Over the past three million years or so, at approximately three degrees south of the Equator, three great mountain blocks have risen above the East African plateau. They form a broken wall, extending for 300 km and more, about half way between Mombasa on the Indian Ocean coast and Mwanza on the south east corner of the vast blue expanse of Nyanza Lake (aka Lake Victoria).
These noble giants are: Kilimanjaro (5895m) our world’s highest free-standing mountain, Meru (4566m) and Oldeani-Loolmalasin-Gelai (3188m – 3648m – 2942m).
Migrating birds, moving within and returning to Africa, often seem to be funneled between these mountains, following the main longitudinal axes of the Rift Valley, as they penetrate deep into the south of the continent.
Over the past two years here in Tanzania I have delighted in the process of piecing together evidence of these avian movements. However, it is often rather frustrating to watch for them, with one’s feet stuck firmly on the ground, even if you are perched-up on the shoulder of one of these magnificent still-wild mountains.
At last we have evidence from my friends Anabel and Geoff Harries (Geoff pilots light aircraft) that birds like swifts and swallows (and butterflies such as the Brown-veined (or Caper) White Belenois aurota) are moving at heights just below these peaks i.e. at nearly 3000m above sea level.
Anabel wrote me yesterday:
Just to tell you that Geoff whilst flying to Nairobi on Sunday, at about 12.30 (East Africa Standard Time GMT +3), passing at 8 to 9000 feet asl, right between the two mountains of Kilimanjaro (5895m) and Meru (4566m), flew among many of the butterflies that we are seeing everyday at our level. At the moment Geoff says the winds at that level are about 15 to 20 Knots from the North...
He never saw butterflies so high before ... however he has seen many swallows and/or swifts this year at up to 8 or 9000 feet, especially near Monduli mountain (20km west of Mount Meru).
