Warbler Guy, what's a good web site to tell warblers from one another? Here's some warbler photos that perplex me for the ID of warblers.

Jessie, try looking at:

http://merlin.allaboutbirds.org/photo-id

As for your warbler photos, below, here's my opinion as to their identities (from top to bottom):

Orange-crowned, Nashville, Orange-crowned, Yellow-breasted Chat

As for apps: iBird Pro (wonderful!)....Sibley Birds (equally excellent, and especially for gull species because the age class for each "cycle" is visually expressed well).

The Warbler Guide app is OK and is complementary to the field guide with the same name....but its breadth and depth is not as advanced as iBird Pro and Sibley Birds. There are several other FINE bird apps, so I don't wish to suggest this communique is comprehensive.

Enjoy the wood-warblers and birding fun, Daniel....warblerwatch.com....(site hosts my "Birding Tours" information.....and danielsmerrittclasses.blogspot.com feature my current "Raptors of San Francisco Bay" college class that continues through 11/12/17.