get the help you’ve been looking for with world-renowned birder Kevin McGowan as your guide. Introducing the most comprehensive online course on warblers.
Read more here.