Seeing the wood for the trees: if you count an orchard you'll get an orchard distribution

Modern orchards are grim. Uniformly grim. They look unnatural. And, of course, they are. Line after line after line, row after row after row, unnatural clones on a parade ground.

Dive into spatial distribution c/o the excellent 'Shorebird ecology, conservation and management', (Colwell) and you come upon the technical term for such even spacing in nature- 'hyperdispersal'. For a pleb like me, the alternative names in use listed there are 'even distribution' and 'orchard distribution'. For a Kentish pleb in the uprooted tree stumps of the now patioed Garden of England, the latter is by far the easiest to remember.

Hyperdispersal/ orchard distribution can happen, but all too often bird flocks really aren't that uniform.

Let's look at a feeding flock of Brent Geese. At first glance they could be thought to be uniform over the field, all spread out in regimental formation. But there's a thining at the edges, a clumping in the middle. Look a little more closely, and those edge scatterings are more to be found at both the front and rear of the feeding direction of the flock as it travels forward grazing. Then notice the depth; the flock isn't rectangular, but ovate.

Age the birds and there will be more youngsters at the front and rear.

Adults are experienced feeders. They can crop grass at similar rates, move more rhythmically together. Youngsters are still learning, and can often find themselves out towards the edges. As the season goes on, the effect becomes more apparent; mum and dad put themselves first. Efficiency in the centre, inefficiency at the edges. Safer in the centre, but you have to have learnt to work in harmony with your neighbours.

(Why one counter often gets a different ratio of adults to youngsters in the same flock. One checks all the birds, one checks, say, the first fifty then estimates. Also why the former finds more Black Brant than the latter.)

Take another of my favourite birds, the Woodpigeon. Once again feeding flocks are following orchard distributions. Much better to keep the youngsters to the edges, where they tend to spread themselves a little more. Easier pickings for a predator. And the adults might clump on the easiest escape route.

Even the fields themselves, be they full of Woodies or Brents, play a part in driving uneven dispersal patterns. They might appear fairly uniform at first glance. But look more closely, there are varying amounts of edge cover, undulations, drainage. Lots of little things, all having an effect.

Of course, the 11,735 acres of our man-made Medway mudflats here might look uniform to start with, but they really aren't. Tidal flow rates, deposition rates, substrata; all why there are so many recognised tidal zones.

And yet some birders still argue for a uniform approach. If there's 100 on 'species X' in this section, there'll be 100 of 'species X' in the next. Here I've been told that that overcounts during surveys (c/o disturbance movements such as when birds are flushed from 'Sector A' to 'Sector B') are acceptable as they make up for any uncounted sectors on the day. They really don't. 'Sector C' might well not have been counted, but you can't just say the overcount in 'Sector B' has made up for that. A species might hate the conditions in 'Sector C'. All sectors vary day to day, tide to tide, neap to spring, ebb to flow, high pressure to low.

Let's look at Avocets again, in/around the western basin. When I first got back in 2013 I was playing at distributions on hand-drawn maps. This map below was based on my sightings during first full month back, January 2013. Heat-mapped pre-roost gatherings with final roosts marked. Nowadays I appreciate much more- how those pre-roost lines on water's edge are connected to low-tide feeding behaviours/areas. Now there's also a new roost site within the Nor/Bishop complex, and a swim-roost just off Bloors often seen thanks to increasing disturbance levels (tidal and human) on the RSPB reserve in the past decade. The Otterham roost is also mainly just neap/low springs. The blue flightlines are still in constant use. Starts off complex, gets more complicated. It might seem that December '21 is similar to January '13, but it really isn't.

Low tide feeding in the Medway is not by orchard distribution.
Intra-tidal movements are not uniform.
High tide roosting does not fit orchard distribution modelling.

The 2013 WeBS Sectors are also marked. Easy to appreciate/evidence nowadays how an Avocet feeding in mid-estuary at low tide the could get as being present in any one of three, four sectors if the counter takes stock at the counts at covering, and could then also end up using up to four different sectors over a single spring high tide, making it all-too easy for duplication.

But does such duplication simply make up for under/non- counts elsewhere?

The 2021 WeBS map on the BTO Website currently shows three vacant count sectors which I've marked in green (one being a split of a 2013 sector, the other two extending further east off the edge of my l'il sketchy map):

Back in January 2013 birds were using southern edge of Millfordhope as a pre-roost gathering, sometimes just moving a little east to Greenborough to roost, other times flighting (off-map) to Funton. Sometimes dozens, sometimes hundreds.

And the recorded flightlines evidenced that disturbance around Motney had pushed those red roosts off east to Greenborough and Funton that month. Nowadays they might use Bloors more when disturbed but, yes, do from time to time make that longer flight.

And still some WeBS sectors have yet to ever hold these main roosts/ large feeding numbers.

My first map cut off about 90% of Barksore marshes (the westernmost green sector) and rightly so as I hadn't yet started walking the Callum ridge for views over them. I had yet to appreciate how well used Barksore fleet could be by Millfordhope/ Greenborough/ Funton birds as a sheltered/safe roost.

TLDNR? Those green sectors really don't have orchard distributions either.

So, could a WeBS sector count where  a species total known to include displaced birds from earlier be accepted as 'true' because it is simply making up for those birds presumed present in an uncounted sector? Of course not.

I chose Avocet for this example as they're big and easy to identify. The same, but different, variances in feeding/roosts, sector by sector, happen for all the wader/wildfowl species here during the winter; they're just a tad harder to pick up on from a few casual visits. Definitely from a once-a-month count.

Orchard distribution simply cannot be expected at the scale of WeBS sectors currently in use here. All of our WeBS sector 'orchards' have differing levels of appeal at different tide heights, times of year, weather conditions. Why WeBS has to be coordinated.

"Such synchronisation is imperative where teams of counters are required to cover large sites.. and the possibility of local, within-site movements by the birds during the counting period is high. Local Organisers should ensure coordination in these cases."

Yes, this is a subject I go on about, some think ad nauseum. But it has big knock-ons. 

Another heatmap with a quote from the BTO's Research Paper on the huge collapse in numbers for many species here. For any local reading this paper the warning lights really should have come on at this point, with regard to there being only small numbers of Redshank found on other sectors of the Medway.

Tell that to the Medway Redshank.

If WeBS is incomplete, if WeBS has uncoordinated counts, you cannot then simply assume orchard distribution.

It has knock-ons. The WeBS results are used by national bodies, and poor methodology will help get an estuary recognised as being in poor condition, and dropping down the national league tables.

The following screengrab is from HM govt's Magic map. Look at the all the red for the western basin where the numbers supposedly collapsed- how much of that is influenced by less than robust data?

(Insert on this slide a reminder WeBS also provides legally required data for international returns as well. Another reason why a need to get right.)

Who in their right mind would throw good money at an estuary where there has already been a huge decline in numbers? Would we expect RSPB to, say, do anything about their Nor marsh reserve when the money can be put to better use elsewhere? Why save Nor when there aren't that many birds? Other considerations as well; the RSPB also wants bang for their bucks, and people can't visit Nor.

Less than robust WeBS data has played a large part in recording such a huge decline in this estuary's standing.

We can't blame the likes of NE, JNCC, DEFRA for it. We've been told for years now that we need full coordinated coverage, robust data, to appreciate fully and help protect our estuary appropriately:

To help meet legal protections for our SPAs we also now have our Bird Wise codes in place. To argue that it is okay to ignore such codes and go disturb birds routinely whilst monitoring for robust data might, just might, justify such bending the rules. But it was already known results were somewhat less than robust before Bird Wise arrived. To simply continue disturbing birds for known flawed data, at a time when all user groups on the estuary are being asked to refrain from roost disturbance, should be unacceptable.

Shouldn't it?