By DickDaniels (http://carolinabirds.org/) (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
Africa and Asia. Much of sub-saharan Africa with a small and declining outlier population in southern Iraq.
During the 1970s and 1980s several zoos thought it would be a good idea to establish free-flying population of Sacred Ibis but they took to the challenge rather well and free-living colonies became established. As many as 1,200 pairs were breeding in France in the early 2000s. Research has identified the Sacred Ibis as being of European concern as an invasive species and it is subject to a control and eradication programme. It is confiding of humans and adapts to urban situations with the offerings of human food wastage in bins and tips and it can be a voracious predator of scarce native wildlife: two birds ate all the eggs from 30 Sandwich Tern nests in the space of four hours. It breeds or has bred in the wild in France, Spain (since 1974), Portugal (since 1998), Italy (since 1989) and the Netherlands (since 2002).
In France, around 1,700 breeding pairs were present in 2006 and 8,327 Sacred Ibises were culled between 2007 and 2016. The task is becoming more difficult as the population declines and the birds become more wary, but the numbers in the Camargue are now almost nil.
Despite a nomadic disposition in its native range and post-breeding movements of up to 1000km, this is an improbabale natural vagrant. British sightings, the first being in 1995, almost certainly stem from introduced continental wanderers. The UK's Non-native Species Secretariat has an action plan to prevent the Sacred Ibis colonising Britain.
The Sacred Ibis in Europe; Yesou et. al. Brit. Birds 110: 197-211; April 2017.