Mystery Photographs

By John Idzikowski

In Wisconsin as throughout much of North America as the hottest days of summer approach in late July and August, birders fortunate enough to have nearby mudflats can observe juvenile and adult shorebirds returning from their arctic breeding grounds. If you can drive up next to these areas without scaring these birds you can occasionally study them closely. The April Mystery Birds quartet of medium-sized shorebirds was taken in Milwaukee, Wisconsin from a car at a municipal harbor dredge dump site with Pentax 20X60 binoculars and a Fuji MX1200 digital camera at 960X1280 in early August. The quality is only fair compared to many current digiscoped or binoxed shots; this was taken when I was just beginning to explore this new technology. But this is an image similar in quality to what you might get in a scope at 50 yards.

Beginning with the two gray birds in the background, the left bird's legs are obscured (the right as well due to poor light) providing us with little help there other than that they seem to be fairly long. We have the obvious dowitchers (or even if you called them snipe) in the foreground for comparison of size and we immediately get the feel for yellowlegs. The bird on the left shows heavy barring on the underparts extending all the way back to the undertail coverts; alternate (or basic) yellowlegs do not show such extensive barring. The back is showing wear with loss of white edgings to the black feathers; yellowlegs would show their characteristic checkered pattern on the back. The bill is slightly down-turned; this all points to adult Stilt Sandpiper; a Greater Ylegs would show a slightly upturned bill. The chestnut face patch is already lost due to moult or wear. I have only seen this twice during migration; it seems to be rather ephemeral. The right bird has all the features of yellowlegs already mentioned except for lacking any barring of the underparts; your best guess considering the fact that you have an essentially alternate Stilt in the shot is that this is a juvenile yellowlegs; an adult would show barring yet as does the Stilt. The short, straight bill with a length less than 2X that of the head points to Lesser.

The two birds in the foreground are marvelous studies if not perfect "Nikon moment" quality digiscoped images. Lets eliminate Snipe by the lack of a strongly striped head; the bodies are not snipe-stubby displaying a more upright posture with bills held at a 45 degree angle whereas in Snipe the bills are usually angled down more. Snipe never show such warm shades of buff and rufous as well. So we apparently have two dowitchers.

In identifying these birds let's throw out bill length due to its variability; although the initial feel for length if one has seen many dowitchers of both species is that these are not at the long extreme; in fact the right bird has a rather short bill. It also displays uniform, fresh and unworn plumage. There are no missing feathers, the buff edges to the back feathering is extensive. The buff on the breast and underparts is warm and rich and extends to the throat; all this makes this bird a juvenile as. A Long-billed (LBDO) would show darker back feathers with restricted buffy edgings and the gray on the upper breast would be more extensive onto the throat and undertail coverts with only a slight buffy wash present on the upper breast and belly. This juvenile Short-billed Dowitcher (SBDO) is the most common dow plumage we see during wader migration here for this early fall season through early September with LB the Dow of our cool fall into late October.

The analysis of last bird in the left foreground is a challenge. There are potential difficulties not so much in ageing but identifying this bird. Initially just look at it and compare it to our juvenile; it’s worn with missing back contour feathers and even some missing tertials: flight feather moult is heavy. The buff-orange of the underparts which can be seen is uneven; the few gray feathers could already be new basic feathers or the remains of an alternate "white" belly; the dark back feathers are broken or absent and are no longer evenly patterned presenting a confusing and not very helpful set of characters. Such a ragged bird at this time of year can only be an adult beginning its pre-basic moult .

No one would be faulted for stopping with only ageing this bird and leaving it unID’d as perhaps I should, but our compulsions are telling us otherwise all the time so let’s examine the bird briefly and see which species seems to present a stronger case. If we assume that the buff-orange is still alternate plumage with wear we should expect to see more barring on the sides even with wear and spotting onto the front part of the neck for LB. The color of the underparts, even for a worn LB should be rustier, not buff-orange. One of the older fieldmarks which is often difficult to see in the field is the relative width of the white and black bars on the rectrices; we are able see that both the black and white are of similar width; the white perhaps being a bit wider, very similar to those on our juvenile bird; a LB should show wider black bars; The darkness of the back here could tend to push one towards LB but the wear here is extensive. The wear on the back of edges to the contour feathers along with absent and developing feathers gives us a totally confusing set of evidence for the upperparts. A LB though might be expected to show more rufous edges and internal markings to the old alternate feathers, even with wear. Overall this bird suggests SBDO, in pre-basic moult.

Another shot is provided of the dowitchers from the original quiz shot; the juvenile is on the right and the adult is on the left. Our take-home project is yet a 3rd Dow- the bird in the middle in very rough condition.

John Idzikowski, Milwaukee, Wisconsin