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New Field Marks

When I was fifteen, I received as a Christmas present the three-volume Audubon Society Master Guide to Birding. Accompanying promotional material promised the reader something on the order of sixty never-before disclosed secrets to field ID. One that I recall was a new way to tell the waterthrushes apart–by the shape of the supercilium.

Thirty years later, that’s old hat. We “all” know–well, okay, some birders know–the difference: prominent and flared out behind the eye on the Louisiana Waterthrush vs. thin and tapering behind the eye on the Northern. But somebody had to figure out that field mark, and take it to the next level: to get that knowledge out there.

There’s something else. Even if waterthrush supercilia are old news, it’s still just as exciting as ever to learn about new field marks. I confess, I don’t refer too often these days to the Master Guide. But that three-volume set retains a special place in my heart: The Master Guide reminds me to stay alert to the possibility of new knowledge and understanding.

14-1-10-03 [Clay-colored Sparrow]

Did you know about the distinctive pattern to the center of the nape of the Clay-colored Sparrow? Photo by (c) Jay Carroll.

I take it as a given that there’s new bird ID knowledge still waiting to get processed and publicized. Here at The ABA Blog, Catherine Hamilton recently described how the “gape notch” is important for distinguishing among the notoriously difficult “peeps” (the little sandpipers in the genus Calidris.) And in the January/February 2014 Birding, Nick Lethaby takes a new look at the old problem of the “Spizella trio”–the Chipping, Clay-colored, and Brewer’s sparrows. These three sparrows are especially tricky in fall and winter, and Nick encourages us to look at them from behind. Click here for a free PDF download of his article.



Here’s my question for you. Are you aware of some little-known field mark? Something that, as far as you know, isn’t depicted or discussed in the major field guides? Don’t worry if your knowledge is a bit provisional. That’s how it is as we push forward together to learn more about bird ID.

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Ted Floyd

Ted Floyd

Editor, Birding magazine at American Birding Association
Ted Floyd is the Editor of Birding magazine, and he is broadly involved in other programs and initiatives of the ABA. He is the author of more than 100 magazine and journal articles, and has written four recent books, including an ABA title, the ABA Guide to Birds of Colorado. Floyd is a frequent speaker at birding festivals and state ornithological society meetings, and he has served on the boards of several nonprofit organizations. Mainly, he listens to birds at night.
Ted Floyd

Latest posts by Ted Floyd (see all)

  • Ted Floyd

    I’ll start us off. These are minor and provisional. Here goes:

    (1) I’ve noticed in the field, in photos, and (especially) in the morphometric data in the BNA Account that Harlan’s Hawks are proportionately long-winged than other Red-tailed Hawks. In particular, the wing-to-tail ratio is greater for Harlan’s than other Red-tailed Hawks in the ABA Area.

    (2) Female American Six-toed Woodpeckers in the southern Rockies, where I bird, are remarkably similar to female Hairy Woodpeckers. What invariably first tips me off to a Six-toed is the bird’s habit of foraging at or even below eye level. Hairies are usually higher up. This is of course a “plastic” field mark, but it sure seems to work most of the time.

    (3) I need to test this one, but I think the common call note of the Yellow-shafted Flicker is more clearly disyllabic than the more monosyllabic call note of the Red-shafted Flicker. If this is valid, it’s surely complicated by the frequent occurrence of hybrids in areas where the two taxa overlap.

  • William von Herff

    I’ve always loved the Sharp-shinned vs. Cooper’s Hawk duo, but I recently realized something. On perching birds, the wingtip of the Sharp-shinned Hawk ends at the end of the second dark band on the tail, whereas with Cooper’s it ends at the start of the second dark band. This is fairly consistent among the two species, but if only really applicable with photos.

  • Scott Pendleton

    I walked the same eBird route weekly for two years through Eastern Ohio’s reclaimed strip mine grasslands and noticed not so much a field marks but field behaviors that help me ID sparrows quickly.
    1) As Savannah Sparrows land, at about six inches off the ground they pull up, turn, drop and land facing what they just flew from. The really interesting thing is over 90% turn to the right. Apparently they are predominately right-eyed.
    2) When Henslow’s fly, which they prefer not to do, they resemble miniature Eastern Meadowlarks. Their flight is strongly arced compared to its length, rapid wing bursts followed by short glides, and they appear as if they could fall out of the air at any moment.

  • Mary

    I found that Mute Swans have very long tails when compared to other swans. I think this is a great field mark to rule them out or in when looking for Tundra or maybe even Trumpeter Swans when the birds are either at a distance, or their heads are tucked. Mute Swan tails are huge and they really stand out. When I mentioned this on a local listserv, a local expert actually replied that it was not a very useful field mark, but I don’t agree. I think it’s great. It helps me a lot. Now I know in a glance if that bird is a Mute Swan, or something I need to examine more closely. But I’m curious why the expert didn’t agree and why it is not referenced in the field guides.

    • Paul Hurtado

      I was going to say the same thing! Super handy for scanning mixed swan flocks out east in search of Tundras and Trumpeters.

  • Jennifer Dudley

    This post is from an “advanced beginner” or dare I day “intermediate” birder, so some of this may not be so interesting to the expert birders here! Neverthelessess….

    1. The Seaside Sparrow and the Savannah Sparrow are terrible difficult for me to distinguish. The beak and breast are the clues. Bur if I only get a fleeting glimpse, I can’t get the id. (I bird a lot in Maine where you can expect to see a Seaside Sparrow).

    2. I actually had trouble sometimes distinguishing the American Tree Sparrow from the Song Sparrow at a distance. Then I learned a new technique. Look at the beak! The adult American Tree Sparrow’s beak is black on top and yellow on the bottom. Also, some people confuse it with the Chipping Sparrow, but the Chipping Sparrow has a black beak and black eye stripe as opposed to the American Tree Sparrow’s brown eye stripe. Those “little brown jobs” can be tricky.

    3. Also, that female Red-winged Blackbird takes me more than a few minutes to identify. At first I’m sure it’s a Sparrow or a female House Finch for a moment. But, once again the beak is key for id, it’s pointier.

  • Paul Hurtado

    Not sure if these are all that great, but FWIW…

    1. This relates to identifying abnormally pale birds, not so much particular species. An issue that often comes up, as people tend to label such odd-balls as rarities or hybrids. A wonderful field mark, when visible, is feather wear. Often, especially in feathers that are atypically solid white or very pale, other microstructures in the feathers are abnormal and lead to rapid feather wear. Feather wear is a great feature to aid in assessing molt, but it’s also a handy indicator of abnormally pale feather coloration.

    2. Among the large “white-headed” gulls (Herring, Glaucous, etc.) I’ve found eye size and position in the face can be a really nice structural clue in separating larger vs. smaller species (e.g. Iceland vs. Glaucous). Not diagnostic, but a useful feature to consider among other characteristics.

    3. Also, among the Herring/Thayer’s/Iceland complex, the extent of pale edges and pale internal markings on the primaries are often a key feature for separating 1st cycle birds. BUT, as far as I can tell, these features are often described in very subjective ways (e.g., in separating Thayer’s from Kumlien’s) and I’m not yet aware of a more careful classification of these patterns that might shed more light on details that help separate some of the intermediates. For example, dark Kumlien’s, in my experience, often have variable-width pale edges to their dark primaries, especially moving towards the base of the feather, while this is often much more uniformly think in Thayer’s. Tertial patterns are quite complex, but I think a few different measures of the extent, variability and thickness of pale margins (along the sides and the tip of the outermost tertial) and some measures of the size, and distribution of paler interior markings, all together would make for an excellent data mining endeavor to try and nail down some more precise attributes that help distinguish these birds (or further confirm that some intermediates just can’t be safely called one or the other! 😉 )

    4. Here’s my first field mark that should be revoked/revised: dark greater covert bars on 1st winter gulls are NOT a good way to find a 1st cycle Lesser Black-backed Gull! Lots of young Herrings (at least in the Great Lakes region) show rather unmarked secondary coverts that look pretty uniformly dark brown on the folded wing. Other than looking at nice flight shots, I’ve found this to be a really weak secondary mark that — when you can see it — usually contributes little to distinguishing Herring from LBBG because of all the other visible characteristics that are more diagnostic.

    5. My second attempt to revoke/revise a field mark: Flank color is not diagnostic for separating male Lesser and Greater Scaup… well, it is, but only if you are careful about AGING them first (which many/most birders are not) and taking into account room for molt. I’ve seen far too many people mistakenly ID bright, lighter Lesser Scaup as Greater Scaup, and I’ve also seen instances of the reverse mistake — people calling younger male Greaters (with some older/darker flank feathers) Lessers purely because of flank color, even when head/bill structure and size were readily accessible. Sure, this is a useful field mark, but probably one that should be considered way more secondary than it’s often presented.

    • Jennifer Dudley

      Paul! If I can’t post a picture here, but maybe you can help me confirm if this bird is a juvenile iceland gull if I have your e-mail address? I hope you get this message.

  • Ryan O’Donnell

    Here in the inland western U.S., American Robins and Townsend’s Solitaires can both be common and overlap in habitats. When front-lit, it is easy to tell them apart. But many distant backlit birds can actually look quite similar. Townsend’s Solitaires are definitely a bit slimmer, which can be distinguished at a distance, but depends a bit on posture (more “fluffed up” and bulkier in cold weather for example). When landing, I have noticed they have different behavior that I think is nearly diagnostic. American Robins tend to land more directly, smoothly coming in to a perch, with at most a couple wingbeats to slow down. In contrast, Townsend’s Solitaires look like novices that haven’t learned how to brake: they kind of flail their wings a bit, and teeter their body from side to side as the come in to a perch, always looking like they weren’t quite ready to land.

  • Ted Floyd

    The recent issue of Birding has an article on a new field mark for separating Black-tailed and Hudsonian godwits:

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