There are several small birds that have a marginal distribution in Extremadura or only in the last few years have started to be recorded. To increase our understanding of such species is a challenge for the developing body of ornithological knowledge in Extremadura. We hope that this note will help to get the ball rolling of one of these special birds: the Western Olivaceous Warbler (Iduna opaca), a passerine that usually will pass by unnoticed, partly because of its scarcity but also because of the similarity of its appearance and song to other species.
To start with we need to clear up its nomenclature, since quite recently its changing name has created some confusion. Up to a decade ago, it was referred to as simply Olivaceous Warbler (Hippolais pallida). The species was split into two, an eastern one which retained its scientific name and the western species, present in the Magreb and the southern half of the Iberian Peninsula, known as the Western Olivaceous (Hippolais opaca). The generic name also has changed, given the close relationship between the reed warblers and the “Hippolais” warblers, which led some authorities to consider both groups as within the Acrocephalus genus. The formula accepted by the official List of the Birds of Spain (SEO) is to give it the genus Iduna as intermediate between the typical Hippolais warblers and the reed warblers (Acrocephalus).
The first records in Extremadura of Western Olivaceous Warbler go back to 1985 and 1990, being mist-netted birds for ringing by Adenex. Subsequently in the fieldwork for the Spanish breeding birds Atlas (1998 – 2002) the species was not detected at all, thus showing a complete blank for Extremadura. This map is shown below, to which later records are shown (see the list at the end of the posting): in red are localities with certain or probable breeding and in orange are records of passage or where the record may be doubtful. In May and June 2013, Western Olivaceous Warblers were seen regularly at two locations on the Guadiana river: in Mérida (two males singing in riverine woodland dominated by ash) and in Badajoz (at least three males in a stretch dominated by willows). As can be seen in the list, these two locations stand out in terms of number of observations, without doubt because of the number of birdwatchers based there. Therefore, it is highly likely that the species breeds more widely on other stretches of the Guadiana and its tributaries. As can be seen in the map, the Western Olivacous Warbler is distributed throughout Andalucia, and there are also smaller populations in the east of the peninsula, especially on the Ebro and the edges of Ciudad Real and Valladolid.
Consulting ringing data provided by SEO/BirdLife, there are five sites where the species has been apparently trapped in Extremadura: four on the Guadiana (mainly Mérida) and the other in Cáceres province (Coria or thereabouts). However, this information is very confused. The data suggest that more than 8,000 birds have been ringed in Spain, the majority between 2009 and 2010 (when more than 1,600 captures took place (see figure below). Taking into account that in the Atlas for Spain the total population is estimated at 4,000 pairs and that this figure is reduced to only 1,000 pairs in the Spanish Red Data Book for birds, the figures given for trapped birds are wildly disproportionate. Numerous birds are claimed to have been trapped in Madrid province, where Western Olivaceous Warbler does not breed. Therefore, it is best to be sceptical about this information.
OBSERVATIONS OF WESTERN OLIVACEOUS WARBLER IN EXTREMADURA
(Sources: Bird Reports 1998 – 2008 and monthy blog summaries)
- One ringed by Adenex in 1985 (José Antonio Román, 2011).
- One ringed by Adenex in 1990 (J. A. Román, 2011).
- Spring 1995: one seen at Valuengo reservoir in oleander and tamarisk (Emilio Costillo).
- One drinking at Fuente de Francés, Monfragüe (CC) on 20/08/1999 (E. Streich y Marc Gálvez).
- Two by River Guadiana, Mérida on 12/07/2004 (Francis Prieto).
- One by River Almonte, Trujillo on 23/04/2008 (Jesús Porras).
- One by River Gargáligas, Vegas Altas on 21/05/2008 (I. Castelao).
- One at Monfragüe on 28/05/2008 and three at Cabeza del Buey on 30/05/2008 (E. Bonavia).
- An adult feeding a fledged young by the Ribera de Nogales stream, between Torre de Miguel Sesmero and Entrín on 29/06/08 (M. Gálvez). First certain breeding record.
- Two by Guadiana River, Badajoz on 26/06/2009 (M. Gálvez y José Guerra).
- Two at Puente Viejo, Badajoz on 30/08/2010 (Juan Carlos Paniagua).
- Two at Montijo reservoir, Mérida (BA) on 30/05/2012 (Francisco Montaño, Elvira del Viejo y A. Ruiz).
- A juvenile of the year trapped for ringing at the Azud de Badajoz on 14/07/2012; could have fledged from the area (Ángel Tomas Mejías).
- A male singing by Guadiana River, Mérida (BA) at least from 13/05/2013 to 30/06/13 (Sergio Pérez Gil, Lorenzo Alcántara, M. Gálvez, Jesús Solana, César Clemente y Manuel García).
- At least three singing males between 27/05/2013 to 16/06/13 at the Azud de la Granadilla, Badajoz (Juan Carlos Paniagua, Atanasio Fernández, Sergio Mayordomo y Eva Palacios)
- Unpublished information, for which there are no available details, of Western Olivaceous Warbler breeding in at least five locations in Badajoz province (Fergus Crystal Robertson).
Translated by Martin Kelsey.