|Hybrid Audubon's x Myrtle Yellow-rumped Warbler. March 30, 2014. San Elijo Lagoon, California. Greg Gillson. |
Click for larger view.
You may know that the western Audubon's form of Yellow-rumped Warbler has a yellow throat and the eastern Myrtle form has a white throat. But, of course, that is not the only field mark.
Myrtle Warblers have thin white eyebrows while Audubon's do not. Myrtle has two white wingbars while Audubon's has a big white wing patch. The under tail on Audubon's has black feathers all the way across the tip while on Myrtle the white reaches the end of the tail. The Myrtle has a hard "check" call note while Audubon's is a higher "tchip."
Intergrade Yellow-rumped Warblers are more often noticed in photos than in the field. In the photographed bird above, there is a bit of white around the edges of the yellow throat. And there is a short white eyebrow behind the eye (it was slightly longer and more obvious on the other side of the head). The wingbars form a messy patch. The under tail feathers are white to the tip in the center. Really, in most aspects, this bird is midway in field marks between Audubon's and Myrtle, except for the more Audubon's-like throat.
Here are two photos of more typical representatives of each form for comparison.
|Audubon's Warbler. Forest Grove, Oregon. March 23, 2012. Greg Gillson.|
|Myrtle Warbler. Forest Grove, Oregon. April 29, 2011. Greg Gillson.|