Northern bald ibis 937
supplementary freshwater has improved breeding productiv- ity (Smith et al., 2008). The population is apparently depend- ent on littoral steppe habitat and a traditional agriculture system where large areas are left fallow and grazed by sheep for several years at a time. This supports high biomass and diversity of the invertebrates and reptiles that are the main prey for the ibis (Aghnaj et al., 2001). There is renewed hope that the birds may naturally re-
colonize former breeding sites in Morocco (as predicted in Böhm&Bowden, 2010, 2016). In 2017 breedingwas confirmed for the first time in several decades in a small subcolony near Immsouane (Aourir et al., 2017), 30 km north of Tamri.
Algeria
In Algeria, most of the data on the historic distribution of the species are from the 1950swhen 12 colonies were known. Another colony was discovered in 1974 in the north-western El Bayadh region, persisting until the late 1980s(Fellous, 2011). Northern bald ibises in Algeria were migratory, arriving at breeding sites towards the end of winter in February and earlyMarch, and departing after breeding in late summer. The Algerian colonies were historically estimated to be
c. 300–400 birds, but signs of population decline were noted in the 1950s (Collar & Stuart, 1985). Causes of decline included hunting, habitat loss caused by overgrazing, and droughts in the 1970s and 1980s, by which time ,20 indi- viduals remained. The northern bald ibis became extinct in Algeria during the late 1980s or early 1990s (Fellous, 2004). Questionnaires circulated by Algeria’s National Agency
for Nature Conservation showed that in autumn 2004 two birds were seen flying at Thiet Ould Moumen, 2km north of the last known breeding site for this species in Algeria; there have not been any subsequent observations.
Eastern subpopulations
Turkey The northern bald ibis was once present through large areas of south-eastern Turkey. By the first half of the 1900s there were five documented colonies, one with as many as 3,000 birds (Akçakaya, 1990). This population underwent a dra- matic decline from the late 1950s, principally resulting from the use of DDT to combat insect pests (Hirsch, 1979, 1980; Hatipoğlu, 2016). Following deaths and reproductive failure, the breeding population was reduced to 23 pairs by 1973 (Arihan, 1999). In 1977 Turkey’s General Directorate of Nature Protection and National Parks (now Doğa Koruma ve Milli Parklar Genel Müdürlüğü) initiated a project in collaboration with the Society for the Protection of Nature, Turkey (the former BirdLife Partner), to save the remaining wild northern bald ibis population in Birecik. A breeding
TABLE 3 Breeding productivity of the northern bald ibis in Birecik, Turkey.
Year 2006
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
Pairs 15
18 12 21 21 20 24 32 38 41 35 47 59
Fledglings 26
30 21 25 30 27 37 49 51 59 56 64
113
Fledglings/pair 1.7
1.7 1.8 1.2 1.4 1.4 1.5 1.5 1.3 1.4 1.6 1.4 1.9
station was established 3 km north of the town of Birecik, and 41 birds were caught during 1977–1989 and taken into semi-captivity. A similar number of birds were left in the wild. The captive birds were initially enclosed throughout the year, but a decision was made to release them from the aviaries each spring (in mid February, around the dates they would have arrived back from migration), and they were encouraged to breed on the rock ledges and in nest boxes outside the aviaries, with supplementary food provided twice per day. This spring release practice con- tinues today, and the free-flying birds forage in the sur- rounding area during the breeding season and until they are recaptured each July. This prevents migration and is believed to improve survival rates, although a few birds (mainly juveniles) have disappeared before recapture, and it is possible some of them have migrated south. Unfor- tunately, the remaining fully wild population continued to decline, and was declared extinct in 1989 (Akçakaya 1990; Yeniyurt et al., 2016). The semi-wild population has increased despite a num-
ber of sudden deaths of chicks and adult birds, notably during 1998–2000, in part caused by contamination of supplementary food. By December 2018 there were 263 birds, of all ages, in seasonal captivity at Birecik (Table 3). Doğa Derneği (BirdLife Turkey) together with Doğa Koru- ma ve Milli Parklar Genel Müdürelüğü have monitored the breeding population since 2003 (Yeniyurt et al., 2016), and are working to enhance veterinary conditions in the breeding sta- tion in Birecik, to increase the size of the semi-wild colony and thereby re-establish the migratory population at Birecik. From2007 the release and tracking of juvenile birds from
the Birecik Breeding Centre confirmed that the Turkish nor- thern bald ibis had not lost the ability to migrate (Hatipoğlu, 2016). In 2007 juveniles moved south, following a similar trajectory to that of the Palmyra birds, and one bird re- turned to the colony in spring 2008, although the overwinter location of this individual was not identified (Lindsell et al.,
Oryx, 2021, 55(6), 934–946 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605320000198
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