BIRDING BY HINDSIGHT: A Second Look at Shrikes

Way down along the Rio Grande in Deep South Texas last week, an adult Black-vented Oriole was frequenting a favored set of feeders. (And little wonder if you've never seen this species or even heard of it, since it's only about the fourth one of its kind ever seen in the U.S.) Its identification is pretty easy, given a decent look: it's a big black-and-yellow oriole readily told from the other yellow Icterids.

As several birders stood around waiting for it to appear, someone called out: "There it is!" When pressed for directions, the birder said it just flew in to a branch near the feeders. But no one else could see it; only blackbirds were in view. After several seconds, a bird landed in clear sight on a feeder, and the same birder again announced, "There it is!" This time everyone saw the bird, since it was the only thing there – an adult male Red-winged Blackbird.

If you don't have a field guide handy, take my word for it: a Red-winged Blackbird looks nothing like a Black-vented Oriole. Still, someone managed to confuse the two for reasons unknown, although it seems unlikely this will be the subject of any future Hindsight installment or other bird identification articles. Indeed, the thought process for some birders moves in unpredictable and mysterious ways.

Another example closer to home. In June last year, a Northern Shrike was included on a list of birds seen near the Twin Cities and reported to the MOU-net listserve. Since only Loggerheads should occur here in summer, the observer was asked for more information and obligingly provided a photo. Surprisingly, the bird was neither a Northern nor a Loggerhead shrike – instead, the image was of a Gray Catbird.

This unexpected case of mistaken identity was likely an isolated event not to be repeated any time soon, but it was a reminder that this column had only briefly mentioned shrikes once, way back in the Spring 1995 issue of The Loon. Another reminder of this shrike-shirking came a few months later with a discussion in the "Frontiers of Field Identification" listserve.

A shrike in New York was seen and photographed by many in November 2010, and there was disagreement among the local observers about its identity. (Photos were posted, and I'd include them here, but look what happened the last time I tried to illustrate a Hindsight article with photos: a swan's vital field mark and its sense of smell simultaneously disappeared from one of the photos during printing – see Figure 4, http://mbwbirds.com/swans-ii.html.

The shrike in question clearly had a paler base of the lower mandible, its facial mask did not appear to extend over the top of the bill, and there was some light gray barring on the underparts – all of these classic Northern Shrike field marks. On the other hand, though, the mask was wide and solid, and the bill was relatively stubby and finch-like – both of these features consistent with Loggerhead Shrike. So, what was it?

As the comments from "Frontiers" readers came in, it quickly became evident that shrike ID is not all that straightforward, even among experienced observers. One renowned birder from the Carolinas declared it was a Northern because of the pale bill color, absence of mask above the bill, and barring on the underparts, and he added its upperparts looked paler gray than on a Loggerhead. But it turns out no one else agreed with him, and it became quite evident that this shrike was an immature Loggerhead.

But, while I agree entirely with this ID, some of the reasons cited by those reviewing the photos were less than convincing....

Upperparts Color

One stated the gray on the upperparts was too dark for a Northern, but shades of gray in the field or in photos are often and easily misleading. Too much depends on light conditions, the bird's position relative to the sun and observer, camera settings, the printing process, and if the digital image was adjusted. True, a Loggerhead Shrike is darker gray than a Northern, but that's very hard to judge without comparison with something else.

Size and Shape

It's also true that Loggerheads are smaller overall than Northerns, but, again, how do you determine that without comparison? Some reviewers based their ID on the shrike looking too "compact" (one said "small and quick", not "large and lanky" like a Northern), but nothing was around for comparison. And besides, the apparent size and shape of any bird can vary with its posture and what it happens to be doing at the time.

Other reasons cited to support the Loggerhead choice were a rounder head shape, larger head, larger eye, a "gentle expression", and even a "serious look"! Really? To put it gently, are you serious? Is it actually possible for any bird to appear gentle and serious simultaneously? And, again, how useful are such subjective conclusions without direct comparison? (Again, the thought process for some birders moves in unpredictable and mysterious ways.)

Bill

At least the comments on "Frontiers" also discussed more useful ID criteria. It was more instructive to consider the shrike's bill, especially since the visibly pale base of its lower mandible is typically considered indicative of a Northern Shrike. While Northerns of all ages do have a pale bill base, the problem is that immature Loggerheads can share this feature. And the bird in question – while mostly appearing to be in adult plumage – was still in its first year, as indicated by the barred underparts and white tips on some wing covert feathers. In sum, a shrike with an all-dark bill = Loggerhead; however, a pale-based bill = either species.

To my eye, the shape of a shrike's bill is more useful than its color, and can be accurately determined with a bit of practice, even without comparison. A Loggerhead's bill is stubby and finch-like, as on the shrike in question; a Northern's bill is shaped differently since it appears larger and is especially longer. The bills of both species have hooked tips, by the way, but the Northern's hook usually looks longer.

Mask

Some of those commenting on the New York shrike also considered the solid, uniform, and wide appearance of its mask, which further supported its ID as a Loggerhead. By contrast, a Northern's mask is narrower (to me, it has always looked more like an eye line than a mask), and it typically appears broken, incomplete, and uneven in width.

And speaking of masks, I'd advise against trying to see whether or not the it extends over the bill. Though long emphasized by some field guides as a useful field mark, it's usually difficult to clearly see this, and I've seen photos of both species which contradict the field guides: i.e., Northerns with masks over bill and Loggerheads without (as on the present shrike under review).  

Another feature of the mask was mentioned for consideration: no obvious white border appears along its upper edge. Typically, a Northern's mask and bill are at least partially bordered above by a white line, while a Loggerhead lacks a conspicuous white border, but I admit I've never paid much attention to this feature. The shrike photos I've randomly looked at recently seem to support this difference, but I suspect this field mark will prove to be variable, helpful with just some birds, and not consistently diagnostic.

Cheek Patch

I also read with interest one comment that the ID as a Loggerhead was supported by the "white cheek patch" (this was even written in all capital letters for emphasis), with the added comment that "this is very important as Northern usually has a gray cheek". It turns out, though, this is not very important at all: I found lots of photos of Northern Shrikes with similarly clear white areas on the cheeks and throats.

Underparts Barring

Just as the pale bill base on this Loggerhead caught some by surprise, so did the barring on the underparts. While this is normally thought of as diagnostic for Northern Shrike, "older" immature Loggerheads in late fall/winter and perhaps some adults are also lightly barred below. It was also pointed out that juvenile Loggerheads in summer/early fall are barred on both the upperparts and underparts, while juvenile Northerns are only barred on the underparts. I assume this is true, but I admit my experience with looking for barring on the backs of juvenile shrikes is essentially non-existent.

There was another comment that the bars on the underparts fit a Loggerhead because they were short, faint, and curved, while a Northern's barring consists of longer, bolder, and straighter bars. However, this opinion was not convincing with no Northerns around for comparison, and besides the nature and extent of a Northern Shtike's barring is quite variable. It can even appear entirely absent, since I have noted several Northerns over the years at close range and in good light with no visible barring. In sum: underparts barring = can be either species; no barring = can be either species.

Season

Finally, the time of year involved in this New York sighting was mentioned, but only in the context of whether a Loggerhead in November would be showing features of  juvenile, immature, or adult plumage. No one commented on if a Loggerhead or Northern shrike near New York City in late November would be more likely. As many readers know, a Northern is more likely then in Minnesota,  especially in the northern half of the state, and there are times when the calendar is your best indication of a shrike's identity.

Generally, taking into account what part of the state you're in, and unless the prevailing weather has been unusually mild or harsh, it's safe to assume that any Minnesota shrike in May through September should be a Loggerhead, and one in December through February should be a Northern. But if it's March, April, October, or November, when both species could be present, I guess you'd better take the advice of some alleged ID experts – be prepared to decide of your shrike looks gentle or serious.

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It seems this column never got around to the problem of confusing catbirds with shrikes. But here are a couple of Helpful Household Hints:

1) When you see a light gray, robin-sized bird with a black mask and wings in hot pursuit of a dark gray, robin-sized bird with a black cap and rusty under tail coverts, the shrike would be the pursuer and the catbird the pursuee.

2) Attach a furry mouse-like object to a fishing line, cast it towards the bird in question, and if it attacks the bait it's a shrike, but if it ignores the bait it's a catbird.... Ah, come to think of it, this controversial practice recently led to some northern owl locations not being disclosed – which made sense, perhaps, but no need to withhold Gray Catbird sightings, too. So, never mind. Just stick with Hint #1.