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 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.
The number of individuals found at Kasigau 5,595 is should be a data input error. I’ve personally visited that patch of forest many times and there might a maximum of 1000-1500 individuals. This species is in steep decline due to continuing habitat loss in most of the other forest patches mentioned.
We conducted the detailed Taita White-eye population studies in 1998, nearly 25 years ago (Mulwa et al. 2007). By then, Mt Kasigau held large numbers of the birds due to its pristine habitat condition – but things might have changed. In all other Taita Hills fragments the birds occurred in low numbers and continue to suffer habitat loss and degradation as well as increased predation pressure on eggs and nestlings from snakes and small raptors as part of key edge effects. The fact that the lower elevation habitats are unsuitable for the species, restrict their movement between fragments, yet the hill top forest habitat continue to diminish!. For the foregoing reason, we also deduced that Mt Kasigau population is insular as concurred by del Hoyo et al. 2020. The implication of this isolation on genetic drift and gene flow for these small and isolated populations have been further investigated by Habel et al. 2013.
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 preliminary proposal for the 2022.1 Red List would be to adopt the proposed classifications outlined in the initial forum discussion. Following the comment(s) above, the uncertainty regarding the subpopulation size at Kasigau has been inputted in SIS, with the smaller estimate included. The information regarding isolated subpopulations has also been included.
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.
The 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.
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 analyse and interpret the new information, and we will post a final decision on this species’ Red List status on this page on 7 March 2022.
Recommended categorisations to be put forward to IUCN
Based on available information, particularly regarding the subpopulation size at Kasigau, 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.
Many thanks for everyone who contributed to the 2022.1 GTB Forum process. The 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.
Maintaining the original status makes alot of sense. Over 25 years baseline would be misleading. Would be good if more recent data could be collected to inform future decision making. This Taita system is extremely fragmented, highly fragile and population crushes likely to edge species closer to extinction is always a possibility
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 Taita White-eye has been reassessed.
It is accepted that there is evidence to allow a continuing decline to be inferred. This is based on both the recognition that the ongoing habitat loss is sufficient to be impacting this species despite its preference for forest edge, and on the observation that the numbers estimated for Mt Kasigau in 1998 (Mulwa et al. 2007) are much higher than the numbers that remain per the personal testimony of M. Adamjee here. In combination with the revision to the size of the Mt Kasigau subpopulation, these revised parameters qualify the species for listing as Vulnerable under Criterion C2a(i).
The exisiting threats to the species continue to indicate that, despite the very small range of the species, the number of locations* remains considerably above 10 for identified threats and the population is not severely fragmented* (as discussed above), hence the species does not qualify as threatened under Criterion B.
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.
A recent paper by Wedder et al. suggest an ongoing hybridization with the more common low-land form Zosterops flavilateralis may lead to an evolutionary rescue of Zosterops silvanus through increased adaptiveness in a future admixed population. This is a thereoretical scenario and hybridization between the two species has not been documented. I would argue that the outcome of hybridization is still fairtly unpredictable and potentially concerning. I still suggest adding this new reference to the species assessment. Vedder, D., Lens, L., Martin, C. A., Pellikka, P., Adhikari, H., Heiskanen, J., Engler, J. O., & Sarmento Cabral, J. (2022). Hybridization may aid evolutionary rescue of an endangered East African passerine. Evolutionary Applications, 00, 1–12. https://doi.org/10.1111/eva.13440
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. We will analyse and interpret the new information, and 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. Taita White-eye is recommended to be listed as Vulnerable under Criterion C2a(i).
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.