BIRDING BY HINDSIGHT: A Second Look at the Calendar

There are all kinds of bird identification problems. Some because the species and their field marks have long been and always will be hard to figure out. Others because the field guides include incomplete or inaccurate information on the birds in question. But some identification difficulties could be more easily resolved if birders made more use of one certain tool. No, not more expensive optics or a larger library of bird books – just a plain old calendar.

Every year there are reports of species during April or March or even earlier that would be unusually early migrants. (Or, conversely, birds during November or later that would be unexpectedly late.) And every year it can safely be assumed that most of these involve misidentifications that might have been avoided if the observer had been aware of the date and that the species being reported then would be unlikely.

There is almost a pattern here. It always seems to be the same birds every year involved in these early spring (or late fall) identification difficulties....

• It is a mild day for late February, and you're in southeastern Minnesota, perhaps at Whitewater Wildlife Management Area, hoping for early migrants. A large raptor glides by with a striking under wing pattern: its pale gray flight feathers contrast with solid blackish under wing coverts. A Turkey Vulture? Perhaps, but a dark-morph Rough-legged Hawk or adult Golden Eagle, both of which have this same under wing pattern, would be more likely since a vulture before mid-March would be unusual.

But you can see the upper surface of the tail and it lacks the Rough-legged Hawk's pattern of white base/black terminal band? It still might be a dark-morph Rough-legged, which has a more uniformly dark tail: it's only light-morph immatures and adult females which have that "textbook" black-and-white tail.

And you say the head and bill appear too small for an eagle? Perhaps too small for a Bald Eagle, but a Golden Eagle's head and bill profile is noticeably smaller than a Bald Eagle's. This, in combination with the Golden's typically dihedral flight profile, give it a surprisingly Turkey Vulture-like aspect.

• Later the same day, a couple of other large raptors are seen. One is perched and its head is mostly white except for a distinct brown band through the eye; the other has distinct, almost round, black carpal or "wrist" patches on the under wings. Obviously a couple of Ospreys, right? If it were April, perhaps. But in February, Bald Eagle and Rough-legged Hawk would perfectly fit these descriptions and be far more likely.

Sub-adult Bald Eagles often have mostly white heads with a dusky line on the side of the head through the eye and are thus easily mistaken for Ospreys. And light-morph Rough-legged Hawks, as well as Ospreys, have dark carpal marks. Note that this mark on a Rough-legged is rounder and more clearly delineated, while the dark area on an Osprey's under wing is larger and elongated, extending beyond the "wrist" along the edge of the wing coverts towards the body.

• Surely, there wouldn't still be other raptors presenting potential difficulties in late winter/early spring? Unfortunately, Broad-winged Hawks are erroneously reported in March, even though the species does not typically arrive until mid-April. A raptor with a broadly banded tail at this time of year is more likely an accipiter (e.g., a Cooper's Hawk) or a Red-shouldered Hawk.

Accipiters frequently soar and fan their tails in the manner of a buteo; however, their tails appear longer than a buteo and have more visible bands (an adult Broad-winged typically shows only three bands, two black and one white). Also, field guide descriptions to the contrary, the dark and light tail bands on accipiters and adult Broad-wingeds are not of equal width. The dark bands on an accipiter are actually narrower than the pale bands, while the one visible white band on the Broad-winged is narrower than the black bands.

Similarly, the dark and light tail bands of Red-shouldered Hawks of all ages sometimes appear to be of equal width, like a Broad-winged is supposed to look, and unlike the field guides' portrayal of its white bands being narrower. Also note, like an accipiter, a soaring Red-shouldered shows more visible tail bands than an adult Broad-winged.

• It is April in western Minnesota and you've found a flooded field with some early migrant shorebirds, including a few dowitchers. If calling, the identification of these dowitchers would be straightforward. But they are silent and the light is poor, so it is hard to see if they have relatively bright upperparts and lightly marked underparts (which would suggest breeding-plumaged Short-billed Dowitcher), or darker upperparts and more heavily barred and spotted underparts (indicating Long-billed Dowitcher).

So are they Short-billeds or Long-billeds? The shakiest strategy would be to assume they are Short-billeds, since these are not normally present until May. The most cautious decision may be to call them "dowitcher, sp.", but they are likely Long-billeds, which arrive earlier in spring and depart the state later in fall.

Actually, the dowitcher problem is more prevalent in fall migration. Silent juveniles are separable by tertial patterns (plainer on Long-billed) and overall plumage (Long-billed grayer), but basic-plumaged adults are not. Consider, then, the calendar. In July it's likely a Short-billed; if September or October it's probably a Long-billed; in August you'd better hope it calls.

• A small adult tern flies by you in mid-April, but the view is too brief and the light too poor to discern bill color or how frosty or dusky the flight feathers are. So, as the name suggests, you assume it to be a Common Tern, right? Wrong. The Forster's Tern is the earlier migrant, with Commons not to be expected until late April or early May. And, despite its name, Commons are not common even later in the year. Unlike the more widespread Forster's, they are only routinely found during migration or summer on the few large lakes where they nest – e.g., Mille Lacs, Leech, Lake of the Woods, and Superior.

By the way, in summer or fall don't rely on bill color or wing pattern to separate juvenile or basic-plumaged Commons and Forster's. Instead, whether the tern is resting or flying, look for a blackish bar on the "shoulders" or leading edge of the upper wing coverts: if present, it's a Common; if absent, it's a Forster's.

• It's just after sunset in early April and you distinctly hear a nasal, rasping buzz: "peent!" It must be the first Common Nighthawk of the year, isn't it? Hardly. Not when you consider the first nighthawks don't usually arrive until the end of April, and one isn't to be expected until mid-May in northern Minnesota.

So what sounds like a nighthawk before then? American Woodcocks are back in March, and their "peenting" is similar enough to the nighthawk's call to cause confusion, although it is thinner and higher-pitched. And there is still another bird that sounds even more like a nighthawk. If you're near a lake or river, odds are that early spring buzz you hear comes from a male Common Goldeneye, a call many experienced birders are unaware of.

• You're studying this nondescript flycatcher and it is April. It lacks any trace of an eye ring and looks too large to be an Empidonax, but it has wing bars. So, doesn't it have to be an Eastern Wood-Pewee, even though that species isn't normally here until May?

Not when you consider that it is entirely normal for an Eastern Phoebe of any age to show wing bars. The field guides inexplicably claim that only juvenile phoebes have wing bars, but many adults have them as well, and, while they may not be as bold as a wood-pewee's wing bars, they are quite noticeable. This frequently misleads observers into erroneously reporting wood-pewees in April. 

• A wren in early April catches the corner of your eye before it vanishes (wren-like, of course) into heavy cover. Is it more likely a Winter Wren or a House Wren? The odds favor Winter Wren, since the first House Wrens don't normally arrive until the last half of April.

But to be sure and if by chance you get another look at it, try to see the tail length (although the stubbier Winter Wren's tail may be hard to tell without comparison), the Winter's heavier under tail barring (careful: the House Wren is also barred here), and the Winter's paler and more contrasting supercilium (but also difficult to determine without comparison).

• Then, just after that wren disappears, a thrush pops into view. But only briefly, of course, and characteristically it lurks in the shade. You look for a rusty-colored tail but see none in the dim light. The face becomes visible and a buffy eye ring seems to be evident, similar to a Swainson's Thrush, but there is also a grayish tone on the face like a Gray-cheeked Thrush. And as it vanishes – thrush-like, of course – you wonder why it isn't a Veery.

So why am I virtually certain you've just seen a Hermit Thrush? The calendar: only the Hermit is normally present in Minnesota before late April. Note that the rusty tail on a Hermit Thrush is often not visible if in the shade (where thrushes always seem to be), and that Hermits typically have a buffy eye ring (like a Swainson's) or a grayish face (like a Gray-cheeked). Because of their subtle coloration, habitual shyness, and fondness for shadowy cover, thrushes seem to get misidentified all the time. But if it is mid-April, start with the premise that it's probably a Hermit and don't call it one of the others without careful study.

(A postscript. Be aware that Veeries have distinctly grayish cheeks, so before identifying a Gray-cheeked make sure you've taken Veery into consideration.)

• The issue of shrike identification is more of a problem in late fall and winter, when only Northern Shrikes are normally present, but when one is sometimes mistaken for a Loggerhead Shrike. The problem arises when a Northern is seen but its underparts barring is not, and an observer erroneously assumes it must be a Loggerhead – unaware that the barring is typically difficult to see. Birders also have difficulty when trying to see whether or not the mask extends over the shrike's bill, which is also hard to tell in most cases.

Besides the calendar (in spring, don't expect a Loggerhead until late March, and in northeastern Minnesota you can expect to see Northerns lingering into April), pay attention to the bill and mask. The Northern's bill is longer, more strongly hooked (stubbier bill with a less obvious hook on Loggerhead), and the Northern's mask is thinner and more fragmented (thicker and more solidly black on Loggerhead). 

• You have a good ear for bird songs, and one April day you hear some familiar monotonous phrases from an unseen bird. But after having listened to the Red-eyed Vireo's ubiquitous song all last summer, you know that it has to be a vireo, right? Perhaps in May you'd be correct, but before then it is most likely a Purple Finch you're hearing. Even experienced listeners are unaware that one of the Purple Finch's calls strongly resembles the phrases of a Red-eyed Vireo song.

(Another postscript. In fall the Purple Finch has another whistling call that to my ear sounds identical to a Pine Grosbeak, and this undoubtedly has resulted in some erroneous Pine Grosbeak reports before that species normally arrives in late October.) 

• A nice wave of warblers happens by you in early May, and among them in the tree tops you get a brief but distinct view of a bold white eye ring, gray head, greenish upperparts and bright yellow underparts. After all these years of searching, have you finally managed to find your lifer Connecticut Warbler, one of Minnesota's most highly sought specialties?

Probably not, especially when you consider that Connecticuts don't arrive until mid- to late May, and that migrants skulk and walk through low cover rather than actively flit around like, well, a warbler. (Only singing male Connecticuts on breeding territory are found in the tree tops.) Take another look at the throat and I'll bet it was yellow, not gray, and you actually had the far more common and more "warbler-like" Nashville Warbler.

• On the first day of April a rusty-capped sparrow appears at your feeder. You can't quite see if it has a black breast spot, but you don't think so, so why not assume it's a Chipping Sparrow? April Fool, as the saying goes, and you're in the company of so many other birders who have mistaken an American Tree Sparrow for a Chipping during late fall, winter, or early spring.

While there are valid Chipping Sparrow records from November to March, they don't usually arrive much before early April, especially in northern Minnesota. And be aware that American Tree Sparrows often fluff up their breast feathers so that their breast spot is difficult to see, resulting in erroneous Chipping Sparrow reports.

• But, speaking of hindsight, what about that mixed flock of blackbirds you saw at Whitewater back in February when you were trying to figure out those raptors? Surely those nondescript ones with the pale eyes and moderately long tails were Brewer's Blackbirds, and those with the brownish heads had to be Brown-headed Cowbirds.

Well, speaking of hindsight, think again. Unfortunately these two species, which generally don't arrive in the state before mid-March, are often incorrectly reported from December through February. The problem is that wintering Common Grackles, especially females and immatures, may appear shorter-tailed and duller-plumaged than males in spring, and they end up being mistaken for Brewer's Blackbirds.

And Rusty Blackbirds, which are rare but locally regular some winters, are brownish then on much of their plumage, including their heads. This results in incorrect reports of cowbirds, which (like Brewer's Blackbirds) are much less likely in winter than Rustys.

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Now that it is April, take another look at the list of birds you've made note of during your birding rounds so far this spring. If it includes any of the species discussed above, and you have no doubts about what you saw, consider yourself fortunate. It either means we're enjoying an earlier than normal spring migration or that you've found something unusual.

But if, after reading this, you think you might have erred in your identification, don't despair. Take comfort that you're not alone, that many others have made the same mistake before you. And at least now you'll be ready to take on these same identification challenges when the calendar says that November has rolled around.