Friday 4 May 2018

The Most Yellow of Yellows 1st May 2018

Farmoor can be a singularly inhospitable and depressing place on some days but at this time of year it comes alive with spring migrant birds and nothing brings it more to life than the regular passage of Yellow Wagtails that appear in a brief seven or eight week window in April and May. Mind you this late and cold Spring with its almost continuous strong winds is certainly testing my resolve and possibly that of the wagtails.

Yellow Wagtails are widespread and breed as a contentious and bewildering number  of sub species over a vast range, covering Europe, Asia and Africa. The Yellow Wagtails at Farmoor are the sub species Motacilla flava flavissima which is found breeding in Britain, southwest Norway, Helgoland in Germany and coastal Netherlands, Belgium and France and is part of the wider western European population that spends the winter in northwest and sub saharan Africa. Other summer breeding eastern European populations winter in northeast Africa and western parts of Asia. The European breeding population as a whole is in gentle decline and has been so since the 1980's due to habitat loss and degradation, although the population in 2004 was still estimated at between 3.9 and 7 million pairs but may now be less. In Britain, sadly it is in rapid decline, the population having fallen by 75% between 1967 and 2013, which is not good news.

To see Yellow Wagtails really well and know a reliable place to find them in Britain is not that easy these days but Farmoor provides one such place, and the grass bank by the waterworks and concrete banks of the central causeway usually harbour a number of Yellow Wagtails, which with care can be approached relatively closely.

The first to arrive at Farmoor are the males which are, to my mind, very much under appreciated. Their bright yellow plumage is simply sensational, bringing something of the sunny and warm climes where they spend their winter, and their Latin name Motacilla flava flavissima, translates as 'most yellow of yellows.' As they are such a small bird they can often go un-noticed or are only given a casual glance but look closer and stop for a while to study their brilliant yellow heads and underparts, their green upperparts also suffused with yellow and their closed wings with a corporal's two stripes. This lovely amalgamation of colour and pattern is finessed by a black bill, legs and tail, the latter sporting white outer tail feathers.

Male Yellow Wagtails
There is much variation in the plumage of the males, some, especially when the sun shines, show almost luminescent yellow heads whilst others, at the other extreme, have duller, greener tones on their head especially the crown and ear coverts.The females also exhibit much variation and again some can be quite bright but others are dull and more pale green than yellow on their heads and upperparts and insipid  lemon yellow on breast and belly.

Female Yellow Wagtails
For the last three years the 'normal' Yellow Wagtails at Farmoor have been joined by a beautiful hybrid male wagtail,  the progeny of a pairing between 'our' Yellow Wagtail Motacilla flava. flavissima and the Blue headed Wagtail Motacilla flava flava, the latter being found breeding as close as the northern coastline of France in conjunction with flavissima, hence the nickname Channel Wagtail being given to hybrids. Studies in 1998, 2000 and 2001 around Calais, Dunkerque and Cap Gris Nez on the northern coast of France have shown that  the majority of the male Yellow Wagtails there showed intermediate plumage characters between flava and flavissima and this may well be the origin of the male hybrid at Farmoor. 

For more detailed information see Alstrom P. & Mild K. 2003 Pipits and Wagtails of Europe, Asia and North America. London

The plumage of the Farmoor hybrid appears virtually identical to a male flavissima Yellow Wagtail apart from the head which is not yellow at all but a subtle shade of blue grey, forever changing in tone in the variable light and with a bold white supercilium and white chin.This variation gives it a certain elan amongst its all yellow headed companions but the blue grey head can be surprisingly hard to discern at any distance without the aid of optics.

Male Channel Wagtail
Invariably the male Yellow Wagtails are the first to arrive at Farmoor and it is some time later that the females join them and never, it seems at Farmoor, in the same numbers as the males.

Apart from lovely plumage they also have the engaging personality that all wagtails possess, constantly active, prinking up and down in search of the flies that hatch forth in their billions on the reservoir and calling a bright cheery note to match their bright colour as they fly around.

Although such a dazzlingly yellow bird would be thought to stand out they can be surprisingly difficult to pick out in the grass as their small size and greenish upperparts provide an effective camouflage. If they sit still in the grass, which they sometimes do when uncertain about my approaching them or sheltering from the strong southwesterly winds which often beset Farmoor, they can appear as no more than a bright yellow spot amongst the grass as their yellow heads and breast are all that is visible but even here they can be camouflaged as much by deception as colour, for they are sharing the bank with numerous low growing dandelion flowers which are almost the same colour, if a slightly richer golden yellow.

I try to visit Farmoor as often as possible to see them, knowing that I only have a limited period of time in which to see them at their best and before they depart to breed in central and eastern Britain or further. Sometimes I do not bother to wander far from the grass bank but just sit on the wavewall, content to enjoy watching them going about their lives. 

My most recent visit was in a very strong southwesterly wind and the wagtails had abandoned the unsuitable windswept grass bank to feed on the more sheltered concrete bank of Farmoor One, the smaller of the two reservoirs. I sat on the wavewall and watched a male and female feeding amongst their more numerous close relatives, Pied Wagtails. They had much trouble with the wind and found their feathers and tail blown asunder by the gusts coming over the water, which caused them to promptly turn and face into the wind

A windblown female Yellow Wagtail
While I watched, the male Channel Wagtail arrived at the water's edge and his grey head turned palest blue in a burst of sunshine and then back to grey as the sun was obscured by a cloud. 

It is such a beautiful bird and although dismissed as a hybrid, to me it is much valued and the highlight of any trip to see the Yellow Wagtails at Farmoor. 

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