Girton Birdwatch - July 2011
I wonder if you've seen a linnet around the village recently? There doesn't seem to be very many. I occasionally see one or two in the hedgerows down the Oakington Road, although they are more likely to be found in scrub, heathland and at the coast, especially when gorse is present. Outside the breeding season they may be found in flocks in open country. The linnet is an active finch, mainly brown, but especially appealing in the breeding season when the male displays a red forehead and breast, although the less frequently used term 'carmine' probably describes the colour best. Its upper parts are a warm chestnut-cinnamon, while the striking white in its wing and tail most usually betrays its presence. It is duller in the winter and loses the red on its head. The female lacks the red and is streaked and dark brown above. It is a most attractive bird and in days gone bye its appearance and pretty song - a series of calls developing into rapid trills and fluting - had a deleterious effect upon its numbers as it fell victim to the Victorian passion for cage-birds (some authorities regard its song as the most beautiful of any British finch). Just like the white stork, mentioned last month, the linnet has become part of our popular culture and most older readers will be familiar with the early twentieth century music hall song, popularised by Marie Lloyd, My Old Man, in which the child of an evicted family followed the van with 'me old cock linnet', while Tennyson in his poem In Memoriam A.H.H. mentions 'the linnet born within the cage, that never knew the summer woods'. Happily we no longer take pleasure in caging wild birds but neither are we likely to encounter, as W.B.Yeats does in The Lake Isle of Innisfree, '(an) evening full of the linnets wings'.
Explanations for recent declines in linnet numbers must be sought elsewhere and are usually attributed to problems with its food sources. The name 'Linnet', which derives from the French 'Linette', is supposed to come from the bird's liking for flax seeds, Linium usitatissimum. While the second element in its scientific name, Carduelis cannabina, alludes to Cannabis sativa, from which hempseed, and latterly, marijuana, is obtained. Hemp was supposed to be one of the bird's favourite foods and with the restrictions placed nowadays on its cultivation and use - I remember as a boy throwing handfuls into ponds and rivers to attract fish! - some people suggest the linnet has suffered. However, the more likely villain of the piece, as so often, is the over-use of herbicides. Each and every application of herbicide depletes the soil's seed bank with seeds turned to the surface by farmers being killed before producing plants and further seeds. Linnets enjoy all small and medium sized seeds and are especially partial to fat hen, chickweed, dandelions, thistles, groundsel, shepherd's purse etc which could once be counted in thousands per square metre on newly turned farmland soil, whereas now, after years of herbicide use, they have virtually disappeared from the soil of cereal growing regions like our own.
I read recently that part of the explanation for the drastic fall off in cuckoo numbers - 65% since the early 1980's - might be attributed to the decline of the linnet but, as the linnet is primarily a seed eater and feeds seeds to its chicks, it is now thought not to provide a congenial host for the cuckoo. Moreover, the link between the cuckoo and its hosts is by no means straightforward. The cuckoo spends winter in Africa and arrives back in the UK during late April and early May, timing its arrival to coincide with the breeding season of its host species. It has been suggested that declines in its host species and/or climate-induced shifts in the time of breeding of its hosts could have reduced the number of nests available to parasitize, initiating decline in cuckoo numbers themselves. The main UK hosts are dunnock, meadow pipit, pied wagtail and reed warbler and recent research has attempted to establish whether changes in numbers or the timing of breeding of these species lies behind the decline of the cuckoo. The research appears to indicate that of the four host species, the meadow pipit is the only one to have declined during the period studied (1994-2007). A relationship was established between declining meadow pipit numbers and cuckoos, but this only accounted for 1% of the observed cuckoo decline. At the same time, dunnocks, pied wagtails and reed warblers have brought breeding forward by about 5-6 days which means that dunnock and pied wagtail nests are likely to have become less available to cuckoos, but the late breeding reed warbler has become more so. Moreover, the lack of a relationship between shifts in dunnocks and pied wagtails and cuckoo abundance in the following year suggests that the shifts in these two species also do not explain cuckoo declines. It seems that the explanation might lie either in the non-availability of the cuckoo's caterpillar prey during the breeding season, or deterioration of conditions along migration routes or on over-wintering grounds in sub-Saharan Africa.
No one knows for sure, so the British Trust for Ornithology - as followers of the BBC's Springwatch will be aware - have fitted fingernail-sized satellite tags to five birds, which are capable of transmitting location data for ten hours, before shutting off for two days to recharge their solar batteries. They should be able to send back data for three years and give conservationists important new information about the cuckoo's lifestyle and perhaps a clearer indication of what exactly is happening to them. If any one is interested their progress may be followed on the BTO's web-site. I neither saw, nor heard, a cuckoo this spring.