A tale of the unexpected

There’s nothing up my sleeve!

Over the decade since I first started training as a T-permit holder I’ve experienced a few instances when birds do something completely unexpected. On Wednesday, I had just finished processing a Goldcrest but, when I opened my left hand to release the bird, it did not fly off immediately. It didn’t look stressed and certainly wasn’t hypothermic so I tilted the palm of my hand slightly to encourage it on its way. I wasn’t ready for what happened next.

In the flash of an eye, the bird rotated through 180o and then disappeared straight up the sleeve of the jacket I was wearing. Trying to work out where a bird weighing just 5 grams was hiding in a quilted sleeve was never going to be an option so I was left with no alternative but to gingerly slip my arm out and take the coat off. Gentle exploration located the bird at around about the elbow, whereupon it was easily extracted and flew off apparently non the worse for its brief experience as a troglodyte.

Wednesday 12th January 2022

Tristis Chiffchaff

The first ringing session of the year, with perfect weather, wind strength and direction. The reedbed is currently both unproductive and underwater so I concentrated on the area downwind of the sewage works. This proved to be a good call and 65 birds were trapped with 44 Chiffchaff, including 3 tristis and 2 UK control collybita. Also 6 Goldcrest, 3 Bullfinch, 3 Blue Tit, 3 Great Tit, 3 Robin, 1 Dunnock, 1 Blackbird and 1 Wren.

Two of the tristis were classic birds with olive limited to the margins of their flight feathers and tail and completely lacking in yellow tones except in the underwing coverts. A few years ago, the third bird would have been relegated unceremoniously to the form colloquially known as fulvescens, showing more olive on the mantle, a hint of yellow in the supercilium, undertail coverts and around the thighs. It was assumed that these birds were intergrades from the zone of overlap between tristis and abietinus. However, all the mtDNA analyses done on these birds for me by Martin Collinson’s team at Aberdeen University have come back as 100% tristis. Whilst this method only gives the maternal ancestry, I think it unreasonable to assume that hybridisation only occurs between male abietinus and female tristis.

The current thinking seems to be that if it looks like a tristis, sounds like a tristis and has tristis DNA then that’s what it is. Fortunately, all the birds were attracted into the net using a tristis song lure and gave the soft, short ‘peep’ call on release, which, as far as I am concerned seals the deal! I have posted photos of all three birds and a collybita Chiff below for comparison purposes.

tristis 1 with more olive than usual and a hint of yellow in the eyestripe.
tristis 1 – note hint of yellow in the undertail coverts and around the thighs.
tristis 1 – yellower underwing coverts than usual
tristis 2 – a ‘classic’ example
tristis 2 – note lack of yellow tones apart from faint underwing coverts.
tristis 3 – another ‘classic’ bird
tristis 3 – no yellow here either
collybita Chiff for comparison
collybita breast and underwing coverts

Tuesday 4th January 2022

The bridge to Marsh Ride on 3rd January 2022

Firstly, a happy new year to all those readers waiting anxiously for my next instalment. Don’t hold your breath!

I know from experience that, in the middle of winter, my mist nets beside the sewage works at South Milton Ley are only productive when it’s either flat calm or when there is an easterly element in the wind. The rest of the time the prevailing south-westerly breeze concentrates the chironomid midges and the birds on the opposite and inaccessible side of the works. With a seemingly endless stream of wet and windy westerlies in recent weeks, I have been keeping my carbon footprint low by staying at home.

To be honest, Covid vaccination commitments currently occupy two days a week and I also have an allotment, which desperately needs digging over prior to the spring planting season, assuming the ground ever dries out enough to work! With my main reedbed ride unproductive until the middle of March, there is little incentive to travel to SML. The flocks of roosting Reed Buntings, which used to form a significant part of the winter catch, are a thing of the past, with just one bird trapped this winter.

Added to this, the gradual and intentional silting up of the main drainage channel is beginning to have the desired effect of raising the water table in the middle of the reserve, (see the photo above), which means that, as a lone worker, I won’t risk accessing Marsh Ride. There’s over a metre of fast-flowing water under the bridge at the moment and another 60cm of soft sediment under that. The boards along the net ride are covered in a layer of silt, which turns them into a skating rink. It’s just too dodgy, trying to carry bird bags without slipping into the mire!

I haven’t been totally idle though. The first draft of the next management plan is completed and will be published as soon as I have addressed the comments received from various interested parties. I discovered that, deep in the darkest reaches of the Devon Birds’ website, someone has digitised all the annual reports from 1929-2018 into one massive pdf file. I have been searching this document for records relating to SML. I also have acquired a digital copy of “The Birds of Devon” by D’Urban and Mathews from 1892. Scouring both has enabled me to increase the bird list to 215 documented species. Only two of these, Little Bittern and Long-tailed Skua pre-date the establishment of the reserve in 1969.

If anyone wants copies of these two historical documents, leave a comment and I’ll stick them on Dropbox for you.

Wednesday 14th December 2021

Tristis 1

After three weeks with two named storms and seemingly endless days of wind and rain, I finally escaped the house and got in 3 hrs ringing at South Milton Ley before the next band of drizzle swept in. In reality, it was windier than I had hoped for and, with leafless trees and the reeds having died back for the winter, the breeze was sweeping up the valley unimpeded, keeping most birds on the opposite side of the sewage treatment works to my net rides. Just 10 new birds were trapped, which is not a good return on the six litres of fuel it takes to get there and back from Plymouth. There were compensations though; First out of the net – 2 tristis Chiffchaffs followed by 5 collybita Chiffchaffs, 2 Goldcrests and a Blue Tit.

Tristis 2

One of the Chiffchaffs had an overgrown upper mandible. This is first time I have seen this in in over 2,500 Chiffs I have ringed there. It didn’t seem to have affected its feeding though with a healthy winter weight of 7.7g.

Finally, in May this year I heard a female sparrowhawk soliciting food from a nearby male quite close to one of my net rides. On two subsequent visits I heard what I assumed to be nestlings begging for food and saw the female carrying prey into the same, inaccessible clump of trees. When I mentioned this to the reserve manager, he was, to say the least, dismissive, telling me “Sparrowhawk has never bred inside the reserve.” Not one to take kindly to having my field skills questioned, I had been waiting for the leaves to drop before investigating further and the lack of birds today gave me the perfect opportunity.

Nest located and photographic evidence secured!

Sparrowhawk nest

It was a few metres from where I had expected to find it and the tree was surrounded by impenetrable bramble, which was a shame as I’d been hoping to get close enough to look for rings in regurgitated pellets or to get a ladder up to look in the nest itself. Never mind. It was a moral victory anyway!

Wednesday 24th November 2021

Weather conditions were pretty benign today, both in terms of wind speed and direction and in terms of the temperature, which, after an overcast night, was high enough (just) to prevent ice from forming on the mist net poles. There was even a small hatch of Chironomid midges in the neighbouring sewage works, only a few hundred or so but enough to keep the wintering Chiffchaffs distracted. Numbers were about average for the time of year with 39 birds trapped: 5 Blackbird, 2 Blue Tit, 2 Cetti’s Warbler, 19 Chiffchaff, 3 Goldcrest, 1 Great Tit, 1 Long-tailed Tit, 1 Reed Bunting and 5 Wren.

Benthic Diatoms, 112 new species – November 2021

Cocconeis placentula

Way back in the year 3 b.p. (before pandemic!) Natural England sent me a document detailing their conservation objectives for South Milton Ley SSSI and tucked away in the comments section was a reference to a South West Water, AMP 4 investigation. This document proved to be of critical importance as it states that 90% of the phosphorus loading into the SSSI comes from the outflow of the adjacent sewage treatment works and just 10% from the catchment. I realised that, in order to arrive at the 90% figure, there must be some data on the actual levels of phosphorus reaching the Reserve from both sources.

Attempts to track down a copy were initially fruitless but, after a bit of detective work and with assistance from the Environment Agency, I identified the full title of the study as “South Milton Ley Habitats Investigations: Nutrient Investigations”, conducted by Faber Maunsell in 2006. Armed with this information I submitted a request for a copy to South West Water last month under the Environmental Information Regulations (2004). Their response, although timely, was disappointing, “Unfortunately, SWW have been unable to locate either a hard copy or electronic copy of the 2007 document”.

Not one to take “no” for an answer, I submitted a second request stating that I did not believe that SWW would not retain the results of a study they had commissioned and, in its absence, asking for any data they had on nutrient levels reaching the SSSI from the catchment. This seems to have galvanised them into action and miraculously, I have just received a copy of the 132-page report together with nutrient data from 2006 up to 27th August 2021. Result!!

The 2006 study was comprehensive and included examination of sediment cores from several sites in the lower Ley. One of the parameters studied was the number and diversity of the benthic diatom flora. Having spent many hours identifying and counting phytoplankton in marine and benthic samples during my career as a marine microbiologist, I know what a labour of love these analyses must have been and am thankful that someone else did the work! Consequently, I have just been able to add 112 species to the lists for the reserve. These can be found in the South Milton Ley Species Lists section of the blog. Unfortunately, I have not been able to work out how to put in shortcuts to the relevant sections yet, so readers will have to scroll down through the lists until I unravel the complexities of the WordPress editor.

Monday 15th November 2021

Female Cetti’s Warbler – 15th November 2021

A steady morning’s ringing with enough gaps to enable me to complete a few more non-urgent maintenance tasks without any great pressure. Normally, by this time of year, the trees at South Milton have just about finished shedding their leaves but the continuing mild weather and the lack of wind-blown salt spray has left many of the Willows hanging on to theirs. Once all the leaves have fallen, the margins of the sewage works become the focus of attention but, at present, birds are spread thinly throughout the ringing area. There was a welcome sign that wintering numbers are beginning to build with four Goldcrest and seventeen Chiffchaff amongst the total.

I uncovered a heavy, rubber, fencing support block some time ago, which was buried in the undergrowth and might have been there since the sewage works was constructed many moons ago. It’s now sitting under the reedbed end of my bridge to Marsh Ride, hopefully raising it clear of future floods in the stream and further reducing the risk of it being swept downstream again.

I have also been nurturing a selection of Rowan, Hawthorn and Bird Cherry saplings at home as an insurance policy in the case of widespread Ash dieback. A number of young Ash trees are now showing clear signs of disease so I planted twelve of my saplings to replace them. Hopefully, all three species will prove attractive to passage thrushes in the future and maybe even the occasional Waxwing!

38 birds were trapped: 6 Blackbird, 3 Blue Tit, 2 Cetti’s Warbler, 17 Chiffchaff, 1 Dunnock, 4 Goldcrest, 2 Great Tit, 1 Robin 1 Song Thrush and 1 Wren.

Tuesday 2nd November 2021. Water, water everywhere!

A light frost, the first of the autumn, greeted me when I arrived at the Reserve this morning but, as the day wore on, I found myself peeling off layers of clothing in brilliant sunshine with almost no breeze. Perfect conditions for the nets, if a little bright. The birds weren’t cooperating though. There was little sign of overhead passage, just a few hundred Woodpigeon and a couple of Redwing and Mistle Thrush and not much on the ground either. In the end, just 23 birds were trapped in five hours and half of these were re-traps. The final totals were: 1 Blackbird, 2 Blue Tit, 3 Cetti’s Warbler, 4 Chiffchaff, 2 Dunnock, 3 Goldcrest, 3 Great Tit, 3 Robin and 2 Wren.

However, with no pressure from the nets, I was able to complete a number of minor maintenance tasks, which had been accumulating. The first job was to replace the snapped mist net pole in Blaca ride. I had measured its diameter on my last visit and made up a sleeve at home to cover the break. Tightening a couple of self-tappers fixed it in about five minutes. A good start.

The bridge to Marsh Ride – now suitably restrained!

After the wet latter half of October with 60% more rain than average, South Milton Stream was pretty full and the water table had clearly risen in the reedbed. The stream was lapping around the base of my bridge to Marsh ride. It has been swept off its mountings a couple of times before so I hammered in two scaffolding poles to stop it drifting downstream in the future. Marsh ride is the lowest point in that part of the reedbed. Years of walking up and down the net ride have created a channel, probably only 10-20cm lower than the surrounding marsh but enough to show up as prone to flooding on Environment Agency maps.

Surface water in Marsh Ride
Changes to the depth of South Milton Stream following the cessation of dredging

Whilst on the subject of flooding. The northern boundary path, in the region of the boardwalk, is regularly inundated when the coastal sandbar is high and the reserve manager was concerned that the cessation of dredging in South Milton Stream would exacerbate the problem. Today gave me the perfect opportunity to take some photos and measure the current depth of the channel. About an additional 20cm of sediment has accumulated since my last measurement but the boardwalk area remained accessible, confirming mine and Nick’s assessment that it is water impounded behind the sandbar rather than the stream that causes the flooding. The chart above shows the amount of sediment accumulated since the last dredging operation in 2014.

No flooding at the Boardwalk bridge despite the accumulation of sediment in the stream!

The water levels in South Milton Stream, between the sewage works and the boardwalk, lapped between 10 and 30cm below the banks and it now has a much more natural appearance when compared to the 2m deep, steep-sided channel left after previous ditching operations. There is no doubt that this will raise the water table leading to a healthier reedbed and, as an added bonus, at no cost to Devon Birds or the ecology of this part of the reserve. It’s still early days but, at the present rate of sedimentation, my hope is that the stream will eventually look like this in the height of summer, albeit with much lower flows. The images below, travelling downstream from the public footpath towards the boardwalk, show the gradual raising of the water table and the transition from almost no reeds to a much denser stand of almost pure reed.

South Milton Stream above the STW, where the gradient is now too steep for sedimentation to occur. Note the depth of the channel and the absence of reeds.
South Milton Stream 100m downstream at the STW outflow. A shallower channel and reeds beginning to appear.
South Milton Stream a further 200m downstream, just below Marsh ride. Contrast this with the first image above.

Water Vole follow up

As ever, Nick Townsend has been the voice of reason and acting as mediator between myself and the South Milton Ley Reserve manager. My sense of frustration has reached the point where I no longer see any future in continuing a dialogue. The feedback I have received is limited and no explanation has been offered as to why the Water Vole habitat was destroyed. Apparently, there were no signs of Water Vole in the area at the time! Not surprising when you consider that in the eleven years since they were reintroduced at South Huish Reserve or the six years since they were first reliably reported at SML the manager has consistently failed to secure any hard evidence of their presence at either site. Maybe his skillset is more limited than he realises as the experts from Devon Biodiversity Records Centre identified signs of burrows, latrines and feeding at 14 locations at South Huish and a further 13 locations at SML. All in one day!

The left-hand photo above shows the results of the 2021 water Vole survey at South Milton Ley (red dots) and the four brown areas in the right-hand, aerial photo the margins strimmed down to bare earth. A depressingly close match in my opinion. All very confusing when the agreed plan for the vegetation at Horswell Ditch was to encourage Sedge and Cetti’s Warblers to breed in the margins. Maybe my ecological knowledge is out of date and both species actually prefer short-mown turf!

My original inclination had been to report the incident to the Devon and Cornwall Police Wildlife Crimes Group but, having calmed down and, in the absence of anyone currently willing or able to take on the manager’s role, and also being reluctant to jeopardise my ringing activities by antagonising Devon Bird’s Council, I have agreed to include a comprehensive ditch management protocol, incorporating all the legal and best practice requirements relating to Water Voles, in the draft 2021-2026 management pan for the site. My suggestion to Devon Bird’s Council is that they should consider making it a requirement that reserve managers must consult with their local Conservation Officer before commencing any operation not already covered in an existing management plan.

Old age and SML – Part 2

The intention of the previous post was to stimulate debate and perhaps a response from Council. With hindsight, this might have been more effective if I had drafted it on velum and had it delivered by messenger on horseback! How I yearn for a governing body with the youth, foresight and drive of David Attenborough or Prince Charles rather than the ingrained conservatism of Council members and reserve managers.

Rant over, it seems that South Milton Ley is not only the last refuge of aged birders but also equally popular with aging birds. Two Reed Warblers, ringed as first years at SML in 2014 were re-trapped there this year, seven years later, having made 14 trips across the Sahara. Even this feat was trumped by another Reed Warbler, ringed as a 1st year on 7th August 2010 and re-trapped on 27th May 2021, 3,946 days and 22 Saharan crossings later.

This last bird still falls some way short of the UK longevity record for the species of 12 years 11 months 21 days and is eclipsed by a Wren, HHT003, ringed as an adult at SML on 1st December 2013 and re-trapped there on 21st September 2021, 2,851 days later. Given that the bird must have been at least 18 months (550 days) old when ringed and therefore around 9 years 4 months old when re-trapped, it smashes the current BTO longevity record for the species of 7 years 3 months 6 days.