Review the whole thing for links per WP:MOSDATE. There's no reason to link e.g. July.
Also make a good run to strip spaces before refs.
revise references in a Last, First format.
Article switches between "color" and "colour" (double check other spelling: it seems to use both "molt" and "moult").
I think that the plural, as used in Common Raven, goes much better for bird articles. Compare "The American Goldfinch is found in residential areas [...]" vs. "American Goldfinches are found in residential areas [...]"
The entire leads need to be rewritten. Prose is at best subpar, at worst horrid. Certainly not "engaging, even brilliant." Consider starting with "is a bird..." (cf. WP:OBVIOUS)
It fails to account for the "human relationships" section.
The wording is misleading. Was the bird first in Carduelis, then moved to Spinus, then replaced in Carduelis, or in Spinus since Linnaeus and then places in Carduelis? Looks like the former, but I can't tell because of the darned zoological authority.
What makes this species a member of subgenus Spinus?
Consider sourcing the merging to a more direct source, if only because the linked page is hardly legible (doi:10.1007/BF01673245 is Ackerman 1967, fr the record).
The source for the species epithet etymology only confirms the meaning of "tristis", it dioes not draw any link to the call.
referring to feeding preferences.
Subpar prose
The genus name of the American Goldfinch, carduelis
"The genus name Carduelis"
Spinus was merged into the genus Carduelis, and retained as a subgenus
stronger white markings, and larger black cap of males
The shape and size of the beak are a result of adaptation, to aid in the extraction of seedss from the seed heads of thistless, sunflowerss, and the other plants which make up its diet.
What is this doing in a "Description" section?
The second half of the second paragraph is unsourced. At least source the "only finch to undergo full moult" bit!
Decide whether you want to use "moult" or "molt" and stick to it!
I think it is proper to capitalize "golfinch" when it is used as an abbreviation of "American Goldfinch"
possesses different colouring
"is coloured differently"
Is "upperparts" the proper word?
buff-coloured, rather than white, markings
I'm not sure that second comma is needed.
This coloration is identical regardless of gender.
is bounded on the north by Saskatchewan, and stretches south across the North American continent to North Carolina in the east and northern California in the west.
Move the comma from after "Saskatchewan" to after "east"
Link range (biology) when describing the summer, not the winter one. Done
"Includes X, Y to Z" for regions is not a regular construction.
It creates a lone subsection (which you know I don't like (-: )
The North American Breeding Bird Survey, which tracks the population of common bird species, has shown a decline in the breeding populations of American Goldfinch.
Per WP:GTL, switch "External links" and "Further reading" around
I recommend dropping the "Theses" part of "Further reading". It's just too restricted to be of used.
That's one hefty bibliography! Maybe some/many of these could be used to actually improve the article instead of sitting there?
Quite a few of these can be supplement with external links, either direct or via DOIs and PMIDs. Auk, Wilson Bulletin and Journal of Field Ornithology are fully available online via SORA, for example. Johnson 1998 is abstracted at doi:10.1093/beheco/4.2.138, Marsh 1982 is PMID6211105, McGraw 2004 is doi:10.1111/j.1439-0310.2004.01011.x...