Monthly Archives: December 2014

Nest-boxes, new homes for choughs

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DSC01433By Liz Corry

Last month we gave you an insight into Cornish choughs and what people are doing there to help them. This month we continue our travels and will take you north across the border to Wales. Known for its lush valleys and majestic mountains, Wales is also home to about three-quarter’s of the UK’s choughs.

visit wales website image

www.visitwales.com

The Welsh name for a chough is brân goesgoch meaning ‘red-legged crow’.

Wales is broadly categorised into four regions; north, mid, west, and south. Choughs can be found more or less along the entire Welsh coastline from the Gower Peninsula in the south to the isle of Anglesey in the north.

They can also be found inland from the coast nesting in abandoned quarries or mineshafts. Most famously at the Llechwedd slate caverns , North Wales, where a pair are known to nest much to the delight of the tourists deep underground. A video made by the RSPB gives you more of an insight and can be viewed here.

Over the past two decades researchers working with these choughs have seen more and more inland nests becoming abandoned and breeding pairs disappearing. Ceredigion had five breeding sites in the late 1980s. Ten years later it was down to one. Montgomeryshire has seen a complete loss. It is believed that the boom in natural predator numbers, namely peregrine and goshawk, has not helped matters.

Silurian shale coastline in Wales.

Silurian shale coastline in Mid Wales.

Coastal nest sites are also under threat, but in this case it is due to natural erosion. A lot of the coast is limestone, sandstone, or shale and easily erodes. Looking at the photo on the right you wouldn’t think a bird would chose to build a nest on these cliffs. Yet they do, often with success, although a few years down the line the ledge might give way falling into the sea and a new nest will need to be built.

Nest-site availability is a very strong limiting factor in population expansion. In the late 1980s Scottish researchers had already shown the effectiveness of providing choughs with artificial nest-sites. Wales took on board this advice and started providing nest-boxes or ledge supports at various coastal sites. Within a few years just over two thirds of the artificial sites were being used. As of 2008 choughs at 22  artificial nest-sites successfully raised a total of 335 fledglings!

On a recent holiday to Wales I had the privilege of meeting Tony Cross, a champion chough supporter and the person responsible for designing the artificial nest-boxes (which we use at the Wildlife Park). Tony very kindly spared time to show me around some of the sites and teach me more about the Welsh choughs. Having ringed over 4,000 choughs and followed many individuals for several years there is a lot we can learn from him.

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This area was once used by choughs to raise chicks, but has now been abandoned.

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An abandoned mine shaft once used by nesting choughs.

The first stop was at an abandoned mining area where a pair of choughs used to nest. It is hard to see from the photos, but they chose a spot down a deep shaft which kept them fairly well protected from nest predators.

The land around looks quite healthy in terms of insect availability with cattle grazing pastures and its away from built up areas.

This is probably one of those sites which ‘suffered at the talons’ of the goshawk (although great news for the goshawk I guess).

As it was outside of the breeding season we didn’t disturb any nesting choughs. Tony is a licensed ringer and licenced to approach nests. I would not have been able to do this without him.

We then drove to the coast to take a look at some of the nest-boxes Tony and his colleagues have fitted to the cliffs. It is quite a challenge as they have to find a site that they can access, but at the same time deter egg collectors and the like from reaching it. In recent years Tony has sadly found activity at boxes suggestive of human raids rather than natural predators (and we thought those days were over). One clue being that ravens don’t need to use ropes!

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Nest-boxes are positioned away from potential land predators in areas where choughs are trying to breed naturally but fail.

The boxes are constructed from either marine grade plywood or Ecosheet©, a recycled plastic boarding. The shape is designed to mimic a natural cavity so they are quite narrow and deep.

Tony Cross indicating how far back the nest box reaches.

Tony Cross indicating how far back the nest-box reaches. This one is unusual in that it is positioned on top of the cliff.

The front of the box has and overhang which, apart from acting as a deterrent to something trying to reach in, makes it feel a bit more enclosed and sheltered for the birds.

cropped nest box

An chough nest-box facing the sea (the black dot in the sea is a seal, trust me)

One factor Tony did not consider when first designing these boxes was how badger-proof they would need to be. Don’t be alarmed, Welsh badgers have not adapted to have opposable thumbs and learn rope skills. They do, however, burrow and at one particular sight they have given the nest-box a bit of a battering pushing it out of place.

One nest-box needs re-positioning after a run in with badgers.

The boxes need to be checked each year as they do suffer from being exposed to the sea air. As long as the roof remains dry and there is no risk of collapse the boxes can be used for several years. It normally takes a year before a breeding pair move in to a new box. Lots of HSE forms to fill in, quality control tests, and the long wait for the Royal Court date (Jersey in-joke sorry).

It is clear that the work Tony and his colleagues are doing has made a great difference to the Welsh chough population. Jersey’s choughs may well benefit from the same practices as these birds have no experience of wild nest sites and will need some encouragement.

Choughs in South Stack, Anglesey

Choughs at South Stack, Anglesey

Many thanks once again to Tony for taking time out. You can find out more about his work at www.ecologymatters.co.uk

A murder of crows?

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Carrion crow (2). Photo by Mick DrydenFrom British Ornithologists’ Union

They steal, raid nests, and keep the company of witches. But the unpopular crow may not be the menace people think.

A new study, published in the BOU’s journal IBIS (here), has found that crows – along with their cousins the magpie and the raven – have surprisingly little impact on the abundance of other bird species.

Collectively known as corvids (a group that includes choughs, jackdaws and even jays), these birds are in fact being menaced by mankind in the mistaken belief that removing them is good for conservation. This new study found that in the vast majority of cases (82%), corvids had no impact at all on their potential prey species.

Magpie. Photo by Mick Dryden“Many nature lovers have been distressed to witness a crow or magpie raiding the nests of their beloved garden songbirds, stealing their eggs or eating their defenceless chicks,” said study co-author Dr Arjun Amar from the Percy FitzPatrick Institute for Ornithology. “Although this predation is entirely natural, these observations can be upsetting to witness and often leave people wondering if these predators might be reducing bird numbers.”

“However, our global review suggests that we should be cautious before jumping to conclusions over the impacts these species may have. Just because a predator eats something occasionally does not always mean that they have an impact,” Dr Amar said.

The study reviewed all published evidence on whether predation by corvids actually reduces the overall breeding performance of birds or, more importantly from a conservation perspective, reduces their numbers. Data were collated from 42 studies of corvid predation conducted across the globe over the last 60 years.

Not only were corvids unlikely to have any impact on their potential prey species, if there was an impact it most often affected the breeding success of the prey species rather than their subsequent numbers. Half of cases found that corvids reduced breeding success whereas less than 10% of cases found that they reduced prey numbers in the long term.

Raven (3). Photo by Mick Dryden“These results have big implications for the likely benefits of corvid control,” Dr Amar said. “They suggest that killing corvids will be of most benefit to those interested in gamebird shooting rather than conservationists.” He added: “Bird hunters are usually most interested in increasing numbers of birds available to shoot immediately after the breeding season and this appears to be where corvids have most impact”. “Conservationists on the other hand, are usually interested in increasing a species population size and our results suggest that only in a very few cases did corvids have an influence on this aspect of their prey,” Dr Amar said.

The review analysed the impact of six corvid species on a variety of prey species including gamebirds, songbirds, waders, herons, cranes, sea birds, wildfowl and raptors. The 42 studies incorporated into the review included 326 cases of corvid – bird prey interaction Most of the data stemmed from field research in the UK, France and the United States. The impacts were determined partly by comparing bird counts before and after corvids were either removed or their numbers reduced.

The review also found large differences between the impacts of crows, historically considered the most ‘cunning’ corvid, and magpies which are sometimes killed by home owners hoping to protect songbirds in their gardens. Crow species were six times more likely to have an impact on bird prey species than Magpies.

Magpie (2). Photo by Mick Dryden

Mistaken assumptions about corvid predation were possibly explained by the birds’ diurnal nature and the fact that they are conspicuous nest predators: “Their importance in prey population regulation is often assumed prior to any assessment of the evidence,” the study warned.

Chrissie Madden, the lead author on the paper, hoped that the review would challenge the perception that all corvids were bad, thereby preventing needless killing: “Our results suggest that this is a mistaken belief and that generally speaking people would be wasting their time killing corvids to increase bird numbers”.

“Overall therefore, our study points to the fact that we are often too quick to jump to the conclusion that crows and magpies may be the cause of bird population declines,” she said.

You can download A review of the impacts of corvids on bird productivity and abundance here

Wind turbine warning for wildlife

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Urbine221dcFrom University of Stirling

Careful planning measures must be put into place to ensure small wind turbine developments (such as those that fit on house roofs or in the garden) do not cause bat and bird population decline, according to research from University of Stirling.

Small domestic wind turbines or ‘microturbines’, which can kill bats and birds, are becoming an increasingly popular means to generate clean energy for home owners.

The Stirling team, whose research was published in Biodiversity and Conservation, found that the careful positioning of these turbines – and the avoidance of installing them in areas where bird or bat activity is likely to be high – is vital to ensure rare species of wildlife are not forced to abandon their homes in search of safer habitats.

Although previous research has shown that birds and bats may be killed in significant numbers by colliding with turbines in large wind farms, the Stirling research – carried out in collaboration with the British Trust for Ornithology – is the first study to examine whether small wind turbines could have a similar impact on wildlife.

The study looked at data, questionnaires from turbine owners and computer modelling, to assess the likely levels of bird and bat deaths caused by all small wind turbines across the UK. Results showed that between 1,567–5,510 birds and 161–3,363 bats may be killed per year by small wind turbines in the UK.

Dr Jeroen Minderman from the University’s School of Natural Sciences said: “Bird and bat deaths are a reality at small wind turbine sites.

“Whilst our findings show the relative extent of this problem is much smaller than other causes of wildlife deaths, such as cats or road collisions, our previous work has shown that bats avoid microturbine development areas – which may explain the relatively lower number of bat deaths estimated.”

Dr Kirsty Park, who led the Stirling research team said: “While our estimates of bird and bat deaths may seem high, it is important to realise that this is across a range of species and across more than 19,000 small wind turbines currently installed in the UK. Moreover, such estimates are several orders of magnitude lower than estimated numbers of deaths due to other human-related causes.

“However, this avoidance of microturbine sites by wildlife might have an adverse impact on rare or sensitive species if it causes bats to abandon what would otherwise be suitable feeding areas.”

She stressed: “Appropriate siting decisions that avoid such effects are therefore very important, and our work can help inform this.”

Microturbines are much smaller than their large wind farm counterparts and used mainly in domestic and farmland settings. Normally they are installed individually and can make a substantial contribution to household energy needs.

The increase in installation of such turbines is due to rapid technological developments and the introduction of financial incentives in the form of feed-in tariffs: schemes which pay people for creating their own ‘green’ electricity and offer additional bonuses for exporting electricity into the grid.

Abstract of the paper Estimates and correlates of bird and bat mortality at small wind turbine sites can be read here

Research published by the Stirling team in 2012 (full paper here) suggested that, while further research was needed, turbines should be sited at least 20 metres away from potentially valuable bat habitat. This will help to maximise the benefits of renewable energy generation whilst minimising potentially adverse effects on wildlife.

Recommendations for siting small turbines can be seen at Bat Conservation Trust, Scottish Natural Heritage and Cornwall Wildlife Trust 

Permissions etc. to install a turbine in Jersey can be read here 

Chough report: November 2014

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Radio antennes 1 - Binoculars 0

Radio antennas 1 – Binoculars 0

By Liz Corry

Thanks to the blanket fog, gales, and torrential rain we have been experiencing, plus the reduced daylight hours, November’s report is probably the shortest on record. Both the chough team and the equipment have taken a bit of a battering. A few tracking sessions have been cancelled whilst we shelter in cars or with the choughs in the aviary.

To be fair the start of the month was fairly pleasant. A bit bracing in the wind, but the sun was out and the chicks were on the move. Considering how much of the Island a chough can cover in just a few minutes the tracking team tried to be cunning and set up at three strategic vantage points; Sorel, Devil’s Hole/Crabbe, and Grantez.

Dawn tracking at Grantez.

Dawn tracking at Grantez.

Without sounding too bitter our plan failed on all but one occasion. Since I returned from holiday on the 8th the chicks have only flown south once…on my weekend (there is probably opportunity for a research paper into that correlation).

They decided to start exploring the north-west corner of the Island. Only ever seen flying, never touching down to feed, and only really on a few occasions. As the weather started to turn they hunkered down in Mourier Valley and haven’t really left since.

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Juvenile choughs probing for food on the cliffs at Mourier Valley. Photo by Liz Corry

Thanks again to everyone who sent in sightings this month. They have definitely helped to solve one mystery disappearance and have now made it onto five of 22 bird monitoring transects in Jersey.

To distract from the lack of content this month here are some photos and a video of what the choughs have been up to….

Seconds before the shutter clicked three choughs had been perched with the kestrel exchanging daily gossip perhaps.

Seconds before the shutter clicked three choughs had been perched with the kestrel, exchanging daily gossip perhaps.

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Cauvette and Dingle having a squabble over a prize insect Cauvette had dug up.

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Dingle begging for food from Bean (she wasn’t too impressed).

Hedges in farmland: good for birds, good for farmers!

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Kestrel (2). Photo by Mick DrydenFurther evidence of the importance to birds and farmers of hedges in agricultural land comes to us from a rather unlikely source. Studies from Akot, Maharashtra State in central India revealed how strong the difference in bird numbers and diversity between different farmland sites with and without hedges can be. Hedges in the study area were shown to provide important nesting, feeding and sheltering sites for birds in agricultural areas with highest numbers of birds in those fields with hedges.

During the Indian study, 64 bird species from 34 families were observed. Most of the birds were recorded actually in or very near hedges. An earlier study (here) in Germany reported that increasing hedge length enhanced significantly the number of bird species and that adding hedges or introducing organic farming practices should be primarily promoted in simple landscapes, where it really makes a difference for biodiversity.

These studies show that hedge length has a stronger effect on bird richness than management and that the increasing length of hedges enhances birds in conventional, non-organic, fields too. Bird conservation even in intensively used agricultural landscapes should concentrate on hedges or green lanes.

OLYMPUS DIGITAL CAMERAProviding more hedgerows and carefully managing them, can significantly contribute to the conservation of declining farmland birds. Birds forage in the agricultural fields, using the hedges for resting and breeding. Highest diversity of birds was also directly connected to diversity of plants as the greatest number of plant types gave more choice of food for the bird species. High numbers of bushes and plants at the boundary of agricultural land will benefit the largest numbers of birds. Thus planting trees in agricultural lands and well managed hedges can increase the bird diversity and large scale cutting of hedges should be avoided.

Not only will populations of birds benefit from increased hedges but the birds can themselves benefit the farmer. Insectivorous and predatory birds play a very useful role in controlling insect and rodent pests of crops. Presence of healthy numbers of birds in the farm fields is an eco-friendly and useful way of controlling the pests on the crop so, hedgerows must be saved to conserve farmland bird diversity. Hedges should, however, be maintained properly and not allowed to become invasive and reduce the utilizable area of the field.

Studies on farmland avian diversity with special reference to importance of hedges in conserving farmland bird diversity can be downloaded here.

Chaffinch (5). Photo by Mick Dryden