AVIS-IBIS

Birds of Indian Subcontinent

Comparative foraging adaptations of small raptors in a dense African savanna

Publication Type:Journal Article
Year of Publication:1990
Authors:Thiollay, JM, Clobert, J
Journal:Ibis
Volume:132
Issue:1
Date Published:1990
ISBN Number:1474-919X
Keywords:Accipitridae, Butastur, Butastur rufipennis, Buteo, Buteo buteo, Dissodectes, Dissodectes ardosiaceus, Falco, Falco ardosiaceus, Falco tinnunculus, Falconidae, Kaupifalco, Kaupifalco monogrammicus, Tinnunculus
Abstract:Our aim was to investigate how ecologically similar species with different evolutionary adaptations may coexist in a moist Guinean savanna, which is the optimal habitat of the Lizard Buzzard Kaupifalco monogrammicus whereas the Grey Kestrel Falco ardosiaceus and the Grasshopper Buzzard Butastur rufipennis are of more Sudanian origin. Activity budgets, foraging behaviour and success were assessed by focal sampling and were related to habitat parameters and prey availability. Each species had its own daily foraging pattern which seemed to be related to the activity patterns of their main prey, grasshoppers or lizards. Interspecific habitat segregation reflected their morphological and behavioural adaptations and their respective tolerance to grass height, the most important factor in habitat selection. The resident Lizard Buzzard selected the densest woodlands, whereas the Grey Kestrel was restricted to the most open areas and the dry season migrant Grasshopper Buzzard to intermediate, recently burnt, savanna types. The main foraging variables (perch height, inter-perch distance and frequency of moves) differed significantly between species. Maximum detection distances increased with perch height but decreased with increasing grass cover. Perch height was lower when the grass became too high. When attack rates increased, birds tended to move more often, but for shorter distances, and stayed longer within restricted patches. The highly insectivorous Grasshopper Buzzard had the highest and least variable attack rates, negatively correlated with grass height. It exhibited a behaviour typical of a migrant—superficial and opportunistic exploitation of superabundant, easily accessible, and seasonal food sources. Conversely, the residents were associated with denser, more stable habitats and larger, less abundant, but more predictable prey.
URL:http://dx.doi.org/10.1111/j.1474-919X.1990.tb01015.x
Short Title:Ibis
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith