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Carter, Jo Ellen – Home range, habitat utilization, and prey delivery patterns of the Mauritius Kestrel (Falco punctatus)

Photo of Mauritius Kestrel

Photo courtesy of Bush Warriors via World Parrot Trust

The forest-dwelling Mauritius kestrel (Falco punctatus) is considered to be the rarest falcon in the world. Since colonization of the island, the kestrel’s available habitat has been reduced to the steep ridges and gorges. These remaining areas are being altered by the invasion of exotic plant species. In this study I used radio tracking data to determine home range sizes of kestrels nesting in mixed native and non-native habitats. Home range size averaged 1.173 km2 and ranged from 0.079 to 1.610 km2. Chi-square analyses were used to determine what habitat types within the home ranges were used more or less than expected based on availability. Mixed exotic woodland, a habitat similar in structure to native habitat, and agricultural areas were used significantly more than expected. In some instances, native forest was used significantly less than expected. These results suggest that the kestrels are not exclusively dependent on native habitat but are able to utilize certain non-native habitat types.

Hunting effort and success of the Mauritius kestrel were examined by studying the rate and patterns of prey deliveries to the nest. Two-way ANOVA were used to determine if prey deliveries depended on time of day or weather type. I compared patterns of prey deliveries to the activity patterns of Phelsuma, the primary prey species, to assess whether or not the kestrel was an optimal forager. Prey deliveries varied significantly with time of day revealing a clear pattern. Prey deliveries were highest in early to mid-afternoon when Phelsuma were most active. Weather also had a significant effect on prey deliveries, primarily owing to a decrease in prey deliveries during rain. The highest rate of prey deliveries occurred during cloudy weather possibly owing to greater prey vulnerability during this weather type. At one site, the kestrel regularly brought in a larger prey species and had a lower prey delivery rate than kestrels at other sites. These results suggest that the kestrels may pattern hunting effort after the activities of their prey, and that they may adjust effort based on experience. Optimal foraging could be one conclusion drawn from these findings.

Thesis Abstract