Reunion Harrier

Adult Reunion Harriers exhibit a striking plumage with a blend of gray and brown, which provides excellent camouflage in their natural habitats. Males typically show a lighter gray body with darker wingtips, whereas females are larger and have more pronounced brown streaks across their plumage. Juveniles are usually browner overall, lacking the distinct gray tones of adults, making them somewhat harder to identify. The harrier's wings are long and broad, which facilitate its soaring behavior, a key identification feature when seen in flight. Its tail is relatively long and rounded, assisting in agile maneuvering during hunting. When perched, the Reunion Harrier maintains an upright posture, with its sharp talons prominently visible, ready to grasp prey. Confusion with similar species is mitigated by its unique size and coloration, but birders should note the distinct barring patterns on the wings and tail when identifying this species. The silhouette of the Reunion Harrier in flight, with wings held in a slight V shape, is also a good field mark for identification.

The diet of the Reunion Harrier primarily consists of small mammals, birds, and reptiles. Rodents form a significant part of its diet, particularly introduced species that have proliferated on the island. The harrier also preys on small birds, taking advantage of its agile flight to capture them mid-air. During the breeding season, when energy demands are high, it may increase its intake of larger prey items. The Reunion Harrier employs a variety of hunting techniques, including soaring and quartering over open fields to locate prey, followed by swift, low-level attacks. Its keen eyesight allows it to spot potential prey from a considerable distance, making it an effective hunter. The harrier is predominantly diurnal, with peak hunting activity occurring during the early morning and late afternoon.

The Reunion Harrier exhibits solitary and territorial behavior, particularly during the breeding season when pairs establish and defend their nesting territories aggressively. Courtship displays involve aerial acrobatics, with males performing impressive sky dives to attract females. These displays not only reinforce pair bonds but also establish territory boundaries. Unlike some other raptors, the Reunion Harrier does not form large flocks, though loose associations may occur outside of the breeding season when individuals exploit abundant food resources. The bird's response to predators involves alarm calls and defensive postures, particularly when defending nests. Daily activity patterns are largely dictated by prey availability, with most hunting occurring during daylight hours. The harrier's adaptability to different environments reflects its flexible behavioral strategies, allowing it to capitalize on diverse ecological niches.

The Reunion Harrier constructs its nest on the ground, typically in areas with dense vegetation that provide cover from predators. Both males and females participate in building the nest, using materials such as twigs, leaves, and grass. The typical clutch size ranges from two to four eggs, with the female primarily responsible for incubation, which lasts about 30 to 34 days. Males play a crucial role in providing food during this period. After hatching, chicks remain in the nest for approximately six to eight weeks before fledging. Parental care continues after fledging, with both parents involved in feeding the young until they are fully independent. The Reunion Harrier typically raises one brood per year, although favorable conditions may occasionally allow for a second.

The Reunion Harrier's vocalizations include a series of sharp, high-pitched calls often heard during flight or when alarmed. Its primary song consists of a repetitive 'kek-kek-kek' sound, which serves as both a territorial marker and a communication tool between mates. Alarm calls are more abrupt and louder, signaling the presence of potential threats. During the dawn chorus, the harrier's calls can be heard echoing across its territory, asserting its presence. These vocalizations bear resemblance to those of other harriers, though the Reunion Harrier's calls are notably sharper and more frequent.

• 1The Reunion Harrier is the only endemic raptor of the Mascarene Islands, highlighting its unique ecological role.
• 2Unlike many raptors, the Reunion Harrier builds its nest on the ground, making it vulnerable to invasive predators.
• 3The population of the Reunion Harrier has fluctuated significantly due to habitat changes and conservation efforts.
• 4Females are larger than males, a common trait among harriers, aiding in their role as primary nest defenders.
• 5Despite being endangered, the Reunion Harrier has shown resilience by adapting to various habitats on Reunion Island.
• 6The harrier's flight displays during courtship are not only for attracting a mate but also for reinforcing territory boundaries.
• 7Reunion Harriers can spot prey from over 100 meters away thanks to their exceptional eyesight.

The Reunion Harrier is classified as endangered by the IUCN, with population estimates suggesting fewer than 500 mature individuals remain. Habitat loss due to agricultural expansion and urban development poses the most significant threat, alongside predation by introduced species such as cats and rats. Conservation efforts focus on habitat restoration and predator control, with several protected areas established to safeguard critical nesting and hunting grounds. Historical population declines underscore the importance of these measures as the harrier's survival hinges on continued conservation intervention. Public awareness campaigns also play a role in fostering local support for preservation initiatives.