Inca-Finch vocalizations
Inca-Finches (genus Incaspiza) are entirely endemic to Peru, and in general are rather poorly known. The five species are restricted to arid areas in the central and northern part of the country, with four of those species at least somewhat associated with the Marañón Valley.
Ecologically they are somewhat similar to Black-chinned Sparrow (Spizella atrogularis) from North America, which they also vaguely look like. Inca-Finches are found on arid slopes, in association with ground-bromeliads, and, in some species, tall columnar cactus. Many sources make a point of their notable shyness, especially after dawn chorus, but I found this to be somewhat overstated. They are shy, but I would not classify them as especially hard to find, even mid-day.
The vocal repertoire of Inca-Finches isn't very well described in the literature, and, I believe, at least some of the descriptions are misleading or mistaken. In general each species of Incaspiza has a thin, high pitched whistled song, most often given in the early morning from an exposed perch. They also have a high-pitched 'seet' call note that, for most species, is heard more often than the song. Finally, there are apparently also some alternate calls that are not described in the literature and only rarely heard in the field.
In these descriptions I use recordings I made in the field of each Inca-Finch species, my (admittedly limited) personal experience with them, recordings available from other sources such as Xeno-Canto, the Macaulay Library, and published sound collections, and printed sources to describe various sounds that these birds make. Acronyms used below for printed sources include BotHA (Birds of the High Andes by Fjeldså and Krabbe), SoSA (Songbirds of South America: Passerines by Ridgley and Tudor), and BoP (Birds of Peru by Schulenburg et.al.).
Songs | Calls
Each species of Inca-Finch has a distinctive high-pitched song. For some species this is the most commonly heard vocalization, for others it is rarely ever heard (and I haven't even been able to find a recording for one of them!). While singing is also when Incaspiza species are most conspicuous; they typically sing from tall exposed perches in the early morning.
Great Inca-Finch (Incaspiza pulchra)
The song of Great Inca-Finch is a very high evenly pitched (~8 kHz), rapid warbling trill. A bird I recorded in central Ancash ended the trill with a clear falling note, while another recorded by Ted Parker from Lima ended with just the trill. The bird I recorded was singing from the tops a tall flowering stalks of a large ground bromeliads, gave the songs at regular intervals of 3-4 seconds, and was highly responsive to playback of it's own song.
24-01-2010 Near Huaylas, Ancash, © Andrew Spencer
BotHA describes the song as "a vibrating, very high-pitched, short note repeated every 5s"; SoSA as "high-pitched whistled song a simple 'tic-sweee-eee?'"; and BoP as "a series of high, thin whistles: 'tsew tswee? tsew tswee?...'".
The only two recordings that I have been able to find of anything resembling song match the description from BotHA and not the other two sources. I personally think that they may be mistaken in their description of the song of pulchra and are instead describing the song of Rufous-backed Inca-Finch, but without knowing where they got their source material for their descriptions that remains just a guess. BoP also describes a call: "a short, descending, quavering high note: 'tsee'le'le'le'le'le'le'"; I believe what is being described as a call in BoP is in fact what I am describing as the song.
ML13331 song from Lima, 22-04-1978 by Ted Parker
Rufous-backed Inca-Finch (Incaspiza personata)
The song of Rufous-backed Inca-Finch, based on a recording I made in Ancash, is a high pitched "tic" note followed by a clear, whistled, overslurred by rising overall "sweee". Another version of the song I recorded in Ancash consisted of three clear, high pitched, rising underslurred whistles, the whole series also rising. A recording by Ted Parker from Ancash is quite similar to the first of mine, except the second note is less smoothly underslurred and more rising at the end. Another recording from Ancash, by Peter Boesman also matches the first song type.
24-01-2010 Near Huaylas, Ancash, © Andrew Spencer
Birds that I observed singing sang from the tops of tall stalks on arid slopes, per usual for an Inca-Finch. They were fairly strongly responsive to playback of their song, though less so than pulchra; this may in part be due to the fact that my observations of this species were later in the morning.
An interesting behavior was observed between a pair of birds, though - one bird was giving the simpler song I describe above, while the other appeared to be duetting with the more complex song. The two birds did not appear to be intraspecificially territorial, and to me appeared to act more like a male-female pair. I can find no source discussing female Inca-Finch song, and I am not entirely sure what was going on.
24-01-2010 Near Huaylas, Ancash, © Andrew Spencer
BotHA says "no data" for voice. SoSA describes the song as "a simple, repeated 'tic sweee-eee?' similar to Great"; BoP a "weak, high 'tisew-ti'TSWEE?'". I personally find the song descriptions of this species more accurate than for Great, except for the comparison of Great and Rufous-backed in SoSA.
ML10479 song from Ancash, 30-05-1975 by Ted Parker.
Gray-winged Inca-Finch (Incaspiza ortizi)
This species has the most complex song of any Inca-Finch species; a bird I recorded in Cajamarca gave an alternating series of three different note types: a highly modulated rising and falling whistle, a clear ascending whistle, and a moderately quavering rising-falling whistle, all high-pitched. There are ten other recordings of this species on xeno-canto; all of them are similar to the above description, with some minor variations. The combination of highly modulated and clear rising notes is distinctive.
14-01-2010 Lucma, Cajamarca, © Andrew Spencer
Gray-winged appears to be the most vocal inca-finch, when it comes to song. While being probably the least common on birding trips (pretty much all birding tours get this bird in one spot), it has more recordings than any other Incaspiza on both xeno-canto and Macaulay. All of the birds I observed were singing, and I never heard a single call note from any of them. BotHA calls this species "more shy and hidden than other inca-fs", and what I observed of them certainly bears this out. How this behavior correlates to their greater liklihood to be observed singing I am not sure.
BotHA describes the song as "3 very high-pitched insect-like notes", BoP as "a series of weak, quavering, high whistles: 'seeew sweeee? seeee? seeew sueeesu...'". SoSA simply says the song is like other Inca-Finches, which, given that this is such a distinctive song, is a severe oversimplification in my opinion.
Buff-bridled Inca-Finch (Incaspiza laeta)
If you go by the number of recordings available, Buff-bridled Inca-Finch is the least likely to sing of all the Incaspiza. I was unable to find any recordings of the song, and despite seeing FAR more individuals of this species than any other (it is quite common in appropriate habitat), I never heard anything approaching song. Given how common this species is I must assume that it sings only very rarely, or during a time of year when few people visit its range.
The only description I was able to find of the song is in SoSA, "song a repeated 'tsueet, tsu-tseee" (E. Barnes recording)". Since I have never heard this cut I can't comment on it, but the written description sounds rather like the song of Rufous-backed to me.
Little Inca-Finch (Incaspiza watkinsi)
Little Inca-Finch is another that seems to sing only rarely. There are no publically available recordings of the song of this species on the internet, and the only one I know of at all is from the new Bird Songs of Peru collection. Courtesy of Peter Boesman I am able to include a spectrogram and clip of it here.
The song of Little Inca-Finch, based on this recording, is a short, simple, sharply rising then more slowly falling clear, high pitched whistle, far simpler than other Inca-Finch songs. Also note that while many vocalizations of Inca-Finches are polyphonic, none of the ones that I include spectrographs for are so strikingly so as Little.
27-12-2007 Bagua Chica, Amazonas, © Peter Boesman
SoSA describes the song as "a weak 'pseeu'", and BoP as "a high, thin 'tsee-TSEW! swee?'". To my ears the description from SoSA is far closer to the one recording I've heard, but with such a small sample size I can't make any accurate comparisons for the species as a whole.