BIRDING BY HINDSIGHT: A Second Look at Escapes and Hybrids

Well, I was going to write about identifying birds with abnormal plumages – you know: partial albinos, melanistic birds, etc. After decades of birding, I even figured out what the heck leucistic birds are. But someone beat me to it with an article in the September/October 2007 issue of Birding magazine ("Color Abnormalities in Birds"), and the author presents his "simple scheme" which proposes that terms like albino and even leucistic are no longer politically correct. Instead, we're "simply" supposed to use words like amelanism, hypomelanism, hypermelanism, aeumelanism, hypoeumelanism, hypereumelanism, aphaeomelanism, hyperphaeomelanism, aporphyrinism, and hyperpterinism.

No, really, for once I'm not kidding! This guy is serious about using these words, and, believe it or not, there are no typos in the previous paragraph. But rather than have you wrestle with the mental gymnastics of unraveling the spelling and pronunciation of his terms, let's move on to other kinds of atypical birds and situations that birders occasionally and potentially face.

Bird identification can be complicated by external environmental factors: e.g., oil stains resulting in anomalous black areas on a bird's plumage; mud making a Least Sandpiper's legs look dark rather than pale; a bleached-out gull appearing whiter than normal and mistaken for a Thayer's or Iceland; and abnormal color on hummingbirds, warblers, or orioles caused by pollen, nectar, or fruit stains. Excessive plumage wear and atypical molt also might alter a bird's appearance enough to cause ID problems, as would a bird with oddly shaped or proportioned legs, bill, or body.

ESCAPES

But even normal-looking birds can cause special difficulties for all those who particularly enjoy the listing aspect of birding. Remember, to just say that birders are interested in seeing birds is not entirely true. If it were, we'd be spending time looking at budgies in a pet store or visiting the aviary in a zoo. The point is that birders (not to mention ornithologists and records committees) are interested in wild birds, and it is often difficult – even impossible – to tell when a bird is wild or not.

At the time of this writing, for example, a Black-bellied Whistling-Duck is being seen in the Twin Cities. But is it a naturally occurring stray that wandered north here on its own, or is it an escaped or released bird from some waterfowl collection or zoo's aviary? While this question may seem irrelevant to some, the answer is of real importance to a lister and to this state's official list of bird records. Or consider that falcon seen earlier this fall in Duluth (its ID is still only tentative, by the way). If really a Gyr migrating south from the tundra, then it counts; if a falconer's bird of some kind that got away, then it doesn't.

Similar difficulties arise when dealing with birds introduced into the wild. Eventually, some establish a self-sustaining population and become "countable," but, if so, when does that happen? I have no problem listing Wild Turkeys as truly wild in, say, Houston County, but I doubt I'd do the same if I saw some in St. Louis County, and I'm not at all sure what I'd think of a flock in Pine County – especially if I knew they had been released there just two or three years ago. Would I feel any differently if the release had been four or five years ago? Or in Carlton County? And would it matter if some local sportsmen's club set them free, rather than the Minnesota D.N.R.?

Sometimes, there are clues which make it easier to determine if a bird is of captive origin. For example: excessively frayed feathers, faded plumage, non-standard leg or neck bands not issued by the U.S. Fish & Wildlife Service, clipped wings, a waterfowl's clipped hind toe (but not always done by collectors and hard to see), tame behavior (a flock of turkeys staying put or approaching my car when I stop is suspect; a flock walking or running away is more likely to be wild), and atypical or park-like habitat (I'd be more comfortable counting a Mute Swan at Agassiz N.W.R. than at Como Park in St. Paul).

Also consider how far out of range the bird is and whether the species has a tendency to stray off-course. Consequently, the origins of a Common Black Hawk found near Bemidji in 1976 (The Loon 50:31-34) were deemed more suspicious than those of a Crested Caracara seen in Scott County in 1994 (The Loon 67:59-61). As a result, the MOU Records Committee eventually judged the black hawk to more likely have been an escape and deleted it from Minnesota's checklist, while the caracara was thought to have had a better chance of being a genuine vagrant and was included on the list.  

Finally, it helps to be aware of how frequently a species and others like it are kept in captivity. Relatively few North American passerines, for example, are kept, so they would not be strong candidates for being escapes in Minnesota. (Places like Florida, Texas, and California have far more potential for caged songbirds escaping into the wild.) Some corvids, though, are apparently raised as pets, and some Black-billed Magpie records in states east of here were considered suspicious. All European Goldfinches seen here and elsewhere in the U.S. have been dismissed as escapes, but that's about it for the passerines. (Some might speculate that some of Minnesota's Painted Bunting and Eurasian Tree Sparrow records could involve captive origin, but I see no reason to think so.)

Non-passerines have a higher potential for being escapes, although there's little need for concern if you encounter an out-of-range loon, heron/egret, or shorebird. But you need to consider the possibility of prior captivity when that rarity is a duck, goose, or swan, since almost every species of waterfowl can be suspect: besides Mute Swan and Black-bellied Whistling-Duck, note that past Whooper Swan, Tufted Duck, and Smew records in Minnesota are known to have involved escapes. Note as well that introduced Trumpeter Swans by now may have established themselves in Minnesota, but I wouldn't necessarily consider every Trumpeter I see as truly wild.  

Also beware especially of the possibility of escapes when finding any of these out of range: gallinaceous birds (besides turkeys, game-farm Northern Bobwhites and Chukars are literally possible in any Minnesota county), raptors (escaped from falconers), Whooping Cranes (the ones from Wisconsin have yet to establish a viable population), gulls and pelagic birds (mostly a problem in coastal states where ship-assistance is possible), pigeons/doves (especially the Ringed Turtle-Dove), and parrots/parakeets (Monk Parakeets are apparently established in Chicago, and there have been at least three published Minnesota sightings).

HYBRIDS

An equally difficult issue is the occurrence of birds suspected to be hybrids. As with escapes and non-established exotics, birders and records committees generally won't include a hybrid in their records of a particular species. (Curiously, though, if two species are known to interbreed and successfully nest, I understand that many ornithologists would consider this a confirmed nesting record for both parent species!) And too often it is difficult to tell in the first place if a bird is a hybrid, and, if so, what the parent species were. Thus, it is preferable to qualify the word hybrid with an adjective such as presumed, possible, apparent, or suspected – although, for simplicity's sake, this article will often just say hybrid.

While some birds you find are odd-looking enough to signal they are indeed hybrids, keep in mind that a hybrid individual in the field can appear entirely identical to a normally plumaged species and not be detected as suspect. More disturbing, however, is that not all hybrids will show a combination of plumage characteristics which are intermediate between its parents. Some can show colors or patterns not found on either parent species. A duck found in California in 1984, for example, was eventually determined to be a hybrid American Wigeon x Northern Pintail, but some of its anomalous features were not part of either a wigeon's or pintail's plumage and made it looked much like a vagrant Baikal Teal (see David Sibley's sketch in Birding 26:170).

Consider as well that a hybrid with normal-looking plumage could still exhibit other intermediate or atypical features inherited from another species. Perhaps its behavior, habitat, vocalizations, size, or shape will seem at odds with the species it looks like and raise suspicions. More intriguing is the possibility discussed in that Birding article (26:162-177, "A Guide to Finding and Identifying Hybrid Birds"), which I highly recommend reading. Sibley's sobering thought is that a hybrid could often end up with a faulty migration "compass" and be just as inclined to wander out of range as a non-hybrid species. In fact, the argument could then be made that all lost vagrants might be suspect if hybrids indeed inherit atypical or defective migration tendencies!

Of course, it would be ridiculous to consider everything out there a possible hybrid, especially if nothing about the bird appears out of the ordinary. Note as well that hybridism in the wild for some bird families is relatively unlikely – at least for birds in this area – or rarely documented: e.g., hawks (except for falconers' birds, and see Birding 37:256-263), shorebirds, owls, vireos, corvids, wrens, and thrushes (except bluebirds).

Also consider that several hybrid combinations may be relatively unknown only because the species are so similar and their hybrids would be especially difficult to separate in the field. Some examples might include: Trumpeter x Tundra swan, Greater x Lesser scaup, Arctic x Pacific loon, Clapper x King rail, American x Pacific golden-plover, Short-billed x Long-billed dowitcher, Thayer's x Iceland gull, Rufous x Allen's hummingbird (see Birding 29:18-29), Alder x Willow flycatcher, Carolina x Black-capped chickadee, Gray-cheeked x Bicknell's thrush, Nelson's x Saltmarsh sparrow, Snow x McKay's bunting (see Birding 37:618-626), Boat-tailed x Great-tailed grackle, and Common x Hoary redpoll.

Another consideration worth keeping in mind are those species with integrades among their races or subspecies, which have in the past been – or could be in the future – involved in lumping or splitting and  affect personal and state checklists accordingly. These would include: Snow Goose, Canada Goose, Cackling Goose, Brant (see Birding 38:48-55), Green-winged Teal, Red-tailed Hawk (see Birding 33:436-446 and 36:500-506), Iceland Gull, Northern Flicker, "Solitary" Vireo, Yellow-rumped Warbler, Spotted and Eastern towhees, Dark-eyed Junco (see Birding 34:432-443), and Red Crossbill (see Birding 27:494-501).

By their very nature, hybrid birds are not the norm and are only infrequently recorded. But the combinations listed below are known to occur with enough frequency that birders should keep them in mind when finding one of the species involved, especially if it's an out-of-range rarity. This list only includes those which have a reasonable potential to turn up in Minnesota, with some of these already having occurred here (some documented hybrids published in The Loon are cited):

• Waterfowl hybrids. Odd-looking ducks and geese are probably found by birders more frequently than any other kinds of birds, so that the possibility of hybrid waterfowl of various types is always something to keep in mind. Many are easy to dismiss as tame or escaped birds, but others present far more serious ID challenges, and following are apparently the most widespread hybrids you might encounter:

- Greater White-fronted x Canada goose (see The Loon 42:34-35; white-fronted

   hybrids with domestic geese are also possible)

- Snow x Ross's goose (see Birding 25:50-53; a common hybrid combination which

   has apparently been seen several times here)

- Canada Goose x almost any goose species, wild or domestic

- Wood Duck x Hooded Merganser (see The Loon 50:208–209)

- Eurasian x American wigeon (see The Loon 67:109-110; two apparent wigeon

   hybrids were reported here in 2007, making this a potential ID problem to be

   especially aware of)

- Mallard x American Black Duck, Mottled Duck, American Wigeon, Northern

   Pintail, or Muscovy Duck (and probably others, wild or domestic; Mallards

   hybridizing with black ducks are especially common, resulting in frequent

   erroneous reports of "pure" American Black Ducks)

- Blue-winged x Cinnamon teal (several cited in The Loon; an obvious ID problem,

   since hybrid teal in Minnesota may be nearly as common as actual Cinnamon Teal)

- Blue-winged Teal x Northern Shoveler (see The Loon 77:260-262)

- Blue-winged x Green-winged teal (see The Loon 39:59)

- Canvasback x Redhead

- Ring-necked Duck x scaup, sp.

- Tufted Duck x scaup, sp. (see Birding 30:371-383; proving that a "pure" Tufted

   Duck is seen in the state might be as difficult as determining that it isn't an escape)

- Common x Barrow's goldeneye (see Birding 26:104-105)

- Common Goldeneye x Hooded Merganser (see The Loon 52:37 and 66:103–104)

• Sharp-tailed Grouse x Greater Prairie-Chicken (where these two prairie grouse share display leks, hybrids can occur – e.g., in Polk County)

• Western x Clark's grebe (see The Loon 61:99-106; there are several records of presumed hybrids: more than once I have seen grebes with one side of the bird having all Western-type features on its bill, face, and flanks, and the other side with entirely typical Clark's field marks!)

• Snowy Egret x Little Blue Heron

• Glossy x White-faced ibis (see North American Birds 57:136-139; as both ibis species continue their range expansions, apparent hybrids are becoming more frequent and complicating the already difficult problem of ibis ID)

• Falcon hybrids. Falconers are known to interbreed all three of our largest falcon species (Gyrfalcon, Peregrine, and Prairie), with Eurasian species (especially Saker and Lanner falcons) also involved; accordingly, the possibility of a large falcon of unknown identity and dubious ancestry appearing in the wild has to be a consideration.

•  Sandhill x Common crane

•  Black-necked Stilt x American Avocet

• Gull hybrids. The largest species seem especially prone to hybridization, and gulls with anomalous features are frequently found and their identities discussed – too often without resolution; many would agree that such apparent hybrids present the most "impossible" ID challenges of any kind, and the following combinations are the most frequently encountered:

- Laughing x Black-headed or Ring-billed gulls

- Black-headed x Ring-billed gull

- Herring Gull x Lesser Black-backed, Slaty-backed, Glaucous-winged, Glaucous

   (often called "Nelson's Gull"), Great Black-backed, or Kelp gulls (see Birding

   37:266-276, The Loon 66:196-197, and The Loon 71:54-55; because any

   combination of these large gulls can hybridize so freely, a hybrid could be as likely

   in Minnesota as a "pure" Slaty-backed or Glaucous-winged)

- Western x Glaucous-winged gull (a common hybrid and serious ID problem along

   parts of the Pacific coast; could some apparent Glaucous-wingeds reported on the

   Great Lakes have actually been this hybrid?)

• Roseate x Common tern

• White-winged x Black tern

• Eurasian Collared-Dove x Ringed Turtle-Dove (see North American Birds 53:348-353; an apparently common hybrid in some areas, with domestic turtle-doves possible anywhere, so don't assume that all "collard-doves" you see are the real thing)

• Hummingbird hybrids. Oddly plumaged hummingbirds of various kinds have been occasionally reported in many places and are assumed to be hybrids; Anna's Hummingbird seems to be involved most often, apparently hybridizing with Black-chinned, Costa's, or Allen's.

• Golden-fronted x Red-bellied woodpecker (I vaguely recall a record of a Golden-fronted photographed in the Midwest: might it have been a hybrid?)

• Yellow-bellied x Red-naped sapsucker (see Birding 37:288-298 and 38:42-51; sapsucker hybrids are common enough that an actual Red-naped vagrant in Minnesota might be hard to prove)

• Western x Eastern wood-pewee (see The Loon 49:169-170 for the account of a possible hybrid pair nesting in Roseau County in 1977; a hybrid pair may have also nested in 2007 in Jackson County)

• Western Kingbird x Scissor-tailed Flycatcher (see The Loon 69:183-185)

• Cliff x Cave swallow (the Cave Swallow is long overdue as an addition to the state list, but could a hybrid appear here before the real thing?)

• Barn x Cliff or Cave swallows

• Eastern x Mountain bluebird (see The Loon 58:194-196 and 66:149-150; a relatively common hybrid on the Great Plains and always something to consider here)

• Blue-winged x Golden-winged warbler (see Birding 37:278-286, and several records cited in The Loon; this is certainly the most famous passerine hybrid combination, with more plumage variations than most birders are aware of: it's often reported – but seldom actually documented – in Minnesota)

• Northern Parula x Yellow-throated Warbler (also known as "Sutton's Warbler")

• Townsend's x Hermit warbler (see Birding 33:342-350; a widespread hybrid in parts of the western U.S.)

• Mourning x MacGillivray's warbler (see Birding 22:222-229 and 25:350-351; apparently a relatively common hybrid, of which there is a Minnesota specimen, so an actual MacGillivray's record here might be impossible to prove unless a specimen, a carefully measured banded bird, or a closely photographed adult male singing a perfect song)

• Summer x Scarlet tanager (see The Loon 75:221-225, 75:226-230, and 79:7-10)

• Scarlet x Western tanager

• Spotted x Eastern towhee

• Clay-colored x Chipping or Brewer's sparrows (I once heard a Chipping Sparrow singing a typical Clay-colored song and, on another occasion, a Clay-colored singing just like a Chipping: could these have been hybrids?)

• White-throated Sparrow x Dark-eyed Junco (see The Loon 38:110-11)

• Harris's x White-crowned sparrow

• White-crowned x Golden-crowned sparrow

• Rose-breasted x Black-headed grosbeak (see The Loon 45:64-65; with Minnesota relatively close to where these two overlap in the Great Plains, grosbeak hybrids could be as likely here as actual Black-headeds)

• Lazuli x Indigo bunting (see The Loon 37:47; a situation similar to the potential grosbeak problem exists with buntings)

• Eastern x Western meadowlark (a meadowlark with an odd song just might be a hybrid; I still wonder about the one I heard singing a perfect Eastern song in Rock County, where only Westerns should occur)

• Bullock's x Baltimore oriole (see The Loon 38:73-74 and 52:36-37; a situation similar to the grosbeaks and buntings)

• Gray-crowned x Black or Brown-capped rosy-finches (such hybrids are relatively frequent, so don't assume any rosy-finch here would have to be a Gray-crowned)

• House x Eurasian Tree sparrow

*          *          *

You know, I just realized that article about color abnormalities failed to discuss hypophaeomelanism! Now I have a subject for the next Hindsight article. After I've been so critical recently about some dubious dowitcher ID advice (see http://mbwbirds.com/dowitchers.html and http://mbwbirds.com/photographs.html), it's time to present my simple scheme for identifying them. So, stay tuned for "Loral Angles in Hypophaeomelanistic Dowitchers"....