Chico's Tyrannulet Zimmerius chicomendesi Scientific name definitions

Chico's Tyrannulet is one of the least known species of tyrant flycatchers. This tiny bird was completely unknown to ornithology until it was detected in 2009. Currently Chico's Tyrannulet is known only from a small area in south central Amazonian Brazil, where it occupies campina vegetation (low stature forest and scrub) on sandy soils. It is primarily frugivorous, often feeding, like other species of Zimmerius, on the small fruits of mistletoes. In appearance, Chico's Tyrannulet is extremely similar to Mishana Tyrannulet (Z. villarejoi) of northern Peru; these two species also are very similar vocally, but the calls and songs of Mishana Tyrannulet are slightly higher in pitch than are those of Chico's. The known distributions of Chico's and Mishana Tyrannulets are ca 1400 km apart, but it is possible that these, or other previously unknown tyrannulets, may occur somewhere in between.

10 cm; 5·5 g (one male). Typical Zimmerius tyrannulet, with uniform olive-green upperparts  from head to uppertail-coverts, becoming paler green over face  , throat, breast and flanks, which parts are washed with yellow (and streaked weakly greyish yellow on throat), and then bright yellow on belly  and undertail-coverts; tail and wings are dull blackish with faint olive cast, but lesser wing-coverts have olive-green fringes and those to the median and greater coverts are better-defined and clearer yellow; outer webs to primaries and, especially, secondaries also very narrowly fringed yellow; underwing-coverts pale yellow; iris white  , maxilla brownish red, mandible reddish pink, and legs and feet blackish. Sexes alike in plumage, but male is 5–15% larger in wing and tail length, and can be up to 21% heavier in mass (although range of biometrics unavailable). Differs from closely related, but entirely allopatric Z. villarejoi solely in relative size (see Taxonomy) and vocally (see Voice).

C Amazonian Brazil (R Madeira to R Aripuanã and R Madeirinha, in SE Amazonas; possibly also in adjacent NE Rondônia and NW Mato Grosso).

Diet appears to be heavily based on fruits of the mistletoe Oryctanthus alveolatus (Loranthaceae), which plant is also important to the closely related Z. villarejoi; to date, arthropods have not been recorded in the species’ diet to date, but presumably are taken, at least seasonally. At ecotone with taller forest, is apparently outcompeted for mistletoes by Z. acer. Frequently recorded in pairs. No further information.

Four types of vocalizations  known—song, common call, call series and a snarl (the latter probably only used in agonistic interactions)—all of which are given by both sexes, but samples not always large (see Taxonomy), e.g. call series heard just twice (once in the field and once from a bird in the hand); dawn song is believed to be a single note, similar to that given as the common call, and repeated at 3–5-second intervals. The most frequently heard vocalization, the common call, is a distinctly double-noted “tweep-tweep” (occasionally single- or triple-noted), with variants and different inflections. Also, males observed to give single, brief, quiet, mechanical buzzes with the wings when flying between neighbouring trees, once in response to playback. See Taxonomy for differences from Z. villarejoi.

Not globally threatened. Currently considered Near Threatened. Difficult to find unless voice is known and was previously overlooked, even by observers with substantial experience of Amazonian birds. Species estimated range is small (c. 20,500 km²) and lies entirely within the so-called Arc of Deforestation; furthermore, it is restricted to a naturally patchy and comparatively rare habitat type within Amazonia (potentially less than 5500 km² within its total range may harbour appropriate vegetation), while surveys indicate that Z. chicomendesi does not occur in all potentially suitable campinas within the known range (thus its actual area of distribution may be as little as 3572 km²). Furthermore, recent fieldwork at several localities in such habitat both W of R Madeira and E of R Aripuanã has failed to locate the species. The Brazilian government has declared an intention to pave the important Transamazônica highway (BR-230), which traverses the range of Z. chicomendesi and, if enacted, this would surely wreak irrevocable damage on its habitat, given that the raw materials needed to effect this, would surely be quarried from immediately adjacent areas, specifically the slow-growing campina habitats occupied by this species, as well as the also recently described Aripuana Antwren (Herpsilochmus stotzi). Although part of the species’ range is already nominally protected within the newly gazetted Campos Amazônicos National Park and some of the rest lie within indigenous territories, further protected areas should be declared within the distribution of both species, free from disturbance by road-building and other associated settlement activities.