An assessment of ecological conditions and threats at the Ethiopian wintering site of the last known eastern colony of Critically Endangered Northern Bald IbisGeronticus eremita

Abstract

The long-range, migratory eastern relict population of Northern Bald Ibis Geronticus eremita has been steadily declining since the time of discovery in 2002, despite the protection programme in place at the breeding grounds in Syria. Assessing the ecological conditions and threats along the migration route and at the wintering site, both discovered in 2006, has become a priority for this "Critically Endangered" species. Adult ibises spent the winter at the same site on the central Ethiopian highland plateau, from August until mid-February during five consecutive winters (2006)(2007)(2008)(2009)(2010)(2011). The wintering site was surveyed during four field visits and assessed through a spatial analysis of 1,067 satellite locations. The site is in an agro-pastoral landscape, inhabited by a settled community of people living in relatively poor and isolated conditions. Home range analysis based on kernel distributions showed that the bald ibises used a core range area of 9.1-19.0 km² (confirmed by direct visual observations in the field) and an extended range area of 61.0-126.1 km². These figures are c.20 and 60 times smaller, respectively, than those calculated for the breeding site in Syria. Eighty-one percent of the core area in Ethiopia was used in all five years confirming the birds' fidelity to this wintering site. Ibises preferred to forage in wet or dry pastures and in recently cut hayfields, and avoided tall grass, uncut hayfields and cultivation. Despite dependence on human-created habitats, human disturbance observed in the field was minimal. The main short-term threat for the ibises was judged to be the potential raising of attention on the part of the local community specifically towards these few individual ibises. In the medium term, the main threat comes from the conversion of pastures into crops and the potential use of fertilisers and pesticides.

Accounting for the low survival of the Critically Endangered northern bald ibisGeronticus eremitaon a major migratory flyway

“…Their route is part of a major flyway for several threatened Afro-Palearctic migrants (BirdLife International, 2010), thus factors driving the decline of ibis in this region may also be of concern for other species. Although we did not observe any short-term threats at the wintering site in the Ethiopian highlands (Serra et al, 2013), no immature birds were observed in Ethiopia during four consecutive winters (2006–2010) despite their confirmed departure from the breeding site (Serra et al, 2007; Serra & Wondafrash, 2009).…”

“…In summary, the observed difference in survival rates between immature and adult northern bald ibises can be accounted for by their use of different wintering areas and the relative threats in these areas. Since immature ibises spend more time than adults in western Arabia during the year they are exposed to greater threats to their survival for a longer period compared with the adults wintering in Ethiopia (Weimerskirch et al, 2006; Serra & Wondafrash, 2009; Guillemain et al, 2010; Serra et al, 2013); the relative inexperience of immature birds increases their vulnerability to these threats (Francis et al, 1992; Van den Bossche, 2002; Menu et al, 2005).…”

“…Since immature ibises spend more time than adults in western Arabia during the year they are exposed to greater threats to their survival for a longer period compared with the adults wintering in Ethiopia (Weimerskirch et al, 2006;Serra & Wondafrash, 2009;Guillemain et al, 2010;Serra et al, 2013); the relative inexperience of immature birds increases their vulnerability to these threats (Francis et al, 1992;Van den Bossche, 2002;Menu et al, 2005). Since immature ibises spend more time than adults in western Arabia during the year they are exposed to greater threats to their survival for a longer period compared with the adults wintering in Ethiopia (Weimerskirch et al, 2006;Serra & Wondafrash, 2009;Guillemain et al, 2010;Serra et al, 2013); the relative inexperience of immature birds increases their vulnerability to these threats (Francis et al, 1992;Van den Bossche, 2002;Menu et al, 2005).…”

Influence of feeding ecology on breeding success of a semi-wild population of the critically endangered Northern Bald IbisGeronticus eremitain southern Turkey

“…While the birds breed mostly inside and adjacent to the breeding station, the principal habitats that are regularly used by free-roaming Northern Bald Ibis are: (i) short grasslands and marsh lands along the banks of the river Euphrates, which are grazed by sheep and cattle and used to dispose of human and animal excrement from nearby sewage treatment plants and poultry farms. These grasslands are similar to the habitat used by the species at breeding grounds in Syria (Serra et al 2008) and at wintering grounds in Ethiopia (Serra et al 2013), and have generally loose soil, with very short vegetation (< 20 cm) and often extensive areas of bare ground. (ii) A tree nursery with tall shady trees of various native and exotic species, interspersed with irrigated fields of small tree seedlings on fertile dark soil.…”

“…In contrast to the surviving sedentary population in Morocco, the population in Syria and Turkey is migratory and spends the winter in Ethiopia (Serra et al 2013). However, of 21 birds tracked with satellite transmitters from Turkey since 2005, none returned to breeding grounds (Taner Hatipoğlu pers.…”