New post - focusing on an old observation. The date: May 12, 2007. The location: Point Pelee, Woodland Nature Trail. We came across a dramatically different Common Grackle foraging in a slough. Rather than the typical (iridescent) blue head/bronze body of our expected "Bronzed" subspecies (Q.q.versicolor) - it had a bright purple head and a green body.
Getting suitable photos of the iridescence in the dark understory of the slough forest was.... tough... and these two images above were really all I was able to manage (which required a fair bit of brightening afterwards, with an odd colour cast due to the trees etc...
Long story short, given the dramatic appearance of the bird (which was shared with others nearby on the path, all of which were rather taken aback at the unique colouration) I assumed it could be a different subspecies - and the only other Common Grackle subspecies I was aware of was the "Purple" Grackle, (Q.q.quiscula) - and that would make sense right!? The birds head was purple for cryin' out loud...
Ultimately, these photos were circulated and the verdict was a general "no' for Q.q.quiscula - and I also started learning about another subspecies - Q.q.stonei - which at the time I interpreted as a large intermediate population between the Florida-living "Purple" Q.q.quiscula and the "Bronzed" interior continental birds Q.q.versicolor . I find it interesting to note that today, both Q.q.stonei and Q.q.quiscula are considered the "Purple" subspecies in ebird... It is worth noting that at the time, Michel Gosselin at the Canadian Museum of Nature noted they had specimens not dissimilar to the Pelee bird from Pennsylvania. The Birds of North America Online page covers the current subspecific breakdown:
Common Grackle: Plumage coloration varies regionally. Breeders west of Appalachians and north of s. New England have brassy bronze body and purple glossed tail, whereas birds east and south of there have purplish body with green to steely blue glossed tail. Birds of extreme southeast (Florida) have green backs. Wide zone of intergradation stretching from s. New England to Louisiana where intermediates occur. Wing length and body mass decrease north to south, whereas bill length and width increase along that cline.
Q. q. versicolor. Often called the Bronzed Grackle, this race breeds over most of the range of the species north and west of a line running from central Louisiana to s. New England along western margin of the Appalachians. This race is highly migratory, wintering south to s. Texas and east to South Carolina, thus overlapping with the next 2 subspecies. This race is less variable in coloration than the next and typically shows a uniformly brassy bronze back and belly and purplish tail. The head color is somewhat variable but usually blue-green. This race was formerly considered a separate species.
Q. q. quiscula. Known as the Florida Grackle, this race is essentially resident from se. Louisiana east to se. North Carolina and south to s. Florida. The back is typically dark green and the tail blue-green; the head is usually purple and the belly purple-blue.
Q. q. stonei. Often referred to as the Purple Grackle, the distribution of this race is not well-defined but generally given as lying between the above 2 races east of the Appalachians from se. New York (formerly to sw. Connecticut?) south to central Alabama and west to central Louisiana. Back and belly typically purple; tail usually blue-green. Formerly considered a subspecies of the Florida Grackle when that and the Bronzed Grackle were considered separate species. Along the area of contact between versicolor and stonei from Louisiana to Connecticut, a narrow band of intermediate forms have been designated Q. q. ridgwayi by Chapman. These "Ridgway's Grackles" show a strong barred effect on back. These intermediates and the status of stonei as a valid subspecies are questioned
Beyond that, I did a bit of my own (style of) research - which essentially means: searching through the eBird media database in order to see if I can find any pattern / record of similar looking individuals... and... I found a (select) few! Check it out: May 18, 2018 from Pennsylvania: - https://macaulaylibrary.org/asset/101339711 (unspecific subspecies)
April 25, 2014 from Pennsylvania - https://ebird.org/checklist/S18070239
(one of the Northwestern most "Purple" Grackles in ebird with media) March 16, 2019 from Pennsylvania - https://ebird.org/checklist/S53920074
(note observer comments: "1 Grackle had Purple head, unlike the remaining 37 - unsure if possible Purple form or unusual color for Bronzed form?") After this reading and photo-searching, I now have the feeling that the bird from Point Pelee would represent an individual from the generally "undetermined" population of Grackles near the north and western limits of Q.q.stonei. Although not currently an accepted subspecies, I wonder if birds like this were part of the attempt to define Q.q.ridgwayi - or if they would be better served with an intergrade label as Q.q.stonei x versicolor? I am mildy confident it does represent a "population" as opposed to a colour variation of "Bronzed" Q.q.versicolor, as I would expect to see photos like this scattered throughout the range, rather than clustered south and west of Lake Erie (generally in Pennsylvania, but presumably elsewhere).
There is also a standard conundrum in determining subspecies ID, or subspecies range limits, where one could take the stance of "any bird that is obviously not "Bronzed" Q.q.versicolor could/should be considered the "Purple" Q. q. stonei / quiscula; however, I'm (personally) not a fan of that approach - as it tries to oversimplify a difficult identification (not unlike identifying non-perfect Hoary Redpolls as Common Redpolls, which reduces our ability to understand the variation in Hoary Redpoll or to label intermediates).
Given the ubiquitous nature of Common Grackles in Ontario, and the propensity for migrants to "overhsoot" during the spring migration, one could assume that there are more intermediate and/or proper Q. q. stonei that occur in Ontario from time to time, with the ability to detect them among the masses of the regular Q. q. versicolor likely the primary barrier to confirming records (particularly in flight / reverse migration).