Michael See was in the vicinity of Lim Chu Kang one night in June 2012 when he noticed two moving white patches in the darkness of the trees there. He suspected that these were White-bellied Fish Eagle (Haliaeetus leucogaster) as he had seen them regularly during the day. And from the calls the birds were periodically making that night, he was confident that they were indeed sea eagles.
Early the next morning Michael visited the site and was “surprised to see many more eagles than I’d expected, flying off for the day. I noted at least six separate birds flying off (I didn’t want to risk double counting, so that’s the most birds I saw flying off at one time; there were almost certainly more), and I could see others perched on the trees.”
“Since then, every time I visited the area in the evenings, I checked the stand of trees and always saw multiple eagles even though the light was poor,” wrote Michael. “I’ve never seen so many White-bellied Fish Eagles together before, usually I see a pair at most. I don’t think I’ve ever read about communal roosting behaviour in these birds, so I was wondering how well known this phenomenon is.”
According to Thiollay (1994), “Most of the colonial and semi-colonial species [of raptors] tend to spend the night in communal roosts… These roosts take place in trees, cliffs or marshes, and the same site is regularly used, sometimes involving up to 1,000 birds… At such sites, when the birds feel secure, they drop into a deep sleep, with the head tucked under the scapulars.”
(Image by Wei Chun LINK)
Thiollay, J. M., 1994. Family Accipitridae (Hawks and Eagles). In: del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 2. New world vultures to guineafowl. Lynx Editions, Barcelona. Pp. 52-205.