Saturday, 11 December 2010

Sociable sparrows make a welcome return

It is good to see the House Sparrows return to the garden in force. Each morning they arrive from further down the street, a boisterous posse of grey-capped males and chattering females. This chattering becomes all the more evident once the birds have fed, the flock retiring to the thick of next door’s jasmine to indulge in communal banter. ‘Social singing’, as it is known, appears to be an important component of House Sparrow behaviour, its role tied in with social status and flock cohesion.

These are sociable birds and the winter flocks bring together individuals from several local colonies. Many of the youngsters present within these flocks will roost together in thick vegetation, while established pairs often retire to their nest site. Winter flocks of this kind not only provide benefits in the form of greater knowledge of food availability and lower individual risk of predation, but they also serve as the opportunity through which young birds can disperse away from the colony in which they were born.

Cohesion of sparrow society comes from the social hierarchy that is established through plumage and display, and ultimately backed up by force if necessary. In the eyes of a female, the badge which illustrates the suitability (and hence status) of a male is the size of his black bib. The most successful males are those with the biggest bibs and you will see subordinate birds quickly defer to these high-ranking males in many social situations (most notably in access to food, dust bathing opportunities and females).

Our House Sparrows were visitors when we first moved into this house but we lost them soon after, the landscaping of a neighbouring garden removing the cover they favoured and they ceased to venture this far up the street. Now that the vegetation next door has matured, we have seen their return. House Sparrows rarely venture far and for several years it has been frustrating to hear the colony further down the street, knowing they would only rarely reach our garden.

Cover is important for House Sparrows, providing feeding opportunities, protection from predators and a platform for the social singing. Other factors also play a major role in determining House Sparrow numbers, and key changes in the nature of urban landscapes have seen the House Sparrow population effectively halve since the early 1980s. The loss of nest sites, following the introduction of new designs of roofing tile and barge board, coupled with the clearance of scrubby habitats, increased use of pesticides within our gardens and increasing numbers of competitors and predators have all been linked to sparrow decline, even though we have yet to determine which of these is the most important.

Friday, 10 December 2010


It is one of the coldest mornings of the year and I am glad to be on the move, working my way around the local lanes and tracks for Bird Atlas 2007-11. I have written of this national stock-take of Britain’s (and Ireland’s) birds before, a periodic mapping of their distribution and numbers. It is the last leg of the Atlas, with two winter visits over the coming three months and then two summer visits next year, and I find myself in an area of open farmland and small woodlots up near Shipdham. This is a place that I have not visited before.

As my two-hour mapping exercise continues so I come to realise just what an excellent piece of Norfolk countryside this is. A large flock of Yellowhammers and Skylarks is feeding on some stubble, a rare sight these days, and Lapwings lift from a piece of damp pasture upon my approach. It is the hedgerows that surprise me most of all. Although they have been cut back hard, they rise to a decent height and hold a larder of berries and fruits, attracting in Fieldfares, Blackbirds (by the dozen) and various finches. They also carry last year’s nests, including a surprising number of Chaffinch and Goldfinch nests, neatly constructed in the forks of the taller shrubs, alongside those of Wren, Blackbird and Wood Pigeon.

A soft whistling note alerts me to the presence of a Bullfinch, old billy black cap, and then I spot him just ahead of me above the bramble. He is not alone; two other Bullfinches slip from the hedgerow, their striking white rumps evident as they fly. The Bullfinch is a wonderfully engaging bird, with its little black cap, pinky-red breast (in the male) and stubby little beak. I used to watch them as a child, feeding on the seed heads of dandelion and sorrel with delicate precision. They are birds of scrubby woodlots and thick hedgerows, often overlooked despite their colourful attire. Both the song and the call are subtle and easily missed.

Our Bullfinches are largely sedentary in habits but they will make small local movements out from favoured woodland sites to search for seeds in nearby farmland. These movements are more pronounced in those years when Ash seeds, their staple food, are in short supply. Interestingly, the larger Scandinavian birds can make substantial movements in some years. This is such a year and several have been reported around the Norfolk coast. Bullfinch numbers have declined since the 1960s, most notably within farmland, and they are one of the birds that is often missed when doing Atlas fieldwork. To stumble across this trio of billy black caps has made my morning.

Thursday, 9 December 2010

Birds of a feather roost together

The bird table and hanging feeders are busy first thing in the morning, underlining the urgency with which many of the smaller birds need to replenish energy reserves lost overnight. Winter is a difficult time for small birds, the long nights and low temperatures placing strain on the small fat reserves these birds carry. If temperatures hover around freezing, or dip below, then these reserves are quickly depleted, something that can be a particular problem for our smallest birds, like Wren, Long-tailed Tit and Goldcrest. Research has shown that both Blue Tits and Great Tits lose some 5-10% of their body weight over the course of a typical winter night, possibly a lot more if the conditions are particularly poor.

Heat loss is, in part, dependent on where you choose to roost. Pick somewhere warm and you’ll be able to maintain your body temperature at a safe level more easily than if you pick somewhere cold. It is for this reason that some of our birds will roost communally, seeking the warmth from street lighting (Pied Wagtails) or from huddling together in a nest box or roosting pouch (Wren, Blue Tit or Coal Tit). Others roost within vegetation, a behaviour which sees Long-tailed Tits form up in a line along a branch or stem, huddled together within thick cover and out of the wind.

The use of nest boxes for roosting is something that is easily overlooked, especially if the birds pile into the box just as it is getting dark. There are some records of observers witnessing these arrivals; in one case at least 60 Wrens squeezed into a single box, but the behaviour is likely to be more common than these occasional reports would suggest. It is for this reason that the British Trust for Ornithology (BTO) has asked us to look at our nest boxes over the course of the next few weeks. If you take a look at your nest box one afternoon and then another the following morning, you should be able to tell if it has been used as a roost. This is because you are likely to find fresh droppings come morning if a bird has used the box overnight.

You might be fortunate enough to have a nest box camera attached to your box. If so, turn it on each evening to see if a bird is using the box for roosting. More details will shortly appear on the BTO website: Other birds form roosts that are more obvious. Starlings, for instance, gather together in very large flocks, which pulse and whirl about the sky prior to the birds dropping down and into the chosen site – often a large conifer.

Wednesday, 8 December 2010

We are not alone

I watch her some mornings as she moves across the wall; her eight, stiletto-tipped legs find unseen purchase on the plaster, gravity-defying and assured in their hold on this world that exists in a vertical plane. Her body is just a few millimetres in length, darkly patterned and with an arc of tiny glistening eyes on the top of her head. I have not worked out which of our many spider species she is, in part because I do not wish to disturb her daily routine.

She is not alone, as other spiders lurk in the corners of this old house. Some are rarely seen and I suspect that they indulge in nocturnal scurryings long after we have turned in for the night. Others are chance encounters, seen briefly as they race across the carpet and dash under the sofa; big hairy beasts that spook our rather feeble hounds. Then there are the daddy-long-legs spiders, Pholcus phalangioides, that hang in untidy webs where wall meets ceiling. These fragile looking spiders gyrate their bodies if disturbed, the motion so fast that the spider becomes little more than a pale blur, an effective and surprising defence for something so small.

Despite the ungainly appearance Pholcus will tackle other spiders, including those from outside that have ventured into the house in late autumn. Any that touch her web are approached and it is then that the long legs come into play. They give her greater reach, allowing silk drawn from the spinnerets to be flung over another spider with minimal risk. As well as other spiders, Pholcus will tackle small moths and mosquitoes, both unwelcome visitors to many homes, and I sometimes spot the body of a White-shouldered House Moth, partly wrapped in her silk.

One of the reasons why this house is so popular with these spiders is its age, lacking the dry warmth of modern houses, with their central heating and double-glazing. Like other house spiders, Pholcus can survive long periods without water but even she must descend to find it from time to time. Her eggs are thought to be prone to desiccation and presumably cannot cope in a modern house.

I do not mind sharing our house in this way. Most of these other residents are innocuous enough and have little or no impact on our lives. The occasional visitor may go away with the impression that we are a little untidy, perhaps, but the scatter of webs and their delicate residents provides a sense of connection during these bleak winter months. We are sheltering together from the elements outside, a community of lives whose daily routines sometimes bring us into contact with one another.

Tuesday, 7 December 2010

What is our problem with rats?

With a reputation for spreading disease and for damaging foodstuffs, the Common Rat is regarded by most people as little more than a pest. Point out a rat to the wrong person and not only will they utter the most disparaging of responses, but they might even shudder and take a subconscious step backwards. Of course, our problem with rats is just that; it is ‘our’ problem and of our own making. We have cast the rat as villain because it interferes with (or is perceived to interfere with) our way of life.

There is no doubt that rats do damage foodstuffs, such as grain stored on agricultural premises, but if we are going to harvest and store food in this way, then we should not be surprised when some other creature exploits the opportunity being offered. Interestingly, the damage to foodstuffs comes primarily from contamination (with faeces, urine and hair) rather than from consumption, and rats do surprisingly little damage to the standing crop. Control measures tend to be focussed on killing rats or deterring them, rather than on the logical (though more expensive) option of properly excluding them from where we store our food. Rats also spread disease, notably leptosprirosis, but the risks to us are small relative to the other risks that we face in our daily lives.

Much of our problem with rats comes down to perception. The Common Rat is perceived as an invader, the aggressive Seventeenth Century colonist that ousted our ‘native’ Black Rat (a smaller and more delicate creature), but the Black Rat is itself a colonist (arriving with the Romans). It is also wrongly assumed that the Common Rat arrived here from Norway, an error perpetuated through its scientific name Rattus norvegicus. In fact, the Common Rat did not reach Norway until nearly half a century after it had first arrived here, most likely on a ship out of Russia.

Rats are perceived to be dirty, disease-ridden creatures, in part because of their association with the underbelly of society. Rats do well in urban areas; they establish colonies in our sewers, on the underground, alongside our inner city rivers and around our refuse tips. But this says more about us, about the rubbish and the waste that we create. The rats I see most often are those that inhabit the banks of the river running through town. These rats feed on the waste food dumped by passers-by, too lazy or ignorant to take their waste home. We have become a disposable society and it is our excesses that support the rats that we transported across the globe in our ships. Perhaps their presence says more about us than it does about them.

Monday, 6 December 2010

Tufted duck gather for the winter

Good numbers of Tufted Ducks are gathered on the flooded gravel pits near home. Scattered among the more abundant Coot they prefer the quieter corners, away from the fishermen and their Sunday afternoon radios, tuned to the football. They are our most abundant and widespread diving duck, quite capable of sustaining dives down to 14m in search of food, something that gives them access to waterbodies unsuited to dabbling duck like Mallard and Shoveler. Tutfed Ducks are, therefore, a familiar sight during the winter months on many of the county’s flooded gravel workings.

Some of these Tufted Ducks are likely to be the same individuals that were here during the summer, perhaps even the individuals that managed to raise a family on the site. Many others, however, will have come from elsewhere. Birds from Fennoscandia and Russia may have arrived here as early as July, initially favouring much larger waterbodies (like Abberton Reservoir) where the birds gather to moult. Because Tufted Ducks breed so late in the year, with eggs often hatching during July or even August, many of the birds gathering to moult will have been males, the females remaining elsewhere to tend to the needs of their growing chicks. Smaller numbers of females may have arrived in August. Most of these birds remain here for the winter, dispersing from the favoured large reservoirs to smaller waterbodies, like the pits just south of Thetford. They will only move on if the waterbodies freeze over, halting access to the molluscs and invertebrates that they favour.

The numbers wintering here are dwarfed by the vast numbers that winter around the Baltic or on the Ijsselmeer in the Netherlands. Some winter further south, reaching the Black Sea and the Mediterranean. Although our breeding population has undergone a period of substantial growth, no doubt helped by the increasing number of gravel workings being flooded, wintering numbers have been fairly stable. This might underline the contribution of winter immigrants from elsewhere. One interesting aspect of the winter flocks is the dominance of male Tufted Ducks. On average, the males outnumber the females by 1.4 : 1, a reflection of the late breeding season and the early movements of the males. The males are instantly recognisable, with their black bodies and white flanks. Females are less striking, with dark brown bodies and paler brown flanks. A flock of ‘Tufties’ is always worth a scan with your binoculars, as it can sometimes hide one of our less common diving ducks; perhaps a Scaup or even a Lesser Scaup. I do like to see the Tufties on our local pits, since they seem more in keeping with the image of a wild duck than the usual Mallards.