“While in Taiwan we saw the African Sacred Ibis (Threskiornis aethiopicus aethiopicus) that accidently entered the wild more than 35 years ago when a zoo enclosure (aviary) in the north (Hsinchu County) was damaged during a typhoon. Populations soon mushroomed from 200 in 1998, 500-600 in 2011 and 2,500-3,000 in 2018, with birds found on islands 190km off the coast near mainland China.
“I have been reflecting on the impact of feral/imported birds on local bird populations after watching them and my write up on the African Sacred Ibis as an invasive species is found HERE.
“I tried to estimate change over time and it appears exponential, although in Europe it has been linear (but effective culling is taking place there). In Taiwan attempts have been made since 2016 to reduce the numbers by egg oiling, removing its eggs, destroying its nests and removing young hatchlings. But none of these measures have yet proven to be effective.
“Many of the birds we saw were first winter birds. Yesou & Clergeau 2005 (Sacred Ibis: a new invasive species in Europe. Birding World 18 (12): 517-526, Available online) differentiates first-winters from juveniles: ‘Juveniles show a feathered neck and head; the tertials and tips to the remiges are brownish-black.’ ‘First-winters are intermediate, with the head and neck still well-feathered and some blackish ornamental plumes. They also show a variable amount of black along the centres of the tertials and greater coverts and even, in a few birds, on the median coverts.’
“Yesou & Clergeau 2005 also refer to these birds as the nominate form T. a. aethiopicus with a dark brown iris and black tips to the primaries and secondaries, which form a black trailing edge to the wing in flight. They state that the subspecies T. a. bernieri and T. a. abbotti ‘lack the black trailing edge to the wing and show a white iris (bernieri) or pale blue iris (abbotti).’
“I think the birds in the first three images above are first winter birds. The above shows 2 adults feeding. They have a wide selection of prey and peck or probing in mud or soft earth or shallow waters (see second and above images).
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
14 & 19th January 2019
Location: Dayuan Township, Taoyuan City County, Taiwan
Habitat: Wetlands farming area near the sea