Saturday, 24 May 2014

Shy visitors

It is early and the local jackdaws have sneaked into the garden to take beak-fulls from the suet balls that reside in next-door’s bird feeders. This is the only time of the day that I see these playful birds using the garden and the food presented in the hanging feeders. It is a pattern that is repeated in many other urban gardens, the jackdaws seemingly shy in their feeding habits and restricting visits to that quiet time before the town is properly awake. This may change as the season progresses and as the birds respond to the growing demands of their newly hatched chicks. As the demand for food increases, so the jackdaws become increasingly bold, dropping down into narrow urban gardens from the safety of their rooftop kingdoms.

As the semi-colonial nature of their urban nest sites reveals jackdaws are sociable birds. All across this old part of town there are pairs of jackdaws, each occupying its own chimney pot within which a scruffy nest of sticks and other material will have been constructed. The bigger the cavity in which the nest has been placed the more nesting material that will be added. No matter how big the nest, there will be a smaller nest cup, lined with wool or other fine material and it is into this that the clutch of 4-5 eggs is laid. Each egg is pale blue in colour, with darker spots and splodges over the surface.

Jackdaw chicks are particularly unattractive, at least until they are properly feathered. With their bony-faced features and potbellies, they are prehistoric in their appearance and, seemingly, have an appetite to match. The young grow quickly but remain in the nest for about a month, meaning that things can get a little crowded if the nest cavity is a small one.

The jackdaw pair bond is long-lasting one and individuals will remain together even if they have been unsuccessful in their nesting attempts over several years. It has been speculated that the pair bond is essential for a jackdaw because of the amount of effort that has to go into provisioning the brood of chicks with invertebrate food. Regardless of the reason, it is a delight to watch the birds interact with one another.

Friday, 23 May 2014

A narrow escape

The two Egyptian geese are watching something. Stood on the riverbank by the ancient crossing point they are alert, their heads focussed on the river and their whole bodies rigid in posture. On the river itself is a female mallard, her mate in attendance close by, and both birds protectively close to a brood of young chicks. While the chicks huddle together, close to their parents, the adults have adopted the same rigid, straight-necked posture as the geese. My immediate thought is ‘otter’ but it takes me a few moments to pick up the tell-tale trail of bubbles that reveals its underwater presence.

The otter surfaces close to the far bank, deep in the shadow of an overhanging willow, before the head slips back beneath the surface and the trail of bubbles begins once again. This particular individual seems to be working the bank and can’t yet have noticed the mallards and their vulnerable youngsters, exposed in the middle of the gentle flow. I too am now watching nervously, waiting to see if the trail of bubbles moves away from the bank and out towards the mallard family.

Again the otter emerges for air, this time exploring part of the riverbank in greater detail while on the surface. Surely it must have noticed the ducks just a few metres away? By now the otter is parallel with the ducks and this is the critical moment. Will it continue to work the bank or slip out into the current to take one of the ducklings? The next time the otter surfaces will be crucial.

The bubbles continue upstream, close to the bank and I feel my body relax as it becomes clear that the otter will not strike out at the ducks. I watch it disappear upstream. The ducks, however, remain tense and the chicks hang in the current, almost motionless beside their parents. Finally, after what seems an age, the birds relax and turn to ride the current downstream and away from the otter. As I continue on my way I replay the scene in my mind. How did the otter not see the mallards and their young? Perhaps more importantly, how did the ducks – not to mention the geese on the riverbank – spot the otter? Was it chance?

Thursday, 22 May 2014

Rowan blossoms for a while

The creamy white blossoms of our rowan, which last week stood out against the dark leaves behind, have already faded. Each of the tiny flowers – just 6-10 mm across – is now edged with brown; the flat disc formed from many such flowers, and which is known as a corymb, has taken on the appearance of a discarded handkerchief, soiled by mud. The passing of the rowan blossom seems particularly early this year, even allowing for its early emergence, and I wonder if the low overnight temperatures have brought about the change.

The rowan is a tree from my childhood, ever present on the sandy heathlands not far from home. Its presence in the garden here reminds me of those days and planting a native rowan here seemed to offer a connection with the landscape that I left behind when I first moved to Norfolk nearly a quarter of a century ago. There are many cultivated varieties of rowan and its near relatives, some with berries of different colours and others adopting a different growth form, but for me it is the richly red berries of the native form, delivered in autumn, that remain important. These provide food for birds, including the first blackbirds of autumn, and for many different insects too.

I feel somewhat cheated by the loss of the rowan blossom so early into the season. It often attracts interesting insects and this year there is the sense that these have yet to get going. A run of warm days, to follow on from the cold and wet, is likely to boost the numbers of insects on the wing and nectaring on the available blossom. Only time will tell just how well the spring’s blossom will translate into autumn fruit.

Some wild foragers harvest the berries of rowan. These are unpleasant when eaten raw, and there is some evidence of side effects, particularly in children, but the berries can be cooked to make a pleasant-tasting jelly, though not one I have ever tried myself. The berries do have an appealing smell, as does the blossom, and I’d recommend taking a sniff if you ever get the chance. To my nose, the berries smell of apple and take me back to autumn afternoons on the heath.

Wednesday, 21 May 2014

Snails prove a fascination

I can remember being fascinated by snails as a child. Our garden seemed to abound with them and it was the large garden snails, Helix aspersa, which most often held my attention. I could spend hours watching as each emerged from its shell, extruded a grey tube of body and then inverted the pair of curious eye stalks; the latter behaviour still fascinates me to today.

Although widespread across a host of habitats in the south of its European range, Helix aspersa becomes more closely associated with gardens as you move north. Its size, coupled with the patterning on the shell, makes it pretty much unmistakable. There is a related species, Helix pomatia, larger in size and with less complex patterning on the shell, with which it might just be confused. Helix pomatia is restricted to a few chalky areas in the south of Britain where its presence is the result of ancient introductions, the snail providing a source of food for the supper table. Its populations, which had been threatened by entrepreneurial wild foragers, are now protected by the Wildlife and Countryside Act.

My childhood interest in garden snails, much like my wider interest in natural history, was stimulated by books written to encourage young naturalists. Each was packed with ideas for experiments or other activities and I can recall marking the shells of our snails with paint to see how individuals moved between different parts of the garden. I might even have used this approach to calculate the size of the snail population in different parts of the garden through a simple ‘mark-recapture’ calculation. Such calculations, though more complex in form, were a staple of my university fieldwork on small mammals many years later.

Garden snails are so accessible that I would hope that today’s generation of children still gets to ‘play’ with them and to learn about natural history and to respect the other creatures with which we share our gardens. Mature garden snails are robust creatures, well able to cope with the curiosity of youthful fingers. Importantly, they are also fun, particularly when blowing bubbles or rolling out their eyes. What child could fail to be impressed and educated by snails, hopefully carrying that childhood impression with them into adulthood.

Tuesday, 20 May 2014

The swifts return

It takes a few moments for the soft, drawn out, screech to penetrate my memory but then, instinctively, I tilt my head back and scan the sky for the source of the sound. The screech comes again, this time overlapped by a second, and my eyes pick out the crescent-shaped forms of two swifts against the deep grey of the passing shower clouds. They are back, these sentinels of summer; these all too brief visitors from south of the Equator are here and I feel a surge of joy.

The return of the swifts draws out a stronger response from me than my first calling cuckoo, twittering swallow or scratching sedge warbler. Quite why this should be is impossible to explain. Being brought up in the countryside, I came to live alongside swifts rather later in life than I did these other returning summer visitors. Perhaps it is because I have spent the past decade living in an urban centre, where swift is virtually the only summering migrant, that this bird has come to signify summer so much more strongly than any other species.

Still watching the sky I pick out a third individual, the small party twisting and turning as they feed before sweeping across the sky in long and shallow arcs. The swifts continue this display for many minutes before drifting off behind the rooftops of a neighbouring street. Are these ‘my’ birds, the individuals that will breed in the roof-spaces of some of the houses along my street, or are they passing through, still on their journey north? Over the next few days I expect to see more individuals gathering in the sky above the garden and to hear that soft screech of summer.

For a swift the passing of a year is all about the journey; ever on the move, swifts spend such a small part of their year here in England that we can hardly claim ownership over them. This is, however, the one place where they come down to ‘touch’ the Earth, where they settle briefly to breed, so perhaps our connection with these wonderful birds holds greater significance than for those over whose lands they are merely passing while on their great annual journey.

Monday, 19 May 2014

Stormy spring troubles

The stormy weather that made an appearance during the second week of May interrupted what had otherwise been an ‘early’ spring. The battering wind, drop in temperature and spells of heavy rain will have caused problems for many nesting birds. Some mistle thrush nests, placed high in deciduous trees, were dislodged and I suspect that the same fate befell a good number of nesting rooks. For some smaller birds, such as the blackcaps nesting in bramble only just beginning to leaf over, the young chicks could quickly chill, while their parents struggled to find sufficient insect food.

Nesting early increases the risk of catching a spell of bad weather, of spring being interrupted, but for many birds it is a risk worth taking. Research has shown that the young from early nesting attempts often do better in the long run, having more of the summer over which to learn their skills and attain independence.

Most small birds feed their chicks on invertebrates, which suggests that breeding birds should time their nesting attempts to deliver chicks at a time when the abundance of invertebrate prey is moving towards its peak. This is particularly true for tits, whose breeding success hinges on them being able to match the peak in their chicks’ demand for food with the peak availability of the caterpillars on which they feed. The caterpillars time their own emergence to match the availability of young leaves on the deciduous trees on which so many of them feed. We know that a changing climate has shifted the timing of bud burst and resulting leaf emergence, something to which the caterpillars have responded. The concern is that although tits and other small birds have shifted their breeding seasons too, they may not be able to keep up with the speed of change being seen in the populations of their caterpillar prey. If the two get out of synch then this could be disastrous for tits and for the security of their populations over the coming decades.

Most of the tits breeding locally now have chicks and the wet and windy weather, which has dislodged caterpillar prey, could have a big impact on the success or otherwise of this breeding season. Let’s hope for better weather ahead.