LC
Mishana Tyrannulet Zimmerius villarejoi



Justification

Justification of Red List category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The species is considered uncommon (Álvarez et al. 2012). Based on the population density of a sympatric congener (Z. gracilipes in Peru: 4 mature individuals/km2; Santini et al. 2018) and assuming that only 10% of the range are occupied to account for the species's rarity, the global population may number c.12,000 mature individuals. To account for uncertainty, the population size is therefore here placed in the band 10,000-19,999 mature individuals.
The population forms two disconnected subpopulations in Loreto and in San Martín. Based on the range area and suspected density, both subpopulations may be of roughly equal size, numbering 5,000-9,999 mature individuals each.

Trend justification
The species is suspected to decline slowly due to the loss of its habitat. Over ten years, about 6-7% of tree cover is lost within the range (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein). The species is forest-dependent; however, it appears to tolerate selective logging (Socolar 2020). Therefore, population declines are thought not to exceed 10% over ten years.

Distribution and population

Zimmerius villarejoi is known only from an extremely limited habitat type in the río Nanay and río Tigre drainages near Iquitos, Loreto, the lower río Mayo and middle río Huallaga, San Martín (J. Díaz in litt. 2012, Vásquez-Arévalo et al. 2018, Socolar 2020), and a 1912 specimen taken from Moyobamba, San Martín, Peru. While surveys indicate that it is genuinely absent from the intermediate areas in western Loreto, the distribution range may be larger than currently known, probably covering further areas in northern Peru and even southern Ecuador (Socolar 2020).

Ecology

The species is confined to scrubby 'varillal' habitat - poorly drained, 12-18 m tall forest on white-sand soils. The species's distribution seems to coincide with that of two or three tree species, mainly Dicyumbe uaiparuensis (Socolar 2020). It is uncommon and very patchily distributed. It forages in the canopy for small arthropods and fruit, notably the berries of the mistletoe Oryctanthus alveolatus (Socolar 2020).

Threats

The limited extent of appropriate 'varillal' habitat, and the continuing extraction of trees for building materials and posts, means that much of the population is threatened by habitat loss. Outside protected areas, white-sand forests are being exploited for timber and other products. Currently, tree cover is lost at a rate of 6-7% over ten years (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein). While forests within the distribution range in Loreto appear secure and not under imminent risk, habitat loss is much more severe in San Martín (Global Forest Watch 2021).

Conservation actions

Conservation Actions Underway
The species occurs within the Allpahuayo-Mishana National Reserve.

Conservation Actions Proposed
Search for this species in sandy-soil forests in the Tarapoto-Moyobamba region of Peru, and perhaps in eastern Ecuador and Colombia. Quantify the population size. Determine the extent of occupied or suitable habitat. Assess the impact of current threats. Research the species's tolerance of habitat degradation and loss.
Grant protection to occupied sites and areas of suitable habitat. Improve the protection of 'varillal' habitat in the Allpahuayo-Mishana National Reserve.

Identification

10 cm. Rather non-descript greenish-yellow tyrannulet. Uniform olive upperparts. Most of underparts also olive, but this grades into yellow on the belly and undertail coverts. Wings dull black with faint olive cast and fringed (along with median and greater coverts) with yellow. Similar spp. Differs from sympatric Slender-footed Tyrannulet Z. gracilipes in having pinkish lower mandible. Voice Song is a simple series of two to four evenly spaced notes, the first being longest and each subsequent note being shorter.

Acknowledgements

Text account compilers
Hermes, C.

Contributors
Benstead, P., Díaz Alván, J., Pople, R., Sharpe, C.J., Symes, A. & Wege, D.


Recommended citation
BirdLife International (2024) Species factsheet: Zimmerius villarejoi. Downloaded from https://datazone.birdlife.org/species/factsheet/mishana-tyrannulet-zimmerius-villarejoi on 26/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 26/02/2024.