New BTO cuckoo research and what it might mean for Dartmoor

The British Trust for Ornithology (BTO) has just published a paper in Nature Communications entitled “Population decline is linked to migration route in the Common Cuckoo”. Scientists at the BTO led by Chris Hewson have been using tiny satellite trackers attached to cuckoos so that they can plot their progress and routes. This is what part of the abstract of the paper stated

” ….by tracking 42 male Common Cuckoos from the rapidly declining UK population during 56 autumn migrations in 2011–14. Uniquely, the birds use two distinct routes to reach the same wintering grounds, allowing assessment of survival during migration independently of origin and destination. Mortality up to completion of the Sahara crossing (the major ecological barrier encountered in both routes) is higher for birds using the shorter route. The proportion of birds using this route strongly correlates with population decline across nine local breeding populations.”

You can download the paper here along with the supplementary tables here. Nature Communications have kindly made this paper ‘open access’ for there is no charge.

BTO cuckoo migration map

This is a graphic from the recent BTO News magazine which summaries the findings regarding route choices. In essence UK cuckoos either use the eastern route through Italy / The Balkans or the western route through France / Spain when migrating south. Interestingly all birds use the western route to return to Britain. The research statistically proved that mortality of birds travelling south via the western route was significantly higher than for birds using the eastern route even though the western route is shorter.

The paper includes this graphic with the following caption ‘Cuckoo migration route use and breeding population change for each tagging location’.

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From this we can see that 6 Dartmoor birds were tagged four used the eastern route and two used the western one (yellow/red pie charts). The undying pink / grey dots on the UK map show the change in abundance of cuckoo populations across the UK as measured by the BTO Atlas Projects in 1988–91 and 2007–11. Dark pink indicates a good increase and dark grey a big decrease (see the colour scale on the right side of the map above +0.75 = 75% increase in abundance and -0.75 = 75% decrease in abundance between the two survey periods. It is currently not clear why the western route is more hazardous – it might be land use change and drought in southern Spain – more research on this required.

The BTO team then correlated the route data with the abundance change data – this is shown in Supplementary Table 2 – I have turned that data into a little graph so it is easier to understand.

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The axis which runs along the bottom of the graph shows the proportion of cuckoos using each route, 1 = all birds using the eastern route and 0 = all birds using the western route. The Dartmoor birds score 0.58 = 58% of Dartmoor cuckoos use the eastern route and 42% use the western route. The scale which runs up the graph shows the change in abundance of cuckoos between the two BTO Atlas survey projects. The Syke / Kintail population score 0.433 = a 43.3% increase. The Sherwood Forest population score – 0.465 = a decrease in abundance of 46.5%. The Dartmoor population is -0.242 = a decrease in abundance of 24.2%. The BTO work proves that there is a statistically significant correction between these two factors i.e. the proportion of birds using the western route strongly correlates with population decline across nine local breeding populations.

With the publication of the Devon Bird Atlas late last year we already knew that cuckoos in Devon were in big trouble.

Cuckoo3
This is the distribution of cuckoo in Devon between 1977-85

Cuckoo2This is the distribution between 2007 and 2013 – approaching a 75% decline in 20 years

The Devon Atlas does show a strong population still on Dartmoor but as I have argued before this population is also declining (see here). I produced a graphic which showed the changes on Dartmoor between the two survey periods.

Cuckoo change data
Four 10 x 10km squares had increased numbers of tetrads (2x2km squares) where cuckoo bred, three showed no change but nine showed declines. Overall cuckoo bred in sixteen fewer tetrads  in 2007-13 compared to 1977 to 85.

The data in the BTO paper ascribes the decline to 24.2% on Dartmoor using the BTO Atlas data (comparing 1968-72 with 2008-11). The paper also clearly shows that the 42% of Dartmoor cuckoos which migrate via the western route suffer a higher mortality rate than the 58% which use the eastern route which goes some way to explaining the decline.

However mortality rate on migration cannot be the whole story – it cannot explain the 75% decline in Devon. Away from Dartmoor and Exmoor the cuckoo is now virtually extinct in the county when 30 years ago it was common. The change in land use in lowland Devon is almost certainly the culprit here. I have written about this before – see here and have discussed the decline in the population of large hairy caterpillars which cuckoos are so fond of.

Cuckoo 3
A Dartmoor cuckoo this year at Emsworthy

Fortunately further  research is being conducted at Exeter University by Professor Charles Tyler and his team which includes Sara Zonneveld and Lowell Mills who are both conducting PhD research on this very topic. I am very much looking forward to hearing about what they have discovered. Their work along with the BTO’s migration work (and other relevant research from the RSPB) will I hope help us piece together what has happened to our cuckoos so that we might have a chance in the future to do something about it.

I was also pleased to see Devon Birds credited in the acknowledgements section of the BTO paper. I understand that Devon Birds provided funding to help acquire some of the satellite trackers.

The curious case of the Dartmoor Forest Plan has just become more curious

On the 17th June I wrote a piece about the Forestry Commission’s plans for their Estate on Dartmoor entitled ‘The curious case of the Dartmoor Forest Plan’ – see here. In essence their plans set out the FC’s actions up to 2046. Greater thought will be given to wildlife and archaeology, access will be encouraged  but the primary plans centre on the Forests as places where commercial timber will be grown predominantly from conifer crops. There is a small increase of broadleaved species especially around the edges and there is a diversification of the species of conifer that will be planted.

Under conifers

According to the FC website a consultation had been held on their proposals and this had ended on the 1st April this year. Most of the comments received appeared to be minor comments about the detail of what was proposed and there seemed to be no comments actually challenging the principle of re-planting conifers at all. A number of key organisations such as the Dartmoor Preservation Association or the Dartmoor Society appeared not to have commented at all.

The consultation had been a very low profile affair, belatedly the media picked up the story following the publication of my blog and Kate Ashbrook General Secretary of the Open Spaces Society gave an interview on BBC Radio Devon – listen here 1 hour 59 minutes in calling for a debate on a wider options for the future.

Now here comes the even more curious bit, a lady called Jan Corlett had read my blog and heard Kate on the radio and wanted to comment on the plans, she contacted the Forestry Commission and was told that the consultation was still on-going although the FC website is showing that it has closed – see here. Good work Jan and thanks for letting me know.

The consultation on the Dartmoor Forest Plan runs until the 25th July (according to the FC email to Jan) but on another page of the FC website it says the 19th July so if you want to comment on the plan let the FC know what you think by the 19th July. You can no longer comment via their website (the hyperlink you press just brings up a map) so instead send comments by email to adminhub.bullershill@forestry.gsi.gov.uk or write to them at Forestry Commission, West England Forest District, Haldon Forest Park, Bullers Hill, Kennford, Exeter, Devon, EX6 7XR.

I can smell a small furry rodent!

 

The curious case of the Dartmoor Forest Plan

I like to think I know what is going on, on Dartmoor but sometimes I really don’t. The curious case of the Dartmoor Forest Plan is one such occasion. The Forestry Commission issued a consultation document in March on how it intended to manage its forest estate (Fernworthy, Bellever, Soussans and Brimpts) into the future. Comments had to be submitted by April.

You can download and read the Plan here – part 1here – part 2here – part 3here – part 4 and here – part 5. There are also 4 appendices which you can read here for 1here for 2here for 3 and here for 4 – the consultation comments and replies.

I only found out about it a couple of weeks ago after being contacted by Matthew Kelly, the historian and author of Quartz and Feldspar who has written a blog about it (see here) and was seeking my view on it.

I think it must have been a pretty low profile consultation – nothing has appeared on my social media feeds about it for three months and it is often by that route I discover what is going on. I suspect that the FC sent consultation documents to their formal consultees and a select band of NGOs.

In essence the documents set out the FC’s plans up to 2046. Greater thought will be given to wildlife and archaeology, access will be encouraged  but the primary plans centre on the Forests as places where commercial timber will be grown predominantly from conifer crops. There is a small increase of broadleaved species especially around the edges and there is a diversification of the species of conifer that will be planted.

From BelleverBellever
Bellever Forest from Bellever Tor

The coming years will see the current crop (predominantly Sitka Spruce) mature and be clear felled. At Fernworthy for example 40% of the forest will be clear felled by 2031. Sitka Spruce monocultures will not be replanted as it is now considered that due to climate change the Forests need to be diversified to make them more resilient. Instead a mix of Sitka Spruce, Noble Fir, Pacific Silver Fir, Douglas Fir, Norway Spruce and Wellingtonia, plus in a few places Willow, Birch,  Alder, Wych Elm, Swamp Cypress and Sycamore will be planted.

The 4 Dartmoor Forests in question were planted up (largely) in the 19th and early 20th centuries and managed by the FC (it is a complicated story which I have simplified here – see Quartz and Feldspar pp244-265 in the paperback edition for the full details). As well as being productive forests they have also become important places for wildlife in their own right harbouring a number of rare species such as goshawk, hobby, nightjar and for a short period of time Britain’s only breeding location for the red-backed shrike.

The FC acknowledges (and is indeed proud) of this wildlife asset and the plan addresses it. The Plan also takes steps to undo some of the brutalism of their earlier plantings where conifers were grown on top of Scheduled Ancient Monuments (SAMs). Once the trees have been felled the SAMs will be left open and managed for their archaeology. This is a step forward but isolated SAMs within a forest environment is not the same as an open historic landscape from whence they came.

Sousson's Stone Circle
A stone circle adjacent to Soussans Forest.

The Plan also acknowledges the impact that forestry has on water quality. Conifers acidify the soil and therefore the water and when fellings occur sediment / soil ends up in the water courses and ultimately in the rivers. Acidified waters with a peaty sediment load are not good for river wildlife such as salmon, dippers and grey wagtails along with their invertebrate prey.

These issues are potentially significant at Fernworthy with its adjacent reservoir which many of us rely on for our own drinking water. There are lengthy comments from the Environment Agency and the Devon Wildlife Trust on this topic (in appendix 4) which the FC have taken on board in addition to their own initial mitigation plan.

The other comments from the conservation bodies (RSPB, DWT and DNPA) largely consist of advice around how the existing Forest based wildlife can be enhanced along with a few words urging a higher proportion of broadleaved plantings.

Interestingly the comments don’t include anything about the potential species the FC are proposing to plant. The FC have invested a lot of time and money into producing a database which enables foresters to select suitable species to plant against the backdrop of a changing climate – see here. You simply type in a number of site variables and the database provides you with a long list of suitable exotic trees to plant to make the forest / woodland more resilient to climate change.

I have been a long time sceptic of this approach. The FC (and the rest of Government) use the UK Climate Prediction 09 dataset (produced by the scientists at the Hadley Centre and the Met Office in Exeter) – see here. This model compared to the previous version acknowledges the considerable uncertainties and as a result provides a probabilistic approach to future climate scenarios. Firstly there are 3 emission scenarios Low, Medium and High – which one of these is the Earth currently embarking on regarding its emission of greenhouse gases? You have to choose one. You then choose a climate variable e.g. Summer Mean Maximum Temperature.

Sum_Tmax_Med_2080s_large
© UK Climate Projections 2009
And this is the outcome – so on Dartmoor under the medium emissions scenario by 2080 the change in maximum summer temperature is very unlikely to be less than 3 degree C and very unlikely to be more than 9 degrees C. That is quite a range!

The maps also come with a health warning from the Met Office. “These maps are useful to communicate the main results of UKCP09 and raise awareness about climate change. When presenting UKCP09 projections using maps you should use a series of maps to show the range of possible outcomes. Here we have put together maps in series of 3 (showing the 10%, 50 % and 90% probability levels) for a range of climate variables. They are available for the 2020s, 2050s and 2080s and for low, medium and high emissions scenarios.”

DEFRA however in their document ‘Adapting to Climate Change – UK Climate predictions’, download here, present the data in a very different way which gives the outcome a much more predictable fate.

Screen Shot 2016-06-16 at 12.15.31
They have decided to use the 50% probability estimates (calling them ‘central estimates’) i.e. there is a 50% chance they will be lower than this and a 50% chance they will be higher.

This data is what is used in the FC tree species selection database which could be interpreted as meaning there is a 50% chance the right species have been selected and 50% chance they might be wrong! Foresters from the FC have got ‘previous’ on this – during their fanatical campaign to plant up the Flow Country in northern Scotland Sitka Spruce and Lodgepole Pine were planted over tens of thousands of acres damaging internationally important peatlands until it was discovered that it was too wet and the tree wouldn’t grow. Conservationists make fun of foresters by saying they don’t need to be accountable for their decisions because by the time it is discovered that a mistake has been made they will have either retired or died. The question for me therefore remains have the FC chosen the right species?

Another curious thing about the Dartmoor Forest Plan in addition to the fact that very few people have heard about is who wasn’t formally consulted. On the surface this may seem a very innocuous matter – the FC is consulting with its close band of stakeholders to sharpen up its thinking. However the history of forestry on Dartmoor tells a very different story which is beautifully described by Matthew Kelly in Quartz and Feldspar. In essence decades of the 20th century saw huge battles between the FC and various preservationists led by the Dartmoor Preservation Association. Had it not been for their efforts the conifer plantations may have stretched continuously from Bellever to Fernworthy! It was really only in the 1980s that things calmed down as the FC metamorphosed into a more environmentally friendly organisation.

I have looked at the websites of the Dartmoor Preservation Association’s and the Dartmoor Society and can find no reference to the Dartmoor Forest Plan. I get the feeling that like me they missed the consultation because I am certain that if they had been consulted they would have had something to say!

I am also surprised that Chagford Parish Council didn’t respond to their formal consultation – over the next 15 years 40% of Fernworthy will be clear felled – that is around 570 acres of conifer plantation and all of the vehicle movements will go through Chagford……. It isn’t easy negotiating Chagford and the subsequent road up to Fernworthy in a VW Golf let along a double six wheel forestry wagon.

I am also intrigued by the DNPA’s position. The comments from them in appendix 4 are from their Senior Ecologist and are specific technical issues relating to nature conservation but the section starts “our Senior ecologist has some additional comments to add”. However the DNPA’s comments which apparently precede this are not published! I wonder what their view is? A previous head of the DNPA Ian Mercer in his Collins New Naturalist book ‘Dartmoor’ said the following regarding Hawns and Dandles conifers – “wholesale removal of a living eyesore (to moorland devotees) has happened at public expense…..“. The DNPA as an organisation don’t like the conifers on the high moor!

I wonder whether the DNPA urged the FC either to not replant or replant with broadleaved trees opposed to alien conifers?

It is also interesting that no comments were received from the Woodland Trust or the National Trust – their partnership project at Fingle Woods would surely have been relevant?

As a result the FC have managed to carry out a very low profile consultation on how they should replant and manage their Forest Estate on Dartmoor without stirring up a debate about whether there should indeed be conifer plantations on the high moor in a National Park, the conservation bodies appear also to have been compliant to this by sticking to their consultation brief.

A couple of months before the consultation George Monbiot was on Dartmoor proselytising about re-wilding. I’m sure if George or Rewilding Britain (the charity he helped form) had known about the Dartmoor Forest Plan they too would have had something to say.

Ironically, whilst the conservationists have been compliant or caught napping or living in blissful ignorance it has taken a historian to come up with a more exciting future vision. In his blog entitled The Dartmoor Forestry Plan. Questioning Conventional Thinking he says:-

This is a moment of opportunity for Dartmoor. The Dartmoor Forestry Plan, despite its progressive gestures, suggests this will be missed. When conventional thinking no longer chimes with the public mood it should be challenged.

Could not at least one of the FC’s Dartmoor holdings be dedicated solely to native broadleaf planting? It is hard to exaggerate what an exciting development this would be for Dartmoor nature. My vote goes to Fernworthy.

The curious case of the Dartmoor Forest Plan indeed!

 

 

 

 

Dartmoor Upland Bird Nest Group – a nice gesture

Earlier in the year I supported a crowding funding campaign for the Dartmoor Upland Bird Nest Group. They raised £3728 from 95 donors which has enabled them to purchase equipment, bird rings and fund additional survey hours in the field.

In the post yesterday I received a ‘thank you’ from the group – a photo and some postcards.

Stonechat - Charles Tyler
The photo is of a stonechat taken by Professor Charles Tyler

Postcards John WaltersThe postcards are lovely paintings by John Walters

A very nice gesture – thank you. It is an important project working out what is happening to Dartmoor’s birds such as the cuckoo, whinchat and meadow pipit.

Find out more about the group and their work by clicking here.

 

Lammergeier 2

Following on from yesterday’s blog about the Dartmoor lammergeier (see here) I can report that on Wednesday 18th May there were no ‘official’ sightings of the bird.

Lammergeier_(Gypaetus_barbatus)_1_(5756164756)
 Noel Reynolds Lammergeier (Gypaetus barbatus) via Wikimedia Commons

However I did receive an email regarding a sighting on Monday 16th May

‘I have also received a sighting from a couple walking their dog nr Cox Tor who looked down on a very large bird flying down the valley from Merrivale towards Whitchurch direction.  They reported a very large dark bird and at first thought Grey Heron and then as it turned instead of seeing legs/feet they saw a “spoon-shaped” tail.  They believe this was the Lammergeier.  The time was 6.30pm on Monday evening (16th May) – if the bird was then seen nr North Hessary Tor the next day that would all tie in.  (Lots of bones in that area!)’

And this one from Wednesday the 18th May.

‘Hate to tell you this Adrian, but my husband saw it today (Weds 18th), as he was mowing the lawn, in the Dart Valley. He said all the small birds and buzzards shot off pretty quickly when it arrived. Don’t blame them, looking at the size of it!’

This intriguing message was also posted yesterday by Birdguides

Screen Shot 2016-05-18 at 21.58.50

I just wonder how easy it will be to ‘acquire’ a dead sheep. Am still waiting for the further details …..

That Birdguides post reminded me of my favourite one of all time regarding a Yellow-browed Warbler in Blackpool from 2002.

Funny Girls

A lammergeier on Dartmoor – the fog of twitching

I spent most of yesterday trying to see the lammergeier, a large vulture with a wingspan of 2.75m, which had been seen on Dartmoor the day before. This is a very rare bird for Britain – indeed it is the first record of the species for the country. However all did not go to plan and I drew a blank.

Bartgeier_Gypaetus_barbatus_front_Richard_Bartz
A lammergeier By Richard Bartz, Munich aka Makro Freak, via Wikimedia Commons


The bird was first spotted last week in mid Wales and was videoed crossing the Bristol Channel last Thursday

The name ‘lammergeier’ appears to have come back into fashion – in the mid 80’s and 90’s it was replaced by ‘Bearded Vulture’. Lammergeier translates from the German as the lamb hawk and such a name was considered an impediment to its conservation so it was changed. It is a very rare and threatened species in Europe and has been successfully re-introduced into the Alps and the Pyrenees. It is a very specialised vulture as it predominately feeds on the marrow from the bones of dead herbivores.

It is mentioned in the Bible (in Leviticus) as a species which should not be eaten by people (presumably on account of it diet) and legend has it that a lammergeier was responsible for the death of the ancient Greek playwright and poet Aeschylus. Lammergeier are fond of feeding on tortoises which they pick up from the ground and then drop onto rocky ground from a great height to break them open before feeding on them. Aeschylus had a bald head and legend has it that a lammergeier mistook his shiny head for a rock and dropped a tortoise on him killing him instantly……

I subscribe to a service called Birdguides which provides detailed updates on the location of rare birds in Britain.

Screen Shot 2016-05-17 at 21.51.07
Here is a screen grab of the Dartmoor records

The specific language used by Birdguides is important and needs some interpretation to the uninitiated. “Immature at Yar Tor” – the first record is unambiguous – the bird was seen there at 15.33. A little later the sighting becomes ‘reported’ i.e. it may not be correct….

Screen Shot 2016-05-17 at 22.01.26The ‘reported’ status is then further questioned as “others believe this sighting relates to a drone”. I must say I have never seen a 2.75m drone on Dartmoor.

Screen Shot 2016-05-17 at 22.37.40The record update then becomes ‘reportedly’ which means it is probably not correct….

Nevertheless I spent most of Tuesday around Soussons Down near to the Warren House Inn. When you are trying to re-locate a first for Britain such nuanced language is lost on you until you have time to reflect …..

My time however was not entirely wasted I did manage to photograph a few of the commoner and more classic Dartmoor birds.

Tree pipit 2
This is a tree pipit singing on top of a hawthorn bush at Soussans

Tree pipit 3

I spent half and hour watching the bird carry out its classic display – flying high into the air and then descending whilst singing onto the top of the bush. Listen to the song here (courtesy of Tweet of the Day)

Stonechat female 1
A little later a female stonechat appeared on the same bush on the way to its nest to feed its young

Meadow pipt 1
Back at the Warren House Inn area I photographed this skylark

Meadow pipt 2
Another view

As I was standing around at Soussons yesterday the lammergeier was seen over Princetown and North Hessary Tor (6 miles away) but unfortunately I didn’t know this as I had no phone reception. I am now waiting for ‘news’ before I head out again.

There are two other essential Birdguide words that would be twitchers need to know.

‘Purported’ – a purported record is one that has been submitted but it not believed. However it is reported in case it turns out to be correct and no one can then be accused of suppression.

‘Putative’ – a putative record is slightly more credible than a purported one but one would be well advised to allow the sighting to be firmed up before travelling hundreds of miles across the country to see it.

So we have a transition of bird sighting terminology.

Purported -> Putative -> Reportedly -> Reported -> Seen

Well worth remembering in the future.

 

 

 

 

 

Four superb Golden Plovers

Steve and I had a good day birding yesterday – we had a long slow walk around St Mary’s and found a few new migrants including grasshopper warbler, a black redstart, a lesser whitethroat and four golden plover in summer plumage in a field at Peninnis. We also saw the Montagu’s harrier over High Moors.

Golden Plover 2
Golden plovers breed in the uplands of Britain (and elsewhere in Europe) and then migrate south for the winter – many spend their winters on our estuaries and on Dartmoor.

Golden Plover 3
The glover plover formerly bred on Dartmoor but it has failed to do so in the last decade.

Golden Plover 6
Work is underway on Dartmoor to further restore the blanket bog and it is possible that this may encourage the species to returnGolden Plover 5However in all likelihood the golden plover is one of Devon’s first species of bird to become a casualty of climate change.

Golden Plover 1
In the winter large flocks of golden plover can still be seen on Dartmoor – see here for a previous blog on wintering golden plovers on Dartmoor.