What is the largest owl of world?
As always with questions of size, it depends on how you measure. Most of the contenders seem to be in the genus Bubo; the Blakeston’s owl and the Eurasian Eagle Owl can sometimes weigh over 4kg, and wingspans of both have been known as long as 2m. Of course, these attributes vary considerably across populations, with region and environmental conditions, and between the sexes.
Thanks for your kind information. Another question, which owl has the highest lifespan as you know. This question is important as I am researching in Asia
Hello @Deepa_Das, fellow researcher who comes from Asia ( Sri Lanka), to answer your question the Blakiston’s fish owl (Bubo Blakistoni) has the largest wingspan of any owl in Asia, with a range of 178–190 cm (5 ft 10 in to 6 ft 3 in) and a possible maximum of 200 cm (6 ft 7 in). It can range from East Asia to the Russian near East. Nice to meet you! - Sohan
Regarding lifespan In Asia, the owl species with one of the longest lifespans is the Blakiston’s fish owl (Bubo blakistoni). This large owl, native to parts of Russia, Japan, China, and the Korean Peninsula, can live up to 20 years or more in the wild, though many typically live around 10-15 years.
Blakiston’s fish owl is one of the largest owls in the world and is considered near-threatened due to habitat loss and other environmental pressures. In captivity, with proper care, they have been known to live even longer, sometimes exceeding 20 years.
Other species of owls in Asia, such as the barn owl (Tyto alba) or the eagle owl (Bubo bubo), may live up to around 10-15 years, but none have a lifespan as long as the Blakiston’s fish owl in the region.
Thanks for your kind information
I know this is quite a late response 
, but no problem!