A bird in the bush

I’ve been out nesting a few times over recent weeks, squeezing in visits on those days when the sun has shone and the wind has stilled. This is not the sort of nesting to be confused with that of uncaring individuals who, with criminal intent, seek out nesting birds to steal their eggs, robbing the potential of a future generation for the sake of a collection arranged like stamps. Instead it is the collation of information invaluable to nature conservation and part of a national scheme.

My trips out have been in the company of nest recorders participating in the British Trust for Ornithology’s Nest Record Scheme. Experts in finding nests (though always learning, so they say), my guides have shown me how to find the carefully hidden nests of warblers, finches and thrushes. It has been a tremendous privilege and I feel that I am developing a skill that I will be able to put to good use in future years, sending in my own contributions to the scheme.

Nest finding involves a range of different approaches, a combination of skills that come together to reveal a hidden nest. One of the most often deployed of these skills is cold searching an area in which the species of interest has set up its territory. This involves a careful and steady search of each bramble bush or nettle bed, looking for the nest, while at the same time minimising the amount of disturbance. Ideally the nest will be found at an early stage, while the birds are still building. Its position can then be noted and a return visit planned for when the birds have started laying their eggs. Several more visits follow, carefully spaced to provide the maximum amount of information with the minimum of intrusion. Each visit contributes to a bigger picture, providing information on how many eggs were laid, how many of these hatched and how many chicks survived through to fledging. Visits can also reveal if a nest has been predated, at what stage and, sometimes, by what sort of predator.

Collectively, the information from many hundreds of nest recorders, delivers a powerful overview of how a species is faring, addressing the question of whether or not it has had a good breeding season and, importantly, alerting Government and the conservation agencies to any sudden declines in breeding success that might signal a wider problem. Nest recording is one of those skills that is being lost, the generation of practitioners an ageing one and with few youngsters coming in to replace those lost to old age. Efforts are being made to engage with a new generation of nest recorders and I hope to be one of them.

Urban Swallows

The Swallow is perhaps our most familiar summer visitor. It is a species for which we have great affection and one that can be found breeding across most of Britain, avoiding only the uplands, the most extensively wooded land and rarely penetrating beyond the fringes of our urbanised areas. For many of us the Swallow is the true harbinger of spring, a symbol of annual renewal and a bird whose arrival we watch for with eager anticipation. For those whose existence is more strongly tied to the urbanised landscape the Swallow is replaced in this role by the Swift, a species which has taken more readily to the built environment.

My walk into work takes me through the centre of one particular urbanised landscape and were it not for my regular birdwatching trips out into the wider countryside, it would be the Swift rather than the Swallow that was my harbinger of spring. Most mornings, my walk through town is accompanied by screeching Swifts but for the last two weeks there has been a very different sound, the twittering song of a Swallow. It appears that a pair of Swallows has taken up residence alongside the formal gardens of King’s House, the male delivering his charming song from television aerials and telephone wires. It seems an unlikely location, especially as his mate has been prospecting for a suitable nest site in the doorways of the neighbouring houses. The large circular wall lights might well make a sturdy platform onto which the nest could be built but I am not sure that the householders will be overly tolerant of their newly acquired neighbours.

The absence of Swallows from urbanised landscapes is linked to the availability of food and the Swallow’s chosen method of feeding. While Swifts will feed high above the rooftops, Swallows occupy a layer of sky that is much closer to the ground, feeding well below the height favoured by both Swifts and House Martins. Here they take larger insects, like flies, and such feeding opportunities would seem rather limited here in town. Perhaps they will be able to find sufficient insects by feeding above the formal gardens but it could prove a costly decision to nest here. My guess is that these are young and inexperienced birds, since breeding adults usually return to the same site in consecutive years and these are the first Swallows I have seen set up territory here since I arrived more than a decade ago. If they are young birds, then they are likely to have been born locally, since most birds return to within 30km of the nest in which they were raised. It will be very interesting to see how they fare over the coming weeks.

Norfolk's deer revela our influence

Norfolk is well represented when it comes to deer, with six species currently established within the county. While it might seem fairly straightforward to divide the six species into native (Roe and Red) and introduced (Fallow, Sika, Muntjac and Chinese Water Deer), things are not quite what they seem. The presence of all six species within the county owes a great deal to our activities and to the deliberate introduction of animals for sporting or personal interests.

Like the Red Deer, the Roe is an ancient inhabitant of Norfolk, its bones present in the fossil and archaeological record. However, both species were lost from the county historically, only to be reintroduced from imported stock. Red Deer had become extinct across much of England and Wales by the end of the Eighteenth Century and the same is almost certainly true for the Roe within East Anglia. The Roe that are present here today are most likely of German origin, the descendents of individuals introduced to Warren Wood, near Thetford, in 1884 by William Dalziel Mackenzie.

Other species have a longer pedigree, as in the case of Fallow, brought in to populate the 40 or so deer parks established within the county since Doomsday. Red and, in one case, Sika Deer were also used to stock Norfolk’s deer parks, which were status symbols for those wealthy enough to be able to build and maintain them. The earliest of our deer parks appears to be Costessey, dating from around 1086. Like the majority of our other deer parks, that at Costessey was lost many decades ago. Many disappeared during the Civil War but three remain today, two well-known and well-maintained and one about which I know rather little (but would like to know more). The two big parks are at Holkham (completed by 1759) and Houghton (completed in 1722); both have magnificent herds of Fallow, that at Houghton managed to favour the white form of Fallow, that at Holkham with the standard form. The other park is at Melton Constable, reputed to support 300 animals, roughly evenly divided between Red, Fallow and Sika, but since it does not have the sort of public access associated with Holkham it is difficult to know how the herds are doing.

One of the reasons for the demise of deer parks was the expense of maintaining them. Holkham has some nine miles of wall (which took six years to construct) and the maintenance costs are high. As land has changed in value, it has not always be easy to maintain large areas outside of agricultural production. Deer have from the parks and it is the descendents of these that are now doing so well in the county.

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.

Encounter with a spitting spider

As soon as I saw her I was pretty sure of her identity; Scytodes thoracica, the spitting spider. Once she was safely sealed in the confines of one of my specimen tubes I checked her identity against a guide and took in her spiderly beauty. Very pale brown in colour, Scytodes is delicately marked with a deeper brown through a succession of spots on her thorax and strongly domed carapace, and bands on her thin legs.

The large, domed carapace is a striking feature and houses a pair of enormous double-lobed glands. The front lobe of each produces poison while the larger rear lobe produces a sticky, glue-like substance. Each gland is linked by a duct to the front of the fang where it emerges through a small opening. By using muscular contractions to compress the gland, the spider is able to ‘fire’ a stream of poisonous glue at its intended victim, easily covering a distance of 10mm or more. At the same time, the spider very rapidly moves its fangs from side to side, creating a zig-zag of deadly spray that quickly immobilises its prey; only then does the spider approach more closely and deliver the coup de grace. If there is any sign of a struggle on the part of the victim, Scytodes will deliver the bite to one of the extremities before retreating and playing her patient game.

As its weaponry might suggest, this is an active hunter which does not bother to build a web, but instead stalks prey with a slow and steady gait. Scytodes is synanthropic in habits, which means that she lives alongside us in our houses and offices. Although widely distributed within southern Britain, south of a line from the Humber to Glamorgan, this spider is either somewhat uncommon or poorly reported. I have only seen her twice in the 10 years that I have lived in this old house and I do not recall seeing her in any of the other houses in which I have lived. This house is quite old and seems to support a good number of spider species. The spider’s powers of dispersal may be rather poor, since it’s young do not disperse on the breeze, so dispersal is likely to be through the movement of household objects from one location to another. Another factor that may restrict the species to low levels of abundance is the length of time (some three years) that it takes the females to reach maturity. We tend to think of insects, spiders and other invertebrates as being short-lived, ephemeral creatures but this is not always the case. Having secured her identity I released her, in the hope that she remains unnoticed by my wife!

Purple Herons find themselves too far north

The months of April and May often turn up rare visitors, birds that have overshot on their spring migration and ended up further north than intended. One of the species well-known for such overshooting is the Purple Heron, at least one individual of which has already be seen in East Anglia this spring. The Purple Heron is a locally occurring but widespread species, breeding from northeast France and the Netherlands east across Europe, into Asia and south into Africa. Birds winter to the south of the breeding range and those breeding in Europe cross the Sahara (a desert crossing of some 30 to 60 hours duration) to winter in sub-Saharan Africa. It is because the species is migratory in habits that some individuals end up reaching Britain each year.

Most of the records of Purple Herons in Britain come from East Anglia, Kent and East Sussex, and most involve single birds. However, a party of four Purple Herons, accompanied by a solitary Grey Heron, were seen to arrive at Salthouse from the northeast on 1^st June 1998. The birds circled over the village briefly and then departed inland. The species can prove a frustration for the birdwatcher, often only stopping at a site for a single day and also tending to remain elusive during its stay. Your best chance of seeing the bird is either in early morning or close to dusk, as it flies between feeding and roosting areas. When foraging, the heron can be very difficult to see, since it tends to stand motionless, waist deep in water, within dense vegetation (like a stand of reeds). Large reedbeds are a clear draw and this may be why the RSPB reserve at Minsmere seems to do so well when it comes to attracting them (a position on the east coast does not hurt either). In 2007, at least three birds were present in the second half of May, with two individuals seen to display on several occasions. Any hopes of a breeding attempt were dashed, however, by the arrival of bad weather.

The Purple Heron is noticeably smaller than the more familiar Grey Heron and sports rufous brown and grey plumage, mixed with areas of black and white. Since the species is most often seen in flight, when size can be more difficult to determine, there is scope for confusion with Grey Heron. Generally speaking, a Purple Heron in flight appears as a wholly dark bird while the lighter coloured Grey Heron shows contrast between the grey wings and the white body. It is worth casting a careful eye over any herons that you see over the coming weeks, just in case they prove to be something more exotic.

In awe of snakes

The other week I visited the garden of Dave Shearing to take part in some filming we were doing to promote a new survey of garden reptiles and amphibians. The garden was a wildlife haven, a formal area stocked with bird feeders and then a gate through into open woodland complete with nestboxes, wildlife pond and corrugated tin plates. The tin provided shelter for Grass Snakes and Slow-worms, both of which proved to be present in the garden in good numbers.

With a careful approach and lifting of the tin it was possible to take a close look at these two less commonly encountered creatures. While some of the snakes made a swift retreat into one of the many woodpiles that dotted the garden, others remained and seemed just as inquisitive about us as we were of them. By being able to watch the snakes in this way I was really impressed by the range of adaptations they displayed.

Snakes are not unique amongst the reptiles in being limbless but this feature does form the cornerstone of their anatomy. The long thin body places constraints on its internal structure and many of the internal organs are highly modified (or absent - most snakes have just a single functional lung). Many organs are elongated and paired organs are often arranged one behind the other, rather than side-by-side; the left kidney, for example, sits behind the right. Each of the vertebrae (and there are usually between 160 and 400 of these) has a pair of ribs attached to it. The ribs themselves articulate and can be swung forward, allowing the snake to flatten out its body to soak up more of the sun’s warmth (I often see Adders doing this) or to allow the passage of a large prey item down the digestive tract. The skull is also adapted to aid the passage of large prey, the two lower jaws not joined at the chin and allowing them to move independently of one another as well as pull apart. This is why even some of the smaller individuals we watched could have tackled an adult frog.

The survey of garden reptiles and amphibians is being organised by the British Trust for Ornithology, Froglife and the Herpetological Conservation Trust. The researchers want to find out which factors influence whether or not particular species of reptile and amphibian will use a garden. As such, they want to hear from anybody who has a garden, regardless of whether or not it contains any reptiles or amphibians. A free survey pack and identification chart can be requested by calling the BTO, by emailing gbw@bto.org or by writing to Reptile Survey, BTO, The Nunnery, Thetford, Norfolk, IP24 2PU.