On average, this (contested) title probably rightfully belongs to males of a species widespread in southern Africa: Ardeotis kori – the Kori Bustard.
They commonly weigh 18 kilograms apiece.
The so-called “World Wide Web” is in fact more than a tad Northern Hemispere-centric/ USA-centric/ Eurocentric; I strongly suspect that Africa has the biggest bustards.
Kori Bustards usually have feet on the ground, but they are strong flyers.
Photo is copyright Doug Spencer, taken in Etosha National Park, 9.10 am, 06 November 2022.
Namibia’s oft-surprising birdlife is hugely diverse.