Tuesday, 22 November 2016

Summers-Grey

In one meeting recently I was asked a question, as an aside, about Grey Plovers on the Medway. Was it true they roost over on the Swale? The question came during a chat on wader declines in the estuary. My answer was short, but deserving of a much fuller explanation so, to keep a promise...

The Swale
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Decline and fall

When I started my estuary counts I took my own year zero of 2013. Prior to that mid-nineties had seen published early winter peaks circling the 2,500 mark, peaking in January at around the 4-5,000 mark. After that time the numbers reported crashed, with the average winter count for the ten full winters to year zero scraping 660 for Nov-Jan- if correct, up to about an 87% crash. And perhaps knocking nearly 10% of the UK population off if they had disappeared completely (some 43,000 in 08/09, per BTO website).


Of course, if the figures were wrong, then so too could be this trend. That, as a simple birder, would be my incentive for getting out and enjoying the Medway. The evidence of a continuing fall via WEBs results remains a worry, but comes with a caveat that counts here are often incomplete, and un-coordinated. Could this be part of the problem?

Focusing in more closely, the BTO produced a report in 2005 in response to the drop in Grey Plovers, and several other species at the same time. Statistical testing suggested the decline in numbers from a level of International Importance had been mirrored somewhat in both the Thames and the Swale.

Big declines in North Kent as a whole. What about next door? Not seen in Essex, not as big in Sussex.

Essex totals had remained on the increase from the mid-80s, doubling to a five year average of 15- 16,000 between 1995 and 2004, with a peak of over 22,000 in 2001.

Next door, the latest Sussex Atlas says a steady increase in the 70s and 80s, but a slow decline thereafter, by only about 25% and intriguingly their best site, Pagham, remaining steady.

Concerns over these low numbers continue to this day (I was pleased to hear about ongoing work on the populations of prey items in Medway’s benthic zone) but in 2013 I was focused on published numbers and seeing for myself if current numbers were indeed correct.

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Comings and goings

A behavioral case study from Motney Hill. (Okay, I admit it, I have ideas above my station- I simply read the behaviour sections in 'Birds of the Western Palearctic' and 'The Tundra Plovers' amongst others, and tried to see for myself...)

A marked Grey Plover was in situ for a couple of winters, allowing me to track regularly. No colour-ring for this bird, but a stand out ‘summer plumage’ appearance. Yes, that’s the wrong terminology and a subject for another time; in short appearance is due to hormones out of whack rather than retention of old feathers or growth of a set at the wrong time. I nicknamed the bird ‘Summers’, so the terminology stuck. (Actually I used Summers-Grey, for all you X-Men geeks out there.)


Summers wouldn’t arrive until November, in line with many of true wintering birds. These are then usually site-faithful, with just a small amount of hard weather movement recorded.

The fun was Summers was what I term an alpha, setting up and retaining a nice little territory close to Motney Hill Saltings. A long, thin territory, based around a shallow gutway, which it defended from other Grey Plovers. Low tide, Summers would be mainly out in the furthest stretch, on the covering, much closer. A long, thin territory with a moving core, easily mapped.

Feeding is primarily by sight, mainly surface-picking/-probing, so having a clearly defined productive stretch to defend from incomers appears a good survival technique. Many Grey Plovers do the same. Her neighbours did likewise, of course I could only presume to be the same birds, Dave, Dave and Dave (for all you Trigger fans). Occasionally one of the Daves would get a little too close and there would be a bit of parading, a bit of running about and calling, but very little actual aggression (why waste energy fighting?).

As the tide rose, the territory shrank until Summers would be up against the edge of the saltings. Now, if you have a territory, and there is safe roosting close by, why fly any distance to a roost? Summers would simply retreat up into the saltings, sometimes joined closely by Dave, sometimes by Dave and Dave, sometimes all the Daves (no feeding to protect, why fight?)

February saw Summers disappear around the same time as the other two regular Summers present (this interesting plumage type was not as rare as I'd originally thought) one from Funton, one from Copperhouse.

The Copperhouse bird tells the rest of the Grey Plover story. Texts hint at only about a third of studied populations being territorial. Large open flats are less easily marked out, so territories are harder to define and defended. Here, loose associations build up which I called the Betas. Small flocks (usually up to about 30/40**) of non-territorial birds would drift about a favourite route of flats.



**Actually, I’m amazed how many times my counts come out as ‘38’. Getting to the point where a group flies goes past and I automatically start writing 38... The texts say usually up to 30, but 38 is the magic number here on the Medway.

Are my terms Alpha and Beta right? Well, most of the recognisable juveniles are in the loose flocks, seemingly rarely holding a territory. An advantage to a territory is a bird with a creek or runnel to call home with a cosy windbreak to hunker down in. It sort of pointed to a dominant strategy to me at first, but I had to remind myself the Copperhouse Summers bird was non-territorial, a Beta (pictured above, with chums at roost) and doing alright. The texts hint at birds adopting one or other strategy for life. Loose non-territorial flocks obviously do work.

So, the birds on the Medway appear to behave much as the birds elsewhere. A question for me now was I could fairly easily count territorial birds on the low tide. Were these local territorial numbers going to come out at around the one in three of the population mark? I doubted it, as every estuary is different, but it would be fun to find a figure.


Roosting patterns

Tides bring the loose flocks into close association with several Alphas as the waters cover. Often a flock just 'appears'. Again, why go that far to roost when feeding is good? Sometimes, yes, several beta feeding flocks congeal into a larger roost flock (especially for higher tides) and you had the idea of the species being a flocking bird, but that is not the whole story.

Take birds around Rainham. As well as trying to roost on Motney and Rainham Saltings on slacker tides, they will often move out to Friars and the old walls of Nor, as well as Darnet. On low tide, these loose flocks might be found on the adjacent mudflats mid-channel. They have a circuit, and whether you pick most of them all up depends on the tidal state.

Down estuary, Lower Halstow sees an assembly on the south side of Millfordhope saltings, moving onto Greenborough by Millfordhope Creek, whilst Funton birds come together close to Barksore or on the Bedlams saltings. Higher tides they move onto the seawalls, a few times over them.  At this point worth remembering they can feed inland at night. From some nocturnal wanderings around Otterham Creek the Greys based there do a lot of territorial calling on a dark rise, before switching over onto grassland for the odd earthworm or six.

Grey Plover ringed inside the seawall, 2016 - note nictitating membrane, the 'third eyelid')


In daylight, close to the Swale, I have seen small numbers pop over the Bedlams seawall. And I have seen them drop back. But never any determined flight at height, suggestive  a longish flight switching water bodies.

I also think this because, when watching at Queenborough, Grey Plovers coming into the Medway off the Roas and Minster Flats always do so over water. Always at a bit of height. I have never had them doing the Curlew trick of routinely commuting overland south of Sheerness from the Minster flats. There is no real rhyme or reason to Grey Plover flights into the Medway. The Thames, Swale and Medway just come together as one body here, the birds don’t know our political boundaries. Sometimes they just feel safer on Deadmans/ Burntwick.

Very, very few of these birds head down the Swale. If they do go past me, they stop at Shepherd's Creek behind Deadmans. The Swale does a narrow s-bend past there, making for a convoluted route to any safe roost further on.

All this is not to say, from time to time, that Grey Plovers do not enter the Swale. Someone may have seen it. It just doesn’t isn't logical for it to be a routine behaviour.

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Number crunching

A conservative estimate of easily countable territorials from the southern sea wall, copmbined with flocks operating between Upnor Reach and Deadman’s reaches the 400 mark fairly easily. And as I did not discover the 30% figure for a while, I was pleased that I hadn't been influenced by it. My estimations came out at about a 40% territorial take up, surely a reasonable margin of difference.

The published WeBS counts of late have not reflected these sort of numbers:

10/11 - 641
11/12 - 373
12/13 - 154
13/14  - 72
14/15 – 198
5 year average 288.
The last Low Tide Count in 13/14 came in at just 120.

And these are, of course, for the whole of the Medway Estuary, not just my southern shore.

The WeBS counts are incomplete. They should take place on high tide when Grey Plover can be tucked up in small groups among the saltings at high tide- it would be hard to count them all at the best of times. Low tide and many of the Beta flocks would be out mid-Channel, where, even with 'scopes hard to pick up unless flighting.


What next?

As far as WeBS is concerned, the local BTO Regional Rep, Geoff Orton, has been calling for more volunteers this autumn @gronto . The more the merrier. When I last spoke with him, the pipedream of a full crew plus reserves to ensure a complete co-ordinated count remained just that. Help is needed. Low Tide Counts, usually every five years or so, were the same last time out.

If you are out along the south Medway and you provide records to the various bodies, do send in and try to refine the site details. Include in your notes whether in flocks, in flight. This will allow more detailed analysis.

If anyone wants, have a go at proving/disprove my figures- here’s how to do it. Gillingham/Rainham side, count the various bays separately from low tide onward on a windless day. Count any groups present (all of which will be 38), then add any further groups arriving from mid-estuary (Bartlett, Bishops, South Yantlet, Middle).

It will start to make sense.

To the east, Ham Ooze is a little more perplexing, but most groups just move into the Greenborough complex, a few might continue into Funton/Halstow. Check the distant edge of Millfordhope where many pre-assemble.

For the far east, 'scope Blackstakes and Queenborough Spit well before the 2.5 metre, then hold out until full tide for stragglers coming in from the Thames.

I’m slightly tongue-in-cheek as I say that, I know I'm one of a small few willing to dedicate so much time on such things, and can’t really expect others to do likewise- but if you do send records in, all of this helps show why it’s worth recording which creek and state of tide- and that your general counts, however small, are worthwhile.


The rest of the year

To complete the Grey Plover year, small flocks do occur in Spring but the bigger numbers are in autumn.

Most winterers leave February into March, and any late March/April counts are transients, often only staying a few days.



Return passage can be encountered from July onward. Present numbers probably best mirror the early-eighties results- an August arrival, mid-estuary, of a flock of 500 or more in summer finery is always a red-letter day. Typically, some will only stay a few days then move, others will spread out and then carry out part of the moult of their flight feathers over several weeks. There is then a gradual drop-off before the November winterers pour in.

This might hint at a reason for the drop in recorded numbers. Typically, birders do not routinely count anymore. And there are fewer birders straying away from the honeypots in North Kent. Always a red-letter day when I bump into a birder in late summer now.

That short window of midsummer is murder, as you are usually tracking down just a single flock of young birds seeing out their first year well away from breeding grounds (yup, 38 again). They will spend a few days on one creek only to then perhaps pop up mid-estuary on Ham Ooze before venturing into another part of the estuary for a short period. Do they ever cross the main channel north? Just once to date, so I can’t yet say this is a regular occurrence.

All in all, there is still an awful lot to find out about the birds here. But from what I’d seen so far- did the Medway Grey Plovers roost regularly over in the Swale? That short answer had been 'nah'.




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