RAVEN (Corvus corax)
Ravens are interesting birds, they feature in folk tales and mythology from many different countries all over the world - it is honoured as the national bird of Bhutan and was revered as a god in the indigenous cultures of the Pacific northwest of America. This also demonstrates the wide distribution of this species - extending all round the world in the northern hemisphere.
Unfortunately the vast majority of the tales around Ravens regard them as birds of ill-omen, harbingers of gloom and generally bad news for anyone unlucky enough to encounter one. But I love 'em ! They are probably the heaviest of the birds known as "Passerines" (perching birds which include Blue Tits and Sparrows), weighing in at up to 1.5 kg or more, they mate for life and are usually seen in pairs and have a strong but agile flight abilities, especially in the mountains where they can use updrafts and wind currents very skillfully and sometimes acrobatically.
In Switzerland it is found in almost all habitats but is more common in the mountains from about 800m and upwards. It is at its best (in my opinion) in the crags and cliffs of the alps where its powerful wings can take it long distances very quickly and where it can course the face of cliffs gliding with wings outstretched catching the air currents that power it along. It seems indifferent to the raw terror of the terrain below, it is a big strong bird and each wing beat can carry it a long way - it can pass over your head at the top of one mountain and then disappear behind a neighbouring peak in the flash of an eye.
It is easily told from the smaller Carrion Crow by the size (remember it is bigger than a Buzzard), slower more deliberate wing beats, thicker heavier bill, and a long wedge-shaped tail.
The basic call is a deep strong "prruk - prruk" which is given both in flight and when perched, but its deep tone and resonance inside its body cavities means it is unmistakable. Here is one perched on a forest edge:
You can hear now the distinctive rasping and rolling sound of the "prruk". Most of the energy is just below 1Khz but in a couple of calls there it was a bit higher:
The same call is also made in flight. They tend to be curious birds, I guess because they are a mixture of both scavenger and predator and are always on the look out for a meal, so I have frequently found that, especially in woodland areas, a Raven will "drop in" on me to take a look and then fly on, when this happens you are not only aware of the tone of the call but can hear the whistle from those powerful wings - if you are listening with headphones you can hear the wings most distinctly in this next piece as a bird flew close by to check me out, the clear whistle at 26 secs came from the wings and was caused when it stopped that steady powerful wing beat and made a steep glide as it turned away:
Here is another that also dropped in to see if I would share a sandwich, circled me and then flew off, but this one made faster higher pitched calls (you can also hear my feet crunch as I turned in a circle to follow it with the parabola !):
So now we know that it can alter the tone of its call when it wants to. I was one day recording a Cuckoo in the mountains when a pair flew high overhead, one of them making a high pitched squawk like a parrot while the partner replied with the "normal" deeper call:
The sonogram of this is quite interesting - you can see the Cuckoo calling away at 600Hz ("Cuc") and 500Hz ("koo"), the longer drawn out squawks of the higher pitched Raven at about 1450 Hz, and the lower shorter grunts of the reply at about 1000Hz, at first the the reply is only a short grunt, but at 18.2 secs in the video the reply comes back like the more regular "prruk prruk" sound:
Finally here is a call that is even more high pitched, more of a "gowk-gowk" type of sound - I must qualify this by saying this particular recording was made near an estuary in North Wales (the rest were from Swiss mountains) and you can hear several wader species in the background (a nice Curlew at the end !):