These two species (recently split) are extremely similar in appearance. No significant differences exist in size or shape, and plumage differences are subtle and mostly overlapping. Songs differ slightly but consistently, and call notes (year round) are the most different. Voice, especially call, will be the best way to distinguish them, and identifying individual birds from photographs may be impossible in some cases.
Voice:
Differences in voice are described in the Sibley Guide, and for more detail and audio I recommend several posts by Nathan Pieplow. One cautionary point is that the difference in pitch alone is not sufficient to distinguish call notes. Both species give an “alarm chatter” that is higher and sharper than their normal call notes, so the key to accurate identification of call notes is ascertaining that you are listening to the normal one- or two-syllabled contact notes, and then comparing the pitch and quality of those.
Plumage:
Arranged generally with more useful features at the top, less useful or unconfirmed at the bottom.
- Overall – Pacific darker, more rufous, and less patterned; vs. Winter Wren paler, grayer, and more patterned. The combination of reddish-brown eyebrow, cheeks, and throat, with smooth unmarked breast and neck-sides may give Pacific a distinctive overall appearance, even though no single feature is reliable.
- Neck sides – Pacific tends to have the pale sides of the neck more reddish and much less patterned than on Winter.
- Throat color – Pacific usually has throat almost as dark and richly-colored as breast; vs. pale throat contrasting with brighter breastband. Note that some (Eastern) Winter Wrens can have smudges of pale buff/orange on throat, and all Pacific have the throat paler than the breast (just not as pale as Winter).
- Pattern on underside – Pacific usually has breast unmarked or with a few faint bars; vs. speckled with faint, short dark and light bars.
- Eyebrow – Pacific tends to have the pale eyebrow stripe tinged rust/orange; vs. slightly paler and more clay-colored on Winter.
- Sides of breast – Pacific may have the darker and more reddish back color spreading down onto the sides of the breast; vs. sides of breast paler than the back on Winter (matching center of breast rather than back)
- Color of upperside – Pacific is dark, deep, chestnut-rufous; vs. paler, grayer brown on Winter. A subjective and subtle distinction that can be quite difficult in the usually brief and shaded glimpses these species afford. The difference might be most pronounced on the crown.
- Color of underside – Pacific darker rufous-brown; vs. paler gray-brown. Some near overlap in color makes this subjective.
- Pale spots on primaries (forming bars on the folded wing) – Pacific Wren has the pale spots on the primaries darker and more brownish on average; vs. Winter Wren with paler off-white to clay-colored spots. Note that even on Pacific these spots are paler than the back, and there is some overlap in color between the two species, so this is a fairly subjective feature and difficult to judge.
- Pattern on upperside – Pacific tends to have upperside smooth rufous-brown with faint dark bars or none; vs. upperside mottled and barred with dark and white. This helps accentuate the darker upperside of Pacific.
- White tips on greater coverts – Both species may or may not have tiny white spots at the tips of the greater coverts. On Pacific these tend to be smaller, but at the same time more conspicuous because they are surrounded by uniform dark brown; vs. Winter tends to have larger white dots, but these are less conspicuous alongside the whitish mottling of back and breast-sides.
All of this requires field testing, and now that birders have a new species to look for there will surely be a lot of new discoveries and refinements over the next few years.
Related posts and pages:
- Red pouches on Brown Pelicans In the Sibley Guide to Birds I illustrated Pacific and Atlantic/Gulf populations of Brown Pelican,...
- Sparrows and central spots Can you identify the sparrow shown in this photo? Read on for the discussion and...
- Distinguishing the subspecies of Purple Finch On this Page Distinguishing features of female-plumaged birds Distinguishing features of adult males Structure...
How about distinguishing Winter Wren from European Wren? Aside from range, how might one do that?
I was just wonder the same things after watching European Wren near London today before my flight back to DC.
My impression is of a more rufous almost orangey brown bird – relatively unmarked, when compared to the US Winter Wren. It also seems less skulking, more readily coming out to investigate light pishing than US birds. This last traite is unusual inUK birds in my experience (with the exception of Goldcrest maybe) which are usually relatively indifferent to such distractions.
A clarification – my comment about ‘rufous’ above refers to upperparts, underparts are contrasting and pale for European Winter Wren (Trogladytes troglodytes still I believe )
I assume there are differences in call, and that’s probably the best way to distinguish these species, although Winter Wren is probably the most distinctive, while Pacific and Eurasian might be fairly similar. The Eurasian Wren is very unlikely to occur in North America, but Winter Wren is certainly a plausible candidate for vagrancy to Britain and Europe, and that’s where this ID question could be a real-world challenge.
To my ear. differentiating on song or call seems to be very very subtle if even possible from my experience and review of recordings
At least a suspicion of a US winter wren should be much easier in the mainland UK but there are dark races eg zetlandicus in the northern and western isles where a US bird could be very difficult to ID