Justification of Red List Category
This species is known from a small range. Forests within the range are lost at an increasing rate; particularly in the lower zones of the range habitat is already largely converted, and logging events are more and more spreading across the range in the higher elevations. The species is therefore listed as Vulnerable.
The population size has not been quantified. Based on observed densities of congeners (H. stictocephalus and H. sticturus: 2-5 mature individuals/km2; Santini et al. 2018) and, to account for the species's preference for humid forests, assuming that 50% of forests within the known range are occupied (i.e. 860-960 km2), the population may number 1,720-4,800 mature individuals. This value however requires confirmation, and an accurate quantification of the population size is urgently needed.
The species is suspected to be in decline due to ongoing habitat destruction.
Over ten years, 8% of tree cover are lost within the range (Global Forest Watch 2021, using Hansen et al.  data and methods disclosed therein). As the species is restricted to forests, population declines are likely steeper than forest loss alone due to the additional impacts of habitat degradation. Therefore, the rate of population decline is tentatively placed in the band 10-19% over ten years.
Herpsilochmus parkeri is restricted to a small area in the drainage of the río Mayo in San Martín, north Peru. Large areas of forests remain close to the known range, and it cannot be ruled out that the species has a wider distribution than currently believed.
The species occurs mostly at elevations between 1,250 and 1,450 m. It inhabits a variety of forest habitats, including humid montane forest with tall trees of 30-35 m height, semi-stunted forest of 12 m height and edaphic stunted forest of 4 m height (Schulenberg and Kirwan 2020). The species favours the mid- and upper-levels of the tallest forest, in areas with a relatively closed canopy and many epiphytes, but is also seen regularly at the savanna-forest ecotone (C. Bushell in litt. 1998). Birds move around in pairs, often with mixed-species flocks, feeding on invertebrates. Breeding is most likely to take place from May to September or October.
Its small known range is coupled with widespread deforestation of the adjacent lowlands in the río Mayo valley. Coca and coffee are widely cultivated in this region, and areas of suitable habitat are gradually being cleared for timber, agriculture, road developments and human population growth (Hornbuckle 1999, J. Hornbuckle in litt. 1999). Forest clearings are gradually encroaching further up onto the mountain ridge; across the known range tree cover is lost at a rate of 8% over ten years (Global Forest Watch 2021, using Hansen et al.  data and methods disclosed therein).
Conservation Actions Underway
The species occurs in Alto Mayo Protected Forest, San Martín.
Conservation Actions Proposed
Search areas of suitable habitat in San Martín to determine the exact distribution and to identify additional populations. Quantify the population size. Research the species's biology, ecology, behaviour and subpopulation structure. Monitor the population trend.
Establish protected areas within the range to safeguard remaining habitat. Enforce the protection of habitat in Alto Mayo Protected Forest, and ensure that high-altitude forest is included within its boundary (Hornbuckle 1999, J. Hornbuckle in litt. 1999). Raise awareness for the species and its habitat.
12 cm. Grey-and-black antwren. Male has black crown and ocular streak. Greyish underparts. Dark grey upperparts with dark mottling. Blackish wings with white tips to wing-coverts forming wing-bars and whitish edges to remiges. Black tail with mostly white outer feathers and large white tips on other rectrices. Female has black crown heavily spotted white and postocular streak. Ochraceous front. Buffy eyebrow. Dark buff throat. Buffy breast with white lower belly and buffy-greyish flanks. Pale grey upperparts tinged buff on back. Tail and wings much as in male. Similar spp. Male Creamy-bellied Antwren H. motacilloides is not as grey below. Voice Accelerating and slightly descending trill introduced by several well-spaced notes.
Text account compilers
Bushell, C., Hornbuckle, J., Isherwood, I., Pople, R., Schulenberg, T., Sharpe, C.J., Stuart, T., Symes, A. & Walker, B.P.
BirdLife International (2022) Species factsheet: Herpsilochmus parkeri. Downloaded from http://www.birdlife.org on 06/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 06/12/2022.