Wednesday, 31 March 2010

Nesting neighbours

It has been something of a slow start to the year and you may well have noticed how behind some of the spring flowers have been. The same is true for birds, with fewer early nesting attempts reported than is usually the case by this time of the year. Following a mild winter I might expect to have heard about 16 or 17 different species with active nests by Valentine’s Day; this year, however, there were just nine and even now things have not really picked up a great deal. Although early nesting attempts often fail, the birds caught out by a return to colder conditions, there are some species that always nest a bit earlier in the year than others. Tawny Owl (recently fledged Tawny Owls are on the wing in Kensington Gardens, London) and Mistle Thrush (a brood of young Mistle Thrushes is being fed in Manchester United Old Trafford stadium) are two for which nesting typically begins early.

For certain other species there are just a few early nesting attempts; these often take place in towns and cities, where it is warmer and where there is food available to help get parents into breeding condition. Interestingly, the urban habitat and in particular the gardens within it, are the one place where we lack a thorough understanding of the size of breeding bird populations. It makes sense really, in that people carrying out surveys of nesting birds can’t very well go and peer into privately owned gardens! This lack of knowledge has prompted the BTO (British Trust for Ornithology) to launch a new survey under the banner of Nesting Neighbours and they are looking for householders to keep an eye out for nesting birds.

Of course, finding nesting birds is not always easy. If you have a pair of Blue Tits using your nest box or a family of heavy-booted Starlings in your roofspace then you are likely to know about it. However, you try finding the Greenfinch nesting in one of your conifers or the Dunnock tucked away in a quiet corner. These are just the sorts of nests that the BTO wants to hear about and to help you with your efforts they have produced a wallchart, detailing the different types of nests and eggs and explaining where and when particular species nest. I, for one, will be out there, poking through the Ivy that adorns the end wall and searching through the climbing rose. You can get your free wallchart and survey pack by calling the BTO on 01842-750050 or by emailing Make a difference to their work by finding out which birds are your nesting neighbours this breeding season.

Tuesday, 30 March 2010

Jackdaws busy setting up home

Leaving work the other afternoon my attention was caught by the sight of two dozen Jackdaws riding on the breeze. There is nothing unusual in this you might think but the flock was loose in its formation and made up of discernable couples. Each pair of birds was separated from every other pair by a certain amount of airspace and it was clear that these were breeding partners, possibly displaying in the sky above the nest sites soon to be occupied.

In fact, there has already been a certain amount of work on the nest sites used last year, with birds collecting new nesting material in the form of twigs and clumps of fur, brushed out from winter coats by the dog owners who walk along this part of the river. Jackdaw nests are untidy in their construction and can be surprisingly large. The birds seem to adopt an approach whereby they keep adding sticks to the nest cavity until it is full and ready for lining with softer material. I remember once checking an old Barn Owl nest site in the attic of a ruined cottage out in the fens; the owls were no longer there but the Jackdaws had moved in and constructed a nest that was at least eight feet across and four feet tall. It was a truly amazing construction.

Although the sight of these birds flying in tandem had suggested to me that the pairs had only recently formed, this was almost certainly not the case. New pairs probably become established in late autumn or early winter and you can see Jackdaw pairs in pretty much any month of the year. This might suggest that pairs remain together for life but changes in partnership do occur from one year to the next. Birds may continue to use established nest sites over long periods of time and it is easy to see why such large nests can accumulate in some cases. Jackdaws are very adaptable when it comes to the choice of nest sites, although very few end up constructing a nest out in the open. Most nest in cavities, either natural holes in trees or those accidentally created by humans. Jackdaws can be found nesting in disused mine shafts, church towers, chimneys and even nest boxes, specially erected for their use. They are gregarious birds and, if conditions allow, you will often find several pairs nesting in close proximity

Since Jackdaws can initiate egg laying from the beginning of April, they are one of the first birds to really get going with the arrival of spring. Most pairs, however, start in the second half of April so expect to see some collecting twigs over the next few weeks.

Monday, 29 March 2010

An overlooked invertebrate

The other morning, while moving some pots from one part of the garden to another, I came across a cluster of snails. They had tucked themselves away in the relatively stable microclimate between the pots and an old flint wall. Part hidden by ivy, this appeared to be a suitable place for them to have sat out the bitter winter we have just experienced. I felt somewhat guilty for having disturbed them but I am sure they would get their own back if I failed to properly protect my spring salad crop with mesh netting.

Snails are so accessible that they quickly become an object of childhood fascination and I remember marking some as a child with spots of model paint, delicately applied with a fine brush. Following the instructions laid out in some book or other on becoming a naturalist, I’d marked the snails to see where they moved to around the garden; did they always return to the same spot or did they move about and mix with others? I wonder whether, if I repeated that experiment now, I would find that some of them turned up on the thrush’s anvil during those few summer weeks when snails become an important food for this industrious bird.

While the garden snail Helix aspersa is a familiar creature, most of our other snails go completely unnoticed. Many are tiny, the smallest just 1.5mm wide and 1mm tall, and are easily overlooked. Others may go unrecognised because they do not conform to the familiar shape that we expect to see in a snail, with its round shell carried on a pale, muscular body. The origins of our snails are aquatic in nature and there is still a strong requirement for damp conditions and habitats. This is one reason why they are predominantly nocturnal in habits, although being nocturnal probably reduces their exposure to potential predators. Many snails are found associated with rivers and ponds and some of the larger species may be familiar to those who have been pond dipping. Soil type also has a strong influence on snails, with a greater number of species associated with lime-rich soils and very few species found on acid soils. This association is linked to the snail’s shell, with the lime used in shell formation. Those snails found on acid heathland tend to have shells that are very thin and fragile.

Invariably, where you find snails you also find slugs and many people regard slugs as just snails without a shell. In fact the division is less clear-cut than this because some snails have very small shells, relative to body size, and while very few slugs have an external shell, others carry one internally.

Saturday, 6 March 2010

The reedbed

I have always found reedbeds to be an enticing habitat; lush and green at the height of summer, brown and brittle in winter but seemingly always in motion and prompted to ‘whisper’ by the softest breeze. There is an apparent contrast between the reedbed in these two seasons – packed with life in summer and seemingly empty during the bleak days of midwinter. While it is certainly true that many of the reedbed’s summer creatures are gone (think of the Reed and Sedge Warblers now wintering in Africa) others remain. Most of the latter are insects and other invertebrates, some of which will have fed on the reeds themselves while others, notably the spiders, will have made a living from their fellow inhabitants. These small creatures will be tucked away, sitting out the worst of the weather either as eggs, larvae, pupae or adults. They are there and can be found if you venture into the reeds with a beating tray and a stout stick.

The winter reedbed does hold some larger creatures as well; the secretive Water Rail, which may only reveal its presence through its unusual (for a bird) grunts and squeals. These are more commonly heard in summer than winter, so catching up with this skulking reedbed denizen can require a degree of patient watching. Water Rails have a very wide diet, feeding on a range of invertebrates, vegetative matter, frogs and newts. When the weather conditions deteriorate then the rails may resort to feeding on carrion, sometimes even attacking small birds or visiting garden feeding stations. The winter reedbed may also hold an equally secretive visitor, the Bittern, whose winter numbers here in the UK may be swelled by birds arriving from further east if waterbodies there freeze over.

Other birds also make use of the reedbed during the winter months, with Pied Wagtails, Reed Buntings and even Starlings using the reeds as an overnight roost, secure from predators. One of my local reedbeds has been well-used by wagtails and buntings, the birds arriving just before dusk and leaving quietly, soon after dawn. The reeds also attract parties of Bearded Tits, whose chattering calls echo the bright personality of these delightful little birds.

Many of our reedbeds are fairly small but the larger expanses found in some parts of the county provide a substantial amount of habitat. Many of these larger beds are managed, either to halt the incursion of scrub or to supply reeds as thatch, and it is uplifting to see reeds being cut by hand, tied and stacked. This form of harvesting seems more in touch with the wider natural world and our place within its annual cycle. Long may it continue.

Friday, 5 March 2010

Woodlark revival

It is another bright morning, a clear blue sky and the crunch of last night’s frost underfoot. Keeping up a good pace along the forest rides means that I am soon comfortable, warmed by the exercise and several layers of clothing. The brightness of the morning has prompted many of the forest’s birds to sing and, in addition to the Coal Tits and Chaffinches, there is the explosive trill of a Wren and the rolling high-pitched song of a Goldcrest. This is an encouraging sign because these small birds may well have struggled with the severity of the winter we have just experienced.

I am soon out of the mature blocks of pine and onto the clear-fell, where two Roe Deer are stirred to move off by my arrival. Roe are curious creatures and the two of them stop to watch me once they feel they have put sufficient distance between us. It is then that I catch a snatch of Woodlark song, a somewhat melancholy series of notes that picks up pace part way through. Glancing up I spot the bird, in flight and over an area where they almost certainly nested last year. Woodlark are partial migrants and many of the birds from the Brecks will winter further south and west of here, returning in March to occupy suitable breeding territories. Colour-ringed birds from East Anglia have been found wintering in the Netherlands and across the south-west of England. Being a partial migrant means that not all of the individuals will move away come winter, some will stay and others may move in one year but not the next.

The Woodlark is something of a success story, a bird whose numbers have increased six-fold since the mid-1980s. This increase has been linked to an expansion in the amount of clear-fell and young plantation woodland, coupled with the restoration of lowland heath and a run of mild winters. Even with this increase, the bird still only occupies part of its former range. The Brecks and the Suffolk Sandlings are important breeding areas, perhaps holding between a third and a half of the UK breeding population.

Clear-fell in the Brecks provides the birds with suitable nesting habitat, the Woodlark requiring a mixture of bare ground or short vegetation in which to feed, taller vegetation in which to nest and the presence of trees from which the males can sing. The matrix of forest blocks provides this nesting habitat and, with the presence of winter feeding opportunities present locally, the birds have done well. This is only my first Woodlark of the year but it won’t be my last. More will begin to sing and soon they will start nest building.

Thursday, 4 March 2010

Nomads on the wing

The number of Short-eared Owls wintering in the county this year suggests an influx of birds from further north, possibly from breeding populations on the uplands of Northern Britain or from Fennoscandia and beyond. We have our own very small breeding population within East Anglia but this has never exceeded more than a few pairs. These day-hunting owls are often portrayed as opportunistic wanderers, nomads that follow the volatile breeding populations of their favoured small mammal prey, the voles. If you read back through the old ornithological literature, you will come across examples that illustrate the fluid nature of the owl’s breeding populations.

Voles breeding within the structurally simple landscapes of the northern uplands and arctic tundra show a strong multi-annual pattern, a population cycle that peaks in one year and falls to a trough soon after to produce a four-year cycle in abundance. This has a knock-on effect on small mammal predators and, for the Short-eared Owl, a good vole year means a good breeding season, but a subsequent decline in the number of voles will see the owls move elsewhere to seek other opportunities. The scale of such movements explains why 116 of these delightful birds were seen to roost at Halvergate in December 1972 but the following winter saw just three birds in the same area. These birds seem to show little in the way of site fidelity and will winter in different areas in different years, depending upon food availability.

Having a good number of individuals here this winter provides an opportunity to take a closer look at these birds. There were four in the air together at Chedgrave Marshes the other day and they appeared to be roosting on the steep bank protecting the lower lying land from the river. Superficially, they are similar to a Barn Owl, in that they have a light and rather buoyant flight on long wings. The similarities between the two species reflect their common habit of quartering open ground for food, a behaviour that is made more energetically efficient by having a low wing-loading. The short-eareds most closely resemble the related Long-eared Owl which, although normally nocturnal, may occasionally be seen hunting during daylight. Short-eared Owls are slightly longer-winged and show a white trailing edge to the upperside of the wing (not seen in Long-eared) and a pale belly (streaked in Long-eared).

Out on the marshes, the Short-eared Owls will be feeding on small mammals and birds, the latter proving to be an important component of the diet at this time of the year and including small waders, pipits and species that tend to roost communally. They will not be around for much longer so make the effort now to see them.

Wednesday, 3 March 2010

Feeling my way towards spring

Even though it has been cold and occasionally wet over the last few days, I sense the end of winter and the first glimpse of an approaching spring.  It is not one single thing that leads me to think that winter will soon be behind us but a combination of small things; an extra warmth in the sun’s rays, the growing number of birds in song, including a solitary Blackbird, and buds that are swelling on the trees. While February can tease, with false starts and broken promises, March feels sufficiently far into the year to offer something more robust.

It has been an odd start to the year, the celandine bright in flower but the snowdrops yet to appear in many of the haunts where I would see them in other years. Will spring all come at once, with a rush of blooms? That’s what some observers are suggesting.

Of course, the end of winter does not mean the arrival of spring; there is no instantaneous change from one to the other. There is this period of in-between – this no man’s land of mixed days; some bright, clear and filled with growing warmth, while others remain dull, cloud-covered and hang with a clawing damp that gets into the bones. What does matter though, what shapes these days, is the knowledge that spring will come, that days will feel longer, that I’ll be able to walk home from work in the light. It is these things that offer hope, lift my mood and fill me with a sense of expectation.

To suggest that other creatures feel the same sense of expectation would be to anthropomorphise but maybe the changing day length, that extra warmth in the sun’s rays, is triggering hormonal changes that parallel my shifting mood. Many of the creatures with which we share this landscape will be responding to seasonal cues, initiating changes that trigger flowering or the establishment of breeding territories. The question I have been asking myself is whether I am responding to these cues in the same way or whether I am responding to their resultant effects in other creatures? It is in these periods of transition, as the seasons shift from one to another, that I feel most closely in tune with the world around me. The feelings that I experience at these times serve to remind me that I am also part of this wider web of diversity, that I too am a creature responding to the environment and the subtle nuances that mark the turning of the seasons. It won’t suddenly be spring tomorrow but I sense that it is approaching and over the coming weeks I too shall slip from one season into another.

Tuesday, 2 March 2010

Out on the marsh

It has been a good winter for Rough-legged Buzzards, with three working the grazing marshes that flank the Rivers Waveney and Yare, inland from Yarmouth. It is one of my favourite parts of East Anglia and getting out on the marshes delivers you back into the wild and into the winter realm of these and other birds.

I had not chosen the best of days for my visit but I had been cooped up at home, head down and working, for too long. I needed to clear my thoughts and re-engage with the landscape and its wild creatures; the north coast would be too busy and so the marshes beckoned. Parking at St. Olaves I struck out north through the boatyards and up onto the bank that skirts Fritton Marsh, leading out onto ‘The Island’. A small team of reed cutters were at work, a stack of recently cut reeds the sign of a productive morning and their distant banter matched by the chattering calls of a passing party of Bearded Tits.

It was a good walk out to my chosen viewpoint and, with many stops along the way to scan and watch a mix of waders and wildfowl, I found that I had used up the best of the weather. No sooner had I settled down by the old mill than the darkening clouds released a flurry that moved from sleet to snow and back again. I had banked on these just being showers but right now this was not good weather for seeing buzzards. In fact two of the Rough-legged Buzzards were here but, like me and like a solitary Marsh Harrier, they were hunkered down and sitting out the shower. One was sat on the stout upright of a farm gate, several hundred metres distant; the other, further off to the right, was on the deck. There is very little that looks more miserable than a raptor in the wet and the mood of one of the two birds was not helped by the fact that it was being harassed by some of the local corvids. For the next fifty minutes we sat out the shower and then, gradually, a growing pale band on the horizon gestured at better weather moving in.

The brightening sky brought better viewing conditions. I was able to watch the closer bird, which also sensed the better conditions, as it shook itself and looked around. I didn’t think I would see it take to the air and begin hunting but it did make one short flight in response to the crows. More showers followed, prompting my departure, but I went away with the sense that I had shared something with these birds today.

Monday, 1 March 2010

Grey Seals little competition to fisheries

It had been a while since I last visited the Grey Seals at Horsey, one of Norfolk’s finest wildlife spectacles. Setting out from Winterton we headed north through the dunes in sunshine before dropping down onto the beach and the lure of the water’s edge. It felt glorious; the warmth in the sun’s rays suggesting a change of season and it seemed as if we’d shrugged off the winter gloom for one last time. Of course, such are the vagaries of the weather that the sunshine proved to be short-lived, a bank of fog rolling in off the sea, dropping the temperature and coating hair and clothing with a sheen of moisture. The fog also reduced the visibility and our first view of the seals was an uncertain one. The bulky shapes of several dozen seals matched those of the rocks, positioned as sea defences to reduce the effects of the North Sea swell. The smell of the seals, however, was sufficient for us to resolve what we were looking at. As we drew closer, still keeping a respectful distance, some of the seals raised or turned their heads to get a better look at us. Content that we posed no threat, they returned to their slumber.

These seals spend a good proportion of their time hauled out during the first quarter of the year. They will have pupped back in November, the females producing a single calf high above the tide line. It is for this reason that the beach at Horsey is closed through into February, allowing the mothers to suckle their pups undisturbed. The pups, which increase in weight from 15kg at birth to 60kg at weaning – just 18 days later – have usually left the haul-out sites by the time that the adults begin their moult in February, so now is a good time to visit.

Our east coast Grey Seals have been doing well in recent years, part of a wider North Atlantic population, and perhaps contributing 2,000+ pups annually. Of course, it will be a good few years before this season’s pups breed themselves; the females do not become sexually mature until they are 3-5 years of age, the males 8-10.

Grey Seals in the southern part of the North Sea often feed close to the sea floor, ‘grazing’ on sandeels or adopting a ‘sit and wait’ approach to snatch unwary cod, ling and other fish. This has brought them into conflict with fishermen (less so here than further north), who may regard them as a threat to their livelihood. Mind you, the numbers of fish taken by the seals are an order of magnitude less than the commercial catch limits operated in the North Sea.