Finally, a day with half-decent weather and no other commitments saw
me making an early journey to South Milton. Although a little windier than I
would have liked (F4/5 SE), an easterly element
had proved quite productive in the past so I was optimistic.
The
reserve is very wet with water levels in the upper reaches as high as I can
remember. The bridge across to Marsh Ride required further remedial work as the
wire mesh had collected a load of vegetation being swept down the ditch
and the whole lot had been moved a few metres downstream. I even found a Grey
Wagtail nest box, which had been attached to the bridge on the public footpath,
200m upstream, beached in Marsh Ride so it looks as though water levels must
have reached the base of the bridge some 2 metres above normal!
The ringing was steady throughout the day with 67 birds processed: 6
Blackbird, 11 Blue Tit, 1 Cetti’s Warbler, 21 Chiffchaff, 1 Dunnock, 9
Firecrest, 12 Goldcrest, 1 Great Tit, 1 Long-tailed Tit, 1 Reed Bunting, 1
Robin and 2 Wren. The Firecrest total is a new day record, beating the previous
figure of 6 during a big influx in October 2017 and three of the Chiffchaffs
were returning wintering birds, one of which was back for its third successive year.
I’ve had to snatch whatever opportunities the weather has presented
recently, looking for gaps in a seemingly endless succession of days which have
been either too wet or too windy. On both dates above the nets had to be closed
regularly as showers rattled through, which limited the number of birds caught.
Water levels in the Ley are very high at the moment and South Milton Stream has
risen until it is level with the bridge to marsh ride. It was quite
disconcerting, knowing that the ditch is now over 2m deep as the boards actually
dipped underwater when I walked across them.
Over the two days 86 birds were processed: 2 Blackbird, 12 Blue Tit, 1
Bullfinch, 6 Cetti’s Warbler, 16 Chiffchaff, 3 Firecrest, 11 Goldcrest, 4 Great
Tit, 1 Great Spotted Woodpecker, 10 Long-tailed Tit, 5 Meadow Pipit, 5 Reed
Bunting, 3 Robin and 7 Wren.
With only one rain free day in Plymouth out of the last 25 and blasting westerly winds as well it was a relief to see a half decent forecast for today. There were still a couple of light showers to contend with but it was pleasantly warm when the sun was out. If anything the weather was almost too good, allowing the Chiffchaffs present to feed in the tops of the trees and pass over the mist nets. I needn’t have worried though as they descended when it gradually clouded over. 41 birds were trapped: 3 Blue Tit, 11 Chiffchaff, 1 Dunnock, 1 Firecrest, 3 Goldcrest, 2 Great Tit, 5 Long-tailed Tit, 2 Meadow Pipit, 3 Robin, 1 Song Thrush and 8 Wren.
After spending two wind-blown and wet weeks at Portland Bird Observatory, with more ringers than birds on those few days when the wind dropped, I was keen to get back to South Milton. In reality the wind today was borderline but the forecast for the rest of the week is even worse so I took a chance. If all the leaves I caught had been birds I would have been kept pretty busy but ended the morning with just 11 new birds: 3 Blackcap, 1 Cetti’s Warbler, 1 Chiffchaff, 3 Goldcrest, 1 Meadow Pipit, 1 Robin and 1 Wren.
Unlike Nanjizal, where a record 618 birds were ringed yesterday, I struggled to get past 40 at SML today. So much so that I even found the time to photograph one of the last few Common Darters lingering around the site. The final total was 44 new birds: 22 Blackcap, 1 Blue Tit, 12 Chiffchaff, 2 Goldcrest, 3 Meadow Pipit, 3 Reed Warbler, 1 Wren
A clear night with a near full moon and a light NE
breeze promised good things on the migrant front. The only problem being that
conditions were so favourable for passage that there was little reason for birds
to stop or linger. The headlands either side of South Milton Ley have always
produced more migrants and greater variety in autumn than the SW facing coastline
between them but I was optimistic and had 90m of nets up by 7am.
There were birds about but little sign of
significant passage overhead, unlike at Portland which recorded their first big
passage day of September. Meadow Pipits were most evident, having
largely replaced the few tardy Tree Pipits and, together with Chiffchaffs and
Blackcaps, they dominated the catch. A nice bonus was the capture of a 1st
year Common Redstart, the first I have ringed here since 2015.
Redstart
55 new
birds were ringed: 12
Blackcap, 2 Blue Tit, 14 Chiffchaff, 2 Dunnock, 2 Goldcrest, 1 Great Tit, 13
Meadow Pipit, 1 Redstart, 3 Reed Warbler, 1 Robin, 1 Sedge Warbler, 1
Whitethroat, 1 Willow Warbler, 1 Wren
I arrived at SML a little too early this morning – fifty minutes before sunrise – and it was pretty dark. However, the timing turned out to be perfect. As I pulled into the ringing area, a bright white meteorite streaked across the sky in front of me, from east to west, breaking up into several orange pieces as it descended. It looked like a plane that had been hit by a missile. Apparently, it was visible across southern England and in western France and resulted in a spate of 999 calls and police helicopters searching Dartmoor for a crashed aircraft.
That excitement aside, it felt autumnal with the temperature around 9oC. Blackcaps dominated the catch again, which also included the first Goldcrests of the season and a few tardy warblers. The final tally was 52 new birds of 14 species: 6 Blackbird, 20 Blackcap, 2 Blue Tit, 1 Bullfinch, 5 Chiffchaff, 1 Dunnock, 1 Garden Warbler, 4 Goldcrest, 2 Great Tit, 1 Reed Warbler, 2 Robin, 2 Sedge Warbler, 3 Willow Warbler and 2 Wren.
The ringing table at 07:00 – with my trusty reed-cutter on the end.
A relatively benign weather forecast saw me arrive
at a chilly SML at 6am. With darkish clouds building to the northwest, I
switched on the rain alarm app on my phone. Unexpectedly, it worked. The
ringing area is in a mobile phone black hole – not much use if I catch a rarity
or, worse still (from my point of view), fall in a ditch and break my leg – but
today there was one bar. It still took about 3 minutes for each radar map to
load though. Consequently, I had advance warning of the arrival of a rogue
shower, furled the nets and sat in the car with the ringing equipment until it
passed. I’ll be glad when the English cricket season ends and the weather settles
down!
Furled nets at 09:00
There
were so few migrants around that a thirty minute break is unlikely to have
impacted much on my meagre totals, which panned out at just 25 birds, dominated
by Blackcaps: 14 Blackcap, 1 Blue Tit, 4 Chiffchaff, 1 Grasshopper Warbler, 2
Great Tit, 2 Reed Warbler and 1 Wren.
An indifferent morning’s ringing, not entirely unexpected with fresh NW winds the night before, saw 33 birds of 17 species trapped with 30 new, 2 re-traps and 1 UK control Reed Warbler. New birds: 2 Blackbird, 7 Blackcap, 1 Blue Tit, 1 Bullfinch, 3 Chiffchaff, 1 Dunnock, 1 Great spotted Woodpecker, 1 Pied Flycatcher, 1 Reed Warbler, 1 Robin, 2 Sedge Warbler, 1 Song Thrush, 1 Tree Pipit, 1 Whitethroat, 4 Willow Warbler and 2 Wren.
Things
tailed off quickly towards noon and I was taking the net down at the southern
end of Marsh Ride when a juvenile water rail scuttled across in front of me.
Fully grown, but with a brown bill, white throat and buffish belly it was the
first time I have seen this plumage. I am assuming that this is indicative of
breeding on the reserve for the second year in a row.
The area around the southern end of Marsh Ride is the
wettest part of the reserve in the summer, which makes me wonder what else
would breed if the reedbed were wetter. Those of you who know me will be well aware
that I have a bee in my bonnet about the way historical drainage works at SML have
adversely impacted on the reserve by lowering the water table, introducing gradients
from north to south and from east to west, which have accelerated the natural
succession from reedbed to wet woodland. In 1991, an independent environmental survey
at the Ley concluded:
“In 1945 South Milton Stream took a more central course down the upper
section of the valley to disappear into the reedbed less than one third of the
way down. By 1989 the drainage pattern had been altered with the new course of
the main channel taking a more northerly route and extending another 500 metres
down the length of the ley before the flow disperses into the reeds. The
construction of this ditch has contributed to the drying out of the adjacent
marsh . . .
. . . The health of the reedbed is dependent on a high water table,
particularly in the growing season from April to August, the very season when
water availability may be reduced. It should be remembered that any measures to
speed up the water flow through the the Ley by ditching, the deepening and widening of ditches, or
their clearance will tend to depress the level of the adjacent water table. The north ditch has been cleared in the past
to enhance the removal of effluent and to separate the flow from the main body
of the reedbed. In the absence of excessive nutrient loading, a better
strategy might be to divert the stream water into the reedbed at a point higher
up the valley and allow the natural reedbed to treat any excess nutrients in
the water. Mass flow of water through the reedbed is preferable to unimpeded
water movement through a ditch system.”
Despite this professional advice, in 1994, just three years later, major ditching work took place and South Milton Stream, which used to be about 0.5m deep, meandering along the northern edge of the reedbed, was straightened, widened and deepened to about 2m.
South Milton Stream – From this in 1991To this in 1994
At the same time in 1994 works were completed on “improvements”
to the public footpath across the reedbed, which was frequently impassable
during the winter months. In essence, a 1m high, earth dam was constructed across
the width of the reedbed using spoil excavated from the ditch. It was
recognised at the time that this would impede the natural flow of water down
the Ley and lateral drains were installed. Unfortunately, in the absence of a
hydrologist, no allowance was made for impact of the ditching works on the
water table and these drains are high and dry apart from periods when the marsh
is already at its wettest.
The public footpath – From this in 1991
To this in 1994
Although suspected by many, adverse impacts have been hard to prove but measurements of hydrostatic pressure made in 1996 show the wettest area at the bottom end of South Milton Stream, where the ditch discharges into the reedbed, instead of the expected gradients down and across the Ley. The wetter area at the end of transect 2 is caused by underground seepage and is now the major source of freshwater into the central reedbed. It is also the area where Water Rails have bred and last year’s Spotted Crake was heard.
Average piezometer readings of hydrostatic pressure in 1996 (blue = wetter areas)
The impact of all these alterations on the reeds
themselves has also been measured and the results from a series of transects across the reserve to
measure reed growth clearly illustrate an adverse effect on the biomass of
reeds with a north-south gradient across transect 1 and significantly reduced
growth across the whole width of transect 2 caused by the deepening of South
Milton Stream and construction of the footpath respectively.
Location of transects used to determine biomass of Common Reed (Phragmites australis) in 1996
Biomass of Common Reed (Phragmites australis) g-1m-2 across three transects at South Milton Ley in 1996
It’s surprising how many of the occasional (and
exclusively elderly) birders I meet at SML claim to have been ringers previously
and how keen they are to advise me on how they used to do things, presumably around
the middle of the last century! In reality, many of them probably held a trainee
permit for a few years or possibly even a C permit in the days when they gave
them away in packets of Cornflakes! I’ve certainly been unable to find any of
them mentioned in the Devon Birds ringing reports and suspect that the 3,500
birds I ringed before getting my C permit in 2014 is more than they processed
in their lifetime. Nevertheless, I’ve had to endure frequent lectures on how
many nets to put up, where to place them and how often to do net rounds etc. Many
of these well-meaning commentators have been oblivious to the fact that listening
to their monologues actually prevents me from getting on with net rounds and
ringing.
Once qualified, ringers in the UK can pretty well ring where and what
they like, (within the limitations of their permits), and activities range from
those who only participate in scientific studies through to what I call “hobby
ringers” who randomly ring at different sites or in their back garden when the
mood takes them. South Milton Ley has had a spectrum of ringers over the years,
ranging from those obsessed with migrants and rarer species who wouldn’t consider
ringing resident birds, through those who cherry pick, turning up only during peak
migration periods, to others whose goal was to trap as many birds of as many
species as possible. I suspect that I fall closer to the latter category but my
scientific background keeps this in check as I recognise the value of systematic
and reproduceable sampling.
After all, as an example, what is the value of targeting Aquatic Warblers? We know where they breed and where they winter and, as far as I am aware, there have never been any recoveries of a British ringed bird. There is far more to be gained from the systematic ringing of the commoner breeding and wintering species both in terms of population monitoring and effective habitat management. For the first time, systematic ringing throughout the year is now revealing quantitative information about populations, distribution, survival and productivity of the birds at SML, something which is sadly lacking from almost all of Devon Birds’ other reserves.
To that end, I am currently working on the second draft of a paper about Chiffchaffs wintering at SML. The first draft was sent to five referees by the journal and returned covered in electronic red ink. Almost all of these comments were constructive but they need to be addressed and the statistical analysis has to be beefed up before I can re-submit. I’ll keep you posted on progress!
