Wednesday, May 16, 2012

Notes on the vocalizations of Greater Pewee

Much more study is needed on all aspects of this topic, especially differences in vocalizations between subspecies.

J.F. Chace & R.C. Tweit, 1999, Birds of North America Online

The Greater Pewee (Contopus pertinax) is found from the southwestern United States (Arizona and New Mexico) south through Mexico to Guatemala, El Salvador, Honduras and northwestern Nicaragua. Northern populations are short-distance migrants, while southern populations remain in their pine-oak habitat year-round. During winter in Central America, Greater Pewees often join mixed insectivorous flocks (warblers, flycatchers, vireos etc) and are usually a prominent member of such flocks, as they perch conspicuously while giving their characteristic "pip-pip-pip" call. 

At the end of the winter, such flocks dissolve as wintering warblers migrate northward and resident species, like the Greater Pewee, stake out territories. I first heard the dawn song of the Greater Pewee on April 3, from outside our bedroom window. Since then, it's been singing that song practically every morning for 15 or 20 minutes or so, a little before sunrise. It's often the first thing I hear waking up in the morning.

That song sounds noticeably different from the many "José Maria" type songs posted on Xeno Canto, which are all from either the United States or Mexico. (The only two recordings on XC from Central America besides mine are of "pip-pip-pip" calls from Guatemala.) The BNA account calls this song, rather accurately I think, "Fred-rick fear", belonging to the Central American subspecies minor. In Cornell's Macaulay Library I found a recording from El Salvador, made by Walter Thurber on 27 November 1975 of that song. 

Today I recorded another Greater Pewee vocalization ("weeew") not previously represented in Xeno Canto. This call is vaguely reminiscent of Dusky-capped Flycatcher — like Greater Pewee a common bird in Central American pine-oak forest. I wasn't able to find this in the Macaulay Library, but it turns out that the Borror Laboratory of Bioacoustics has a recording from Arizona that is similar. I have not seen any descriptions of this call in the literature, and I remember being puzzled by it when I first heard it back in the winter of 2006/2007, during my first field season in Central America.

It actually sounds a lot like the second half of the Central American "Fred-rick fear" song (i.e. "fear"). This occurred to me only after looking at sonograms of these vocalizations.

The bird giving this "weeew" (or "fear") call was perched high on a snag of a nearly dead pine tree. It gave this call for several minutes. When I approached it for a recording, it flew off but quickly returned to the same perch, producing the same vocalization over and over. After a while, however, it started giving a different call. I tried to grab this much softer call ("prrit-prrit-prrit-prrit"), but wind made it difficult to obtain more than a few seconds. Andrew Spencer obtained a much better recording of this call type from Arizona on 20 May 2009, noting in his description that "the first vocalization in this cut is undescribed in BNA; I am not sure what its context is". Perhaps we should have searched for a nest in the tree from which these vocalizations were given.

Cited literature
Chace, Jameson F. and Robert C. Tweit. 1999. Greater Pewee (Contopus pertinax), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:

Tuesday, May 15, 2012

More first records of butterflies for Honduras

Strymon cestri - Tailless Scrub-Hairstreak

Since then, I have found five more butterfly species previously unrecorded from Honduras. Some of them appear to be quite common in the area where we live, just a little south of the Honduran capital Tegucigalpa. Miller et al. (2012) note that the lepidopteran fauna of Honduras remains relatively unknown compared to that of neighboring countries; their own Annotated List of the Lepidoptera of Honduras is a major step forward in closing that gap. 

Their list is a compound of results from their own recent collecting expeditions to Pico Bonito in northern Honduras, and historical data gleaned from Godman & Salvin (1879-1901), Monroe et al. (1967a, 1967b) and other sources. 

The hairstreak illustrated above is Strymon cestri, or Tailless Scrub-Hairstreak, found from southeastern Arizona and southern Texas to southern Brazil, and thus expected for Honduras. It appears to be quite common here. This individual was photographed on May 8, 2012 on Cerro de Hula, but I have also seen it in our own backyard.

Leptotes marina - Marine Blue

Another apparently fairly common but previously unreported hairstreak is Leptotes marina, or Marine Blue. It is similar to Leptotes cassius, already known from Honduras and certainly more common here than marina. However, Leptotes marina is by no means rare in our area. My records indicate an extension of the known range, which is from southern California, the Southwest and Mexico to Guatemala. This individual was photographed on May 5, 2012, near the shore of the reservoir La Concepción, just outside Tegucigalpa.

Echinargus isola - Reakirt's Blue

Another blue, Echinargus isola or Reakirt's Blue, was new for Honduras when I photographed it on February 12, 2012, near San Buenaventura, a small village south of Tegucigalpa. It ranges from southern California, the Southwest, and Texas through Mexico and Central America to Costa Rica, and thus was expected for Honduras.

I also documented a couple more new skippers for Honduras. 

Cynea megalops - Lesser Cynea / Megalops Skipper

Cynea megalops, or Lesser Cynea / Megalops Skipper, is found from eastern Mexico to Colombia and western Ecuador, and thus an expected addition to the Honduran list. This individual was found basking in Reserva Biológica Cerro Uyuca on April 22, 2012.

Urbanus evona - Turquoise Longtail

A specimen of Urbanus evona (Turquoise Longtail) was photographed on April 18, 2012, in pine-oak forest near the village of Las Anonas, between Cerro de Hula and Montaña de Isopo. Its known range is from Mexico to Colombia, so again expected to occur in Honduras.

I submitted all these first Honduran records to Butterflies and Moths of North America, where they can be consulted by anyone wishing to investigate range extensions of these species. It seems likely that (many?) more first records for Honduras will follow.

Cited literature
Godman, F.D. & O. Salvin. 1879-1901. Insecta, Lepidoptera-Rhopalocera. Biologia Centrali-Americana.
Miller, J.Y., D.L. Matthews, A.D. Warren, M.A. Solis, D.J. Harvey, P. Gentili-Poole, R. Lehman, T.C. Emmel, C.V. Covell Jr. 2012. An annotated list of the Lepidoptera of Honduras. Insecta Mundi, Center for Systematic Entomology, Gainesville, Florida.
Monroe, R. S., and L. D. Miller. 1967. A report on a collection of Hesperiidae from Honduras.
Journal of the Lepidopterists’ Society 21: 243-247.
Monroe, R. S., G. N. Ross, and R. N. Williams. 1967. A report on two recent collections of butterflies
from Honduras. Journal of the Lepidopterists’ Society 21: 185-197.

Wednesday, May 9, 2012

Seasonal variation in Central American Sedge Wren songs?

Up here in Cerro de Hula, we have a sizable population of Sedge Wrens. This morning alone, while doing point counts, we heard 13 different individuals vocalize in an area no bigger than 25 hectares (500 x 500 m). The other side of the hill has more Sedge Wrens, and they are also found in nearby areas. We have never systematically searched for all territories in the area, but a conservative estimate would be somewhere between 25 and 50 pairs, possibly more.

We occasionally saw these birds back in December of last year and the following January, but we didn't realize how common they are in these parts until they started singing, in early February. 

At first, the males sang elaborate series of songs, repeating a song only once or twice or not at all before switching to another song. They sang all morning, with multiple afternoon singing bouts as well. Each one of them seemed intent on demonstrating his vocal prowess with a seemingly endless variation of songs.

But now, three months later, almost all of them are singing buzzy, repetitive songs with little variation. Gone are the musical flourishes from earlier. This, this and this to my ears sounds similar. (The last two fragments are from the same individual.) The pauzes between phrases are noticeably longer now than they were back in February.

Curious if this apparent temporal shift in vocal array signifies a different stage in the breeding process, I decided to consult other recordings in Xeno Canto. I speculated that perhaps the elaborate, musical songs were sung by unmated males attempting to attract a female, and the buzzier, more repetitive songs were sung by mated males simply marking the boundaries of their territories. If true, this pattern would be reflected in recordings from the beginning of the breeding season versus later recordings. However, the Sedge Wren has an extremely wide range, from Canada well into South America, with marked life history differences between populations.

Northern populations of Sedge Wren are migratory, and the Sedge Wren is unique among North American passerines in that it first breeds in northern parts of its breeding range (upper midwestern US and southern Canada), then undertakes a short-distance migration to more southern (Nebraska, Kansas, Missouri) and northeastern (Vermont, Massachusetts) parts of its breeding range, to breed again late summer, before it migrates south to its wintering grounds in the southeastern US and northeastern Mexico.

Central and South American populations, however, are sedentary.

This ecological difference has vocal repercussions, as Kroodsma and others demonstrated in a 1999 paper in Animal Behaviour: the semi-nomadic habits of northern Sedge Wrens favor song improvisation, while birds from more sedentary populations learn each other's songs and develop regional dialects. In Costa Rica, for example, Kroodsma's team found that color-banded birds remained at banding sites year-round and that many songs they heard there were shared by neighboring males. Costa Rican birds from a population only 27 km apart, however, sang different songs. In contrast, northern Sedge Wrens do not have these regional dialects; they have large song repertoires that enable them to communicate with other Sedge Wrens from throughout the northern range.

Back to my hypothesis, then: would Sedge Wrens from comparable (i.e. Central American) populations show this pattern, i.e. greater song variation early on in the breeding cycle versus simpler, buzzier, more repetitive songs later on? Xeno Canto has an impressive number of Sedge Wren recordings — no fewer than 145 — but, as is so often the case, the vast majority from the U.S. and Canada, and South America. In fact, besides my own Honduran recordings, there is one brief recording from Guatemala in the XC database, made by Jesse Fagan in August 2008, for all of Central America. Only 20 seconds in duration, it is really too short to assess the vocal variation of that individual. I hear the repetitive chatters, without any of the melodic flourishes that birds here early in the breeding season were producing, but who really knows what else it was singing that day.

If we consider Mexico as biogeographically comparable to Central America, then the two Mexican recordings, from June 2006 and June 2010 respectively, sound remarkably similar to my simple, buzzy 'late season' songs from Honduras. The recordist, Manuel Grosselet, notes that to his ears, the June 2010 recording from near Mexico City sounds "atypical". However, to me it sounds typical of a late season song, possibly — speculation — from a bird that has already attracted a mate and only needs to mark his territory. As the phrase goes, "more study is needed…"

Cited literature:
Kroodsma, D. E., J. Sánchez, D. W. Stemple, E. Goodwin, M. L. da Silva, and J. M. E. Vielliard. 1999b. Sedentary life style of Neotropical Sedge Wrens promotes songs imitation. Anim. Behav. 57:855-863.