Isabelline Warbler Iduna opaca


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 has not been quantified, 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 global population size has not been quantified, but the species is reported to be locally common (BirdLife International 2004). The European population is estimated at 5,200 pairs, which equates to 10,400 mature individuals (BirdLife International 2015). However Europe only forms c.10% of the global range. It is described as 'rather common' within much of its North African range (Svensson and Christie 2013).

Trend justification
The European population is estimated to be decreasing by less than 25% in 12 years (three generations) (BirdLife International 2015).

Distribution and population

This species breeds in Spain and north-west Africa; it winters in West Africa.


This species favours trees and tall bushes in many different habitats: dense gardens, parks, riverine forest, dense tall bushes or trees at lakesides, orchards and plantations, maquis, and similar. It requires open areas or patchy, broken-up woods with glades and much undergrowth but does not enter closed forest. Breeding occurs from late April to June and it lays three to four eggs. The nest is a strong cup of plant stems and soft twigs placed in the fork of a branch, often at one to four metres above ground. It feeds mainly on insects and spiders but will also take fruit in the late summer. The species is migratory, wintering in west Africa (Svensson and Christie 2013).


The species is mainly threatened by habitat loss and degradation. It suffers from: the elimination of gallery forests, inadequate reforestation and intensive commercial forestry; the intensification of agriculture with changes in crop species, irrigation and crop species; modification and destruction of water courses; industrial and urban development; and finally fires (Madroño et al. 2004).

Conservation actions

Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. There are currently no known conservation measures specifically for this species within Europe, however it is likely to benefit from protected areas (Madroño et al. 2004).

Conservation Actions Proposed

Conservation and habitat protection are needed in order to maintain an adequate network of favorable sites. The generic protection tarajales (Tamarix)  near water bodies would be advisable, given their importance to this and other species. Further research should be undertaken on habitat selection in order to assist in identifying priority sites for protection and to guide management practices. A detailed survey of the population and the severity of threats is also needed (Madroño et al. 2004).


Text account compilers
Symes, A., Butchart, S., Ashpole, J, Bird, J.

Recommended citation
BirdLife International (2023) Species factsheet: Iduna opaca. Downloaded from on 01/06/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 01/06/2023.