The impact of man on the Malagasy flora and fauna has been severe. Human hunting and, perhaps, climatic changes probably led to the extinction of several bird species in historical times. At least one species of ground-roller, Brachypteracias langrandi, became extinct after the Holocene, most probably because of natural environmental changes.
During the twentieth century, man’s impact has intensified to alarming levels. Habitat loss and the degradation and fragmentation of forest are by far the most important factors influencing populations of ground-rollers. The loss of natural habitat has been dramatic in some areas, especially in the lowland rainforest. Slash-and-burn agriculture by subsistence farmers has the greatest negative effect on natural forest habitats, but other human activities, such as charcoal production, timber-harvesting and fuelwood-gathering, and the grazing of the understorey by cattle, also cause habitat degradation. As all ground-rollers are forest-inhabiting species, and probably require large tracts of undisturbed forest, these activities represent a serious threat to their continued survival. The species most seriously affected by forest degradation is the Long-tailed Ground-roller, since its natural habitat, sub-arid thorn-scrub, has undergone an alarming degradation rate of about 30% in the 25 years since the mid-1970’s.
Hunting by humans represents a further serious threat to all ground-roller species, and the eggs of at least the Long-tailed Ground-roller are also taken. Bird-hunting is conducted mostly by people walking along forest trails that link different villages, and it is targeted at large-bodied terrestrial species such as rails, couas and ground-rollers (see Relationship with Man). Hunting of this kind may thus reduce ground-roller populations near villages and along well-used paths. In addition, dogs and introduced black rats (Rattus rattus) probably take a toll on ground-roller populations.
As regards conservation status, three of the five species of ground-roller are currently listed as Vulnerable. The Rufous-headed is considered Near-threatened, as, until recently, was the Pitta-like. These status categories reflect not only the restricted distribution of the Brachypteraciidae, but also the continuing destruction of their natural forest habitat. The relentless destruction, degradation and fragmentation of these forest areas result in the distribution of the four rainforest-inhabiting species becoming more and more patchy. In their favour, however, is the fact that these four species are distributed along the entire length of the Eastern Malagasy rainforest belt, and all four occur within a number of protected areas. Both the Scaly and the Rufous-headed Ground-rollers are present in twelve protected areas, while the Short-legged occurs in 14, and the Pitta-like Ground-roller can be found in as many as 18 reserves.
By contrast, the fifth species, the scrub-inhabiting Long-tailed Ground-roller, is restricted to a narrow coastal strip in south-western Madagascar. Moreover, while the four rainforest species are found in several protected areas, not a single reserve has been set up within the range of the Long-tailed Ground-roller. Human activities such as slash-and-burn agriculture, combined with charcoal production, the harvesting of timber, cattle grazing and hunting, threaten its continued survival. This species can with some justification, therefore, be considered the most threatened species of the Brachypteraciidae.
The Short-legged and the Scaly Ground-rollers are also under serious threat, since they prefer rainforest at low to middle altitudes, where levels of deforestation are much higher than those at higher altitudes. Of these two species, the Scaly Ground-roller was until recently considered the rarer, but this conclusion may be erroneous and could be a reflection of the species’ more secretive nature. The Short-legged Ground-roller may even be the more threatened of the two, as it has not yet been observed in degraded forest habitats. These suboptimal habitats appear to be used, at least occasionally, by the Scaly Ground-roller, although that species has a more patchy distribution and is rarely found above 950 m, being most common in lowland rainforest below 600 m, whereas the Short-legged Ground-roller occurs at up to 1500 m. Much rainforest still remains between 800 m and 1200 m, but very little is left below 600 m.
Both the Pitta-like Ground-roller and the Rufous-headed Ground-roller can be found in high-altitude rainforest, and they appear in fact to be commoner there than in lowland rainforest. High-altitude rainforest, because of its very humid nature, its relative inaccessibility and its low timber value, is less vulnerable than that at low elevations. Moreover, both species have been observed in degraded or secondary habitats. The Rufous-headed Ground-roller was until recently considered Vulnerable, but it has now been found to be numerous within its preferred habitat of mossy forest or upper montane forest, and its range has also been found to be more extensive than previously thought. Nevertheless, despite its downgrading to Near-threatened, it is stressed that any notable decline in population or major loss of habitat could rapidly return it to the Red List. The distribution of the Pitta-like Ground-roller is rather patchy, as it occurs in isolated forest fragments, such as Amber Mountain National Park and Ambohitantely Special Reserve; it does, however, have the largest range of any member of the family, and it is often found adjacent to the other species in slightly more degraded or drier forest.
To ensure the future survival of the ground-rollers, serious conservation action needs to be taken. The Malagasy government has acted to preserve biological diversity and to reduce deforestation levels. The network of protected areas is expanding, and at the beginning of the year 2000 the total land area afforded protection approaches 3% of the island’s 587,045 km2. Unfortunately, however, this network so far covers only the ranges of the four rainforest-inhabiting species, while no existing reserve is within the range of the Long-tailed Ground-roller. It is to be hoped that plans to create a new reserve in the south-western part of the island will be realized in the near future. The fact that the entire ranges of all five brachypteraciid species were recently incorporated into the system of Endemic Bird Areas established by BirdLife International should also help to focus more attention on these endemic bird species.
All species of ground-roller, in order to maintain viable populations, will need to be able to live in a landscape that is likely to become more degraded and more fragmented. There is, therefore, a requirement for many more studies to be carried out with the aim of determining each species’ precise habitat requirements, population size, reproductive output, dispersal pattern, and causes of mortality. Such information will be invaluable when it comes to the establishing of detailed conservation strategies. Whether most deaths are due to humans, dogs or introduced rats, for example, would seem to be of some importance.
As a final thought, there remains the hope that the future relationship between man and ground-rollers will be a more mutually beneficial one, as, for instance, through increased ecotourism. It appears that ecotourism is already playing a significant part in the battle for the preservation of biodiversity, but the destruction and general degradation of habitat that are still apparent throughout the island will undoubtedly require specific measures to bring them properly under control.