The restoration of the Mauritius Kestrel Falco punctatus population

Abstract

By 1974. the Mauritius Kestrel Falco punctatus had declined to only four known wild birds, including one breeding pair, as a result of habitat loss and pesticide contamination. A conservation project begun in 1973 has used many management techniques including captive breeding, supplemental feeding of wild birds, provision of nestboxes, multiple clutching, egg pulling, artificial incubation, hand rearing and release of captive-bred and captive-reared birds by hacking, fostering and predator control. A total of 331 kestrels were released in the 10 years up to the end of the 1993-1994 breeding season: one-third of these were captive bred, the rest were derived from eggs harvested from the wild. About 257 (78Yo) released birds survived to independence and 61% of independent juveniles survived their first winter. Although at least 71% of ringed birds attempted to breed in their first year, only 38% of the nests of first-year females successfully fledged young, averaging 1.7 per successful nest. Older females fledged young from 64% of nests, fledging an average of 2.0 per successful nest. The breeding success of hacked birds was similar to that of parent-raised kestrels, though the clutches of hacked birds tended to be larger. Annual replacement of birds holding territories averaged 17% for both sexes. By the 1993-1994 season, an estimated 56-68 pairs had established territories in the wild with a postbreeding population, including floating birds and independent young, of 222-286. Most of the kestrels were in three sub-populations, two of which were derived entirely from released birds. Mauritius Kestrels are relatively sedentary: 89% of ringed birds found nesting were less than 5 km from their release or fledging site. Since the pesticides responsible for their decline are no longer used, the number of Mauritius Kestrels should continue to rise through natural recruitment. The distribution of suitable habitat suggests that an eventual population of 500-600 kestrels on Mauritius is possible. Due to its outstanding success, the release programme for the Mauritius Kestrel ended after the 1993-1994 breeding season, though the population will continue to be monitored carefully for at least the next 5 years.

Population regulation of territorial species: both site dependence and interference mechanisms matter

“…The study area covers 163 km 2 , encompassing a predominantly forested mountainous area buffered by agricultural land (almost exclusively sugar cane). The surrounding agricultural land coupled with the relatively short dispersal distance observed [27,28] ensures that at present this is a closed population remaining isolated from two other kestrel populations in Mauritius.…”

“…The restoration programme involved the release of 46 captive-produced kestrels at six sites in the centre of the study area from 1987/1988 to 1989/1990, plus some additional management until 1994/1995 (see [27] for details). The population increased rapidly from one breeding pair in 1988/1989 up to a stable level of 40-44 breeding pairs since the early 2000s.…”

Climate change and the risks associated with delayed breeding in a tropical wild bird population

“…Our study area covers 163 km 2 , encompassing a predominantly forested mountainous area bordered by agricultural land cultivating primarily sugar cane [19]. Our study population was extirpated by the 1960s, but reintroduced at the end of the 1980s as part of a recovery programme [20]. Subsequent to its reintroduction, the population has grown and has now become stabilized at approximately 42-45 breeding pairs.…”

Restricted dispersal reduces the strength of spatial density dependence in a tropical bird population

“…Agricultural land extends for a considerable distance, to the extent that due to kestrels' short dispersal ability ( Jones et al 1995) it creates a dispersal barrier. Consequently, this population is a closed system.…”