Saturday, 25 May 2013

Confronting the need for good news

Channel 4 News recently ran a series of snappy items on the impacts of a changing climate, loosely hung around the not so snappily titled ‘Terrestrial Biodiversity Climate Change Impacts Report Card’. This ‘card’, which provides an overview of how climate change is affecting UK biodiversity, is based on the latest scientific evidence and is drawn from a wide range of organisations. Channel 4 News should be rightly praised for giving this work some high profile air time, as all too often the environment and its wildlife are pigeonholed into bite-sized snippets, largely centred on creatures that are either large and cuddly or which cut across our economic activities.

Rather sadly, Channel 4 News fell into the trap of wanting to balance or soften the bad news – a changing climate is negatively impacting much of our wildlife – with happy ending. They managed to do this by first suggesting that we should be planting exotic trees, or exotically-sourced forms of native trees, so that we will have woods and forests better suited to the climate we are likely to face by the time they mature. Such plantings are already taking place. The Forestry Commission has already started down this road by planting Californian redwoods in Wales, hopeful that their better drought tolerance will make them more commercially viable under a changing climate. And there’s the rub – missed by Channel 4 News ­– these trees are being grown as a crop, looking for economic returns and irrespective of wildlife benefit.

One of the items broadcast by the news team went on to champion how we can reintroduce creatures that have been lost, implying (at least to those in Government keen to hear such a message) that if we stuff things up then we can always reintroduce the species that are lost. While it is true that there have been some very successful, very high profile reintroductions here in the UK, it is important to note that reintroduction only works under very precise circumstances. Specifically, it requires you to know what has caused the loss of the species in the first place and to have fixed it so that it is no longer a problem. This is why species like white-tailed eagle and red kite have been so readily reintroduced. These are species that were persecuted to extinction across much of their UK range; by removing the persecution we have been able to bring them back. The impacts of a changing climate are unlikely to be so readily reversed, making reintroduction a less suitable tool.

The problem with the media’s need for a happy ending is that it suggests that things are easily fixed, which they’re not. It is time to be more honest about what climate change actually means. 

Friday, 24 May 2013


The presence of a whinchat on the BTO Nunnery Lakes Reserve for a few days earlier in the month hinted at echoes of an older Breckland. This small bird, related to the more familiar stonechat, last bred in the county back in 1992 (at Horsey) and it now only occurs as a passage migrant during spring and autumn. Back in the 19th Century the whinchat was commonly encountered throughout Norfolk, with pairs breeding on heathland sites, including Mousehold Heath where 14 nests were found in 1864. Many of the nests were associated with gorse, something that led to the adopted local name for this bird of ‘furr chuck’.

Over time, and in common with populations elsewhere across south-east England, breeding numbers began to decline, leaving the species increasingly restricted to the old warrens and heaths of south-west Norfolk and, later, to the young plantation forestry becoming established across much of Breckland. The loss of the whinchat from Norfolk appears to be part of as much wider contraction in breeding range, the numbers in the UK falling by 57% between 1995 and 2010 according to the BTO/JNCC/RSPB Breeding Bird Survey.

I still see whinchats most years, typically during periods of spring or autumn passage. Unlike many of the other migrants passing through Norfolk, which appear on the coast, passage whinchats also turn up at inland sites, some of which are former breeding haunts. Very occasionally a pair may turn up together and there also almost annual reports of male whinchats singing from what appear to be suitable breeding sites.

At the end of the breeding season our whinchats depart, migrating long-distance to cross the Sahara and reach tropical Africa. We know very little about the wintering areas used by British whinchats or, indeed, about the nature of the migratory flights that get them there. It is thought that the birds overfly the Sahara in a single hop, having left from stop-over sites in southern Europe but this has yet to be confirmed from ringing studies. Increased understanding of the migration behaviour is much-needed, not least because it might help to explain why the whinchat has declined so dramatically as a breeding species in Britain. It could be that problems on the wintering areas, such as habitat loss or a changing climate, are behind the decline. Alternatively, the birds may be encountering new problems during migration or, possibly, once they return to Britain to breed. Those birds present in Norfolk during spring could be from breeding populations located in northern Britain or they could from populations located further east, the birds perhaps pushed across the North Sea by easterly winds. Either way, it is good to see one here in the Brecks.

Thursday, 23 May 2013

Mini Marvel

With a body weight of less than 125 g the weasel is our smallest carnivore, but what this diminutive predator lacks in size it more than makes up for in personality. Weasels are perhaps most commonly encountered when seen scurrying across a road or path, displaying the appearance of an elongated vole. The small size is even more apparent when you encounter a female; such is the degree of sexual size dimorphism that the smallest female may weigh barely a third of the largest male, the former measuring in at just 18 cm in length (4 cm of which is tail).

Small body size enables the weasel to target mice and voles within their burrow systems, a place where they are usually free from the risk of predation. Two-thirds of the weasel diet is made up of small mammals, making this a small mammal specialist, with a further quarter comprised of rabbits and the remainder a mix of other mammals, birds and their eggs and, occasionally, earthworms. Rabbits may be particularly important in spring, when young rabbits are widely available and small mammal populations tend to be at their nadir. Being smaller, the females tend to concentrate on small mammals, the male’s larger size allowing a wider range of prey to be taken.

The weasel has a reputation for being ferocious beyond its size and this is certainly not a species you would want to handle. I have caught weasels from time to time in live traps set for small mammals. While they usually rush off once released, I once had one face me down in a stand-off that last for several minutes; the weasel was decidedly nonplussed about having been shut in a trap for several hours. Such ferocity might explain why weasels may sometimes attack prey much larger than themselves. Rabbit has already been mentioned but to this species can be added common rat and even brown hare!

Weasels are easily overlooked beyond such chance encounters. In part this reflects their behaviour, with most of their activity centred on hunting under matted grass or within small mammal burrow systems. They seem less inquisitive than the larger stoat, to which they are related, but will investigate other feeding opportunities when favoured prey are less abundant. For instance, they are known to raid nest boxes erected for birds. At some sites, in certain years, weasels have been a significant cause of nestling mortality.

While small size may offer certain advantages, it does leave the weasel at risk of ending up on the menu for other, larger, predators, such as red fox and domestic cat. I’ve even found the odd weasel jawbone in a barn owl pellet, although it remains rather uncommon. 

Wednesday, 22 May 2013

Three birds in the bush

A few distant but instantly recognisable phrases were enough to reveal the presence of a male nightingale at the bottom end of the local nature reserve. It was early in the season, however, and this could easily have been a passage bird, just passing through. Fortunately, subsequent visits to the site have found the bird still present and seemingly holding territory in a piece of scrubby woodland that looks ideal for a future nesting attempt.

There is no mistaking the territorial claim of a nightingale; a richly varied and explosively loud song that has its own delicate rhythm and a confidence in its timing that echoes the very best of our jazz musicians. At times I have heard nightingales burst into song at the approach of a human observer who has, perhaps, strayed too close to the breeding site. The singing bird will often remain hidden from view, the song post buried deep within a tangle of bramble and other thick cover. On occasion, particularly ahead of dusk and early in the breeding season, the male may sing from more obvious perches and be more accessible to the would-be watcher. Once the eggs hatch, male song virtually ceases and the woods again fall silent, the pair becoming more skulking in habits and harder to locate.

The nightingale is not the only bird singing from the brambles at the moment, as both blackcap and garden warbler are busy delivering their rich, melodic warblings. The two species can be difficult to separate on the basis of their song and it always takes me a while to get my ear attuned once the first of these birds return to favoured breeding haunts. To my ear, blackcap song sounds as if it has been scripted, the bird clear in what it is going to sing and for how long; in contrast, the garden warbler seems more hurried, less organised and has the character of a songster who is making it up as he goes along.

Knowing the songs of all three birds is important to me as someone who surveys and monitors birds. All three species tend to make the most of the cover available and so are heard more often than they are seen. Repeated visits to study sites allows me to build up a picture of where the territories of these species are located and I can also use their calls to inform me of the likely stage of the breeding cycle. For example, blackcaps tend to alarm most readily just ahead of egg laying, then they go quiet until the eggs hatch, after which the harsh ‘tacc’ alarm returns, together with a rasping squeak. Such subtleties in behaviour are useful when working with these birds in the bush.

Tuesday, 21 May 2013

Something weevil this way comes

When it comes to global dominance, it may surprise you to discover that the weevils form the largest known family (the Curculionoidea) within the animal kingdom. Roughly one in every four beetle species is a weevil and even here, in the cooler climes of north-western Europe, they are still remarkably well represented. Many weevils feed on particular plants, either a single species or several that belong to the same family, and it is this close association that supports the sheer diversity seen within the weevil family. Weevils are sometimes referred to as botanists’ insects because of this and being good at botany is particularly useful when it comes to attempting an identification.

Weevils show variation in terms of size, colour and structure, though all the true weevils have a distinct snout to the head. In some species this snout (known as the rostrum) is broad, while in others it is extremely fine and narrowed. All of our weevils feed on plant material. Some feed on the roots, including Ferreria marqueti a blind, eyeless species only recently discovered in south-east England. Others feed on the stems, leaves or flowers and some feed on plant seeds. There are also species that feed on dead and decaying wood, some of which are regarded as economic pests as they can also damage the living wood of commercial timber. Perhaps most remarkable of all are the weevils that feed on aquatic vegetation, some of which feed below the water’s surface.

Adult weevils can be found throughout the spring and summer months and most species have a single generation each year, although this may be modified by the seasonality of the plant material upon which they depend. Some of the easiest weevils to track down are those to be found feeding on stinging nettles. These include the green weevil Phyllobius pomaceus, some of whose relatives are pests of fruit trees. Perhaps the most familiar weevils, however, are the vine weevils, notably Otiorhynchus sulcatus (the vine weevil) and O. singularis (the clay-coloured weevil), both of which are important pests of pot plants (indoor or outdoor). In fact, many readers will probably only think of weevils in terms of their pest status, unaware of the many hundreds of other species feeding on wild plants and dead wood.

Perhaps the most famous of all weevils is the cotton or ‘boll’ weevil, a species that effectively halted the cotton monocultures of the southern United States. While the response of this weevil to an abundance of food may have been disastrous at the time, leading to widespread failure in the cotton crop, it has since been recognised by some economists as being the stimulant behind diversification in American agriculture. 

Monday, 20 May 2013

Good things come to those who wait

It is because of a chiffchaff that I now found myself sitting in several inches of mud and stinging nettles, my back resting against an alder trunk and my eyes scanning the rough ground ahead. This is my third visit to this general area in search of the chiffchaff’s nest that had so far eluded me.  A male had been singing from this part of the reserve for a few weeks and the pair had been seen courting, with fluttering wings and soft calling. The ‘action’, so to speak, had taken place in a scrubby meadow, separated from my current viewpoint by a narrow strip of wet woodland.

The key to finding chiffchaff nests is to follow the female back to the nest, using her ‘off-nest’ call to both locate and identify her. This call, a soft and repeated ‘hueet’, alerts the male that his mate is away from the nest; it is not dissimilar to the more general contact call used by the species. The ‘hueet’ is most characteristically delivered when the female has eggs in the nest, providing an ideal opportunity for those involved in nest monitoring to collect vital information on clutch size and laying date.

The technique of following female chiffchaffs (and other ‘leaf warblers’) back to the nest works best in more open habitats, with good lines of sight. Here, however, the feeding female would move through the wood to feed in different places, making watching back particularly problematic. The two previous visits had narrowed down the nest location to the damp ground where I was now waiting patiently. After an incubation bout of 30 to 45 minutes the female should leave the nest to feed and I could then watch her back to the nest.

True to form the female leaves to feed and disappears into the wood. Some 10 minutes later she is back and I follow her calls to a single scrubby hawthorn on a bank. From here she drops down into the grass beneath, leaving me with a mental note of where to look once I have given her another 20 minutes to incubate before making an approach to the nest. The complex structure of the vegetation requires a very cautious approach – chiffchaffs nest as low as two inches above the ground – and it is as I am inching my way forward that I spot the nest, a ball of woven reed and grass stems placed in a tangle of sward. I ‘pish’ through my teeth to alert the female of my approach and then gently tap the nearby vegetation to lift her from the nest. A quick check of the nest contents – six warm eggs – then I leave. Three hours work for an important reward.