The secretarybird, BirdLife South Africa’s Bird of the Year 2019, is vastly understudied, but 10 tagged juveniles have given scientists interesting insight into their dispersal behaviour.
Secretarybirds are apex predators and assist in controlling rodents, insects and reptiles in the grasslands and open savannas of Africa, which makes them more resilient than specialist raptors. They kill their prey by kicking it with a force five times their own body weight. Their presence is indicative of a healthy ecosystem, and losing the secretarybird to extinction would lead to increases in populations of agricultural pest species that cause large-scale damage to crops.
The Secretarybird Project from Birdlife South Africa
From 2012 to 2015, 10 GSM-GPS solar trackers were fitted to 10 juvenile secretarybirds on their nests at the age of approximately eight weeks. The central region in South Africa was well studied, with two siblings, Archer and Strider, emerging from the same nest in Calvinia in the Northern Cape. The birds spent an average of 83–100 days in their natal territories before dispersing. Subadult birds have grey eyes, brownish plumage over most of their body and shorter tail rectrices, with yellow bare facial skin.
The immature birds showed high variability in maximum distance travelled from the nest and timing of dispersal from their natal territories. Kizuna only travelled 9km, whereas Archer travelled over 1 000km within two weeks of leaving the nest. Most of the birds dispersed more than 150km from their natal nests, before returning to their natal region. Taemane travelled to the coast of KwaZulu-Natal and back to Warden in the Free State, suggesting evidence for natal philopatry in this species.
Taemane provided interesting insight into breeding ages. He was the only bird in the study to hatch two chicks of his own, two years and nine months after hatching.
The wide-ranging nature of the juveniles exposes them to a diverse range of threats and a better understanding of their movements will help develop appropriate conservation strategies for this terrestrial raptor. Sadly, two of the young birds, Koffie and BLiNG, perished in the study due to human-related infrastructure. Artemis, due to inexperience, flew into a cliff while flying on a misty morning.
Dispersal movements of young secretarybirds
Large dispersal movements in large terrestrial birds are common and the general consensus is that it aids gene flow. In a perfect world, this would potentially lead to range expansion of the species to new habitats. It is not clear what drives these big movements. The birds flew over 330km of plantations, monoculture and farmlands that did not constitute as viable secretarybird habitat, so increasingly lack of suitable available habitat could be one of the factors driving these big movements.
Threats to secretarybirds
Secretarybirds face a myriad of threats from collisions with motor vehicles, electrical infrastructure, and fences, to drowning in uncovered farm reservoirs and secondary poisoning from ingestion of prey containing pesticides. During our study we were able to confirm three mortalities of our tracked birds – two as the result of infrastructure. Mortality rates in juvenile birds of prey are high, leading to slow recruitment of young birds into the breeding populations, which is cause for concern. Losing the secretarybird to extinction would mean the loss of the sole member of a unique African bird family – the Sagittariidae.
How the secretarybird got its name?
Many believed this 1.5m terrestrial raptor was named after the European secretaries of the 1800s because of the quills on their heads. However, it is more likely linked to its Latin name, Secretarius serpentarius, meaning ‘archer of snakes’.Frontier farmers of the 1700s in the Cape of Good Hope attracted secretarybirds to their homesteads as pest controllers, naming the bird Secretarius,which loosely translates to a sentry or guard. The secretarybirds were redescribed as archers as they moved through fields hunting snakes
How to manage secretarybird populations in the future
In response to this Birdlife South Africa is trying to recreate the culture of 1700s farmers among local farmers through the Secretarybird Project. Birdlife South Africa hopes that by understanding the ecology of secretarybirds they can develop scientifically robust conservation strategies. Initiatives such as biodiversity stewardship are proving to be effective, whereby private landowners are encouraged to manage their properties in ways that provide areas of suitable habitat for these birds. An example is the Wilge Stewardship Initiative, which has been rolled out in the eastern Free State. The project has brought approximately 45 000 hectares of grassland into the stewardship programme, which promotes positive land management practices that benefit secretarybirds. If we don’t protect these birds the last place they will be seen is on the front cover of the second edition of Roberts Bird Guide.
Written by Melissa Whitecross
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