The phrase as the crow flies means in a straight, direct line, as opposed to the longer route required by a road.
The equivalent French phrase does not refer to a specific bird species: it is à vol d’oiseau, literally by bird flight.
Although in reality birds in general, and crows in particular, do not fly in straight lines, both the English and French phrases refer to the fact that obstacles on the ground do not affect their flight, which came to represent the shortest distance between two points.
The earliest instance of as the crow flies that I have found is from Sentiments relating to the late Negotiation, published in The Gentleman’s and London Magazine: and Monthly Chronologer (Dublin, Ireland) of December 1761:
Between the two Carolinas and Louisiana, are many nations of Indians under a variety of names […]. The nations are […] the Cherokees, Creeks, Chikasaws, Chactaws, and another nation; which other nation I take to be the Alibamous, or else the Flat Heads. Now the country which those Indians inhabit is upwards of 400 miles broad, and above 600 long, each as the crow flies.
The second-earliest occurrence that I have found is from The Bath Chronicle (Bath, Somerset) of Thursday 11th August 1774, which reported that, during a trial, a witness
proved that the churches by the travellable [sic] road were 48, in the direct line, or as the crow flies, 43 measured miles asunder.
Another early use of the phrase appeared in A Journey from Gibraltar to Malaga; with a View of that Garrison and its Environs; a Particular Account of the Towns in the Hoya of Malaga; the Ancient and Natural History of those Cities, of the Coast between them, and of the Mountains of Ronda. Illustrated with the Medals of each Municipal Town; and a Chart, Perspectives, and Drawings, taken in the Year 1772 (volume 2 – London, 1777), by Francis Carter:
The Spaniard, if on foot, always travels as the crow flies, which the openness and dryness of the country permits; neither rivers nor the steepest mountains stop his course, he swims over the one, and scales the other, and by this means shortens his journey so considerably, that he can carry an express with greater expedition than any horseman.
Finally, the following is from The Lincoln, Rutland, and Stamford Mercury (Stamford, Lincolnshire) of Friday 21th January 1791:
Tuesday se’nnight the hounds of Sir John Nelthorpe, Bart, of Barton-upon-Humber, had a remarkable chase; They went away with a hare from South Ferraby Marsh, running over six lordships, viz. Ferraby, Horkstow, Saxby, Bonby, Worletby, and Elsham, nearly to Broughton Bridge, where they kill’d. They had but one check for the space of three or four minutes, occasioned by much water in the grounds. The distance, as the crow flies, is upwards of ten miles. Out of a very numerous field, the huntsman, and a very few horsemen only, were in at the death.
So-called ‘etymologists’ have often—and ludicrously—claimed that as the crow flies originated in a practice of early navigation at sea; the following, for example, is from the site See the Sea:
Before modern navigational systems existed, British vessels customarily carried a cage of crows. These birds fly straight to the nearest land when released at sea thus indicating the direction of the nearest land was.
Of course, those ‘etymologists’ have never provided any evidence to support their asinine theory (how could they?) but, regrettably, they have created a semblance of solidity and consensus by the mere fact of copying from one another.
Unfortunately for them, as mentioned above, all the earliest instances of the phrase refer to distances measured, and journeys made, in the interior of a country.
I have exposed several other folk etymologies, in particular in the following articles:
– origin of ‘Indian summer’ and French ‘été sauvage’
– The usual explanation of ‘Hobson’s choice’ is fallacious.
– the authentic origin of ‘to rain cats and dogs’
– origin of ‘once in a blue moon’
– Kilkenny cats
– the authentic origin of ‘a pretty kettle of fish’
– to buy a pig in a poke vs. to let the cat out of the bag
– origin of ‘to buttonhole’ (to detain in conversation)
– origin of ‘point-blank’
– between the devil and the deep blue sea
– meaning and origin of ‘the devil to pay’
– origin of ‘to turn a blind eye’