Updated: Mar 19
Subspecies, groups, and intergrades. Oh my! Learn how to properly tick your Yellow-rumped Warbler subspecies with this helpful (or miserable) post!
Warblers are some of the most sought-after birds to birdwatchers and wildlife lovers. Their unique colors and patterns create a viewing opportunity of great joy. This post focuses on the identification of one of the most common warblers in North America.
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This post will hopefully build your skills when it comes to identifying the subspecies groups of the Yellow-rumped Warbler. However, if you want to truly master identifying warblers, check out The Warbler Guide!
The History of the Yellow-rumped Warbler
The Myrtle Warbler and Audubon's Warbler were previously considered two species. If you did not know that, you might have been born after 1973 (raises hand). The two "species" were lumped into the "Yellow-rumped Warbler." Some people, such as Kenn Kaufman, hated this move by the AOS (previously AOU). Kaufman called the Yellow-rumped Warbler-name "bland" and "unflattering." I say this to Kenn Kaufman: you bite your tongue, Kenn Kaufman! Any bird that has "rump" in its name has a great bird name. Without "yellow-rumped," we might not have the affectionate nickname "Butterbutt." And certainly, it is a much better name than a bird being described using a surname like Cassin's, Baird's, or some other flowery tart (that's called throwing shade at the Duke of Rivoli - long live the Magnificent Hummingbird).
Everyone calm down. We can agree this is an amazing bird, with striking features. Back to the serious information. Well, serious-ish.
The Yellow-rumped Warbler (YRWA) is one species according to current* taxonomy. However, it is still split into four subspecies, with two of those subspecies being common in the US and Canada: coronata (Myrtle) and auduboni (Audubon's). For this post, we will only use the common English subspecies names.
The two subspecies that are the topic of this post, Audubon’s Yellow-rumped Warbler and Myrtle Yellow-rumped Warbler, can breed together to create an intergrade. Fun fact, an intergrade is not the same as a hybrid. The difference? An intergrade is the product of two subspecies or subspecies groups, and a hybrid is the product of two species. Confused? Do not fear! Most of this post is images.
Let's do a quick recap:
1972: Audubon's Warbler and Myrtle Warbler
1973: Yellow-rumped Warbler with 2 groups: Audubon's Yellow-rumped Warbler and Myrtle Yellow-rumped Warbler.
1989: I was born. Not really an important part of this timeline...
2016: Kenn Kaufman insults YRWA
2017: RIP Magnificent Hummingbird, flowery tarts get birds named after them
2019: I am writing this article.
Identification of the Yellow-rumped Warbler Subspecies
We will start with basic tips for the two common subspecies. Be patient, the images may take a moment to load, unless you have some blazing internet. Most people should by now, right? The focus of this post is on spring males, as they are much easier to ID in the field. Females are generally duller and have more buffy/brown/gray than males. Fall birds follow the same basic rules, they just are much less flashy.
Audubon's Yellow-rumped Warbler Identification
1. Yellow throat that does not extend to auriculars - (Myrtle Warbler: white throat and extends to under auriculars)
2. White eye-arcs only - (Myrtle Warbler: a white supraloral spot and white supercilium stripe)
3. Blue to slatey-blue auriculars and "under-auriculars" - (Myrtle Warbler: black to slatey-black auriculars with a white or white-ish "under-auricular)
4. Solid to mostly-solid black chest (Myrtle Warbler: distinct bold streaks)
Take better warbler photos! Use the proper birding camera!
Myrtle Yellow-rumped Warbler Identification
1. White throat that extends to under auriculars (Audubon's Warbler: yellow throat, does not extend to auriculars)
2. White eye-arcs with a white supraloral spot and white supercilium stripe (Audubon's Warbler: white eye-arcs only)
3. Black to slatey-black auriculars with a white or white-ish "under-auricular (Audubon's Warbler: blue to slatey-blue auriculars and "under-auriculars")
4. Distinct bold streaks (Audubon's Warbler: solid to mostly-solid black chest)
Yellow-rumped Warbler Intergrade Identification
1. A white throat with yellow centralized OR a yellow throat with white-edging (occasionally yellow is faint to nonexistent)
2. Obvious white supraloral spot or supercilium OR very faint to non-existent supraloral spot or supercilium
3. Black to blackish auriculars with white to whiteish "under-auriculars"
4. Bold chest streaks OR solid black OR combination
No single trait can guarantee an intergrade. Attempt to use a combination of traits to identify the bird in question. Remember, this post focuses on spring males; females add new elements to this discussion as do fall birds.
Yellow-rumped Warbler Range Maps
The range maps below will not provide a foolproof method for Yellow-rumped Warbler subspecies identification. Instead, they are another piece of the identification puzzle that can help to support your identifications. Note that the Audubon's Warbler breeds in the mountain-west region of North America, while the Myrtle Warbler breeds across the northern and eastern reaches of North America. Intergrades of the Yellow-rumped Warbler have been documented along the boundary of the two subspecies groups during the breeding season. Are they breeding? More information is needed!
Audubon's Yellow-rumped Warbler Range Map
Myrtle Yellow-rumped Warbler Range Map
Yellow-rumped Warbler Intergrade Range Map
Yellow-rumped Warbler Quiz
Decide if each pictured bird is an Audubon's Warbler (AUWA), Myrtle Warbler (MYWA), Intergrade Yellow-rumped Warbler, or cannot be determined and must be called a Yellow-rumped Warbler (YRWA) only. Never be afraid to use only the species name, Yellow-rumped Warbler. Not every bird can be identified down to subspecific levels.
All answers will be at the bottom of this post. HINT: Use your numbers!
Want to get better views of warblers? Check out our post on the best birding binoculars!
Now for some photos with no help!
Answers to Quiz:
3. Myrtle Warbler (I would not argue against an intergrade on this bird. There may be a faint amount of yellow, and the white supercilium is limited.)
5. Audubon's Warbler
7. Myrtle Warbler
9. Audubon's Warbler
10. Myrtle Warbler
How did you do? Share in the comments section!
*Final Note: This all may be irrelevant very soon. There is much genetic work being done that may lead to a split of the Yellow-rumped Warbler into 3+ species. But thanks for reading...