Saturday 28 March 2015

Next Term 3: Yellow 'flava' Wagtails

 Yellow Wagtail

The Yellow Wagtail is one of my favourite spring birds, and is still hanging on as a breeding species in East Yorkshire. This isn't a bird we will be specifically going somewhere to see, but hopefully our luck will hold, and we will enjoy good views of a stunning male. The male has the most vivid yellow upperparts, which extends to just above the eye. The back is green with darker wings edged with white and the tail being almost black with white outer tail feathers. It's rather strange that we can delight in a bird with such bright colours, but many of us would shirk from purchasing a car with that same garish trim! 
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Yellow Wagtails are some of the earliest spring migrants to return, usually in about the 3rd week of April, and are quite often seen among the feet of sheep, cattle or horses. This has led to them being known in some parts of the country as milkmaids. Although they are very brightly coloured, they have one of the most uninspiring songs, which mainly consists of just 2 notes, which approximates to a "sweee-swee." 
Blending in on Oilseed Rape
 Failing to blend in
Yellow Wagtails were traditionally known to breed in areas such as partially flooded wildflower meadows. In East Yorkshire they can still be found nesting in agricultural areas such as fields of oilseed rape, winter corn and potatoes. Researchers have discovered that if Yellow Wagtails breed in a potato field, they can comfortably produce two broods in a season, but in oilseed rape they can only manage one, as it becomes too thick for them to attempt a second family. They often line the road to Sunk Island just inches away from the drainage ditches, but the latter often dry up. However, it's only a short flight to the river Humber, which is never more than a quarter of a mile away. They can also be often found on muck heaps, which attract the kind of insects, which are becoming harder to locate in over-sprayed fields. 
Less photogenic with droppings
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 Blue-headed Wagtail (c) 2015 Chris Cox
Yellow or 'flava' Wagtails are found all over Europe, but the colour of the head markings varies from country to country. At migration time, and depending on prevailing weather conditions, many of these variant races may turn up on the east coast, especially at Spurn. 2 years ago the Friday morning session found what looked like a Blue-headed Wagtail at North Cave Wetlands, but this was a paler blue than normal, so was reclassified as a 'Channel' Wagtail, not a bird, which you can find depicted in the standard bird books. It is regarded as a cross between the Blue-headed Wagtail, the commonest flava wagtail found on the near continent, and our own Yellow Wagtail. The only other variant we have come across so far in the past 11 years was an Ashy-headed Wagtail found at Spurn. This is most commonly found on the Iberian peninsula. 
Blue-headed Wagtail (c) 2015 Chris Cox
 'Channel' Wagtail (c) 2015 Chris Cox
 Ash-headed Wagtail
 Yellow Wagtail
Yellow Wagtails are another species whose population has fallen in the last three decades, but they continue to be seen in a few pockets of our area. When the construction works at North Cave have been completed, and some flooded meadows are created perhaps the Yellow Wagtail will return to breed in the vicinity of that reserve too? 
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