The swollen river

The river is a powerful force, especially now that it is swollen with last week’s rain. For much of its length the river gives the illusion of being inert; a soft-brown gently flowing mass that moves down an imperceptible gradient on a course that will, eventually, bring it to the sea. It is only where the river is divided, with part of its volume squeezed through a narrow weir, that its true power is revealed in a roar of spray and noise.

This winter river is very different from that of late summer and it is difficult to picture how it looked just a few short months ago. It is brown, rather than clear and the lush growth of aquatic vegetation has long since gone, rotted down and now part of the detritus held in suspension like some full-bodied broth. The bank-side willows are bare, their slim fish-shaped leaves cover the banks like a mass of sardines, once silver but now brown with the stain that decomposition brings.

While there is an air of decay about the river, the riverside creatures bring a sense that spring will soon be upon us and the river will once again return to life. On bright days, early Mistle Thrush and Great Tit can be heard singing, while three Great Spotted Woodpeckers indulge in ‘chase-me’ games high among the bare branches. The Grey Wagtails are often heard calling, their bouncy flight catching the eye as they move up and down the stretch of water near the weir. They have bred here in the past but in recent years have favoured a different nest site further downstream. It seems that there are still sufficient insects along the river to sustain them through this difficult season. A pair of Goosander hints that these sawbills might breed on the river again this year, a new and recent pattern that adds an exciting dimension.

The other week I heard of an Otter sighting a mile upstream; a cub just a few weeks old and the first confirmed breeding record for some years. It is another encouraging sign but, with the river rising by over a foot in recent days, I worry for its safety and hope that its mother will have found a secure holt. There is something remarkable about the river. Perhaps it is its changing moods, matching the seasons but also, in some small way, independent of them. The fact that on a bright summer day one part of the river can be shallow and babbling like the proverbial brook, while another, shaded by the willows, can be dark and sullen. Even in the depths of winter the river can be many things, always changing and ever my companion.

Regular watching pays dividends

Spend any time watching garden birds and you’ll soon realise that there is a great deal going on in your average garden. However, what you see is merely scratching the surface of what is really happening and much remains hidden from view because, to our eyes, most individuals of a given species look alike. The handful of Blue Tits that you see daily at your hanging feeders may, in reality, be many dozens of different individuals, which use your garden on a daily, weekly or seasonal basis.

As a trained and licensed bird ringer, I have been able to appreciate the numbers of individuals that may make regular use of a garden feeding station. Even so, I still need to catch the birds regularly to discover which individuals are still popping in for a feed. One way in which it is possible to build up a more complete picture of the lives of individual birds is through colour ringing, a technique by which licensed bird ringers fit birds with unique combinations of coloured rings. Once fitted with such rings a bird can be identified as an individual without the need to recapture it.

Colour ringing is best used for targeted projects, seeking to look in detail at a population of birds within a given area. This might be at the scale of the Blackbirds using a series of gardens in Holt (as is the case for one Norfolk-based project) or it might be at the scale of Black-tailed Godwits moving between Iceland and various sites in Britain and continental Europe (research being carried out by staff at UEA).

Looking in detail at a particular population invariably adds to our knowledge, revealing more about behaviour, ecology and survival. Colour ringing of birds has, for example, been used to look at breeding behaviour, highlighting which birds hold which territories and with whom they breed. At the same time it can change your perception of the numbers of birds that make up your ‘local’ population. Colour ringing of Great Spotted Woodpeckers at Croxton, just on the edge of Thetford Forest, has been taking place over the past six years. Some 63 different individuals have been colour ringed at the feeding station in this time and resightings by the site’s owner have revealed much about how these local birds are using the feeders. One female visited the feeders almost every day for five years, while another was a regular visitor for three years, only to disappear and then return two years later.

Colour ringing also enables members of the public to report any colour-ringed birds that they may see. Simply contact the British Trust for Ornithology’s ringing scheme (www.ring.ac) and let them know what you have seen and where.

Antics in the tree-tops

It may seem a little early but the Great Spotted Woodpeckers at West Stow are just starting their breeding season. As well as the familiar drumming, there is plenty of chasing as rival males cavort through the tops of trees uttering short, sharp sounding calls. Breeding proper will not begin until April but the courtship taking place now may have been initiated back in December.

The birds usually only pair for a single season, choosing to maintain individual feeding ranges once the business of rearing chicks has finished, but pair bonds lasting up to three years have been recorded. An established male will tend to retain ownership of his breeding territory from one year into the next, drumming from favoured trees in an attempt to attract a mate. If successful, the pair will cement their bond and excavate a new nest hole into which the eggs will be laid.

Great Spotted Woodpeckers are not the only species to be drumming at the moment; although less common, Lesser Spotted Woodpeckers may also be heard, their drumming somewhat weaker and of more even tempo. The changing fortunes of these two species have been rather different, with great spots increasing and lesser spots in decline. The sparrow-sized lesser spot seems to have been constrained by being more selective in its requirements than its larger relative. Great Spotted Woodpeckers have shown their adaptability by exploiting garden feeding stations and also the rich protein available from wooden nestboxes used by nesting tits. Lesser Spotted Woodpeckers feed almost exclusively on invertebrates, taken from the surface of bark during summer and extracted from dead wood in the winter. Our increasing tendency to remove dead wood and to maintain over-tidy woodlands may have reduced the amount of invertebrate food available to the species, bringing about the pronounced decline witnessed since the early 1980s. Great Spotted Woodpeckers exploit a wider range of foods, including tree seeds, and this may have helped them to do well, buffering the effects of changing woodland management practices.

Early spring is a great time to catch up with these two woodpecker species. With their breeding seasons and associated courtship behaviour in full swing, there is plenty to see. Not only are they especially vocal at this time of the year but there is virtually no foliage on the trees to mask their courtship behaviour from prying eyes. Choose a bright, warm and still day and take a wander along a belt of mature trees or through one of Norfolk’s blocks of deciduous woodland. One of the best places to try is Holkham Park, particularly the woodland to the right of the entrance and around the lake. Here you are likely to encounter both species.

Woody's return

Back in June I wrote about the launch of a new survey, set up to establish the extent to which great spotted woodpeckers make use of gardens during the breeding season. The survey was a collaboration between the British Trust for Ornithology (BTO) and Radio 4’s “Shared Earth” programme (which is back on our airwaves for a second series today at 3pm).

The results of the survey have just been announced and they make very interesting reading. Reports were received from gardens across the country, including a number from here within Norfolk. Collectively, the contributions have enabled researchers at the BTO to build up a detailed picture of just how the woodpeckers change their use of gardens as the summer progresses. Early on in the season, from late June, adult woodpeckers begin to increase their use of garden feeding stations – arriving to tuck into peanuts and fats. The results suggest that males make greater use of this resource than females, something which almost certainly reflects the fact that females typically remain in the nest cavity during daylight hours, tending to their eggs or young chicks. During this period the male brings food to the female so she does not need to visit garden feeding stations. This pattern continues for several weeks and then, from early June, adults begin to arrive with youngsters in tow. These young great spotted woodpeckers can be separated from their parents by the red cap covering the top of their head and by the fact that the area of red under their tail is rather pale, seemingly appearing washed out. The adult male has a small patch of bright red at the back of his head and bright red underneath his tail. The female also has this patch of red under her tail but lacks the patch on the back of her head, all very useful features when it comes to working out just who is visiting your garden. Adults continued to arrive with their young over the following weeks but then left them to visit on their own. Having introduced their young to a suitable feeding opportunity their parenting was done.

Another aspect of the study looked at the extent to which these birds break into nestboxes containing broods of young tits. Many people do not realise thay the great spotted woodpecker is a predator of other birds’ nests but the study showed that many of those participants with a nestbox in their garden had experienced such predation. There are also reports of woodpeckers breaking into the mud nests of house martins to reach chicks.  It seems that the great spotted woodpecker is a resourceful bird, able to make the most of opportunities.

Have you spotted a Great Spot?

Today sees the launch of a new national survey of great spotted woodpeckers. A collaboration between the British Trust for Ornithology (BTO) and BBC Radio 4’s new nature series ‘Shared Earth’, the survey aims to find out how great spotted woodpeckers use gardens during the summer months. Results from the BTO’s year-round Garden BirdWatch scheme have revealed that great spotted woodpeckers increase their use of gardens from the end of June through into early August. This ties in with a period during which newly fledged woodpeckers are seen to visit garden bird feeding stations alongside their parents. The team running the project want to establish which types of food are used and the extent to which visits to gardens are driven by the nature of surrounding habitat. As a woodland species, the great spotted woodpecker is most likely to use gardens close to woodland but the team want to find out how far the birds will go to make use of the food provided by garden birdwatchers.

The survey also aims to find out more about one of the less pleasant aspects of great spotted woodpecker behaviour, that of nest predation. These woodpeckers are known to drill their way into wooden nestboxes to predate young tits but it is not known how widespread this behaviour is. When you think of nest predation you tend to think of cats, magpies and rats, rather than woodpeckers, so it may come as something of a surprise to some readers to discover that these striking birds don’t just feed on insects taken from dead wood. In fact, they also eat a lot of seeds (particularly of pine and spruce).

Adult male and female great spotted woodpeckers are readily distinguishable. The male has a small patch of bright red at the back of his head and a larger area of red underneath his tail. The female also has this patch of red under her tail but lacks the patch on the back of her head. Young birds can be separated from adults by the red cap covering the top of the head and by the fact that the area of red under the tail is rather pale, almost washed out.

If you have woodpeckers breeding close by then you may find them putting in an appearance in your garden over the coming weeks, providing you with an opportunity to contribute to the project. The survey itself is web-based and will be accessible from today through until August and can be accessed from www.bto.org/gbw. The Radio 4 ‘Shared Earth’ programme is being broadcast at 3pm today and has more information on this project and on other projects that should help get you out and about in the countryside.