Fenland in all its glory

It is a glorious morning to be out for a walk, the sky a bright expanse of blue tinged with the softest wisps of fine cloud. Such a dramatic sky is enhanced by the dark, peaty flatness of the fenland landscape, the land reduced to a narrow band, linear beneath a great and vibrant canvas. The ultimately circular walk will take me along Burwell Lode, north towards Adventurer’s Fen (with Wicken beyond) before looping back around to follow smaller ditches and fenland drains.

The going is easy, the land flat and the tracks relatively free from mud. My progress, however, is slow, such are the distractions of this vast expanse over which I can scan with my binoculars. The fields that sit neighbourly with the village are farmed but, while they hold partridge, Brown Hare and (surprisingly) a good number of Roe Deer, it is the distant wet fens that draw my gaze. It is these that will hold the hunting Short-eared Owls, wildfowl and waders.

Small parties of winter thrushes, Starlings and finches pass overhead, as do larger groups of Black-headed Gulls and the occasional swan. Even with the unseasonal warmth you can tell it is winter by the light and the calls of the birds that pass overhead. Spaced along the lode are groups of fishermen in their twos and threes, their large ‘Day-Glo’ floats sitting high in the dark water, unmoving. Despite the unseasonal warmth, the water must be cold and I wonder just how active the fish will be. From the reeds that line the far bank comes the harsh scolding chatter of a Wren. Holding a larder of insects, these waterside habitats can prove a lifeline for Wrens and other small birds in winter. Such is their importance that many Wrens will establish and defend feeding territories here for the duration of the winter.

A couple of miles in to the walk and I leave the arable behind, the ground becoming rougher and I sense that this is the place for hunting owls and harriers. Almost immediately, a Short-eared Owl catches my eye. It is quartering the ground, dropping down periodically onto unseen prey, though often unsuccessful in its strike. This is the first of several owls that I see over the course of the morning, the best of which comes within 40 m of me, perching on a post and staring with its intense yellow eyes. I never tire of these birds, such is their charm and character.

This winter, the fen is proving a reliable site for the owls, with up to six birds in the air at a time. Their presence draws birdwatchers, most of whom drive to fen but for me the walk is more rewarding.

Kestrel springs a surprise

I was a little taken aback the other morning when a Kestrel flew up from beside the gravel drive that marks the entrance to the British Trust for Ornithology’s (BTO) offices in Thetford. Although I have seen them occasionally from the BTO grounds, it has been many years since they nested here and could be seen hunting and feeding alongside the 12^th Century ruins with which we share the site.

This particular bird flew a short distance to land in one of the trees that mark the boundary of the grounds. Favouring a perch that was in part shadow, the Kestrel had something in its talons that it had clearly just taken from the ground. My immediate thought was that the bird had caught one of the Wood Mice or Bank Voles which do well here, but closer inspection through my binoculars revealed that it had, instead, caught a rather sizeable earthworm. Kestrels are opportunistic enough in their habits to take a range of prey species, from small mammals and birds through to reptiles and various invertebrates.

That Kestrels will take worms may surprise some readers; perhaps it is because these soil-dwelling invertebrates seem so inconsequential, hardly worth eating because of their small size and a belly full of decaying plant material. Yet earthworms feature in the diets of many larger birds: Common Buzzard and Tawny Owl being two species that spring to mind. Tawny Owls take earthworms on damp nights, when the worms venture from the safety of their burrows to search for a mate or for fallen leaves to be dragged back underground.

The appearance of earthworms in Kestrel diets has a strong seasonal component, with early spring the period when they are most likely to feature. In part this highlights a scarcity of the favoured small mammal prey at this time of the year but it also reflects an increase in the availability of earthworms, which tend to be more surface active when the ground is waterlogged. As you might expect, Kestrel diet varies with region. Those Kestrels breeding in the upland fringes of northern Britain take a lot of small mammals (mostly voles) with some earthworms and small birds. Those breeding in the warmer climes of southern Europe tend to take more birds, lizards and larger invertebrates. Such differences underline the adaptability of this bird, a hunter that will take whatever prey happens to be locally abundant.

It didn’t take long for the Kestrel to finish off the worm before slipping from its perch in a short glide. It was only the briefest of encounters but it was one that made an impression, one of those moments when you get a real sense of nature at work.

Peregrine

The distant Golden Plover are nervous, rising to the air as a pulsating mass that flashes white and then gold as if these were the only two states of a dichotomous existence. The switch in colour that ripples across the flock comes about as the birds twist and turn in the air; one second it is the golden brown backs the show, the next the white underparts.

This flock must hold more than two thousand individuals, a decent size and one of the largest I have seen on these marshes. That they are so flighty suggests that a Peregrine has been through or is, even now, somewhere in the cold brightness of this winter sky. As I scan with my binoculars I pick out the distant smudge of another plover flock but there is no sign of the Peregrine.

It is not until a few minutes later, scanning the back edge of the marsh beyond the grey forms of wintering geese that I chance across the Peregrine. It is perched on a pile of earth next to one of the ditches that criss-cross this watery landscape. It sits with an upright stance, the head turning with irritation to stare at the two crows seeking to drive it away with swooping strikes. Every so often it has to duck to avoid a glancing blow. The crows eventual tire of their game and begin to feed nearby, though still watchful. Even on the ground there is a powerful presence to this our most majestic of falcons.


There Peregrine seems fairly settled and my attention drifts elsewhere; when I look back the Peregrine has gone and the plovers are, once again, a pulsating mass of white and gold.

Redpolls roll up

I have just filled a bird feeder up with nyger seed in the hope that it will draw some redpolls into the garden. This small black seed is so fine that it requires a special feeder, one with tiny feeding ports, otherwise the seed would pour from the feeder like water. Because the seed is so fine it only really suits certain birds, those with small or narrow bills that come to a delicate point; included among these are Goldfinch, Siskin and Lesser Redpoll.

Funnily enough, I have never succeeded in getting my visiting Goldfinches to feed on the nyger unless it is the only thing on offer in the garden; they much prefer the sunflower hearts and mixed seed. While others have reported a similar pattern, there are gardens where the addition of a nyger feeder has delivered feeding Goldfinch for the first time. I have a suspicion that it is not their preferred food because so often it seems to be the young birds that end up on the nyger feeders, while the adult Goldfinches dominate those containing sunflower hearts. This is why I only use it during the late winter months, when it is likely to be used by some seasonal visitors.

Where the nyger seed does work, however, is in attracting Lesser Redpolls. These delightful little birds are very much winter visitors to garden feeding stations, the numbers using feeders increasing noticeably over the last three winters. Lesser Redpoll is a bird of pioneer woodland, those scrubby birch and alder woodlands characteristic of poor soils. Pressures on this habitat may be one reason why the species has undergone a significant population decline since the 1970s, prompting placement on the list of UK Biodiversity Action Plan species, but there have also be declines in breeding success and survival.

It is encouraging to see Lesser Redpolls coming into gardens in increased numbers to feed on nyger. Several researchers have suggested that the ‘discovery’ of nyger by the redpolls may help the population to recover. The availability of seed at garden feeding stations during the difficult winter months may improve overwinter survival and help take more birds through into the following breeding season. While many farmland finches underwent population declines during the 1970s and 1980s, we saw Goldfinches turn to garden feeding stations to a greater degree than others species and this may have contributed to the buoyant Goldfinch population that we see today.

Looking at the pattern of garden use by Lesser Redpolls, the main movement into gardens takes place during January and February, so it is not too late for you to purchase some nyger seed and a feeder, and to attract some of these great little birds into your garden.

A price worth paying

The environment has been taking something of a battering over the last 12 months. It seems that when the economy is struggling, it is the environment that is one of the first things to suffer. In an attempt to reduce costs, cuts within Government and its agencies seem to have fallen hardest on those responsible for looking after the countryside. Elsewhere, in a bid to get the economy moving, there is talk of loosening planning legislation and weakening the already poor environmental regulations. Then there has been the criticism of conservation-based NGOs, often from within their own ranks, with the suggestion that such organisations have been all too ready to rollover.

For me, perhaps the most worrying thing has been the increasing tendency to put a price on the environment and its natural processes. This approach argues that we undervalue our environment and that, as a consequence, the best way to address this is to give a monetary value to each natural process, something referred to as ecosystem services. The ‘value’ of pollinating insects to UK agriculture has, for example, been put at £400 million per annum. In some ways I can see the benefit of this. By presenting wildlife ‘value’ in the monetary terms that Government and industry are used to dealing with, we can at least communicate with them in a language that they understand. It is no longer just a chalkstream but an ‘ecosystem service’ chalkstream that delivers ‘x’ million pounds of value per annum. The problem with this approach, however, is that this is a measure of ‘value’ based purely on what the species, process or ecosystem has to offer us.

Wildlife and natural processes should have their own intrinsic value, something that exists beyond our rather narrow and selfish frames of human reference. The Buff-tailed Bumblebee should be considered as having ‘value’ simply because it exists and not just because it pollinates our crops. The value that we put on a single bee should be the same as that which we put on a Hedgehog, a Barn Owl or, for that matter, a human being.

The fundamental problem that I have with ecosystem services is that the approach is about what other creatures and natural processes do for us; it is not about our responsibilities towards our fellow creatures. We should judge the consequences of our actions by the impact that they have on the environment within which we live and the creatures with which we share it. While an ecosystem services approach may appear to go some way to doing this, it rather misses the point by incorrectly presenting value purely in monetary terms.

Look out for abnormal birds

Every now and then I come across a bird sporting some white feathers. Perhaps it is because these white feathers stand out most on a bird that is otherwise black, that the species involved is often a Blackbird, Jackdaw or Carrion Crow. Such plumage abnormalities are, however, likely to be more widespread than this and this is why the BTO is carrying out a study to examine the incidence of abnormal plumage across a range of species.

The presence of one or more white feathers often results from some non-heritable cause, such as disease, food deficiency or trauma. In other cases, the cause may be under genetic control. Perhaps the best-known of these is albinism or partial albinism. However, the definition of what constitutes an albino or partial albino is rather precise and most of the cases involving aberrant white feathering in birds are usually either a form of leucism or result from some non-heritable cause.

White feathers can occur where the normal colour pigments (e.g. melanin) are missing. The resulting feathers are often weaker because of this and, therefore, more prone to wear and damage.

In some instances, the process works the other way and too much melanin is produced, resulting in feathers that are far darker than usual. There is, for example, a population of Great Tits in southeast England that have completely black heads, the white cheek feathers turned black by abnormal levels of pigment.

Other aberrations can produce feathers that appear washed out or, alternatively, more strongly coloured with a particular pigment. In some cases these may result from diet; I can recall a case from a few years ago where House Sparrows that had been feeding on fish pellets at a Salmon farm in Scotland had feathers that were a muddy shade of pink! The pellets contained a natural pink dye, used to give the Salmon a stronger colour, favoured by customers.

One of the main problems with understanding the different abnormalities is that the naming of aberrations is based on the relevant gene action on the pigmentation process and not on the appearance of the final plumage colour. As observers, we see the final result not the process that brings it about, making it difficult to interpret which abnormalities occur in the wild. The BTO survey will provide some useful background figures but it will require detailed work to more fully understand the processes operating on individual birds. If you have seen a bird with abnormal plumage then the BTO would like to hear from you. You can either complete the survey online (www.bto.org/gbw) or request a paper recording form from, BTO Plumage Survey, The Nunnery, Thetford, Norfolk, IP24 2PU. Alternatively, email gbw@bto.org.

Tawny Owls already setting up home

The gap between one breeding season and the next is surprisingly short, with some birds already initiating this season’s attempt. The earliest of our nesters is the Tawny Owl, so it was unsurprising to hear of a pair busy settling into their nestbox well before Christmas. This particular nestbox has a camera fitted, allowing the owner to watch the nesting antics of the resident pair. Although I refer to them as the resident pair, it is likely that the male of the pair is new, the previous male having disappeared part way through the 2011 nesting attempt.

Tawny Owls are highly territorial birds and their characteristic hooting calls will have been heard by many through the dark evenings of November and December. Territory is extremely important to a Tawny Owl; not only does it contain the nest site but it also holds the small mammal prey that the owls rely on. Hunting in the dark is not easy, so knowledge of a local patch – in the form of a territory – is likely to be particularly important, the owl soon learning the best perches from which to hunt.

Most Tawny Owl nests are located in large tree cavities, though they will take to nestboxes and have sometimes been found using the old stick nests of other species, like crows. Very occasionally, Tawny Owls have been found nesting on the ground, something that tends to reflect a lack of suitable nesting cavities (e.g. within coniferous woodland). The nest itself is really just a shallow scrape, made in any debris that the cavity happens to contain. Two or three eggs are typical, each laid with a gap of a couple of days, but clutches of up to five or even six eggs are possible.

Female Tawny Owls are very good parents, sitting tight on the eggs and they are not easily put off the completed clutch. This can cause them problems in some (rare) cases, where a Jackdaw or other species builds a nest on top of the owl, effectively entombing her within the cavity. Once the eggs hatch, the female will readily attack human intruders, striking at them with her talons. There are even instances where unfortunate observers have lost an eye or been scarred by a female Tawny Owl.

The earliest Tawny Owls may already be on eggs, but most pairs will not get started until late February, the first young appearing in the nest from mid-March. Our other owls start breeding a little later but even they may have young in the nest from April. While spring may still seem a long way off, it is heartening to think that the nesting season has started and that new life is on its way.

Beechmast is the key

Find a stand of mature Beech trees this winter and you have every chance of catching up with some Nordic wanderers. Beechmast, the seed of the Beech tree, is an important winter food for birds like Chaffinch and Brambling. The mast is rarely plentiful in the same place in successive years, so birds that feed on it tend to move around, often covering large distances until they find areas with a sizeable crop. In the case of Brambling and Chaffinch, such movements can see them arrive in Britain from breeding grounds spread across Norway, Sweden and Finland. The flocks that congregate elsewhere in Europe, however, invariably dwarf the numbers wintering here. For example, roosting flocks of up to 20 million Bramblings have been recorded in central Europe but here the largest tend to be limited to a few thousand individuals.

Over the last couple of weeks the stands of Beech at Holkham Park have attracted a sizeable flock of Brambling, while smaller groups have been reported at other sites across the county. Sometimes, where a stand of Beech sits alongside a road, the birds dice with the traffic, fluttering down to grab fragments of mast, smashed by the tyres of passing cars and lorries. Both species feed mainly from the ground in winter, a contrast to the summer preference for feeding on insects in the canopy of trees and shrubs. Both species have comparatively large bills, with that of the Brambling being the more robust of the two, and this may explain why Bramblings show a greater preference for the seeds of Beech than any of our other wintering finches.

Bramblings winter as far north as the availability of Beechmast will allow. In those years when the more northerly crops have been poor, the birds are forced to move further south and west in search of food. Movements can also be influenced by winter weather, since a covering of snow can make any remaining mast unavailable. A combination of a poor crop and heavy snowfall, can see vast numbers arrive in Britain and, to a lesser extent, Ireland. Our relatively mild winter weather offers more favourable conditions for the birds, even if we have relatively little Beechmast available compared to the Continent.

It is not until later in the winter that we tend to see Bramblings visiting garden feeding stations to take peanut granules and sunflower hearts, something that may result from Beechmast and other seed crops coming to their end. Although weekly observations from the BTO Garden BirdWatch survey show the first Brambling arrivals in gardens during October, the peak does not occur until late March of early April, before falling away steeply by the beginning of May.

Patriarch of the woods

In dawn’s half-light a dark silhouette sits hunched at the top of a tall birch. In one smooth motion it expands to a ragged-winged form to slip silently from its perch. This is a Carrion Crow, patriarch of these woods, and a territory-holding bird whose mate will be somewhere nearby. It is easy to see why these dark sentinels have featured so prominently in legend and lore. There is something ominous and broodingly expectant about the way in which they loiter, ever watchful for the next meal. Our interest in crows, and more widely in other members of the crow family, is rather ambivalent. Kept as pets, shot as pests, viewed with respect but sometimes fear, there is a long history that exists between us.

The Carrion Crow is an adaptable species, quick to learn and thus able to exploit new opportunities. They are one of the species to have benefitted from the new opportunities on offer in our ever-urbanising world. Even here, in the centre of town, a pair has taken up residence and can be heard proclaiming the ownership of their territory.

Crow populations can be divided into the territory-holding pairs and a floating population of non-breeding birds, the latter predominantly comprised of immature birds waiting for an opportunity to take on a territory. This suggests that territories are a limiting factor, the resources and nesting opportunities they contain restricted in their availability. Each territory, which can be up to 110 acres in size, is defended with vigour by the male, supported by his partner. Established neighbours, familiar to the territory-holding pair, are treated less aggressively, leading to some overlap in neighbouring territories and a shared defence of this airspace. In fact, neighbouring pairs may work together to chase off intruders and would-be predators like Buzzards.

During the nesting season, activity is centred on the nest and birds spend less time at the fringes of their territory. The males, however, continue to advertise the ownership with much calling and posturing. Birds from the non-breeding flock frequently test the resilience of established pairs by making territorial incursions, with such activity peaking during the first third of the year. Both the nest site and the breeding territory are defended throughout the year, so even now my local birds are on the lookout for possible trouble.

Despite the rigid territorial structure, Carrion Crows form large communal roosts (often with other crow species). These are a familiar feature of the winter months and are dominated by the non territory-holding birds, although territory holders may join them. For me though, it is the solitary pairs that sit and watch from their territories that are a feature of the dark winter mornings.