Girton Birdwatch - July 2009
Some birdwatchers are obsessive in the lengths they are prepared to go to add bird species to their 'list'. This will often involve them in expensive travel to all corners of the land and, in some cases, the world. I must admit to keeping a yearly list - which seldom exceeds the low 100's; the big tickers reach 400 - but this is just intended as an aide memoire and is not yet out of control! However, if one is interested in seeing a large number of different birds then there are a few simple steps which one can take to help ensure this: visit a wide variety of appropriate habitats, at the right time of year and when conditions (such as wind direction) are favourable. If you go to places where (according to the 'experts') particular birds are to be found they will invariably be there, providing the other conditions are fulfilled. Given the limited habitat offered by Girton there are certain birds we are not likely to see (although never say never). I don't know if anyone has seen a Marsh Harrier in Girton - or any of the other Harriers - but this is unlikely given their preference for marshes, reed beds, heathlands etc but we are lucky in having on our doorstep places like Fen Drayton, Wicken Fen, Fowlmere and the Cam Washes where the chances of observing these elegant raptors are quite high. I was prompted to write this, however, by the reported sighting of a Montague's Harrier - one of our rarest and most attractive birds - which was seen passing over Barhill on 29th April. We might not expect to have members of the Harrier family dropping in on the 10 acre field but there is a slight chance, if like me you wander the village scanning the skies, of catching a glimpse of a rarity or a more common bird out of context, passing over-head. After all no one has yet reported, to my knowledge, encountering a Common Buzzard or Red Kite strutting across our fields or perched in a local tree or bush. Surely this is just a matter of time, given the increasingly frequent visits of these birds to our 'air space'? (Not that there's much carrion to be had around the village!) Just a few weeks ago I virtually came eye-to-eye with a Buzzard, hanging at head height, on the roundabout by Hacker's fruit farm.
The Marsh harrier, should one turn up, is a buzzard-sized bird but is much slimmer and narrower-winged and possesses a longer tail. The male's tail is a pale grey as is its upper wings, contrasting with otherwise dark plumage and wing tips. Unusually for the bird world the female is probably the 'prettier' for, although dark, she has a cream coloured head and shoulders. The elements of the bird's flight were beautifully captured by Mark Cocker when, writing recently from Claxton, Norfolk, he enthused that: 'The normal mode in a hunting harrier is a low-level manoeuvre angled against any breeze for lift and shaped by passages of deep, slow, languid beats interspersed with effortless glides, when the wings are upheld in a shallow v'. I can see it now.
The history of the Marsh harrier is a relative success story, for one would have to look to the 18th century to find a time when they were more common than they are now. They had been reduced to a miniscule rump in Norfolk by the 1870's and by the 1970's one of my battered bird books is proclaiming Minsmere, Suffolk, as one of its remaining strongholds, with most of the birds there being summer visitors, suggesting that 'as a breeder, the marsh harrier is one of our rarest species'. The draining of fenland had a deleterious effect, as did the attentions of skin and egg collectors, while a slow increase in numbers was halted, in the 1960's, by the use of organochlorine pesticides which hit the harriers, as top of the food chain, particularly hard. However, the withdrawal of these chemical killers was to lead the way, eventually, to an encouraging increase in numbers - an annual rate of 20% - so that be the end of the 20th century there were 206 breeding females, the majority concentrated in Lincolnshire, Norfolk and Suffolk, although their spread to places as widely separate as Orkney, Kent and Somerset is equally pleasing. Ornithologists, when discussing the bird's breeding success, tend to avoid the more usual term 'breeding pairs' in favour of 'breeding females' as Marsh harriers, like the more familiar Dunnock or 'Hedge sparrow', often form bigamous relationships. (The Dunnock probably 'wins' hands down here given the complexity of its breeding arrangements. A great deal of partner swapping goes on and its mating system embraces polygyny [two females with a single male], polyandry [a female with two or three males] and polygynandry [two or three males sharing two, three or four females]). Marsh harriers have also demonstrated a surprising adaptability in their willingness to nest in arable crops wherever, as is unfortunately often the case, their preferred reed-bed habitat is limited or unavailable. Equally interesting is the harrier's growing inclination to remain in Britain for the winter. Most books tend still to list the species as a summer visitor from Africa but more and more seem to be abandoning this long migration. If you visit Wicken Fen at dusk, winter or summer, you'll probably be treated to the sight of resident harriers returning to their communal roost in the reed-beds.
A visit to Fowlmere in early May was enlivened by calling Cuckoo and Turtle dove, although one Cuckoo per Spring is hardly cause for celebration.