This discussion was first published as part of the 2022.1 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2022.2 Red List update this post remained open and the date of posting had been updated.
AOO = 832 km (ICMBio, 2018), calculated using 2 x 2 km grid cells based on the points of current confirmed, inferred and suspected records, is below the threshold for VU B2, but above VU D2. It is not severely fragmented and the number of locations does not apply, as it is much greater than 10. There is continued decline in: (i) extent of occurrence; (ii) occupation area; (iii) area, extent and/or quality of habitat. It could be NT approaching VU B2b(i,ii,iii).
In the Brazilian national extinction risk assessment conducted in 2018, the species was categorised as Data Deficient (DD).
Assessors: Alexandre Luis Padovan Aleixo; Alexander Charles Lees; Diego Mendes Lima; Edson Varga Lopes; Luís Fábio Silveira; Mario Eric Cohn Haft; Pablo Vieira Cerqueira; Vítor de Queiroz Piacentini.
Criterion A – in the assessment conducted in 2018, we found no long-term population estimate data to evaluate decline using observed data (a), and the decline of AOO and EOO (c) do not meet the thresholds for a threat category. Habitat loss calculations performed with tools available from MapBiomas (https://mapbiomas.org/) over three generations do not meet the threshold for population decline from habitat loss within its range.
Criterion B – Calculation of EOO (32,411 km2) does not meet the thresholds for categorisation as threatened. Its AOO (832 km2), calculated by superimposing a grid with 4 km2 squares to the points of confirmed, inferred and suspected current records, meets the quantitative threshold, but does not meet any of the sub-criteria.
Criterion C – No information is available on population estimates. We did not use estimates of density of congeners such as, for example, P. exilis and P. spilogaster, as they have a different ecology from P. varzeae. Besides this, they are old estimates from other countries, in different contexts, which could introduce substantial under-estimation or over-estimation. Using such information would introduce more uncertainties and caveats. Also at the time of the evaluation, there were no observed, estimated, projected or inferred data on population decline. Only that decline is suspected. Thus, we do not have information for application of IUCN criterion C.
Criterion D – No information available on population estimates. We did not use estimates of density of congeners such as, for example, P. exilis and P. spilogaster, as they have a different ecology from P. varzeae. Besides this, they are old estimates from other countries, in different contexts, which could introduce substantial under-estimation or over-estimation. Using such information would introduce more uncertainties and caveats. The calculation of AOO is over 20 km2 and the number of locations is uncertain, without detailed information on the effect of threats on the species.
The greatest threat is habitat loss due to deforestation for cattle and buffalo farming. There are no protected areas in the species’ distribution. The entire range of its occurrence (EOO) is downstream of two hydroelectric power plants and the impact of these enterprises on the floodplain vegetation is still unknown. Any future changes in floodplain use could affect the species (M. Cohn-Haft, pers. comm., 2018).
Picumnus varzeae is included in the National Action Plan for the Conservation of Birds of the Amazon, which foresees the execution of research on population dynamics, ecology and genetics in sample stretches of the Amazon River and the identification of relevant floodplain areas for the conservation of the species (ICMBio, 2015).
There is no research related to the natural history of P. varzeae; this type of work is a priority in order to better understand the species. It is important to develop studies that can assess possible impacts of threats such as habitat loss due to deforestation for cattle and buffalo farming and the installation of hydroelectric power plants.
Criterion E – in the assessment carried out in 2018, we found no information on population viability assessment.
JUSTIFICATION: Picumnus varzeae is endemic to Brazil, occurring in the states of Pará and Amazonas, restricted to floodplain environments of the Amazon River, only between the mouths of the Negro and Trombetas rivers. It needs mature forests to survive, and tolerates slight habitat degradation. Its range has been undergoing alterations due to logging and cattle and buffalo farming. There are no protection areas in its range, which makes it more vulnerable. The entire range of the species (EOO) is downstream of two recently installed hydroelectric power plants and the impact of these developments on the floodplain vegetation is still unknown, being a serious threat to the species, but it is not possible to specify how rapidly impacts will occur, which may imply a risk of extinction in the near future. Thus, P. varzeae was categorized as Data Deficient (DD).
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments until 21 February 2022. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’s Red List status on this page on 21 February 2022, when discussions will re-open.
Preliminary proposal
Based on available information, our proposal for the 2022.1 Red List is to pend the decision on this species and keep the discussion open, while leaving the current Red List category unchanged in the 2022.1 update.
There is now a period for further comments until the final deadline on 27 February 2022, after which the recommended categorisations will be put forward to IUCN.
Final 2022.1 Red List categories will be published on the BirdLife and IUCN websites in July 2022, following further checking of information relevant to the assessments by both BirdLife and IUCN.
This is a tricky species to evaluate for all the reasons already mentioned. It indeed appears to be reasonably tolerant of disturbance as long as some forest is left moderately intact within its homerange. It occupies tall and medium height varzea forest along the main Amazon river and lower Madeira and will cross clearings and forage in scrubby vegetation near forest. It probably depends on moderately thick (> 10cm dbh) tree trunks for nesting, which as far as known is always in cavities in trunks. The species also may have considerably higher population densities than estimated for other congeneric species, as it appears to be common and easy to locate (in pairs or small family groups) in appropriate habitat throughout its very limited range.
The question of impact of hydroelectric dams on its habitat is interesting and debatable. I’m unaware of any described alteration in varzea habitat along the Amazon attributed to present dams, however, theoretically alterations seem plausible and, in smaller rivers (such as the Uatumã), have been detected to occur gradually over decades.
Another relevant question is that hybridization with an ecologically very similar population of piculets, treated currently as P. cirratus macconnelli, occurs freely in a very narrow contact zone in front of Obidos (Pará). Although reinforcement of the phenotypic differences between the two species suggests that hybridization is not leading to reduction of P. varzeae populations, the manifestation of macconnelli-like traits far from the hybrid zone suggests profound genetic introgression within P. varzeae. (This topic is treated in the master’s thesis by Hevana Lima, whose title was not cited correctly in the references above.) Thus, the long term future of the species in light of this contact, and potentially exacerbated by habitat loss or alteration due to ranching, dams or climate change, may be precarious.
The main feature that distinguishes its vulnerability from that of other strictly varzea species is its very restricted geographic range. If its small range can be joined with criteria related to population reduction (or habitat reduction), then it may be reasonable to treat it within some class of endangerment, despite its seeming abundance within that range. A superficial evaluation based on field sightings would suggest a “near-threatened” status to me, unless the lack of relevant data are taken as thoroughly debilitating and a “data deficient” categorization applied.
Future studies recommended include careful population estimates, habitat description, reproductive success, varzea forest structural stability over time, and population genetics dynamics over time. Some (perhaps sufficient) genetic samples for this last topic are already available at INPA, but long-term monitoring is recommended.
Just qualifying the comment above, my reference to effects of hydroelectric dams is specifically to destructive impact on forest downstream from dams. That is because there are no dams within the species’ distribution, but two very large ones on the Madeira upstream from the species’ range.
To reply to the 3 specific questions:
1) It would seem unlikely that the Madeira dams would have a major impact on the species given that they are c. 700 km upstream (Lees et al. 2016) and the river is the mainstem Amazon such that changes in sediment loads may be diluted by so many sources of sediment – other restricted range species on the Madeira and Negro may well be impacted however (e.g. Laranjeiras et al. 2021)
2) No new work AFAIK
3) piculets can occur at quite high density and varzea communities in general tend to be more species poor but with higher abundance of constituent species. However there are still so many uncertainities that erring on the cautious end of the estimates here seems prudent.
Lees, A.C., Peres, C.A., Fearnside, P.M., Schneider, M. and Zuanon, J.A., 2016. Hydropower and the future of Amazonian biodiversity. Biodiversity and Conservation, 25(3), pp.451-466.
Laranjeiras, T.O., Naka, L.N., Leite, G.A. and Cohn‐Haft, M., 2021. Effects of a major Amazonian river confluence on the distribution of floodplain forest avifauna. Journal of Biogeography, 48(4), pp.847-860.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested in commenting. The window for consultation is now closed and we are unable to accept any more comments until 18 July 2022. We will now analyse and interpret the new information, and we will post a preliminary decision on this species’ Red List status on this page on 18 July 2022, when discussions will re-open.
Preliminary proposal
Based on new information submitted via this discussion, the Red List status of Varzea Piculet has been reassessed. It is now recognised that the construction of the two large hydroelectric power plants upstream of the distribution range is currently not altering varzea habitat along the Amazon River. The assumption that the species is restricted to only two locations*, determined by the two dams, is now considered overly precautionary. Nevertheless, while there are currently no measurable impacts on varzea forests, these dams have the potential to immediately threaten the entire population. Therefore, our preliminary proposal for the 2022.2 Red List would be to list Varzea Piculet as Near Threatened, approaching the threshold for listing as threatened under Criterion D2.
There is now a period for further comments until the final deadline on 24 July 2022, after which the recommended categorisations will be put forward to IUCN. The final 2022.2 Red List categories will be published on the BirdLife and IUCN websites in December 2022, following further checking of information relevant to the assessments by both BirdLife and IUCN.
Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed and we are unable to accept any more comments. We will post a final decision on this species’ Red List status on this page on 1 August 2022.
Recommended categorisation to be put forward to IUCN
The final categorisation for this species has not changed. Varzea Piculet is recommended to be listed as Near Threatened, approaching the threshold for listing as threatened under Criterion D2.
Many thanks for everyone who contributed to the 2022.2 GTB Forum process. The final 2022.2 Red List categories will be published on the BirdLife and IUCN websites in December 2022, following further checking of information relevant to the assessments by both BirdLife and IUCN.