Goals:
Using Augur buzzards as indicators of ecosystem health to assess the affects of rapid population growth and land-use changes within the Rift Valley.
Objectives: To establish a long-term baseline of Augur buzzard populations around Lakes Naivasha by documenting breeding territories and nest sites. To incorporate analyses of the affects of development and human population growth on Augur buzzard populations, in particular to assess the affects of a booming horticultural industry on the Lake Naivasha ecosystem. Using this data to identify potential threats to this and other similar Rift Valley ecosystems.
Background:
The Augur buzzard (Buteo augur) is considered to be one of East Africa’s most common birds of prey, and is renowned for its ability to adapt to habitat changes. However, survey data over the last three decades have indicated sharp declines in the populations of this once ubiquitous raptor. Due to its relative abundance around Lake Naivasha, coupled with the rapid human population growth and horticultural development in the vicinity, the species and location serve as an ideal case study of the effects of development on top avian predators, and therefore on the ecosystem as a whole. The ecology of the Augur buzzard was studied in detail at Lake Naivasha in the mid-1990’s, when reasonably healthy number of breeding territories were documented. This study provided the baseline with which future surveys could be compared and population trends could be monitored. Further, existing satellite imagery allows for detailed analyses of land-use changes over the last several decades with which survey data can be compared.
Recent Results:
A detailed survey of the Augur buzzard (Buteo augur) population around Lake Naivasha, Kenya was conducted from April through July 2010. In this study, well over 300 distinct Augur buzzard sightings were recorded in nearly 200 hours of direct field observation, resulting in the identification of 24 active breeding territories. In many of these territories, active nests were documented, observed, and recorded for future reference. Further, extensive time was dedicated to observing areas where Augur buzzard territories had been documented in the 1990’s, but which yielded no consistent pair sightings presently, in order to verify territory abandonment. Lastly, a few Augur buzzards were trapped and banded for an ongoing study of adult survivorship around the lake. Overall, there has been a decline from 36 to 24 active Augur buzzard territories within the study area since the 1990’s, for a loss of 33 percent. While declines of territories have tended to be most extreme in areas of highest human disturbance (up to 60%), it is notable that declines have also been significant in control-like sections of the study area, including Hell’s Gate National Park and Mundui, a private ranch managed for wildlife. Both of these areas have remained largely unchanged over the past 15 years, as they are managed for land and wildlife preservation. However, declines in the numbers of active territories in these areas have been documented at 33 percent and 29 percent respectively, roughly reflecting the overall trend. This may insinuate a background collapse in the “floating” Augur buzzard population, which would yield fewer individuals to fill vacancies, even in territories that have been recently active and have suffered no noticeable habitat degradation.
Challenges:
Project Links:
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Location Note:
Lake Naivasha: 80 km North-west of Nairobi, 1890 metres above sea level, 120 square kilometres. Hell’s Gate National Park: 75 km Northwest of Nairobi, 1900 metres above sea level, 68 square kilometers.
Species involved
- Augur Buzzard — Buteo augur
People involved in this project:
Combined Federal Campaign # 10639
