Northern tanzania raptors project
An in-depth study of the secretarybird in the Serengeti and Tarangire ecosystems
Northern Tanzania is suffering from habitat degradation and loss of biodiversity. As a result of the growing human and livestock population, the grasslands in this region are severely overgrazed, woodlands have been exploited and conflict between wildlife and residents has greatly increased. Serengeti National Park itself, the most famous and largest protected area of northern Tanzania, has suffered in the recent years from encroachment by farmers and an increase in human settlement and mining activities on the western boundary. In the future, these activities could severely compromise this ecosystem and wildlife survival.
Since Serengeti National Park has never been systematically surveyed for diurnal raptors and records the highest number of secretarybird sightings in the Country, our study will initially focus on the secretarybird population of this Park.
The project undertakes a raptor road survey to gather accurate data about density and diversity of these birds. Our work will focus foremost on the secretarybird (Sagittarius serpentarius), including its ecology and some unknown aspects of its behaviour, such as vocal behaviour.
Since 2020, the secretarybird has been classified as Endangered in the IUCN Red List of Threatened Species; however, despite its conservation status, the species has been investigated in less than 20 studies and from what it is known to date, there are no published studies of this species across East Africa. The drastic reduction of the entire population in recent years and the ecological characteristics of the species, including territoriality, monogamy and potential philopatry, could lead to a decline in genetic diversity and inbreeding. In fact, conversion and fragmentation of habitats often lead to smaller and isolated populations and can reduce a species’ ability to disperse across the landscape. In these conditions, the stronger effect of genetic drift can quickly lower genetic variation and increase vulnerability to extinction.
Secretarybird provides essential ecosystem services and can be considered an excellent environmental indicator: for this reason, the assessment of its conservation status in Serengeti ecosystem along with the comprehension of its ecology and behavioural patterns will offer valuable insight into the balance of the ecosystem itself. Moreover, the project is giving the possibility of establishment of collaborations with Tanzania Wildlife Research Institute, with the primary focus of training students and Park’s personnel on bioacoustics and ecoacoustics for wildlife management and biodiversity conservation purposes.
We firmly believe that Serengeti National Park (SNP) could represent one of the last strogholds in East Africa that sustains numerous large-sized raptors, thanks to the stability of trophic resources and suitable environmental factors, despite the increase in human activities across the western borders.
The main objectives consist of establishing a precise estimate of secretarybirds’ density within the SNP and identifying the highest density areas, the key-conservation sites and the most important nesting areas. This includes the evaluation of abiotic and biotic factors which drive the spatial distribution and the realised niche of the target species and the potential threats to its survival.
The project has been approved by Tanzania Wildlife Research Institute (TAWIRI) at its 67th Joint Management Research Committee Meeting held in Arusha. Field work started on January 2023.
Sagittarius serpentarius (Miller, 1779)
IUCN Red List status: Endangered
Since 2011, the secretarybird has been classified as Vulnerable and in 2020 as Endangered. The species is also included in the Appendix II of CITES (CITES, 2021). Unfortunately, accurate data on population trends are not available, although monitoring of raptors in South Africa, Kenya, Botswana and a few other countries witness a significant decline, probably owing to habitat degradation, land-use changes, human disturbance and hunting. Current estimated population size ranges between 6,700 to 67,000 mature individuals.
The secretarybird is a large bird of prey widespread in Sub-Saharan Africa; it is instantly recognisable for having an eagle-like head and body on crane-like legs. The weight ranges from 3.74 to 4.27 kg and females, slightly larger than males, can reach a wingspan of 2.1 meters. Singles, pairs and pairs with juveniles are locally common in grasslands and wooded grasslands often bordered by open woodlands (from sea-level to 2000 m); it is not found in forest or in habitats excessively rich in shrubs. Its preys are mostly locusts, grasshoppers, beetles, small mammals, lizards and snakes. While hunting, secretarybird runs after prey, often with the wings spread and kills by striking with swift blows of the feet. The species is monogamous and territorial, leads a terrestrial life and the breeding period varies according to latitude and different environments. Females lay from 1 to 3 eggs per clutch and the juveniles tend to fledge after 10-12 weeks. Its territory, which can vary between 20 and 100 square kilometers per pair, depends on food availability and the type of habitat. It would also appear that the species is philopatric.