Aerial surveillance by a generalist seed predator: food resource tracking by Meyer's parrot Poicephalus meyeri in the Okavango Delta, Botswana

As a proven food resource generalist, Meyer's parrot (Poicephalus meyeri) was expected to track the availability of all significant food resources in its diet over time. Here we recorded all feeding activity during 366 standardized road transects for correlation with an index of relative food resource abundance over 18 mo. As expected, Meyer's parrot made food resource decisions according to relative abundance at landscape level. Feeding activity on food resources available throughout the year (e.g. ripe Kigelia africana fruit) or not visible from the air (e.g. unripe Diospyros lycoides fruit), however, did not correlate significantly with fluctuations in their relative resource abundance. In addition. over 70% of all feeding bouts were in the high canopy and over 70% of all food items consumed formed bi-coloured displays. The influence of estimated protein and energy acquisition rates from different food resources was insignificant. Therefore, important selection criteria for utilization by Meyer's parrot include relative abundance and visibility from the air (i.e. food resources with the highest probability of encounter when dispersing from a central roost). Sensitivity to fluctuations in resource abundance at landscape level demonstrates the relative importance of maximizing net gain per unit foraging time by minimizing foraging flight distance.