CORN BUNTING (Miliaria calandra)

Bruant proyer

As the name implies this rather dull, streaky seed-eating bird is basically a grassland species that has adapted well to the grain crops that we grow. It is distributed throughout Europe as far east as Kazakhstan and can reach impressive numbers in some parts. Despite the apparent availability of food in agricultural areas it is a species that has undergone a decline in recent decades, the reason for this is not completely clear but is undoubtedly linked to changes in farming practises, including timing of crops, removal of weed species and perhaps loss of insects which they also need in their diet. The map of the distribution of this species show a "hole" around Switzerland and Austria where it is clearly a lot less common than elsewhere - not sure why this is but could be related to the altitude of these countries. In Switzerland it can be found in every month, but the largest numbers occur in the breeding season and also during the autumn migration. Even so it is very thin on the ground, only occurring in the lowest areas around 600m, and even then in only a few places, so it is limited to the plains in the north and a few major river valleys. As in other countries numbers have declined in recent times.

Corn Buntings can be polygamous, one male may mate with up to 3 females, rarely the other way round. To defend his territory and maybe his harem too the males will sing from fence posts, wires or medium sized trees and so are usually easily visible. The song is a somewhat monotonous rattle that tends to accelerate like a bouncing table tennis ball rising slowly in pitch throughout. The most common description is of someone rattling a bunch of keys - but that takes a bit of imagination in my view. Here is one in the grasses at the edge of an insect and frog infested marsh in mid-summer:

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and this is how two phrases (the space between shortened) look in the sonogram:

The wavy line through these sonograms at 5 Khz is the stridulation of a nearby grasshopper, if you listen carefully you can detect it - unfortunately it coincides almost exactly with the fundamental frequency of the bird call and theoretically could be a problem for it.

Now, you can see from the sonogram that about 75% of the way through each phrase things begin to get complicated - just where the sounds become really rapid, so let's zoom in on that in a bit more detail and look at just one call:

 

This is all a bit fast, let's look at the still of the phrase:

 

 
The black area from 7.3 to 7.8 secs (note that is only half a second in timing) clearly has some complex things going on there - so let's focus in on it a bit closer:

 

Unfortunately that does not help as there is so much going on in such short spaces of time that it all becomes too murky to understand, and anyway what do all these funny shapes actually mean in sounds ?

In his book of bird songs and calls Geoff Sample suggests that if it is played at a slow speed the detail in this part of the song becomes more apparent. Now if you slow down these songs the tone drops as you alter the frequency of playback, but the pattern becomes more understandable to our ears as everything happens more slowly. So let's give it a go - here is one phrase played at one-fifth of normal speed - check what happens in that short half-second of complexity:

During that little space of time the vocal apparatus of the Corm Bunting is working overtime, but other Corn Buntings probably can detect that detail and get information out of it - this is the wondrous thing about animal communications - a human nervous system only gives us access to part of what is going on. Here the singer must have the nervous and muscular abilities to make such rapid changes in singing and the listener has to do the reverse - detect the changes and have the nervous system in the ears tell the brain what is coming in and the brain then to process it.

For other examples of this high speed communication see also the Wren or Savi's Warbler

 

 

 

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