I saw this bird near the Platte River of Nebraska in March of 2006. There is about a one week overlap in mid-March where both shrikes are equally likely (which is about when I saw this bird) before which NSHR is more common, and after which LOSH quickly becomes more common. Though both are still possible throughout March and early April.
|Graph showing Frequency of LOSH and NSHR in March and April in the Nebraska [ebird.org]|
Alright - so if we have equal or near equal probabilities of seeing either shrike, we need to focus closely on the field marks we see in the image. To me, on first glance I see a dark-backed, white-throated, plain gray-breasted (i.e. no barring/scaling), large/round-headed shrike with bill that is neither very short nor very long, and neither very hooked nor very unhooked. So far the evidence is pretty good for LOSH. A lot of people used bill shape and size to identify this bird and got it wrong for having ignored other major field marks, and assuming that factors acting against them were due to lighting issues. Just as the bill is intermediate, the mask becomes somewhat broad posteriorly, but doesn't necessarily rule out NSHR. Many people actually thought the mask looked too narrow for LOSH, but even though some of the mask is blocked by a twig, to me, it doesn't look overly extensive or limited enough to decide one way or the other. Another tweener here is the supercillium. A white supercillium is present, but to me it is indistinct, and is more supportive of LOSH than NSHR.
Even if you thought the bill was too long and hooked for LOSH, there are other, less subjective (i.e. presence-absence) field marks to use. NSHR usually has a pale base to the mandible of the bill (though sometimes this becomes black in spring), which LOSH will not have (although I saw a photo of a fledgling that had a pale-ish base). Similarly, NSHR almost always (or maybe always) has gray or mixed gray and black lores and nasal tuft, whereas LOSH generally has black lores and nasal tuft (less frequently gray, but variable). The presence of these characters connects the left and right masks around the bill. I'd like to ID this bird by just these two field marks, but it has been pointed out to me that there is some variation in NSHR bill color and LOSH lore/nasal tuft color (as I pointed out above). However, in my opinion there is no single field mark that obviously supports NSHR over LOSH, but there are several intermediate characters and a several that point towards LOSH. Thus, I choose LOSH, but challenge you to prove me otherwise. Truthfully, when I originally saw this bird, I was told it was a LOSH by another birder, and now, 6 years later had to make sure that's really what it was.