Proposal (10) to South American Classification Committee

 

Continue to retain usta as a subspecies of Otus watsonii

 

Otus watsonii. I'm not convinced by the published data that usta should be recognized at the species level. Birds that I've recorded in Guyana (LNS # 42754) sound very similar to birds from along the Rio Napo, Ecuador (Hardy et al. 1999). However, my recordings of birds at the base of the Ecuadorian Andes (prov. Morona-Santiago, Santiago, 3o 03'S, 78o03'W; LNS # 49232, 49255, 49401) sound intermediate to birds from the above localities and those south of the Amazon (Hardy et al. 1999). Clearly, study is needed in western Amazonia where the two forms might come together, i.e., southeastern Ecuador and northeastern Peru.

 

Mark Robbins, Dec. 2001

 

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From Tom Schulenberg: ""Yes.  I am not even certain of what the characters are that separate usta from watsonii.

 

Chapman (1928, American Museum Novitates) diagnosed them as follows:

 

"In watsoni watsoni, the more northern form, the ground color of the underparts is ochraceous tawny, the white markings absent or comparatively restricted, and the black bars average fewer and broader. In the form from south of the Amazon the ground color of the underparts averages paler, the white markings are more extensive (present in all of our six specimens) extending from breast to, or even on, lower tail-coverts, and the black markings are finer and more numerous giving a vermiculated appearance wholly absent, or less highly developed in watsonii watsonii. For this southern form it is probable that we may use the name Otus watsoni usta  (Sclater) described from Ega, Brazil, in the south shore of the Amazon.  While it is true that I have seen no specimens from Ega, the comparative stability of the species warrants this proceeding pending the receipt of topotypical specimens. It should be said, however, that Sclater's plate suggests watsoni watsoni rather than the bird for which I accept the name usta."

 

A reasonably clear diagnosis, although he manages to throw our use of the name usta into some doubt.

 

Compare this to the account in Handbook of the birds of the world (where usta is regarded as a subspecies of watsonii):

 

"Race usta similar in pattern, but slightly smaller, rufous overall, broader streaks below."

 

which seems to contradict, at least in part, Chapman's characterization.

 

König et al. (1999) regard usta as a separate species. With regard to morphology, their description is equally skimpy:

 

"Very similar to [watsonii], but slightly larger ... with a rufous wash above, a darker crown, and more broadly streaked underparts."

 

Contradicts HBW with regard to size, contradicts Chapman with regard to streaking on the underparts. Who to believe?

 

Granted, "all" differences between watsonii and usta could be in voice (and in genes), but since Chapman was the only author to specifically tie his description to specimens that we can trace (albeit a small sample) he still is the place to start. I can't take seriously either of the other characterizations.

 

König maps geographic overlap of the watsonii and usta in northern Peru, but does not tell us how (or if) this apparent sympatry was documented.

 

With regard to voice, there is variation within the "complex". I don't know whether this variation is individual or sexual or contextual, clinal or stepped. What I am not inclined to do is to listen to a song from here and a song from there, or even a song from here, a song from there, and a song from somewhere in between, and make decisions based on that. I also am not likely to get excited about changes in species level taxonomy for small Otus until someone examines *all* vocal material available, instead of listening to (or making sonagrams of) one or two examples only.  Harrumph.

 

From Alvaro Jaramillo:  "Yes, although with some reservations. From my limited experience with this owl there do appear to be two song types, one in the south and one in the north. The southern song type (I know it from Bolivia) is very slow, strikingly slower than songs of watsonii from Ecuador or Venezuela. I think that birds in the Napo of Ecuador give the northern song, so it is not surprising that they sound like birds from Guyana. Just listening to the two song types back to back I can see why the southern bird has been proposed as a split. However, there are several questions to be resolved before I can be comfortable with a split. First, are these song types stable over large geographic expanses and meet up abruptly, or are they clinal? Second, where is this zone of contact, or song change? I would like to see the song types mapped, to make sense of this, rather than looking at subspecific (i.e. morphological) distributions. Third, do birds from the type locality of usta sing the southern song, or are they in fact part of the northern group? In another words, if there is a different taxon with a separate song in the south, is usta part of that taxon or is a new name needed (or elevation of an old name)? With regards to visual differences between northern birds and southern birds two features have attracted my attention. The birds in Ecuador show a contrasting and very clean (largely unmarked) tawny belly, while the ones in Bolivia are more heavily marked on the belly so it does not stand out as contrasting from the heavily patterned breast. Furthermore the birds in Bolivia have brown eyes, yet the ones in Ecuador have dark amber eyes."