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

Abstract

SummarySafeguarding threatened species in captivity is a promising management approach, but evaluating the performance of captive programmes is essential to assess reintroduction potential. The eastern population of the Northern Bald Ibis, Geronticus eremita, used to be a locally common migratory bird species, but catastrophic population declines throughout the past century have resulted in a single population in southern Turkey that forages freely during summer but only survives in captivity during winter. We examined whether breeding success of this semi-wild colony was comparable to breeding success of previous wild populations, and to what extent breeding success was influenced by supplementary feeding and wild foraging in habitats near the breeding station. Average productivity from 2009 to 2015 was 1.12 fledglings per nesting pair (range 0.96–1.19). In 2013 and 2014, there was no correlation between attendance at supplementary feeding events and productivity, and breeding birds attended on average only 35% of supplementary feeding events. Birds that were frequently observed at a local tree nursery raised fewer offspring, while birds observed more frequently in poldered cultivation, and in particular in mint crops or in fields covered with manure, raised on average more offspring. Foraging success was highest in meadows and cropland, particularly in mint crops and fields covered in manure, and lowest at the tree nursery. We speculate that selection of highly suitable wild foraging habitat such as mint crops or fields covered in manure allows the Northern Bald Ibis to raise more fledglings than exclusive reliance on supplementary food provided at the breeding station. Establishing a second breeding colony of this species in Turkey will therefore require a careful assessment of the suitability of wild foraging habitat in the vicinity of suitable nesting opportunities.

Back into the wild: establishing a migratory Northern bald ibis Geronticus eremita population in Europe

“…In Europe, the birds reach a state of migratory readiness at the beginning of August. There are indications, from different release projects, that juvenile Northern bald ibis during their first autumn migration follow an internal vector that heads them south/ south-west Serra et al, 2015;Yeniyurt et al, 2016). However, as known from studies of White stork Ciconia ciconia and other species, juveniles depend on social information from more mature conspecifics to reach common wintering sites for the first time (Chernetsov et al, 2004;Flack et al, 2016).…”

The Northern Bald Ibis Geronticus eremita in Morocco since 1900: Analysis of ecological requirements

“…For future recolonisation inland and along the coast, suitable feeding habitats within a radius of 5–15 km provide favourable conditions for successful chick rearing, while far away feeding grounds with a radius of 25 km and more lead to corresponding additional costs (time and flight energy) which may have a negative effect on the breeding success. The restriction to a distance of 5–15 km for suitable foraging habitats corresponds to published field observations (Rencurel 1974, Collar & Stuart 1985, Akçakaya 1990, Boehm 2016, Yeniyurt et al 2017) and a questionnaire (Fellous 2011). Distant feeding habitats 25 to 35 km away probably reduce the breeding success due to higher exposure to predation (Serra et al 2009) and deaths of chicks in the nest suggesting starvation (Bowden et al 2003).…”

How human intervention and climate change shaped the fate of the Northern Bald Ibis from ancient Egypt to the presence: an interdisciplinary approach to extinction and recovery of an iconic bird species

“…This was generally assumed to be the end of the last wild colony in the Middle East (27). But in fact, it was not.…”

“…From historical reports this is evident for the former European population (11–13,16). It is also known for most former breeding sites in Moroccan and Algerian Atlas (6,60), in Turkey (25,27) and for the former wintering site in Ethiopia (57). It is assumed that the presence of the species in various regions was dependent on human beings which cleared or drained the land and kept it open through farming or grazing (12,13,16,60).…”