Until the end of the twentieth century, the Nairobi National Park witnessed the second-largest herbivore migration after that of the Mara and Serengeti, with thousands of wildebeest and zebra streaming in from the south in July and August for the good grazing. Before 1946, when the park was created, only the physical barrier of Nairobi itself diverted what was a general northward migration on towards the Aberdare range and the foothills of Mount Kenya. The erection of fences along the park’s northern perimeter closed that migration route, while the steady encroachment of housing, industry, farms and livestock grazing along the southern boundary is also tightening the wildlife corridor there. The wildebeest you see nowadays are mostly sedentary individuals that stay in the park all year, and the migration has been reduced, in most years, to a trickle. Conservationists are, however, determined to keep the southern corridor open, claiming that to fence the park (partly a response to fears about lion and rhino poaching) would effectively suffocate its ecosystem, which depends on free-ranging wildlife to be sustainable. The “Friends of Nairobi National Park” (t0723 690686, wfonnap.wordpress.com) have the full story on this and much more about the park.