Sunday, June 28, 2009

Mystery Bird Revealed

Well, the mystery bird quiz wasn't as much fun as I anticipated. Of course, Donald and Hap were right, with their answers of juvenile Eastern Towhee, but I was hoping for more guesses and discussion. Let me walk you through my thought processes and tell you how I arrived at the same conclusion, albeit more slowly than either of the guys.

After my initial shock, when I had no idea what sort of bird had crashed into the porch window at Terry's studio in western North Carolina, I recovered enough to start working through the clues.

First, habitat. When someone says to me, "I just saw a bird and it was ..." (blue, brown, red, white, big, little, etc.) I always interrupt and ask, "First, where did you see it? In the woods, in a field, at the beach, on a pond," because habitat helps us rule in or out many species, before we start guessing based on color or size. In this case, we are on a porch on a quiet back road in a wooded area of North Carolina.

Next, I looked at its head. One of my birding mentors once told me you could reliably ID any bird by the head alone, using the bill and any field marks. I'm not sure I could do that, but I can usually get pretty close.

In the case of Mystery Bird, we see a short, stout, "finchy-type" bill, often incorrectly called a "seed-eating bill," typical of sparrows. Also looking at the head, we see a decided lack of field marks, like crown stripes, eyelines, eye rings, "eyebrows" (supercillia) or "mustaches." Since most sparrows have a lot of field marks on their heads, this is contradictory. Still, I feel confident this bird belongs in the sparrow family.

Also, I have an odd feeling in my gut that this is a young bird. Maybe it is the faint yellowish wash to the edges of the bill or just something about the GISS (General Impression, Size and Shape) of the bird, but regardless, I think it is a juvenile. That makes my job harder, since young birds quite often have much different plumage than the adults of the same species.

Next, I looked at the breast streaks.
I have seen fine, "pencil-mark" streaking on the breast like this before, on Lincoln's Sparrows.

Lincoln's Sparrow,
image from National Zoo website

I know this isn't a Lincoln's, but it is one more reason why this might be some sort of sparrow. Vesper Sparrows also have this field mark, and I have never seen a Vesper, so I move this to the top of my differential list. It seems bigger than it should be, but I know that Vesper Sparrows are on the largish size for sparrows (about 6.25" long) and I also know that size is deceiving, and is one of the less useful tools when it comes to bird ID. So, I photograph it with the only thing I can find for scale - my 58mm lens cap.

My last field mark is the white on the outer tail feathers.

A key field mark for Vesper Sparrows is white outer tail feathers, so now I am fairly certain this is what I am holding in my hand. I find it ironic that my "Life" Vesper Sparrow is, in fact, dead. Of course, in my excitement, I have completely ignored Rule 1, habitat. Vesper Sparrows live in agricultural fields or sparse pastures, not in wooded areas.

I'm sure you are all laughing at me by now, but please keep in mind, I am working without a net. I have no field guides, no web sites, no helpful expert birder or Science Chimp standing behind me, looking over my shoulder, and I have a cluster of non-birders watching me, eager for an answer. So, I clutched, and called it a Vesper Sparrow.

That identification bothered me till I got home and pulled out my field guides.

Vesper Sparrow,
image from NPS website

Clearly, my bird was not a Vesper Sparrow, even allowing for variations which might occur in a juvenile bird. So, it's back to work.

Using my lens-cap photo from the previous post, I calculated the Mystery Bird was about 8" long, way too big for any self-respecting sparrow. Now, I'm in trouble. I don't even know which page of my field guide to look on, so I revert back to Beginning Birder 101 - start at the front of the book and flip through every page till you see the bird in question.

Of course, I didn't start at the very beginning - I was able to rule out ducks, herons, shorebirds, owls, and woodpeckers right away. Page by passerine page, I carefully looked through my trusty Peterson's Guide to the Birds East of the Rockies, 4th edition (1980) till I found it. On page 276, half-hidden behind the female, is a juvenile Eastern Towhee, what was still referred to at that time as Rufous-sided Towhee.
Note the bill, the streaky breast, and the white on the outer corners of the tail feathers. This is where I messed up in my leap to Vesper Sparrow. As seen in my Peterson's, the entire outer tail feathers are white from base to tip in a Vesper, not just the corners as we see above. (Of course, there are also the chestnut shoulder patches, the riot of field marks on the head, the size, the habitat, and so on and so on ...) Look at two more things. In the first photo of the head, notice the dark eye, which would be red in an adult Eastern Towhee, male or female, but is black in a juvenile, like my victim.

And finally, in the drawing, check out the white "handkerchief" marks on the wings of the adult birds. Peterson doesn't show it, but in his written description of the juvenile he says: "Streaked below like a large sparrow, but with the diagnostic Towhee wing and tail patterns."
I can attest to the fact that the patterns were there, staring me in the face all along. (Gotta love a bird artist who says "diagnostic.")

So, I was close. I was right about the juvenile part and I was in the sparrow family (You do know that Towhees are sparrows, right?) but I missed the species.

When working on a bird ID, I always go to Peterson's field guide first, and I am rarely disappointed. In checking my Sibely's eastern field guide (not the Big Book) I didn't find the juvenile plumage. I Googled "immature Eastern Towhee" and came up with several photos, none of which showed everything that one drawing did, but which helped me confirm my ID. Finally, I sent copies of my photos to Julie and Hap, and they concurred. (BTW, watch the next issue of BWD for Julie's take on "Confusing Summer Towhees."

Thank you, Roger Tory. I promise never to go on vacation without you again, even when I am told I am limited to one suitcase. I will leave out extra socks to make room for you.


donaldthebirder said...

I know that towhees are sparrows, but my mind thinks in more of a "whole situation" type mode (similar birds in similar habitats). If you wouldn't have gave the habitat right off, it would have made me go to books or the net for confirmation on my thoughts.

KatDoc said...

Of course I know you know that towhees are sparrows, Donald, but perhaps others don't. What I was trying to illustrate was one way to work out the identification of an unknown bird, and how it helps to know family groups, like warbler, sparrow, etc., in order to narrow one's search.

donaldthebirder said...

Knowledge is cumulative, the more one knows the better :-)

dguzman said...

Towhees are sparrows?????

I'm sorry I missed all this from the beginning -- but so glad I'm reading it now. Thanks for the step-by-step ID process; I love to learn from the masters.

Still, there's nothing sadder than IDing a dead bird.

Heron said...

Good tutorial on ID process and pitfalls along the way. Your teaching skill is appreciated.

KatDoc said...

"Master?" Not really, Delia, just someone who keeps on trying. Yup, towhees are in the sparrow family. When I first learned this, I was stunned. Watch the "hop-forward, scratch-backward" feeding style of a towhee and a white-throated sparrow, tho, and you will get the connection.

Working thru the process was the basic theme of these two posts, Heron, thanks for noticing. Also, to let people know that we all make mistakes, and learning from them is the bonus. I'll recognize the next (live) juvi. towhee I see, or at least, I hope I will!