The remarkable partnership between East Africa’s whistling thorn trees and their resident ants is well known, but now a new study brings to light the trees’ relationship with birds. Acacia ants will swarm over branches and bite elephants or giraffes who try to eat the leaves of the whistling thorn (Acacia drepanolobium). As an incentive for this service, the tree provides the ants with food and shelter: nectar droplets that ooze from leaf glands, and a home inside the small hollow swellings at the base of some of the trees’ thorns (the trees get their name from the sound of wind passing through holes in these swellings). The new study, published in Biotropica, reveals how superb starlings (Lamprotornis superbus), gray-headed sparrows (Passer griseus) and gray-capped social-weaver birds (Pseudonigrita arnaudi) in whistling-thorn savannas also get help from acacia ants. Researchers studying whistling thorns in Kenya’s Mpala Research Centre and Conservancy found the birds chose to nest almost exclusively in trees occupied by the two most aggressive species of ants: Crematogaster mimosae and Crematogaster nigriceps. Several ant species make their homes in the hollow swellings at the base of some of Acacia drepanolobium’s thorns, feeding on nectar that oozes from the trees’ leaf glands. Image by GRID-Arendal (CC BY-NC-SA 2.0) They found these nests by conducting searches within grassy glades in Mpala’s whistling-thorn savanna. True to their name, social-weavers had built their ball-shaped nests in the same tree; superb starlings and gray-headed sparrows were found to have built one nest per tree,…This article was originally published on Mongabay
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