Mystery calls, high on Kilimanjaro

> Last month I briefly observed a small passerine within the crater of
> Kilimanjaro, at ~5,700 m. Besides the White-naped Raven this is the only
> bird I have seen at the summit, in 5+ weeks of time spent there
> (cumulative).
>
> The following recordings were made during my brief glimpse of the bird
> within an area of boulders. In so doing I was not able to make a careful
> observation, and did not get any photos. Playback was not successful
> because the bird departed as wind speed increased.
>
> Any ideas what species this might be?
>
> Thanks in advance for any thoughts-
> Doug Hardy
> Norwich Vermont, USA
>
> Two clips are available, each in wma or mp3 format:
>
> 11 seconds:
> <http://www.geo.umass.edu/climate/tanzania/audio/kibobird49_42-53.wma>
>
> <http://www.geo.umass.edu/climate/tanzania/audio/kibobird49_42-53.mp3>
>
> 21 seconds:
> <http://www.geo.umass.edu/climate/tanzania/audio/kibobird49_125-146.wma>
>
> <http://www.geo.umass.edu/climate/tanzania/audio/kibobird49_125-146.mp3>
>