Nightjar

Regular readers of this column may have seen my piece earlier in the week which mentioned our efforts to catch Nightjars in Thetford Forest. This work, which involves fitting tiny radio-transmitters to some of the birds we catch, is being carried out to support a PhD student who is looking at Nightjar movements and breeding ecology. Small teams of trained and licensed bird ringers are out several times a week at the moment (depending upon the weather) and we have been fortunate in being able to target and capture a small number of birds within our defined study areas. Our success rate has been such that there have been very few nights when we have failed to catch a bird.

I have been particularly fortunate to have seen a number of birds in the hand and to have caught a breeding female in one of my nets. This particular bird was tracked a few days later, through her radio transmitter, to a nest site just a few hundred metres from where I had caught her. She was found to be incubating two eggs (Nightjars typically lay from one to three eggs) and we will be able to follow her progress as the season continues. She might go on to make a second breeding attempt before departing south towards her African wintering grounds. Nightjar nests are placed on the ground, within an area that is bare or sparsely vegetated, and the female relies on her cryptic colouration (a mottle of greys and browns) to remain hidden from potential predators.

The Nightjar is found across much of lowland Britain but only where suitable breeding and feeding habitats exist, so it tends to be localised within this wider range. Thetford Forest is something of a stronghold for the species, with the birds making use of areas of clearfell within the larger blocks of coniferous woodland. The reliance on areas of clearfell and young plantation woodland means that the size of the breeding population within Thetford Forest is very much dependent upon the area of suitable habitat available. As the newly established plantations mature they become increasingly unsuitable for the Nightjars. Fortunately, the Forestry Commission now manages the Forest with this in mind, maintaining a good area of sufficiently young blocks to provide enough breeding habitat for the Nightjars and other early successional birds like Woodlark. Work already carried out within Thetford Forest suggests that the Nightjars forage for food within a kilometre or so of the nest, so suitable nesting and feeding habitats need to be located close together. The mosaic of forest blocks provides the mix of habitats required by the Nightjars and, with careful management, their future within the forest looks secure.

A glow in the forest

A soft green glow caught my eye the other night, a tiny patch of light in the grass which I recognised as that produced by a female Glow-worm. Soon after, I found other tiny lights, just a handful but a welcome sight nonetheless. Shinning my head torch toward each glow in turn revealed the plump outline of a female Glow-worm, sometimes alone, sometimes accompanied by one or more males. I encounter these insect beacons less frequently these days, a reflection of their general decline within the wider countryside. Gone, too, are the large gatherings of dozens of females grouped together in the vegetation, collectively giving the appearance of a miniature townscape by night.

The light is used by the wingless females to attract a mate, the males being fully winged and sporting the hard wing cases so typical of beetles.  For these are beetles and not, as the name might suggest, worms. In North America they are often referred to as ‘fire-flies’, another misnomer. Globally, there are many different species of glow-worm, although we only have two (possibly three) species in Britain and only one of these is widespread in its distribution and likely to be encountered.

The Glow-worm’s light is the result of a string of controlled chemical reactions which take place within special light organs located in the female’s abdomen. The two most important compounds involved are luciferin and luciferase, the latter acting as a catalyst by bringing together other molecules and holding them in place until a reaction takes place. The reactive process is extremely efficient, wasting less than two per cent of the energy used; compare this with one of the standard light bulbs, now being replaced by low-energy equivalents, which waste 96 per cent of the energy used. A similar process occurs in certain jellyfish, bacteria and even fungi. The light that is produced is a yellow-green colour, which is handy for the human observer as it falls within that part of the light spectrum to which the human eye is most sensitive.

Each species of glow-worm emits its own distinctly-coloured light, effectively a ‘call sign’, which prevents males from approaching a female of a different species. However, a North American glow-worm called Photuris versicolor has been discovered to impersonate the ‘call signs’ of several related species. Males of these other species, fooled into visiting a female Photuris versicolor, may find themselves on the menu!

The almost magical light produced by these insects has attracted our attention for many hundreds of years. In fact, references to glow-worms appear in literature extending back over two thousand years, with, for example, a mention in an ancient Chinese encyclopaedia produced by a pupil of Confucius.

The return of the Buzzard

I feel especially privileged today, having recently visited a Buzzard’s nest on the edge of the forest. Although the Buzzard is a common and widespread bird nationally, it is one that has, until relatively recently, been decidedly uncommon within Norfolk. Buzzard populations have changed dramatically over the last two hundred years. The species was common throughout most of mainland Britain during the early 1800s but from the second half of that century there was a pronounced decline in numbers. The decline was linked to the levels of persecution associated with game rearing interests, the Buzzard all but exterminated from large parts of its former breeding range.

Relief for the Buzzard came following the outbreak of the First World War, as keepers were called to fight for their country. Although the level of keepering continued to fall after the war had ended, new threats appeared. During the 1950s and 1960s Buzzards, like certain other top predators, suffered from the effects of organochlorine pesticides that had found their way into the food chain. Productivity declined, as nesting attempts failed through eggshell thinning and subsequent breakage, and the population again slipped away. Another problem was the arrival of myxomatosis and the rapid and pronounced decline in Rabbit numbers, the Rabbit being a favoured prey species for the Buzzard.

It is only over the last couple of decades that things have improved and we have seen a tremendous eastwards expansion of Buzzard populations, with birds moving out from strongholds in the west of the country. The first modern breeding record for Norfolk did not come until 1992, when a pair in central Norfolk raised two young. The year that I arrived in Norfolk saw just two confirmed breeding attempts and over the time that I have lived here I have seen more and more Buzzards within the county. Over the last few years, they have been regular around Thetford and this spring, for the first time, I have seen one regularly where I walk my dogs in the forest. The most recent Norfolk Bird Report (that for 2007) suggests a population of 30-40 breeding pairs within the county and this will almost certainly increase over time.

Work carried out on populations colonising other parts of the country would suggest that we could achieve a much larger breeding population, particularly as we appear to have a mixture of habitats suitable for hunting and breeding. The light, sandy soils of the Brecks, for instance, support good numbers of Rabbits and there are many small woodlots and blocks of plantation woodland to provide nesting opportunities. So, while I will always feel privileged to see nestling Buzzards at close quarters, I feel especially privileged today to have seen my first ‘local’ Buzzard chick.

Transition

It is still light when we arrive, the brightness of a summer’s day slowly slipping into the softer tones of evening. We are in the forest to catch and radio-tag Nightjars for a PhD student studying their ecology. Having chosen suitable spots, we quickly set our fine mesh nets and retire to a nearby forest ride to await the arrival of night and the stirring of the Nightjars. There is time now for patient watching and hushed conversation.

The background drone of flies dissipates and the final bird song slips towards silence, a solitary Song Thrush a last bastion of the daytime brigade. The time for the ‘night watch’ approaches and the first of the evening’s bats appears; a Noctule, an early riser that can sometimes be seen feeding alongside swifts, hawking the air for flying insects. The bat makes several passes up and down the ride and I curse myself for having left the bat detector at home; it would have been good to ‘listen’ to the Noctule as well as watch it pass.

The colour begins to leach out of the vegetation as the daylight fades to replace greens and browns with silvers and greys. A short squeaking note, much like a child’s toy, catches our attention and we glance up to see the dumpy form of a Woodcock silhouetted overhead. The forest seems to support fair numbers of these rather unusual waders – a woodland bird that probes damp soil for earthworms and other invertebrates. Then we hear it, a soft mechanical churring call – a Nightjar, distant but welcome. Soon it is joined by other birds, two close by and in the area of our nets – this bodes well. The closest of the birds is in flight, the churring interspersed with wing claps and calls, moving around off to our right. Then, it is caught, silhouetted against the sky, its effortless buoyant flight taking it in an arc around us and up into the top of a nearby oak. The bird can be seen perched on its song-post, advertising its presence to other birds.

These first excursions provide breathtaking views and we can stand and enjoy them, knowing that it will be another hour before we can turn on the tape lures that should attract the birds into our nets. Being nocturnal, the Nightjar has excellent visual acuity and would be able to avoid the nets if we tried to operate them in this half-light. A sheet of cloud has formed and by 10.30 it is dark enough to try our luck. Each of us manning a single net, tape lure running, we crouch nearby watching and listening, hopeful that we might catch one of these truly amazing birds.

The old romantic

I’m up and out before the showers; while the wind has dropped, there is still a chill in the air and I am glad of my fleece. The forest remains full of bird song but some of the established pairs have fallen silent, no longer evident on faithful perches. I hope that they are on eggs or chicks and have not failed to attract a mate.

I’d been thinking over recent days that I had not yet heard a Turtle Dove, even though a friend had one just a bit further south nearly a fortnight ago. Today, however, I finally get my bird; not calling but in flight, a frantic party of three that arcs across the clearfell and circles back around. I love these birds, with their soft, soporific purring call; it is a call that reminds me of lazy summer days, the buzzing of a multitude of insects and time enough to spend wandering about the lanes.

The Turtle Dove is rather slender for a dove and it is also our only migratory pigeon, wintering in the Sahel region of Africa and running the gauntlet of Mediterranean hunters each time it journeys north or south. It is not just the guns that have taken a toll on the now rapidly declining population; African droughts and changing farming practices have played their part, making this an increasingly uncommon bird across its former range.

The Turtle Dove has impressed generations of people, from the time of Pliny the Elder (writing in AD79) right through to the present day (see Michael McCarthy’s ‘Say goodbye to the Cuckoo’). For much of this time the dove has been associated with romantic affection; it has been held up as an example of love that is devoted and true. Such an association no doubt comes from observations that Turtle Dove pairs seemingly spend little time apart, feeding together and indulging regularly in courtship preening. Chaucer, writing in about 1380, penned the lines ‘God forbid a lover should change, the turtle dove said and blushed with shame.’ Likewise, Shakespeare used the Turtle Dove to allude to enduring love in more than one of his plays. Such associations explain some of our tenderness towards this bird and they may also explain how the Turtle Dove ends up in The Twelve Days of Christmas. While this is predominantly a summer visitor to our shores, the association with true love may be sufficient to secure the Turtle Dove a place in this unseasonal yuletide rhyme. That we should place the higher human qualities in animals says something about us and our values. Perhaps this is why it always warms my heart to stumble across the Turtle Dove.

The messenger of wisdom

The Hoopoe that arrived at Great Ryburgh on 15^th May quite rightly attracted a good number of birdwatchers. This clown-like bird, with it comical crest, buff-pink plumage, down-curved bill and pied wings, is a truly stunning species. Although not particularly rare as a visitor (there are typically between one and 29 records per year in Norfolk), it is striking enough to attract attention from even the most casual birdwatcher. Some readers will have encountered the Hoopoe when on holiday in France or around the Mediterranean, for it is a southern species with a northern breeding limit that sits just across the Channel from us. Records from southern Britain usually relate to birds that have overshot on their spring migration, as is the case with a number of other species that have turned up here over recent weeks. There are occasional autumn records but these are likely to be of birds from populations from further east.

The species has bred here in the past, including within the last couple of decades, but it seems to be limited by the lack of suitable quantities of its favoured large insect prey. Many early birds were shot; the species was a favourite with collectors and taxidermists because it looked so different from the majority of our other birds. Most of these spring arrivals turn up alone and remain for a few days but there are instances where a number have been seen together. One or two individuals have made more protracted stays and there is even a record of an autumn bird overwintering.

The Hoopoe feeds on the ground, taking earthworms and insects, with an almost Starling-like energy to its movements. However, unlike Starlings it is wary of Man and although it cannot truly be described as shy, it will keep its distance from observers. Mind you, it was approachable enough for collectors to take a heavy toll and, as Sir Thomas Browne noted writing in the Seventeenth Century, ‘it is easily shot!’ The Mediterranean distribution of the species may explain its incorporation into custom, folklore and language. The bird was used by the Egyptians as a hieroglyph and was portrayed by others as a messenger of wisdom. For example, it was the Hoopoe that brought wisdom to Solomon during his courting of Sheba.

Two features of the bird deserve special mention: the crest and the call. The crest is perhaps the most striking feature but it is only rarely raised. Normally it remains flat, curving back across the head to be raised but briefly as the bird alights on the ground. The call, a trisyllabic ‘oop-oop-oop’ is wonderfully evocative and is mirrored both in the bird’s English name and in the scientific name Upupa epops.

A bird in the bush

I’ve been out nesting a few times over recent weeks, squeezing in visits on those days when the sun has shone and the wind has stilled. This is not the sort of nesting to be confused with that of uncaring individuals who, with criminal intent, seek out nesting birds to steal their eggs, robbing the potential of a future generation for the sake of a collection arranged like stamps. Instead it is the collation of information invaluable to nature conservation and part of a national scheme.

My trips out have been in the company of nest recorders participating in the British Trust for Ornithology’s Nest Record Scheme. Experts in finding nests (though always learning, so they say), my guides have shown me how to find the carefully hidden nests of warblers, finches and thrushes. It has been a tremendous privilege and I feel that I am developing a skill that I will be able to put to good use in future years, sending in my own contributions to the scheme.

Nest finding involves a range of different approaches, a combination of skills that come together to reveal a hidden nest. One of the most often deployed of these skills is cold searching an area in which the species of interest has set up its territory. This involves a careful and steady search of each bramble bush or nettle bed, looking for the nest, while at the same time minimising the amount of disturbance. Ideally the nest will be found at an early stage, while the birds are still building. Its position can then be noted and a return visit planned for when the birds have started laying their eggs. Several more visits follow, carefully spaced to provide the maximum amount of information with the minimum of intrusion. Each visit contributes to a bigger picture, providing information on how many eggs were laid, how many of these hatched and how many chicks survived through to fledging. Visits can also reveal if a nest has been predated, at what stage and, sometimes, by what sort of predator.

Collectively, the information from many hundreds of nest recorders, delivers a powerful overview of how a species is faring, addressing the question of whether or not it has had a good breeding season and, importantly, alerting Government and the conservation agencies to any sudden declines in breeding success that might signal a wider problem. Nest recording is one of those skills that is being lost, the generation of practitioners an ageing one and with few youngsters coming in to replace those lost to old age. Efforts are being made to engage with a new generation of nest recorders and I hope to be one of them.