Bioblitz

Last year, with the help of the EDP, Norfolk Wildlife Trust invited the public to record wildlife on its nature reserves during a 24-hour burst of frenetic activity. Some 1,200 different species were recorded by just over 500 people, an amazing achievement.

Another 24-hour ‘bioblitz’ will happen in a week’s time, beginning at 12 noon on 4^th June. This time the focus will not be on nature reserves but on urban areas, specifically Norwich, Thetford, King’s Lynn and Great Yarmouth. As such, it has something of a more competitive edge, especially for those of us that happen to live in one of these four urban centres. Surely Thetford can pull more species out of the bag than King’s Lynn or Great Yarmouth but can it compete with the much larger Norwich?

At first glance, the choice of these urban habitats may seem a strange one; urban areas are not renowned for their wildlife value but, with many more of us living within urbanised landscapes than non-urbanised ones, they are where most of us interact with nature. If urban dwellers become more aware of the wildlife that lives alongside them then perhaps they will take greater ownership of it and make sure that it has space in which to live.

Of course, our urban centres do support some important species. Norwich has its breeding peregrines, Great Yarmouth its Mediterranean gulls, Thetford its otters and King’s Lynn its eels, the latter a species in serious decline. Then there are the more familiar but equally important species: things like song thrush, house sparrow and spotted flycatcher – all of which are flagged as being species of conservation concern. What will be of particular interest, however, are the overlooked species, the invertebrates and plants in particular. Work elsewhere in the UK has highlighted the importance of urban brownfield sites for rare bees, beetles and moths, and we have plenty of these sites in East Anglia.

Much of our urban biodiversity will be found in our gardens – in fact gardens are the biggest contributor to biodiversity in urban areas – so there is plenty of opportunity to spend an afternoon in your garden, searching for insects and other invertebrates. Alternatively, if you want to get out further afield, go along to one of the Norfolk Wildlife Trust events that are being held and discover more about the urban wildlife with which you share your town (details are on the Norfolk Wildlife Trust website).

The chances are that, if you look hard enough, you will turn up something that nobody else does. Don your sun hat, grab a cold drink and take a closer look at your garden – that’s what I’ll be doing!

Don't be too tidy-minded

It seems that the council has decided that the town needs to tidy up its image. Hot on the heels of a campaign to tackle those in our community unable to use the numerous litterbins, has been an assault on ivy and other bits of scrubby cover. It would seem that these habitats do not fit into the ideal of a green environment, rich in wildlife.

Ivy is a plant that is plagued by an unjustified reputation; I have even heard conservation practitioners repeat the false claim that it strangles trees and should be removed at every opportunity. The weight of a mass of ivy might bring down a rotten branch but that is an exception rather than the rule. What has been particularly frustrating about the latest bout of clearance has been its timing, the work coming just as many birds were starting their breeding season. The ‘ever green’ ivy provides much-needed nesting cover for birds at a time of the year when the deciduous cover has yet to get going.

There is another reason for the clearance of this scrubby cover from our urban greenspaces and that is the notion that it can shield and hide undesirable activities. While this may be true, surely the solution is to tackle those undesirable activities head-on, rather than shift them somewhere else.

One of the main reasons for our willingness to allow the reckless destruction of ivy, brambles and other scrubby vegetation is that most people have no idea of just how valuable it is for wildlife. Take someone out into a patch of urban green space and ask them to point out the places where birds might nest and the chances are that they will point up into the trees and taller hedgerows. Tell them that most birds nest within a metre or so of the ground and they will be surprised. Point out a blackcap nest in a low bramble or a robin nest in a nettle bed at the base of a tree and they will be stunned. Of course, it is not just the birds that use these habitats. Ivy is incredibly important for many insects, including those which visit to feed on the flowers or fruit. The holly blue butterfly, for example, has one of its two annual generations on ivy; the other is on holly.

It is our ignorance, and in particular the ignorance of those who manage our urban green space, that is behind this act of habitat vandalism. There is relatively little green cover in our towns as it is and it would seem churlish to prune and mow what remains into weak submission. We must stop being so tidy-minded.

The life-blood of the town

To suggest that a river is the lifeblood of an urban landscape is something of an overused metaphor. Nevertheless, the way in which it pulls life into the heart of the town suggests that this is an appropriate acknowledgment of its pivotal role in shaping urban biodiversity. The river is a corridor, one along which creatures can move into the town, cutting through the barrier of suburban gardens, ring roads and fringing industrial units with their superstores and retail parks. Along much of its urban length it is corralled by concrete, its flow controlled by weirs, gates and pumps, but there are places where it retains a more natural character.

Thetford’s lifeblood comes in the form of the Little Ouse and the Thet, both slipping silently in from the east through the old part of town and skirting what was once the town’s economic heart. It is this first stretch that most often holds the interest of the local otters, one of which now seems oblivious to the passing humans and their four-legged or four-wheeled companions. From the Nun’s Bridges, which mark the ancient crossing point, it is possible to watch pike hang almost motionless in the current or the dark forms of chub that jostle in loose shoals. At this time of the year the surface dances with drake mackerel mayflies, the males swarming through until dusk, the lazy fish rising to gulp down those that tire and drop to the grasping surface film.

Despite the beauty of the river and its valuable role, we treat it badly. The combination of fine weather and a school holiday leave a myriad of coloured debris in the form of drinks cans, crisp packets and discarded clothing. From time to time the appearance of a bicycle, television set or cd player hints at the discarded trophy of a burglary, or the waste of someone too lazy to visit the recycling centre.

Perhaps the worst treatment is meted out through the subterranean pipes that drain into the river along its length. Some of these catch surface run-off from the roads, silently flushing salt and various chemicals into the water, where they mix with nitrates from farmland and who knows what else. More obvious than these invisible additions is the occasional discharge of oil, a black slick of which was seen entering the river just the other week close to the Nun’s bridges. The quantity involved suggested that it was a deliberate act, the oil tipped into a drain that ultimately led to the river. It is incredibly frustrating that people seem to care so little, that they remain oblivious to the damage they inflict on a living system that brings life to their town.

A cuckoo in the nest

Each year we find a few Cuckoos parasitizing the Reed Warbler nests that we monitor at sites in the Brecks. These are invariably found at the egg stage, the Cuckoo egg similar in background colour and pattern to the Reed Warbler eggs but somewhat larger. The degree to which the Cuckoo achieves successful mimicry of the Reed Warbler eggs is important, since it needs to trick the host into thinking the egg is one of its own and not that of another species. If the Reed Warblers are suspicious that they might have been parasitized by a Cuckoo then they will abandon the nesting attempt and start again.

Cuckoo eggs have been recorded from some fifty different host species in Britain but those most often targeted are Reed Warbler, Meadow Pipit, Dunnock, Pied Wagtail and Robin (roughly in that order). I have also seen a Cuckoo egg in the nest of a Wren, though how successful Cuckoos are in using Wrens is debatable. Wrens, like other small birds that build an enclosed nest, seem particularly sensitive to any change in the size of the nest entrance and any damage caused by the Cuckoo during laying is likely to cause the Wrens to desert. Additionally, there is the size difference between the eggs of the two species and the enclosed nature of a nest which seems unlikely to cope with the volume of a growing Cuckoo chick.

Just last week I saw a Cuckoo egg in one of the Dunnock nests that we are monitoring. As you probably know, the eggs of a Dunnock are bright blue and the Cuckoo egg in this nest was brown with splodges of darker colour – the female presumably a Reed Warbler mimic. You would think that a Dunnock would recognise the difference between the two eggs as well, but it seems that this is not the case. It is thought that this is because the Dunnock is a relatively recent host and that it has not yet developed the ability to recognise and respond to the presence of a Cuckoo. That Reed Warblers can and do respond, suggests that they have been Cuckoo hosts for a much longer period of time. However, even the Reed Warblers are fooled if they don’t suspect that a Cuckoo has visited the nest and once the egg hatches the resultant chick is reared as their own.

Finding a nest with a Cuckoo egg in it delivers mixed emotions. The presence of the egg spells the end of the host’s nesting attempt but, with Cuckoo numbers in decline, it gives hope that another Cuckoo will be recruited into a flagging population.

A bed with a sting

Most of us have a natural aversion to stinging nettles. We steer clear of them because of a childhood encounter and the resulting burning sensation of the nettle’s sting. This sting is part of the plant’s defences, an attempt to deter the attentions of grazing herbivores that might otherwise tuck into the nettle’s succulent leaves. The gardener’s tolerance is equally low, viewing these vigorous, long-lived plants as unwanted and troublesome invaders of newly disturbed ground (like flowerbeds). They do particularly well on fertile soils of the type found around human habitation. You have to admire them though, both for their almost universal adaptability and for their resilience.

There are two species of stinging nettle in the county: the familiar Stinging Nettle Urtica dioica (which is a perennial) and the more local Small Nettle Urtica urens (which is an annual). A third species, the Roman Nettle Urtica pilulifera, once occurred around King’s Lynn and Yarmouth but is now considered extinct in Britain. It was last recorded in the county around 1900.

The dioica part of the Stinging Nettle’s scientific name is derived from the Greek (­di-oikos), which means ‘two houses’. This refers to the fact that the nettle has separate male and female plants; male plants have flowers that are dusted bright yellow by the pollen on the anthers, while female plants have flowers which show a silvery, almost furry, appearance. Very occasionally a nettle plant may be found which has both male and female flowers, with part of the inflorescence having male flowers and part female. Other variation is associated with the sting, in that there are forms of the plant that lack the sting altogether. These tend to have rather long and narrow leaves and are most often found in wet situations like fens and marshes. This form of the plant, known by some as the variety subinermis and by others as Urtica galeopsifolia, is fairly common at Wicken Fen.

As someone who spends a lot of time in and around nettle beds I know that nettle clumps support a diverse community of invertebrate life, from bright green weevils, through the caterpillars of various moths to various bugs and beetles. They also provide nesting cover for some of our warblers, particularly where the nettles rise up through thicker material like bramble or the dead stems of last year’s growth. Whitethroats and Garden Warblers seem particularly fond of them. Nettles are an important habitat and it is a shame that we view them with such distaste. One feels that if it wasn’t for the sting we might be more tolerant, and perhaps admiring, of them. Of course, they would probably then be ravaged by grazing herbivores and far less impressive.

A bed with a sting

Most of us have a natural aversion to stinging nettles. We steer clear of them because of a childhood encounter and the resulting burning sensation of the nettle’s sting. This sting is part of the plant’s defences, an attempt to deter the attentions of grazing herbivores that might otherwise tuck into the nettle’s succulent leaves. The gardener’s tolerance is equally low, viewing these vigorous, long-lived plants as unwanted and troublesome invaders of newly disturbed ground (like flowerbeds). They do particularly well on fertile soils of the type found around human habitation. You have to admire them though, both for their almost universal adaptability and for their resilience.

There are two species of stinging nettle in the county: the familiar Stinging Nettle Urtica dioica (which is a perennial) and the more local Small Nettle Urtica urens (which is an annual). A third species, the Roman Nettle Urtica pilulifera, once occurred around King’s Lynn and Yarmouth but is now considered extinct in Britain. It was last recorded in the county around 1900.

The dioica part of the Stinging Nettle’s scientific name is derived from the Greek (­di-oikos), which means ‘two houses’. This refers to the fact that the nettle has separate male and female plants; male plants have flowers that are dusted bright yellow by the pollen on the anthers, while female plants have flowers which show a silvery, almost furry, appearance. Very occasionally a nettle plant may be found which has both male and female flowers, with part of the inflorescence having male flowers and part female. Other variation is associated with the sting, in that there are forms of the plant that lack the sting altogether. These tend to have rather long and narrow leaves and are most often found in wet situations like fens and marshes. This form of the plant, known by some as the variety subinermis and by others as Urtica galeopsifolia, is fairly common at Wicken Fen.

As someone who spends a lot of time in and around nettle beds I know that nettle clumps support a diverse community of invertebrate life, from bright green weevils, through the caterpillars of various moths to various bugs and beetles. They also provide nesting cover for some of our warblers, particularly where the nettles rise up through thicker material like bramble or the dead stems of last year’s growth. Whitethroats and Garden Warblers seem particularly fond of them. Nettles are an important habitat and it is a shame that we view them with such distaste. One feels that if it wasn’t for the sting we might be more tolerant, and perhaps admiring, of them. Of course, they would probably then be ravaged by grazing herbivores and far less impressive.