The most yellow of yellows

I have never been entirely comfortable in the Fens, something that I attribute to growing up within the comforting, verdant growth of the Surrey Weald, with its rich deciduous woodland and shortened horizons. There is just so much sky in the Fens, a great expanse of space that stretches on above; it is this that makes me feel exposed. The Fens are, however, part of my annual calendar, a place to visit in winter for the herds of swans and in the summer for Corn Buntings, Barn Owls and Yellow Wagtails.

It is a Yellow Wagtail that has caught my eye this morning; a sharp flight call alerting me to this cracking summer visitor. These arable lands, with their rich soils and dividing lodes and ditches, seem to suit this bird and here, just inland from the Lincolnshire coast, is one of their remaining strongholds. The Yellow Wagtail Motacilla flava has a massive breeding range, one that extends east across Europe and into Russia to reach Alaska beyond. Many different races occur across this huge breeding range, with ours the most striking of all; it is Motacilla flava flavissima, the most yellow of yellows.

Yellow Wagtails arrive from late March, with most appearing in April or May and with a few birds straggling in during the first week of June. I sometimes encounter them on passage, stopping over on bits of damp grassland. The breeding grounds tend to be in areas of wet grassland but arable landscapes (and crops) are also used. The drainage of favoured sites may be one reason for the decline in numbers that has been seen here over recent decades. This may not be the whole of the story, however, because there has also been a contraction in the breeding range, with the species disappearing from much of the southwest and north of Britain.

I see several Yellow Wagtails during the course of the day, with some carrying food into suitable nesting cover. These are wary birds, the adults feeding the young rapidly to avoid attracting unwanted attention to the nest. A calling pair, alarming with the characteristic sree sripp sripp a sure sign that there is a nest with young nearby. I sometimes get calls and emails from observers convinced they have seen a Yellow Wagtail in their garden. Many of these calls come in the winter, when the Yellow Wagtails will be on their wintering grounds in Africa. What these observers have seen will be a Grey Wagtail, a species that not only breeds across Norfolk but may also winter here. While Grey Wagtails do sport some yellow on their plumage, it does not compare to the resplendent tones of an adult Yellow Wagtail.

The brightest yellow

In his spring finery, a male Yellow Wagtail positively leaps out at you, so vibrant is his plumage. The canary yellow is intense, as if taken straight from a paint tube – an undiluted primary colour that is bold and bright. It is easy to see why our race of this delightful bird goes by the scientific name of Motacilla flava flavissima – the most yellow of yellows. Once seen, there should be no confusing this bird with its less showy relative, the Grey Wagtail, which sports a pale, more lemon yellow across its underparts and grey and black on its upperparts. The two species utilise different habitats, the grey favouring fast flowing rivers and the yellow damp grassland.

Yellow Wagtails arrive here from their West African wintering grounds from late March through into early June. In some springs, as appears to be the case this year, good numbers can be seen at favoured sites, though perhaps not reaching the dizzy counts of 400 seen together at Cley in April 1986 or the 450 seen at Holme in May 1995. These Yellow Wagtails have arrived to breed in damp meadows along river valley bottoms or, increasingly, in arable crops on the dark fenland soils where they favour peas, potatoes and winter cereals. This association with damp grassland can be explained by a diet of small insects and spiders, which do well under the damp conditions, but it does bring with it certain risks. Nests, placed in or up against a tussock, may be lost to flooding or to the trampling of livestock that graze these damp pastures. The impact of localised flooding can be seen from changes in the Yellow Wagtail population using the Ouse Washes, which ebbs and flows depending upon the occurrence of late spring floods. Nests lost to flooding early in the season may be replaced, the birds squeezing in a new breeding attempt in July, alongside a few genuine second broods from successful pairs.

The yellow-headed British race of the Yellow Wagtail is one of a bewildering number of such races which, collectively, make up a species complex that shows extensive variation in head pattern. Birds from our race are not just restricted to Britain, but now breed in The Netherlands, along the French coast, in Denmark and into the extreme south of Norway. Birds from the ‘blue-headed’ race, which breeds over much of continental Europe, may sometimes turn up here in spring and this year there seems to have been a good number in Norfolk, particularly along the grazing marshes of the north coast. Although the Yellow Wagtail population has declined because of changes in land management, it is still a bird you can readily see within the county.