McGILL BIRD OBSERVATORY

The "fall warblers" are one of the classic identification challenges for North American birders, perhaps immortalized best by Roger Tory Peterson's compilation plates of "confusing fall warblers".  However, despite the large number of species involved overall, the situation need not be as daunting as it sometimes seems.  In reality, the full suite of fall warblers can be broken down into several smaller groups, within which specific features can be looked for to further narrow down the identification.  The material presented below is not intended to be authoritative, but rather by offering a somewhat light-hearted approach to the subject from a different perspective than some other references, may help provide some useful memory tricks to apply when faced with a "mystery warbler" in the field.

The WFTU approach
One of the keys to identifying fall warblers (or any birds for that matter) is to know what to look for - there are myriad body parts that you can commit to memory or jot down notes about, but in reality only a few of those tend to provide really diagnostic information about species.  WFTU is a useful acronym to remember, as it stands for two useful messages.  One, focus on What Feathers Tell Us - for the majority of warblers, and also many other species, looking closely at particular feather tracts is where you should concentrate your attention.  Which ones?  Wings, Face, Throat, and Undertail are particularly useful for warblers.

Simplify the search
It's easy to feel overwhelmed by the challenges of identifying an unknown bird, especially if you are relatively new to birding.  The key to remember is that there are never really as many options as there might appear to be at first.  There are 2041 species in North America ... but only 925 in the United States and Canada.  Within Canada there are just 661, and only 464 of those in Quebec.  Narrowing the scope further to the Montreal area, i.e. the pool of birds that might potentially be encountered at MBO, the total drops to 357.  Numbers will be different for any particular location in North America, but the general principle will hold for most - right from the beginning you can ignore half or more of the birds in a North American field guide (conveniently ignoring for the moment that vagrants can occur anywhere, but the intent of this article is to focus on identifying the regularly occurring species, so that's a topic for another time).

From that suite of local species, narrow the field of options further again by identifying the general group of birds to which the candidate belongs, such as warblers or sparrows, or more generally waterfowl and songbirds.  The key to this process is to gradually weed out birds you are certain are NOT what you're looking at, until left with a relatively small group of similar species is left to consider ... and at that point the WFTU system can hopefully take over.

Know the locals
As alluded to above, vagrants can turn up anywhere, and of course their discovery can lead to a lot of excitement.  But in reality, the vast majority of birds you encounter will be the regularly occurring species in your area.  Sometimes the ability to identify those gets taken for granted, but in reality, if you are really familiar with those species and their key characteristics, it will make it all the easier for you to recognize a rarity when it does appear, and to be confident that it IS in fact something different (even if you don't immediately recognize just what it is).  Practice looking for the key features of common birds, and the differences will jump out at you much more obviously when something doesn't fit.

The not-so-confusing fall warblers
Many references have broken down fall warblers into those featuring wing bars and those without, but some further subdivisions are useful in breaking up the species further.  The table below summarizes such a further subdivision for the 30 warbler species seen with some regularity in southwestern Quebec and eastern Ontario.  Below that, the WFTU approach is applied to each group in turn.  Refer to the MBO Photo Identification Gallery for pictures of some of these species, along with further detail on determining the age and sex of individuals once species has been identified.  Note that some of the descriptions below are overly simplified as there is quite a bit of variation within species by age and/or sex; again, this is not meant as a definitive guide, but rather as an alternative approach that may help you focus on important features, in combination with tips from other sources.

"True wingers"
These two species are easy to distinguish, especially by the wings and throat (in this and other tables below the easiest / most reliable distinguishing features are highlighted in bold)

	Wing bars	Face	Throat	Undertail
Blue-winged Warbler	white	black eyeline	yellow	white
Golden-winged Warbler	yellow	black cheek	gray/black	white

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"Greenish streakers"
These three are among the most confusing of the 'classic' confusing fall warblers.  Focus especially on the facial pattern and undertail, as the wing bars are white on all three, and the throat is about as variable within species as it is between them.  Also check the back - it is streaked on Bay-breasted and Blackpoll, but unmarked on Pine.

	Wing bars	Face	Throat	Undertail
Bay-breasted Warbler	white	slight eyering	buffy	buffy
Blackpoll Warbler	white	dark eyeline	grayish	white
Pine Warbler	white	pale eyeline	gray-yellow	whitish

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"Yellowish streakers"
These species generally have a yellowish or brownish overall appearance in fall.  The face in combination with undertail are the best features to focus on, though the more brownish wing of the Palm if often an easy giveaway. 

	Wing bars	Face	Throat	Undertail
Yellow-rumped Warbler	white	white eyering	beige	white
Cape May Warbler	white	dark eyeline	streaked	white
Palm Warbler	brownish	dark eyeline	gray-yellow	yellow

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"Unique faces of the bar"
These are 8 species with prominent wing bars that share little else in appearance - each has a unique facial pattern though, more pronounced in spring, but remaining distinctly recognizable in fall.  In many cases the throat can also be used to help confirm identity.

	Wing bars	Face	Throat	Undertail
Black-and-white Warbler	white	striped	white/black	white
Blackburnian Warbler	white	yellow-orange supercilium	yellow/orange	white
Cerulean Warbler	white	whitish supercilium	greenish	white
Northern Parula	white	partial eyering	yellow	white
Magnolia Warbler	white	white eyering	yellow	white
Black-throated Green Warbler	white	yellow supercilium	yellow - black	whitish
Chestnut-sided Warbler	yellow	white eyering	white	white
Prairie Warbler	yellow	dark eyeline	yellow	yellow

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"Pale 'n' plain"
These species are generally a pale yellowish/greenish/grayish overall.  The Black-throated Blue is more readily recognizable if it has white wing patches (on the primaries, below the primary coverts), but not all females show this.  The Tennessee and Orange-crowned can be particularly problematic, and for them the best feature to look for is the colour of the undertail.

	Wing bars	Face	Throat	Undertail
Orange-crowned Warbler	none	partial eyering	yellowish	yellow
Tennessee Warbler	none	dark eyeline	yellowish	white
Yellow Warbler	none	plain face	yellowish	yellow
Black-throated Blue Warbler (female)	none	pale supercilium	whitish	buffy

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"Yellow-bellies"
These species all have bold yellow underparts, but are different enough in the face and/or throat that they can be fairly easily separated.

	Wing bars	Face	Throat	Undertail
Nashville Warbler	none	white eyering	yellow	yellow
Mourning Warbler	none	partial white eyering	yellow/gray	yellow
Connecticut Warbler	none	white eyering	gray/brown	yellow
Canada Warbler	none	white/yellow eyering	yellow	white
Wilson's Warbler	none	yellow supercilium	yellow	yellow
Common Yellowthroat	none	brownish/black cheek	buff/yellowish	yellow

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"Mini-thrushes"
Brown above and spotted or streaked below, these three warblers look like smaller versions of the Catharus thrushes.  The face and throat provide easy ways to distinguish among them.

	Wing bars	Face	Throat	Undertail
Ovenbird	none	white eyering	white	white
Northern Waterthrush	none	buffy/pale supercilium	streaked	white
Louisiana Waterthrush	none	white supercilium	streaked	white

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"Upstart redstart"
The only warbler in this region lacking wing bars and also entirely different in appearance from the preceding three categories.

	Wing bars	Face	Throat	Undertail
American Redstart	none	gray or black	white or black	white

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Concluding thoughts
Everyone's learning approach and memory techniques are different.  The information presented in this article has proven helpful for some birders, and not for others.  Regardless of which category you fall into, remember that there is no substitute for experience - spend enough time watching the common warblers in your area, and you can develop your own unique personalized ways of identifying each species.

 

 

© 2002- The Migration Research Foundation Inc.