Friday, 27 August 2021

The least turn for Little Terns

The terns were putting on a show. A blink-and-you'll-miss-it show.

Late July is the time of year tern breeding comes to an end, and dispersal starts. Colonies become roosts, and it is always difficult to claim any fledged young seen on the wing were truly local, as dispersal can be quick. And youngsters stay with parents from a while as they hone their feeding abilities.

Just a week earlier I'd have said, with assurance, still some reason to call it a colony; one bird was still sitting exactly where it had done for the previous month, presumably on long cold eggs. It had finally given up the ghost later in the week, and numbers on view had dropped away by the weekend. Time perhaps to call it a post-breeding dispersal roost site.

I say on view, but most of the birds are always on a beach slope hidden away from land. You have to work hard to get a feel for overall numbers. Today I got help.

Just as when breeding, Little Terns don't like to sit things out too high up a beach. Today was relatively calm but, after about an hour, a small group of motor boats were in the main channel, moving at speed for the mouth of the estuary. A good few minutes after passing their wake washed up, and the Little Terns took flight.

Of course, you can never tell if all the birds are up, especially from one unintentional disturbance incident (the boats were well within speed limits and passing more than a kilometre away). Just wait a while, and there'll be another.

Within an hour, there was. The RSPB/KOS WeBS survey rib. Coming at speed, nowhere near as far out. (The red/black buoy is the giveaway, as you'll see on a map later.)

Major disturbance. I'd first noted the rib entering Stangate creek, and didn't expect it to come back out towards the main channel after just ten minutes. But as the tide was in, and they were making to view Deadmans from the Swale, they'd cut well inside the Queenborough Spit Buoy and put the vast majority of the birds up. No time for the longer turn via the navigable channels today.

Why a major disturbance? Not all the birds took to the sky, some birds just flighted for a short while. Well, problem was, an awful lot did leave whilst the boat was racing by. 

Many of the gulls, and nearly all the Sandwich Terns, were up and off, mainly east (over me) and keeping going (presumably following the old canal out to Barton Point making for Sheppey's north shore).

The disturbed Little Terns did one of two things. One group decided to circuit just offshore of the beach, with many not settling again until the boat had completed its count. The other group hightailed it south into the Swale.

And the second group didn't come back. The surveyors had put more birds to flight from roost than the jet skiers today (watching on in teh background).

Low levels of disturbance will always be a thing. Sometimes unavoidable for monitoring purposes, and even then sometimes deemed too dangerous for the birds under normal circumstances. For breeding terns, 'Flush counts' are the "quickest but least accurate way of counting adults or nests" (per RSPB Bird monitoring methods) - and that takes place in early June when FIDs (Flight Initiation Distances) are at their shortest, and the urge to return at their greatest. But this was late July, and a WeBS count.

I've blog-posted on survey boat disturbance before here - and that led to some interesting conversations. Essentially being told then that there is no way to get counts of wildfowl from the islands without flighting them. Which I've proved to be pants.

And similar levels of pants reasoning is behind today's blogpost. For more than a decade I've had to put up with the rib's lead surveyor telling me you can't do 'x' from land. Well, today, from this spot, I got a much higher count of Little Tern species from this little spot on the shore. (You might not have seen me, but that's your rib beyond Deadmans.) 

Anyone could have seen you. It was easy to get a rough plot of the rib's route (orange), it was easy to see the flighted Little Terns waiting to land (yellow circle) and flighting south (yellow arrow) and easy to watch the gulls and terns heading inland over my head (white arrow).

But you keep telling me you can't see them from shore. It must be intransigence. Last year, when Covid stopped the Ribs, one of you somehow got a count of the colony from the north shore, 1.7 km away, looking into the sun. Well done at last. On the promenade I'm 700 metres away in better light, but you know best.

Last year, when I spotted the Sandwich Terns deserting Burntwick, I posted a thread on twitter to highlight what was happening that included a reference (and picture) highlighting the Little Tern colony was still safe. No use of photoshop, honest. You can do this from shore.

I then expanded on them by tweeting a thread explaining exactly how birders could watch the Little Terns from the mainland. I'd finally, finally, decided my policy of a lack of publicity of how the birds could be seen from a public path might not be the best thing for the birds now commercial gangs were active on the islands.

Qualms about revealing all this were tempered by misusing 'Pareto's Principle'. The good old 80/20 rule. In this instance, people might take in 80% of the first 20% they read, but then expect them to only take in 20% of the next 80%. Why twitter threads often aren't opened, why a long-post blogger like me has to accept only the really interested stick this far into a post; the rest will be going 'TLDNR'. And it worked. I didn't see another birder on the prom all 2021 breeding season. Just the Peel Ports surveyor. I do know one birder found them and even then he was looking too far out, his wife had to say 'no, put down your bins for a sec, right here!' 

Yes, I've still concerns about highlighting here again because, in certain conditions/times of breeding season, the adults like to fish right next to the prom. Try and photograph them there, and you keep them from feeding. But that's for another post.

But I will again highlight the ability to view from shore because several boat owners have mentioned landings during the 2021 breeding season at both the Little Tern and the Sandwich Tern colonies. 2020 proved there is a need for extra vigilance, not just at the Sandwich Tern colony.

(Let's see how many birders I spot here next year.)

Confirmed by tweet that night, this rib had been the official WeBS count, not a breeding survey. Any chance to argue a need for a flush count on WeBS? 

What does the WeBS guidebook say about disturbance? "Don't."

Now I wouldn't want to think for one moment this was deliberate. Perhaps no-one has explained the protocols to the rib operator. Perhaps the enthusiasm for getting a useable Little Tern count was running a tad too high. Or perhaps they were oblivious to the fact they, like the terns, could be seen from land.

But as I've been told previously the island birds need to be flushed for a useable count, whilst I wouldn't want to think deliberate...

We now have a Code of Conduct for our SPA to try to reduce disturbance. Surveyors can't just think they're exempt from trying to follow best practices. Those jet skiers in the background may well have clocked them. Why should they follow their own Code, and the BirdWise Code, if birders are seen wake-flushing roosts? People can be quick to post about other estuary users breaking their own Codes, but when it comes to BirdWise, and the (BTO RSPB approved) Birdwatchers' Code, the same people can see fit to just ignore them when surveying.

And why should the boat counters have kept up the pretence that these birds can't be seen/counted from shore, even after all these years? I've also been told that WeBS sector counts can never be coordinated locally because one of these counters has to be both count on the boat and count a second important site, as there's no-one else good enough locally to do it. That's one for the psychology students of Dunning-Kruger University, methinks.

Surely encouraging additional data from their various Society's members has to be welcomed? Surely having more eyes on islands we know suffer from unauthorised landings throughout the year should be encouraged? 

Or perhaps just one twenty minute whizz-bang of a visit a month really does give them enough data? 

Go figure.

Little Tern family from Queenborough Prom, 21/7/21


A postscript

23rd August. I like Mondays. I get a chance of borrowing a car for the afternoon if I drop someone off at their workplace (still don't intend to own a car again unless becomes a necessity), so have chance of a guilty pleasure drive to the furthest reaches of the Medway. Low carbon guilt sets in but usually no more than eleven miles from door.  I can't do more than that- I didn't renew my last passport.

So, a partial Through-The-Tidal-Cycle count over the high tide of Deadmans. And today turned out to be another boat survey day.

A TTTCc set of four counts, made hourly, over the top of a tide will throw up differences. Most of the Curlew went just after I arrived, leaving their favoured pre-roost assembly creek for higher ground inland. The Oystercatchers did similar, but acted as individuals, some staying as long as could hang on, others drifting in small groups to the four compass points; inland, down the Swale, to Grain/Stoke and even a few seemingly back out towards Sheerness. 

Then there were the Grey Plovers. They flighted from Deadmans when the survey boat was a good half-kilometre away. Some resettled almost immediately, but the vast majority of the roost made off north-east as if leaving the Medway. Flighted at a good half-kilometre. No way that was disturbance?

The boat did its job without disturbance. I even got a cheery wave, you know, the energetic sort that 1980s Leeds fans would give to Millwall supporters, often then leading to a cheery aerial exchange of chairs. Clearly they'd now all heard about my previous month's observations.

A short minutes later, when the homeward bound survey boat got to about the half kilometre distance again, something I wasn't expecting to happen, happened.

Those Grey Plovers hurried back to Deadmans, fast and low.

Flight Initiation Distances vs Setback Distances

FID: the distance at which a species will initiate an escape flight.
Every species has an FID. Different distances for different species. (Why a bait digger can assert not really disturbing the birds, some come really close. Then you can reply subtly 'yup, the little ones do. They can take flight more easily. But why you the bigger ones, like Redshanks and Curlew, keep away'.)

VFID: Variable Flight Initiation Distances. Look at it in more depth, and you get to see every species has a series of FIDS, based on internal/external drivers; their recent feeding rates, their migratory condition/weather, day length, .

Setback Distance: What we come up with as the most acceptable tipping point, what we set in codes for estuary users. Here, our BirdWise North Kent initiative has a 'keep 100 metres distant' code for boat users. Trawl the old texts and you'll find Grey Plover have known FIDs of up to a quarter kilometre. You can't have a human Setback Distance that covers all Vs of FIDs. Nor would you want to. Prey species get disturbed routinely.

But on SPAs there is a legal requirement to avoid increasing disturbance. Why BirdWise are working hard with all user groups to abide by codes (written and agreed by many of the same user groups).

So, that's that then. Can't be helped. Nothing else to think about. Well.... there is, once again, the purpose of the survey itself. A part of the full monthly count of the estuary.

In this short instance the boat acts as a once a month 8 minute snapshot of Deadmans. If adjacent land-based counters aren't out over the same tide at the same time, then birds are going to be missed. Many of Deadmans roosters come in from the Roas and North Sheppey. Many move on near the top of the tide. Land-based counters on Chetney count the adjacent spots to the west on the covering.

And those plovers today. Where did they go?


Yup, that package of estuary lost to reclamation that led to our first upholding of mitigation laws in the UK. The flats became a huge parking space for imported vehicles. But there's a kilometre of seawall that you can't view from land. A kilometre of undisturbed seawall. A bonded Port, no tresspass is tolerated here. And about three decades old now.

I finally saw it from a boat only about a month ago. 

Mmmmmm... forbidden shoreline

Out of sight, out of mind. How much still viewable on a spring? How often used as a secondary/temporary roost site? Is this where some of the Minster/Sheerness calidrids end up when disturbed from n. Sheppey? Is this where the Little Terns I think make for the mouth actually spend a lot of time out of sight? 

Ohhh, questions, questions. Love 'em.

Now, here's the kicker. In my fictional Benevolent Dictatorship, any survey would follow the already written imperative that on an estuary all section counts must be coordinated. That's been set in stone because birds move.

In this ideal world full of Unicorns and Sharp-taileds, those parts of Deadmans easily counted from shore would be done from shore. So the boat could then concentrate on the hard to count from land bits.

Does it all matter? Well, last time I chatted with the local coordinator it did seem better coverage wasn't yet producing higher counts. Are they still missing birds? Based on routine movements c/o TTTCCs and the like, yes they are.

The local coordinator and I have had some good exchanges of late and our next has already been touted as a trip to sit and watch Deadmans, to chat on things like supplemental counts. Today's scardy-cat Grey Plover VFID provides yet another interesting element to chat through.

I think I've already suggested bringing a chair...

You so easily forget.
There's a major reason Ribs get a category of their own in disturbance studies.


Disturbance of Non-Breeding Waders by Pedestrians and Boats in a Mediterranean Lagoon is an interesting little study into boat disturbances around Venice, and concludes higher setback distances of c. 270 metres for several species including Grey Plover, Oystercatcher and Curlew.

Thursday, 26 August 2021

Blog relaunches 21/09/21

Watch this space: 
This blog is being relaunched on the evening of September 21st, with a full set of 'Where to watch' pages for the southern Medway, plus an updated 'How to watch' page, in support of the following talk:

Medway RSPB Local Group: 
"Birding the southern Medway"

Tuesday 21st September, 2021 at 7.30pm
(doors open from 7pm)

Parkwood Community Centre
Parkwood Green

 "Since 2013 Kevin has been looking at how internationally important numbers of wildfowl and waders use our estuary's waters, mudflats and islands, through a typical tidal cycle. His talk will focus on passing on tips and tricks for getting the very best out of a visit to the southern shore, from the head at St Mary's Island to the mouth at Sheerness and the deep water channel beyond."