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Technology1 min ago
No best answer has yet been selected by apala1. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.Looking at the previous answer, the spine-tailed swift is probably right -- but the record has been doubted by some. Other large swifts are also, um, swift, and may be much of a muchness with it.
The gyre-falcon is much bigger than a peregrine, so ought to be even faster in a dive.
And what about on land? Ostriches, rheas and emus can run quite fast I'm told. Also bustards, stone-curlews, road-runners, secretary birds etc.
The problem is that it's very hard to estimate speed accurately unless you can get the bird to fly or run parallel to your (accurately measured) vehicle, or fly straight over a measured distance. Even a radar would only tell you if you knew its exact direction. Then there's the wind. In practice most birds have probably never been measured properly.