We don't know everything.
Anyways, here's a breakdown of what (I think) are the KEY features of the Meadowlark we had at Pelee on 25 April 2016, based on a variety of resources and commentary from a handful of experts.
Eastern Meadowlark is the darkest. Has dark centres of the tertials and centre tail feathers. White malar. Rufous or warmer colour tones. Intermediate and variable white on the outer tailfeathers (45-55% white). Crown stripes are dark-black. Eyeline wider on average. Undertail coverts normally streaked. Sides typically "streaked".
Western Meadowlark is pale. Tertials and centre tail feathers are pale with dark barring. Malar has at least some yellow MOST of the time, but not always. Colder/paler tones overall lacking rufous. White on tail variable but mostly (always?) a "dark tail" with a bit of white on the sides (40-50% white). Crown stripes brownish. Eyeline thinner on average. Undertail coverts normally streaked. Sides typically have a more "spotted" look (more oval shaped markings).
"Lilian's" Eastern Meadowlark is pale. Tertials and centre tail feathers are pale with dark barring. Malar white. Colder/paler tones overall lacking rufous. Extensive white on the tail (a white tail with a dark centre stripe - or 55-60% white). Crown stripes brownish to dark(ish)-blackish. Eyeline intermediate (?). Undertail coverts normally have limited markings. Sides typically have streaks - possibly less on average than "Eastern".
SO - I'd say it breaks down to this:
Eastern Meadowlark has an overall pattern of dark markings & rufous that is unlike Western or Lilian's, which show an overall paler plumage. To that end, Lilian's should be different from Western by showing limited markings on the sides - and (maybe) the undertail markings - and especially by the amount of white in the tail feathers. Lilian's has the MOST white in the tail while Western has the least. Should be clear cut, right?
Well - apparently it's not. Here are my thoughts:
The overall dramatic "paleness" to this bird should rule out "Eastern". The head stripes, eye stripe etc. are not blackish, there is no rufous/rich colour anywhere...
And if that doesn't quite do it for you, I think the tail and tertial patterns should eliminate "Eastern". It essentially has pale feathers with thin dark bars. So while these aren't the only reasons, what i've read and heard should eliminate "Eastern" - leaving Western and Lilian's to consider.
An area where Lilian's apparently differs from both Eastern and Western is the streaking on the undertail coverts - it is minimal at best, where the other two should have obvious/numerous marks... This bird is minimal at best, matching Lilians.
Something I haven't noted yet. Meadowlarks have 12 tail feathers (6 on each side). I never expected to have to worry about it, so I didn't get a *definitive* shot showing all the feathers (I took what I could get on one pass, then left the bird alone)...
Using a combination of photos, I think we can confidently say the bird has at least three white tail feathers on its right side (thanks to the first photo - green lines) and 2-3 are visible on the left side (lower photo).
If you're good at math (like me) you'll realize that we're two feather short - which is why I noted above that I failed to get the definitive shot... BUT - in the above photos - I think we can say the bird has a lot of white in the tail.... Not only that but the feathers visible in the second photo on the left side (yellow marks0 show a few tail feathers that are TOTALLY white at the tip. As far as I can tell, even the Western Meadowlarks with an abnormally high amount of white in the tail - show dark markings near the tips of the white feathers. (Like this bird here). (or this one).
So as far as I can tell, this bird checks off all the boxes (visually) for "Lilian's" Eastern Meadowlark. It would have been nice to hear it call, but it didn't. I would be interested to hear if anything on this bird doesn't line up with this identification, or if I have anything wrong in terms of field marks. It just shouldn't be here.
Likewise, IF this bird were not a "Lilian's" Meadowlark, it would break a few established marks in separating the following species.
"Eastern" Eastern Meadowlark - IF it were this subspecies, it would mean that our regular birds can show a very pale plumage as normally associated with Western or Lilians. This wouldn't only include paler markings on the crown/eyeline/back - but a fundamental difference in pattern on the tail, tertials etc.
Western Meadowlark - IF it were this species, it would mean that several "breakable" rules were broken, such as no yellow on the malar or more "streaky" and less "spotted" marks on the side, Another rule that could be broken (but books say shouldn't be) is the near lack of markings on the undertail coverts. I've found a few photos of birds lightly marked here - but the vast majority are nothing like this bird. Finally, if my tail-feather analysis holds water; that this bird has a lot of white - then this bird would be an EXTREME tail pattern for Western. I just cannot find Western Meadowlark tails that have pure white tips on any single tail feathers.
So there we go! Now I can get back to more interesting things - like the weather.
As always - thoughts/comments are appreciated!