938 C. Böhm et al.


2009). None of the other released birds have returned. The release programme was suspended in 2011 when the Syrian civil war started, and satellite tags on three of the released birds stopped transmitting in circumstances suggesting hunting. Nevertheless, releases remain a high priority con- servation action for the eastern flyway of the species.


Syria


The northern bald ibis was previously relatively common in the Al Badia landscapes of Syria (Serra et al., 2004). Little is known of the species’ former distribution in Syria, or the factors driving declines. The birds once migrated through Jordan, Saudi Arabia, Yemen, Eritrea and Sudan, with stop- over sites during the autumn migration between breeding sites in Syria (and Turkey, see above) and the wintering ground in the Ethiopian Highlands (Lindsell et al., 2009; Bowden, 2015). Hunting along the migration route through the western areas of the Arabian Peninsula (Jordan and Saudi Arabia) became unsustainable, and by the early 1900s the Northern Bald Ibis was believed to be extinct in Syria (Aharoni, 1928; Safriel, 1980). This left the last known colony of eastern northern bald ibis at Birecik, Turkey, with ,100 breeding pairs in the 1970s (Bowden et al., 2003). However, the first well-documented observa- tion in recent history was in 1985, when an expedition of the Ornithological Society of the Middle East recorded 12 northern bald ibises in the Taiz wetlands in Yemen. Birds were also sighted in western and south-western Arabia from 1985 (Brooks et al., 1987; Schulz & Schulz, 1992), giving rise to speculation that there was a hitherto undiscovered colony in the region. In 2002 a breeding colony of 7 birds was discovered in Syria’s Palmyra region (Serra et al., 2004). Subsequent


tagging and satellite-tracking of Syrian birds in 2006 con- firmed winter migration through Arabia to the Ethiopian highlands (Lindsell et al., 2009), c. 150 km from Addis Ababa, where sightings of northern bald ibises had been relatively common in the 19th century (Welch & Welch, 2004;Wondafrash, 2010). Historical data (Welch & Welch, 2004) and satellite-


tracking, in combination with field surveys in 2008, suggest young ibises disperse around the southern Red Sea basin to the Ethiopian highlands for 2–3 years before returning to their natal site in Syria, when close to sexual maturity. It is unknown to what extent juveniles rely on adults to guide them to optimum feeding sites, as is the case with the white stork Ciconia ciconia (Bildstein, 1984; Rotics et al., 2016), or whether the greater foraging time typical of ju- veniles mean they could struggle to find sufficient food (Brooks, 1987) and become too weak to migrate long dis- tances (as for the white ibis Eudocimus albus; Del Hoyo et al., 1992). In Arabia, where juveniles tended to winter (Lindsell et al., 2009; Serra, 2010), threats such as hunting and powerlines could be drivers of decline. On the adult wintering grounds in Ethiopia, disturbance and rainfall shortages are potential short-term threats, whereas pesticide use and the conversion of pastures to crops could be signifi- cant in the longer term (Serra et al., 2013). Following the Palmyra colony’s discovery, the site was


protected, but migration losses further reduced the tiny population (Serra, 2003, 2005). During 2003–2009 at least one adult failed to return from each migration, and of 24 juveniles leaving during 2002–2007 only seven returned (Table 4). Evidence suggests high mortality rates as a result of hunting in Syria and Saudi Arabia, in addition to electro- cution on power lines (Serra et al., 2014). Consequently, the Syrian population declined from seven birds in 2002 to five


TABLE 4 Population structure of the northern bald ibis colony at Palmyra, Syria, 2002–2015.Data fromSerra (2009, 2010), Serra et al. (2014), M. Abdallah, pers. comm. (2016) and M. Wondafrash, pers. comm. (2019).


New


Year 2002


2003 2004 2005 2006 2007 2008 2009 2010 2011 2012


20131 2014 2015


Adults 7


6 5 4 3 3 4 3 3 3 2


unknown 1 0


1Reduced monitoring in 2013 because of security situation. 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 breeders


Subadults Nests Fledglings 0


1 1


1 1 0


0 1 1 3 3 2 1 1 0


3 3 2 2 2 2 2 2 1 1 0


3 7 4 0 6 5 0 0 1 2 0


Fledglings migrated


3 7 4 0 6 4 0 0 1 2 0


Birds that left Palmyra


10 13 10 5


13 11 6 5 4 5 2


4 4 4 3


2 3


1


Birds in wintering grounds


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