7 July 2010
I've been working at the RSPB as a wildlife adviser since October 2005. I have been a keen naturalist all of my life with a particular interest in birds, insects and animal behaviour. I have a background in Environmental Biology and Environmental Impact Assessment and regularly contribute to bird surveys. Other interests I have include wildlife gardening and birding as well as keeping track with important issues such as climate change and renewable energy.
Sent in by Colin Burdon, Ashington
This is a popular question and one that may have a number of different answers, depending on how you interpret the different modes of birds' flight.
Peregrines use a specific flying technique when hunting - the 'stoop'. They fly high above their prey and close their wings, going into a downwards dive. Their aerodynamic shape means they reach such a speed that their target is often stunned or killed outright.
A 'stooping' peregrine is undoubtedly the fastest flying bird, reaching speeds of up 200 mph. However, the stoop is gravity-assisted - more of a controlled fall - and is generally not considered as level flight (where they reach 40 mph).
Many swift species reach high speeds during their display flights. A study published earlier this year recorded the swift's flight in these displays as reaching 69.3 mph (Heningsson, 2010).
As these speeds were reached in level and ascending flight you could argue that they are the new holders of the title.
However, their normal flight such as during migration or going to roost was recorded between 22 and 26 mph. If you compare the swift's normal flight speeds with level flight speeds of some other birds, they may struggle to keep up with some of the powerhouses of the avian world.
Surprisingly, the humble eider is thought by many to be the fastest bird in steady level flight. It is difficult to record the steady flight of many species but of those that have been reliably clocked, the eider comes out on top with an impressive 47.2 mph.
How does it achieve such speed? Well the eider duck has an impressive physical claim as well. They have the smallest wing area relative to body size, also known as the highest wing loading.
Because of this high weight-to-wing area ratio, speed is vital to the eider in order to produce enough lift to keep the weight in motion. To achieve this they have very strong wing muscles. These come in handy in the eider's natural coastal environment, as it has to fly in very windy conditions. You can see this amazing species along the east coast of Scotland and Northern England.
Of the other contenders to this title, pigeons, waders and other wildfowl are all capable of hitting speeds over 40 mph. As more sophisticated technology becomes available it is possible that more accurate analysis of the flight speeds of birds will be possible, so other contenders may emerge in the near future.
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