Vocalizations of Willard's Sooty Boubou
Posted by jbates , 17 May 2012 · 219 views
Tom Gonske, Josh Engel and I just reutrned from five weeks in the eastern Democratic Republic of Congo and Uganda. As part of our John D. Catherine T. MacArthure reached field sites along the Itombwe plateau and in Kahuzi-Beiga National Park in the DRC and all along were were on the look out for Willard's Sooty Boubou (Laniarius willardi), which was described based on specimens Tom Gnoske, Ben Marks and Charles Kahindo first collected in Uganda more than 10 years ago. We did not find the bird in either one of the congolese sites we visited, but that was not entirely a surprise. I both Itombwe and Kakuzi-Biega, we were working at 2100-2300m elevation. These elevations are inhabitated by another black boubou, Mountain Sooty Boubou (Laniarius poensis). We found this species to be common at both sites, but forest below 2000m is essentially gone. In Kahuzi-biega National Park, this corresponds with the park's eastern border. The protected status and borders for the Itombwe region have not been established, but one thing that was clear from this trip is that any forest below the top of the plateau on the eastern side is under intense logging pressure. We saw a few intriguing fingers of forest in ravines that reach elevations that might still have a few Willard's Sooty Boubou, but due to insecurity in the region, we did not get the opportunity to survey them.
Josh and I stayed on an extra week after Tom, traveling to Uganda. The goals were 1) to meet with out colleague, Makerere University Zoology Professor Robert Kityo about our permit applications for future work in Uganda, and 2) to reach Buhoma, the low elevation sector of Bwindi National Park where Tom et al. originally collected the specimens that proved to be Willard's Sooty Boubou. Josh and rented a van and successfully reached Buhoma, where we were pleased to meet up with the Alfred Twinomojoni, the Dean of the Bwindi region bird guides and one of the crew who had worked with Tom et al. As a professional bird guide, Alfred was aware of the new species description and he told us he could lead us in the park to loook for the bird. We started early in the morning up the road from Buhoma into the park. This entire region is all below 1800m, what we think is the ideal elevation for willardi. Having not worked in forest at these elevations previously, the dramtic differences in bird species compared to sites above 2000m was impressive. Alfred knew all the calls, but even though he continued to whistle and play a recording of a rapid four noted whistle, no shrikes responded.
The trail climbed and crossed a saddle; it was getting towards noon and threatening rain we stopped and ate lunch under a fruiting tree with several Great Blue Turacos (Corythaeola cristata). Alfred kept saying the boubous were there they just were not responding. We decided to start back to Buhoma. A little way up the trail there had been ants crossing and we could hear Red-tailed Bristle-bills calling (Bleda syndactyla) around that area. We were looking for them when Josh suddenly yelled "I've see a black boobou." I found it with my binoclulars too. Alfred cued up the recording of the four noted whistle on his i-pod. The bird started calling back with the four noted call. Josh started recording and it started to rain. The rain made us retreat to a shelter up the trail, ubt when it stopped we went back down and played the recording. The bird responded and its mate did also. At one point the first bird was doing a raspy note and the other bird was doing a chuck comprising a duet. Josh got some photos, but he and I both could not fully convince ourselves of the color of the eye. There just was not enough light even though we got fairly good looks. We are convinced that this call is something we have not heard from Mountain Sooty Boubous that we have recorded from three other montane sites in the Albertine Rift, so that this is the call of Willard's Sooty Boubou. Alfred comfirmed that he hears this same difference with respect to boubous at the higher elevations at Bwindi. Interstingly, the recording on Alfred's i-pod comes from a set of CDs of African bird songs made by Claude Chappuis. The four-noted call is one of the cuts under what Chappuis calls Laniarius fuelleboorni (poensis) holomelas. The notes for the CDs credit these recordings to the late Jennifer Horne, but the location is given as Bwindi. We suspect these will prove to be from the Buhoma area. So... a mystery has been solved. You can hear a recording of Willard's Sooty Boubou recorded by Josh Engel on 3 May 2012 above Buhoma in Bwindi NP, Uganda; elevation about 1600m.