Friday, 25 December 2015

Bittern - Countdown - 10 Days to Go!

The winter term is traditionally the best time to have good sightings of Bitterns. I believe one icy day at Potteric Carr we saw up to 5 individuals either sliding on the ice, or by the edges of the reedbed, and even one perched on top of the reeds. It is the cold weather that drives them to leave the reeds, and sometimes to indulge in unusual behaviour. In the bad winter of 2010 a Bittern left the Willow Marsh reedbed and speared and then swallowed a rat that used to infest the feeding station. When the weather was at its most severe the Yorkshire Wildlife Trust bought in fish from a fishmonger to ensure the Bitterns survived. The freshwater fish were eagerly devoured, but a cod was left untouched.
Female Bittern at Tophill Low
Bitterns are a large member of the Heron family. When the classes began a dozen years ago there were reported to be only around 10 booming males in the UK, but now I believe 50 have been recorded. Male Bitterns start booming about mid-February to attract mates. It is the deepest sound made by any British bird, and in the correct weather conditions can almost travel a mile. It sounds like a giant blowing over an old-fashioned glass milk-bottle, or a distant foghorn.
Male? Bittern at Far Ings (c) 2014 Maggie Bruce
Bittern in Flight
Bitterns are brownish or warm buff birds with darker vertical stripes, green legs, and the males have blue between the base of the bill and the eye. They sometimes stalk between areas of reedbed, but we have also seen one swimming at the back of a reedbed. The commonest view we've had is catching sight of them flying from one area of reeds to another, and this is probably the view we've had more often than any other. When they think they've been observed they will often freeze, and point their bill upwards and elongate themselves and they seem to merge into the reeds.  This works marvellously in a reed bed, but can look very strange away from the reeds! 
Bittern Skypointing - in the wrong habitat
Skypointing in the right habitat
They are very territorial and are known to have fights with other Bitterns. We think we've only observed this once when a Bittern in a channel between the reeds at Old Far Ings suddenly began to puff itself into strange shapes as it looked into an area of the reeds not visible to us in the hide. I have twice seen them fighting in mid-air, once over the old Far Ings car park, and the second time during an evening class, when 2 birds chased each over all the reserve.  
Aggression towards the reedbed
 Standing on the Reeds (c) 2013 Dave Hill
There are at least 2 venues in which we may catch up with Bitterns next term, but there is always the chance at Tophill Low too, so the odds are fairly high on us encountering this enigmatic species once again fairly soon.

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