Proposal (464) to South American Classification Committee

Change the English name of Zimmerius acer

Effect on South American Checklist: This proposal would change the English name of Zimmerius acer, a taxon recently split from Slender-footed Tyrannulet (Zimmerius gracilipes).

Background: In review, Zimmerius acer was treated as a separate species from Zimmerius gracilipes by Cory & Hellmayr (1927), but Zimmer (1941) treated them as conspecific; Pinto (1944), however, treated them as separate species and noted that both had been collected at Santarem, Brazil (Gyldenstolpe 1945b). Most recent classifications (e.g., Sibley & Monroe 1990, Ridgely & Tudor 1994, Dickinson 2003, Fitzpatrick 2004) have followed Zimmer (1941) in treating them as conspecific. Rheindt et al.'s (2008b) genetic data indicate that acer and gracilipes are not sisters, with acer basal to all other Zimmerius taxa sampled. SACC proposal (proposal 362) passed to elevate acer to species rank. Given the extensive taxonomic discussion of this bird prior to its majority SACC vote, the final taxonomic and geographical limits of acer seem destined for even more discussion.

The provisional English name for Z. acer is “Guianan Tyrannulet”.  This name seems appropriate (although hardly charismatic) because much of acer’s range is centered in the Guianas, the species has few or no distinctive physical features (beyond a slightly paler, more whitish throat), and no really distinctive vocal attributes.

Although we do not dispute that Guianan Tyrannulet is an appropriate name, we propose that we name the species for the person who first pointed out that acer was sympatric with gracilipes and thus deserving species rank: Nils Gyldenstolpe (see references).  Further, Gyldenstolpe also described Z. g. pallidior, and so he has worked on this group of birds. More broadly, Gyldenstolpe’s three major monographs on birds in Brazil and Bolivia (see SACC Literature Cited) are major contributions to the ornithology of South America, yet Gyldenstolpe has received little formal recognition for these contributions.

Recommendation: We recommend a YES vote to adopt the English name Gyldenstolpe’s Tyrannulet for Zimmerius acer. The issue of stability is minor in this case. The provisional name Guianan Tyrannulet was coined, was never voted on separately, and has very little historical momentum (SACC proposal passed in Sept. 2008).

References (and see SACC Bibliography file for rest):

GYLDENSTOLPE, N. 1945b. The bird fauna of Rio Juruá in western Brazil. Kungl. Svenska Vet. Handlingar 22: 1-338.

Steve Hilty and Van Remsen, September 2010

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Comments from Stiles: “A tepid YES; I am not averse to recognizing the contributions of ornithologists past through English names, especially as the distribution of acer may be considerably wider than “Guianan”.”

Comments from Robbins: “NO. Guianan Tyrannulet is a very appropriate name for this species as it conveys the primary distribution of the tyrannulet.”

Comments from Zimmer: “NO. I’m torn on this one, because I actually like the idea of honoring the contributions of ornithologists through English names, and Gyldenstolpe’s contributions were both major and largely unrecognized (at least in any formal way). But in this particular case, I don’t think that recognition is the most appropriate way to go. I base this primarily on my conviction that true acer is truly a Guianan bird, and that the populations currently recognized as acer from southeastern Amazonia and northeast Brazil are vocally distinct. It is entirely possible that the Guianan vocal type (= “true” acer) crosses the lower Amazon in the vicinity of Santarém, which is known to happen elsewhere in the lower Amazon with some other primarily Guianan taxa (e.g. Hylopezus macularius, Cyanicterus, Celeus undatus etc.). However, it has been my experience that populations of “acer” from elsewhere on the south bank have different, single-note calls from the distinctive two-note calls of true acer from the Guianas. I also think that gilvus of western Amazonia has some calls that are consistently different from those of Guianan acer, south-bank “acer” and gracilipes. If I had to bet, I’d say that when the taxonomic dust settles, we’ll be recognizing a couple more species in this complex, and that the name acer will be restricted to the Guianan birds with the two-note call. As such, the name “Guianan Tyrannulet” would be the most appropriate English name. As it stands, we can’t even be certain that the Santarém birds that Gyldenstolpe called attention to are even the same vocal-type as the Guianan birds, even though they were identified as acer on morphological grounds. Also, despite Gyldenstolpe’s fine body of work, it seems odd to link his name with a Guianan bird, given that his work centered on western Amazonian Brazil and Bolivia. I would be more in favor of naming gilvus, should it prove to be a distinct species, after Gyldenstolpe, given its distribution in western Amazonia.”

Comments from Jaramillo: “NO. I think that Kevin Zimmer makes a convincing case to keep acer as the Guianan component of what may in fact be several cryptic species. If so, perhaps another of these could be designated to honor Gyldenstolpe.”