Connecticut Warbler -- photo by David Speiser on 9/18/07
Mourning Warbler, photo by David Speiser
When I looked at David Speiser's photos of the Connecticut Warbler and the Mourning Warbler I wasn't sure I could tell one from the other. I asked him if he would write a short description of how he went about identifying these birds, and he obligingly answered. Note, of course, that some of his tips apply only to real-life observation. You can't tell whether the bird walks or hops from a photo. Nevertheless, I thought you'd be as impressed as I was by what goes through the mind of a great birder as he studies a bird before making an identification:
I am not really an expert but I can provide a few I.D hints when trying to separate a Fall plumaged Connecticut warbler from a Fall Mourning warbler. When identifying a bird I generally look at structure and behavior first and then an overall impression of the coloration and at any immediate glaring field marks that are present. If time permits, then I am able to actually study the feathers and come up with an ID. Though this full process is not always possible, a combination of behavior, impression (size, shape) and color usually comes up with a correct ID.
The first difference I would notice is that a Connecticut warbler walks. If I see this right away I know I am looking at a Connecticut warbler. The next prominent feature is the bold often complete eye ring. However, in the photos there is a slight break of the eyering at the back. In fact, I find that birders will mis id a Connecticut, confusing it with a Nashville or Fall Common Yellowthroat when using the eyering as the only field mark. The eyering is also a main issue when separating Mournings from Connecticuts. Mournings in fall will also have a bold white eyering which sometimes can be complete. If you look at the photos you can see a slight break in both the front and back of the Mourning's eyering. The CT's break is only in the back.
The Connecticut is a big bulky warbler. The Mourning is also large but not quite so. When looking at the behavior, both acted similarly so that was not really helpful with this ID. Since both birds were feeding on the ground, this could help to eliminate Nashville because they rarely feed on the ground even in migration.
The next characteristic most birders look for is the big complete bluish-grey hood. In the photos you can see that the CT has a complete hood; the Mourning does not. Also, the Mourning shows yellow or paleness in the throat while the Connecticut will always show a complete hood with no yellow present.
When adding everything together, at least with these two birds: one was walking, had an almost complete eyering, had a full hood and no yellow in the throat. Therefore -- Connecticut!
One was hopping, two breaks in the eyering, not a complete hood, and yellow in the throat: you have your Mourning.
When separating Mournings and CTs from Common Yellowthroats and Nashvilles, it is important to notice structure. Mourning and CT are large and bulky with big strong bills. Yellowthroat and Nashville are small. A yellowthroat will usually show a whitish belly , while a Nashville will show a yellow - white - yellow pattern. A Nashvile and Common Yellowthroat also have smaller finer bills, especially the Nashville. The Nashville, as stated above, will generally not be below eye level.
Also, CTs and Mournings show long undertail coverts, the triangular feathers under the tail. In fact the undertail coverts almost reach the end of the tail in CTs and about 50-75% of the tail in Mournings. Yellowthroats and Nashvilles both show short undertail coverts, projecting slighlty into the tail.
I hope this helps.