Black Harrier

The Black Harrier (Circus maurus) is a medium-sized raptor, cloaked in a predominantly dark plumage. When perched, it appears almost entirely black, but reveals a striking white rump and flight feathers when it takes to the air. Its wingspan stretches between 105 to 115 centimeters, and it measures 44 to 50 centimeters in length. The species exhibits the characteristic morphology of harriers, with narrow wings, a slender body, and an elongated tail. Both sexes don similar plumage, while juveniles are distinguished by buff underparts and a heavily spotted breast.

Distribution and Migration

This African harrier's range spans from South Africa to Botswana and Namibia, favoring the Western and Southern coastal plains of South Africa. Its distribution is polarized, avoiding transformed and cultivated lands for nesting, though it may forage in these areas. The Black Harrier undertakes a unique west-east migration within the southern half of South Africa, including Lesotho, with individuals showing variability in their migratory patterns. They do not migrate as pairs and exhibit different non-breeding areas. Migration is thought to be a response to food scarcity, with the post-breeding migration occurring at almost twice the speed of the pre-breeding migration.

Diet

Specializing in small mammals, the Black Harrier predominantly preys on rodents such as the Four-striped Mouse (Rhabdomys pumilio), supplementing its diet with birds and occasionally reptiles. Diet varies regionally, with a greater consumption of birds inland compared to coastal areas. Seasonal changes and local weather conditions, such as temperature and rainfall, influence the proportion of small mammals in its diet.

Breeding

The Western Cape province hosts the majority of breeding pairs, with loose colonies forming around coastal wetlands. Breeding in Namibia is suspected but unconfirmed. The Black Harrier nests on the ground within tall vegetation, laying eggs from June to November. Clutch sizes range from two to four eggs, incubated for 35 days. Fidelity to breeding areas and natal philopatry are observed, though significant breeding dispersal can occur. A phenomenon of taking a 'Sabbatical year' from reproduction after a breeding year is suggested but requires further evidence.

Pollutants

Carotenoid pigments, which contribute to the yellow, orange, and red coloration in avian species, are affected by pollutants. These pigments are crucial for communication and social interactions. In Black Harrier nestlings, diet influences carotenoid levels, and pollutants such as DDT have been shown to reduce circulating carotenoids and coloration, potentially impacting communication processes.

Diet and Feeding

The Black Harrier feeds by flying low over its hunting grounds to catch prey, with a diet that varies depending on regional and seasonal factors.

Conservation Status

With fewer than 1000 birds remaining, the Black Harrier is currently listed as Endangered on the IUCN Red List. Habitat destruction, particularly of the fynbos shrubland, due to agriculture and urban expansion, as well as alien plant invasion, has led to a decline in population. Displacement to montane habitats has resulted in less successful breeding compared to coastal sites with fynbos.