Three species of confusingly similar large greyish - olive coloured warblers are now beginning to arrive in Tanzania at this time of year. Some individuals will continue southwards to Zambia, Malawi, Mozambique and even South Africa whilst many will remain in Tanzania for the duration of the boreal winter.

Until recently these three were placed in the genus Hippolais but in the last year, as a result of recent DNA-DNA hybridization research, they have been moved into the genus Acrocephalus.

So even the museum men, and the 'boffins of DNA' have difficulties dealing with this group.

We will begin now to try and reveal some of the mysteries which surround these three enigmatic species.

Our first picture is of an Eastern Olivaceous Warbler it was taken by Martin Goodey near Kilimanjaro Internationl airport in early February 2006.

The locally severe drought must be forcing many individuals of bird species that should normally thrive in a certain area to move on in search of adequate foraging opportunities elsewhere rather than perish in an attempt to remain in an environment that can no longer sustain them. Many birds which breed in the Palaearctic and ‘winter’ in East Africa are being more nomadic than usual, even appearing beyond their ‘known range’, in response to rapid climatic changes. We are entering interesting times indeed.

With regard to Upcher’s Warbler my recent observations are all from the edge of the Somali-Masai zone at the outermost fringe of ‘Mount Meru’s moisture island’.

The first was in the east-west jacaranda and acacia avenue at the prison pools by Arusha airfield on November 8th.
The next was the bird found with Annabel Harries and photographed by Martin Goodey on January 26th which was just north of the Robin Hurt residence - beside the narrow korongo east of Kisongo.
In the subsequent three weeks about six walking excursions into the dry woodland around the north eastern fringe of Osugat plain (the Beesley’s Lark site) produced at least one, and once four, individuals in the course of a morning’s visit. As Martin mentioned we also saw a couple of Upcher's Warblers at KIA on February 8th in the trees within 50m of the pool where in addition there was three Barred Warblers feeding on the small green berries of a small shrub.

Often one can locate an Upcher’s by call: a single, soft ‘tucc’ that is deeper, softer and less frequently uttered than the insistent sharp ‘tack’ of the Eastern Olivaceous Warblers (H. elaeica) who are currently calling and singing all over the place, seemingly wherever there are any large acacias.
In anything more than a passing glance Upcher’s should show a longer, fuller and darker tail, a character which is accentuated greatly by the combined deep wagging and sideways switching movement that is such an enjoyable feature of this species.

When they arrive in East Africa in October most Eastern Olivaceous and Upcher’s are very worn so that separation at that time solely by plumage features would be difficult should an Upcher’s fail to call or use its tail in the proper manner! Those that have found sufficient food and survived thus far should now be coming into fresh plumage.

The literature (chiefly ZTP) describe various structural and plumage field marks, in particular on freshly-moulted birds a pale panel on the secondaries of the closed wing, such characteristics could be checked in the coming month before the Upcher’s depart for their natal homes in the Caspian region.

Regarding recent confusing changes in the taxonomic position of these three warbler species Killian Mullarney wrote me in February 2006:

"The proposal that Eastern Olivaceous Warbler be regarded as an Acrocephalus first gained widespread notice when it appeared in Dutch Birding and so far as I remember it was based on some taxonomic work carried out on Upcher's Warbler. I do remember that they moved Upcher's to Acrocephalus before the others, and once there was an id feature on Upcher's v Olivaceous W that featured almost identical in-hand photos of the two species, one being captioned Acrocephalus languida, the other Hippolais pallida! I'll have a look for the most significant reference material."