Motley Crew

The fifth and final part of the seawall walks guide for St. Mary's Island to Motney Hill has just been added here.

Joking with a friend a few weeks ago, he said he thought the place would have been better named Motley Hill- I was quite pleased to pull up an old Ordnance Survey map from the 1930s and send him a copy;

A nautical aside. The obvious 'wreck' off of the northern end of Motley/Motney, marking the tip of Wallop Stone, and tidal rest spot for Cormorants, Turnstones, the occasional Grey Heron, Peregrine or Shag, is not an old boat, as some would have it. It was in fact a caisson, one of the special watertight containers that allowed workers down to set up foundations for bridges, locks, etc.

I recently found it mentioned in 'The Jottings of a Thames Ditch-Crawler', by Nick Ardley, an excellent read of tales afloat, ninety-five per cent of the time on the Greater Thames or the Essex saltings, aboard his Finesse class yacht 'Whimbrel', which can still be 'ticked' down here on the Medway from time to time- I'm a bit of a boat-dude, my notes have sightings of 'Whimbrel' as less than annual, whereas the eponymous wader is passing through in fair numbers right now:

On Willow Warblers

The facebook group, 'Kent Birding', recently found itself discussing Willow Warblers.

This cold spring has so far been most like 2013, in that it has been possible to see their spring migration around the estuary; downed birds along the seawall, some days reaching double figures. In the better conditions of 2014 and 2015 records were pretty much singletons only, when and if you were lucky enough to bump into one. And for me they are local breeders no more.

During the Facebook discussion I guided forum users to the excellent BTO BirdTrends pages and to regional results but for this supplemental note I decided to look elsewhere.

One of the old-style correlations for habitat preference, not used so often nowadays but heavily relied upon at the time of  'Birds of the Western Palearctic' and Simms' excellent New Naturalist 'British Warblers', was temperature. Species populations were often judged to breed between relative minimum and maximum isotherm which for the maximum in Chiffchaff was 26c in July, for Willow Warbler, 22c.

One needs only to play on the excellent Met Office website to pull up a map of the UK showing the mean average maximum July daily temperature during 1981-2010, the period for much of the local decline; the whole of the North Kent Marshes is mapped at "greater than 22c". Local warming appears to be just another of the many nails in the coffin for Willow Warbler here.

(For birders in other parts of Kent, bearing in mind the debate on strength of remaining local strongholds, that map is well worth studying. The south face of the North Downs, under a cooling influence from the prevailing south-westerly winds, still came in below the 22c threshold. Perhaps part of any explanation why some in those parts still feel able to comment Willow Warbler remains relatively simple to find there? Another reason to always think beyond the 'political' county overviews.)

It is also easy to stick with those older texts to answer an imprtant question as to what the differencereally  is between a Willow Warbler and a  Chiffchaff- not in appearance, but in habitat preference. They were, after all, 'sister species' (I say 'were' due to the taxonomic fluctuations in species/races- they certainly remain within a recently evolved sister clade) so not really any shock they are hard to separate in the field for some. But there must have been something that triggered the specialisation, something perhaps rooted in habitat/behaviour.

Simplistically, Chiffchaff is more purer woodland, Willow Warbler more a scrub/wood (with good understorey growth) mix.

Scrub has been a long-neglected habitat, with many of the regrowth transitional zones between, say, woodland stands and grasslands, lost in recent decades. Thinking is slowly coming around to appreciating scrub more, but all too often 'scrub bashing' is a required 'norm', and birch automatically cleared (guess which species of tree provides most food for Willow Warblers during the breeding season?).

Are the larger amounts of shade in ideal Chiffs territories why they can put up with higher temperatures? Questions, questions, questions.

In another interesting twist to the local tale, one of the last Willow Warblers holding territory alongside the estuary, a bird at the Lower Halstow Brickfields in 2013 and 2014, was a 'song switcher'. This is a bird that switches between phrases of it's own song and phrases of another species in the same burst (in this case singing Willow then Chiff).

'Song switchers' should not be confused with 'mixed singers', where individual notes from two species' songs are 'mashed up' and come out as an essentially unrecognisable song, not resembling either species. There is some debate to the causes for both conditions- switching being thought down more to copying, mixed song perhaps down to hybridisation. For anyone wanting to know a little more on the phenomenon, this article is worth a visit. Perhaps, when young, this Brickfields bird simply didn't hear enough Willow, and ended up picking up a Chiffy accent? Whatever the reason, it was perhaps a little fitting that such an interesting individual helped note what might yet be the end, locally, for breeding Willow Warbler.

One of this spring's passage birds, ringed April 12th.
Seen to be still carrying plenty of fat reserves for the
remainder of it's migration. 

So, I could say this year's Willow Warbler spring passage has been relatively good so far. Good in the 'selfish' sense there have been a few more to see, but poor in that most of these sightings will have been birds not really wanting to be stopping off here. I'll certainly still try to find a local territorial bird or two over the next couple of months before the return passage in late July/ early August and youngsters start practicing their songs. However they sound.

The annual question

Each year here in Kent around this time the pulses start to quicken; migration, vagrants, rares. Each year around this time pulses start to quicken that little too much- why isn't Kent anywhere near as good as it should be in the early spring, why isn't it as good as some of the other south coast counties?

Each year I try to explain the reasons why. And at least I'll now be able to refer people to this post to explain some of them.

April is early doors. We have returning passerines setting up shop, but not too many in transit for further north yet. There's only really Scandinavia higher up, and when they do make for there, makes a lot of sense for birds to come in along the western edge of the mainland continent- why risk a water crossing? This google earth screenshot oversimplifies things but allows an easy answer to the question- if you want a short journey with fewer risks of drift and overshooting, there's not many other routes you'd choose.

Yes, of course there are passerines spread out on this flyway, coming in through Kent, just in smaller numbers than elsewhere. We just shouldn't be expecting Kent to as good as elsewhere.

And spring migration is not autumn migration. In autumn, passerine migration can be summed up as adults getting out quick, youngsters bumbling about a bit first to try to find good spots to come back to. In the spring, successful returning adults know where they're going; a high level of site-fidelity. Young that have survived the winter have a fairly good idea too, having learnt a lot about their natal area during the weeks leading up to post-juvenile moult and the onset of migratory restlessness. They know where they want to be. The adults have a slight advantage over the young still, they've made the return before, the young haven't.

Read the migration texts and the point is often made that autumn warblers and the like funnel out through the south-east. Never that they really funnel back that way. Kent is, to a fair degree, in the shadow of south coast sites further west for numbers of UK returnees. Funneling up through Iberia and western France, if you come in over Kent, there's a pretty good chance you could find your nocturnal flight lumps you out over the North Sea. If you come in over Dorset, plenty of land to the north. Certain species are genetically pre-disposed not to come in over the Channel from the southeast, but to make landfall from the south- southwest. Welcome to (a small-scale version of) loop migration.

You also get a lot of chat about migrants being held up at this time. The spring passage window is shorter than autumn- the race is on to breed. Adverse weather patterns don't have as much stopping power, birds do strike out in 'sub-optimal' conditions and why numbers of adults on territories continue to rise slowly at present here, even though the weather this year is more like a mild late winter. Take the past week- an obvious local arrival of female Chiffchaffs. Migration carries on. This last week/ ten days in April never really disappoints, just some good years stick out more in the memory than others. The birds' internal mechanisms drive them, there are more on the move right now.

 If someone asks me to pick a good day to witness migration, I usually don't look more than two-three days ahead, the forecasts aren't good enough. What I'm looking for isn't just overnight rain, but the edge of the rain band laying over the estuary at around dawn. Best wind is a south-westerly, moving birds along from the main flyway. We've had one good morning like that so far, and it did not disappoint. A bit of drift from the birds arriving to the west of North Kent, then a reluctance to try to push on through the rain. I chose to ring on a local farm and had a fall of Willow Warblers, Chiffchaffs, Goldcrests (mainly later moving females, if ringed found to be carrying plenty of fat), the odd Ring Ouzel and Wheatear around the site, Yellow Wagtails calling overhead throughout the morning. On an easterly, I'd always expect a lot less here. In fact, an clear south-westerly overnight will still produce a fair number of common migrants. (Don't just take my word for it- there's a lovely barometric chart in the Helm avifauna 'The Birds of Norfolk' showing just such a scenario as good for migration there as well.)

By the time I've answered their question in this way, the penny starts to drop and the questioner might then start asking when best for scarces and rares. Not my cup of tea, but I have a go.

Timing starts to have a play. We get hung up on early dates because of our predisposition towards recording 'firsts for the year' and tend to lose sight of the bigger waves coming later in the month. And at the same time we have the start of larger numbers of passerines heading for northern Europe. About now, the last ten days of April, is from when Kent might start to get excited about a good 'rare' popping up.

A caveat is to remember these internal mechanisms are pre-programmed to wind down and switch off close to base. Every year someone asks why the Bluethroats aren't crossing the Channel to breed, what with global warming and all. Well, they're pre-disposed to return to those natal areas. Their migratory drive is switching off by the time they get to Northern France. Crossing the Channel is so unappealing now. It will be the same with a lot more of the species breeding sur la Manche. It takes a lot to get them to stay. And even if a pair are on our side of the Channel, an argument gaining some strength is that the visual cues for a prime breeding site simply aren't there in the habitat we have- the floral sward is vastly impoverished compared to that present on mainland Europe.

When the Scandinavian Bluethroats are on the move their migratory systems aren't switching off this far south- chances are if they land they will leave as soon as possible. So May always has more of a chance of bumping into something, but more than likely a short-stayer.

This is still based around migrant passerines by the way- non-passerines, with their tendencies not to return to natal areas until old enough to breed, may well find a new site on their wanderings which is to their liking; shorter-lived passerines can't risk that sort of thing, they may well only get the one chance to reproduce in their short lives (why the classic 'overshoot' species are more often non-passerines).

So, come May I'll still be hoping for south-westerlies here. Plenty of 'Brit' migrants pouring through, plenty of good days full of 'common' movement. For an easterly influence to knock rares and scarces down around the estuary up here in north-west Kent, there would have to be bad weather and a lot of birds would be suffering, I never want for that. I'm much more content to try looking for a scarce or two around their appointed dates on their 'migratory calendars'. If that's what you like, check out when certain species are most likely to be pulsing up along the French coast and hope for one with an internal compass on the blink.

Me, I'll be watching the gulls.

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(For detailed general info you cannot go much wrong with Ian Newton's New Naturalist, 'Bird Migration', or Peter Berthold's 'Bird Migration; a general survey', though you might need a bank loan to get them...)

The thin end of the floats

In February I wrote at some length on consultation document for the planned positioning of seaplane operational areas, and the disturbance caused by such operations.

Well, they've published. They kept Half Acre in. Actually, they didn't just keep it in...

...they extended it.

They did drop the Long Reach operational area (which always seemed risky based on the fact it is the main shipping channel) but gave them a second play area in right among all the waders, wildfowl and gulls- Stangate Creek.

Clearly Peel Ports have stuck by their understanding that legally they only have to consider navigation and not conservation law. As it was told to me, "..we have no power to blanket ban any lawful operation within the harbour and the aircraft in question causes little more disturbance than water skiing or jet skiing (when on the water).".

For those that don't know the area, I shall shortly post on the roosts and numbers of birds that use Stangate, but in the meantime an observation about what an operational area is. Yesterday I was fortunate enough to be watching towards Half Acre. It was clear the operational area is for "when on the water". They are not the boundaries for take-off/landing, gaining height off of the water does not matter, and there are no height restrictions around the rest of the estuary. This is shown in the pictures below, when to exit the Half Acre operational area the seaplane cruised almost to the boundary before revving up and then 'cruising' low west along Bartlett past Motney (sewage works and RSPB reserve) before gaining a higher cruising altitude.

While I was watching the area the seaplane did disappear for quite a while, presumably to go take off and land, take off and land, take off and land along Stangate. I'm now quite looking forward to bumping into it when down there to see how much additional 'runway approach' space it needs around that particular operational area, bearing in mind the dog-leg west towards Millfordhope Creek and Halstow/Twinney. Counts are going to be interesting, to say the least.

A picture post, from April 2013

Low down Rookery, Raspberry Hill

Mallard and young, Motney

Hawthorn- in berry and in bloom, Funton

Wheatear, Chetney

Little Grebe, Motney

An old orchard, Upchurch

The Callum Tree

Duelling Shelduck, Rainham

The Old Brickworks, Lower Halstow

Black-tailed Godwits, Rainham Docks East

Rainham Creek

Brent Geese, Twinney

Boom!

Down came another lump of the old Kingsnorth Power Station. According to their spokesperson “The timing for this particular demolition has been planned to coincide with low tide, therefore causing minimal disruption to wading birds and other local wildlife." So what did the Black-headed Gulls do?

The part demolished today is marked at the top of the google earth image by an orange rectangle, and is overshadowed by a much larger part of the old station (yellow rectangle).

The gulls that took umbrage were from the RSPB Nor marsh reserve, marked in yellow. Birds on the closer (and much larger) Bishop saltings colony stayed, in the main, put. Also the birds outside the breached wall marking the boundary of the RSPB reserve, on Friars saltings, largely ignored the explosion.

I have two theories.

The first I liked, but now no so much. The Nor birds are mainly on collapsed seawalls. The marsh was breached by the floods of 1953, and has been eroding ever since (the breach is just above and to the right of the markers). The walls have fallen into disrepair and have little vegetation in many places. The boulders can be 'wobbly'. So, was it down to the vibration?

Problem was that little yellow circle- the birds on one of the few remaining spots not to go under on a spring tide. They went as well. If it was vibration, surely other birds on saltings would have taken fright as well?

So, theory two- and this I'm still liking. Neither the Bishop nor Friars colonies could have seen the collapsing structure- just witnessed the resultant dust cloud. Their visual alarms were never went off.

Bloomin' racket they make at the colonies, small chance of hearing an explosion- even one that a chum of mine heard over five miles away. They shouldn't get too comfortable; they will have bigger worries the next few days with the high April spring tides. I'm expecting just as much mayhem and debris.

Painting by numbers

Dunlin again.

The final third of March, compared to mid-month, showed a continuing drop in numbers, and a bias to the west. The feeding circuit in that half of the southern Medway is a lot more open, more straightforward to work, and shorter flights; perhaps why more birds choose it? Guessing only; without any study on prey items, no way of telling.

With just the aid of a little basic computer literacy and an excel spreadsheet here's these 2016 counts compared to the same periods in the past three years:

March Dunlin nos by 10 day periods, 2013- 2016

This is how you can realise your mind plays tricks on you. Although I moved back in January 2013, I did do some self-employed work for my last employers up to the end of February, so March was my first full month back on the seawall. March 2013 I remember as colder than this year, with very many waders still in situ; if pressed I would have said I's seen greater numbers than this year. Wrong. 2016 I would have put money on as not being as high, but there you go; always check your numbers.

Clearly blocking easterlies and cooler temperatures play a big part in the onset of the main movement out to the Waddenzee.

When exactly did they go this year? For most birders that would be really nice to pinpoint. We like a clearly defined 'last date' after all. Easy when you just look for a last overwinterer, but a lot bloomin' harder with a common wintering/passage species though. Trektellen hinted at flyway movements on the 13th and 18th- the former certainly a date when I noticed a fair drop in the numbers of several wader species. The 13th was also the WeBS Core count priority date, so I suspect any counts done then/before would have reflected the winter numbers more, any counts after hint at passage underway.

There have been less than 20% of the month's opening numbers remaining during this final third, and with no way of knowing whether any are 'arrivals', it does seem fair to claim this years' main departure as around the 13th-18th March, on a par with 2013.

So, will April now bring a small but obvious movements of birds that have wintered further south along the Flyway? Something else to keep in mind on the days when the summer migrants simply aren't moving.

It's about this time of year when counts of two Dunlin
are as exciting as 2,000