Warning: adult content- Shags on the Medway

As a starting point for this blogpost, Oliver's 'Bird Watching on the North Kent Marshes' is a good place to begin- his summary for the whole of the Marshes fits published records for the Medway in the 21st century "one or two individuals are reported in almost every winter... they favour the tideway in the Medway... most are from September to March, with a preponderance in mid-winter. There is no evidence to suggest that the increase in records is attributable to anything but an increase in the number of observers..."

Is that right?

Most local birders catch up with the bird when an individual takes a liking to the ready food source held within the Chatham Maritime basins, suitably served in a decent depth of water all day long. Up to the mid-eighties these basins were out of bounds in the old Chatham Dockyard Naval base, and Oliver was published in 1991.

Are there still Shags to be found on the tideway? Simple answer, yes. Thanks to being in the position to visit the estuary almost daily, that can immediately be revised to an annual visitor. To find your own, once again you have to think about food and roosting.

The old records point to deeper creeks, with no mention of tideway state when seen- Motney (so, Bartlett Creek), Greenborough/Stangate Creek and Kingsnorth (Damhead Creek, Long Reach). The comments under Cormorants regarding prey concentration during the running of the tide apply equally well here: a bird can be found actively feeding, a bird might be found hauled out on the rockier flats over the lower tide. 'Might', because they can often choose to use their favoured high tide roost, or go elsewhere to continue feeding.


Safe roosting

The Kent Bird Report of 1996 draws a conclusion that four Shags visiting the basins were the same as four seen roosting some four and a half kilometres away. Fair conclusion? Never seen moving to and fro, but much of that flightline is underwatched. The roost, the Oakham jetty at Kingsnorth, is one of the few Shag-friendly roost sites on the Medway. They do not join the Cormorants a short distance east on the crumbling metal framework of the Bee Ness Jetty; Kingsnorth is more substantial, designed to take traffic and made of concrete with, thanks to the support design, a series of suitable roost ledges tucked just under the roadway. Roosting birds can be well hidden, and were often only found by leaning out and scanning a long way back along the jetty.

In recent years when asked why a basin bird might be missing, I have suggested only really down to lure of easier concentrated fishing in the creeks and that a middle of the day search, especially around the high tide, is the best way of guaranteeing a good chance to tick-and-run. Over the tide, even if well-fed and looking to day-roost, buoys on the calmer waters right next to snackfood beat returning to the main roost.


Occurrence

It is fair to say Bill Jones has seen more Medway Shags than any other birder, thanks to his years as Environmental Initiatives Officer at Kingsnorth Power Station. His assessment of Shag timings for the Medway differs from that published- most have occurred around Oakham/Kingsnorth in early-/mid-spring, notmid- winter.

With most observers only having Shag on their 'radar' in winter, just as there are fewer birders on the Medway in the spring, there are fewer searching for them (sightings are often far from the shoreline). Even so there are March, April sightings popping up in the records, including from recent bird cruises on mid-estuary.

As discussed in several old blogposts, this estuary is 'non-coastal', so 'migration' often go undetected- late autumn movements such as those recorded from time to time on the north Kent coast do not happen.

Taking the North Kent Marshes as a whole, Shags have turned up in every month of the year (an exceptional story follows below) so they should never really be off a birder's radar. They do vary in numbers from year-to-year, which is most likely down to food abundance elsewhere; many do not bother to move that far from breeding areas- they just need to move on to the next easy fishing.


Origins

Ringing recoveries trace many Kent birds back to coastal eastern Scotland. Fewer Farne Island birds move as far- the Scots leapfrog them. Perhaps island fishing is better? Certainly onshore winds make fishing harder, and prolonged strong easterlies force Shags along the coastlines.

They do not come from the continent in any number. As per Cormorant, they do not like leaving sight of land- they need to haul out to dry off, so better to locate new feeding close to shore.


Are we really seeing adults?

In describing plumages some forty years ago, the first volume of Birds of the Western Palearctic used a phrase now out of favour- 'first adult plumage'.

Shags usually do not breed until their fourth year. Now another Shags can tell an age easily, but can struggle after the first couple of immature years. The problem, left out of many of the guide books, is the three year olds. As BWP went on to explain this first adult plumage is "acquired gradually between second and third autumn; some specimens, however, like adult in March of third calendar year..."

So, a third winter youngster, one not set to try breeding until the spring, may well look like an adult.
To ramp up the problem, the recent 'Identification of European Non-passerines' by Baker, seems to say this is a real problem. To quote,  "3w- most not ageable but a small percentage of birds (2% of males, 4% of females retain (an immature type) outermost primary until summer of fourth calendar year."

So, us southern softies, with our limited experience of Shags, and certainly not that many close up views, have a habit of going and claiming 'adults' when we often might have no way of ruling out a sub-adult (and probably never consider that age).

Does this really matter? Well, if you want ot publish official records as adults, yes. Philopatry. In rough terms, in many non-passerines long-lived species take several years to mature; they might not migrate routinely during their lifetimes. A successful adult will often winter close to the breeding grounds if food is available. Out-competed, outranked youngsters have to move. They may stay at a chosen wintering site first year, they might venture closer to natal breeding grounds in second summer and they might even stop awhile at the start of the third breeding season, but they are recognisable to adults and usually not taken on as 'risky breeding stock' unless, say, something has happened to a chosen mature partner just as the colony reassembles.

In Shags, variability in feeding can lead to varying numbers of adults moving more often in some winters, but for anyone trying to study Shags in the south-east any apparent increase in adult numbers does not reflect any real change in adult patterns- they are still not likely to go further than they need to. But read the bird reports and it seems adults are visiting. It is just as likely to be immature birds finding our recovering waters more suitable again. Ringing recoveries do show that adults are appearing, but we cannot presume adulthood as easily as we do.

Chatting with Bill Jones on the Kingsnorth Shags, he certainly wondered if any birds hanging on into spring on his artificial ledges along Oakham jetty signalled older youngsters with increasing hormones. Could loitering third summer birds ever lead to a claim of possible breeding?


The Kemsley young 'uns

A nice published history from older Kent Bird Reports from the neighbouring Swale:

1991- "two wintering in Ridham Dock in the last quarter"
1992- "in the north three first year birds were resident on the Swale at Kemsley to June, with two second years then remaining to year end"
1993- the two remained at Kemsley throughout the year and were joined by four others from Nov 18th to 28th"
1994- birds were present at Kemsley... for most of the year, with numbers increasing from one in January to six by Feb 12th, with peaks of three in March, six in April and four during July to October"

Now that is something- a great chance to have noted all these different Shag plumages through the years here in north Kent; juvenile/first winter changing to the paler first summer to the off-adult second winter and then into the more confusing second summer. I'd opine there'll never be anything as rare and exciting as that around that part of the Swale- though I'm sure others would disagree with that this very week.

Okay, so I might have to let that slip. But do expect a few hard questions if you try to tell me a Shag on view on the basins is an adult.

An eminent Shag researcher writes

Thankfully, this e-mail does contain some birds and some estuary (although more central and north estuary than I like).

Once again the e-mail in-box has been dominated by a Mr Trellis of the Gower, south Wales (I really hope he works out the 'comments' button here one day soon). It followed my recent post on Cormorants and the promise to follow up with a short note on Shags on the estuary.

Mr Trellis kindly supplied me with a photograph he took some years back at Kingsnorth, on the northern shore of the Medway. Birders will instantly recognise Shags, local birders might also recognise a youthful Bill Jones.

Two ridiculously tame young birds came to recognise the stench given off by Bill, prone as he was to collecting specimens from the Power Station intake grilles (leading to a massive fish species list for the site, a story for another day). Actually, the smell may have been his specimen bucket, we were never too sure. Over the course of a few weeks the birds came to appreciate both Bill and his bucket, which in turn led to their gaining BTO rings. There is no such thing as a free lunch with Bill.

In addition to the photograph, Mr Trellis supplied me with some interesting observations on Shag behaviour and timings for Kingsnorth and Nor, so I really have no excuse for not finishing the note. Watch this space...

------

(Bill and his bucket have featured before, see this Little Egret story)

Raving about 'ranting

Say to a birder 'what's a pelagic?' and you'll get a reply along the lines of 'a boat trip out to sea, to search for seabirds'.

Say to a birder 'what's the pelagic?' and quite a few will be hard-pressed to answer.

They might make a stab at ocean waters or similar (the ancient Greek word, pélagos, meant 'open sea') but technically the pelagic zone is something that occurs in oceans, in estuaries, even in lakes. It is the name for the distinct ecological region formed within any column of water that sits away from shore, and above the floor (the latter being the benthic zone, the ecological region at the bottom of a water body which includes sediment and sub-surface layers).

All of which came in useful when I was thinking about the number of Cormorants vs the paucity of Shags on the Medway. Uber-simplistically, the favoured diet of the former consists mainly of benthic fish species, whereas the latter tend to go for the more pelagic fish species.

Part of why there are just a handful of Shag records each winter as against a jettyload of Cormorants.

Some of you will want to look away now; from this point on the post is purely about Cormorants, in particular their feeding behaviour, their loafing areas and their roosts. And their numbers- what is a jettyload?

Feeding

Cormorants are such a successful feeder they only need spend an hour or two a day hunting and can spend the rest of the time lounging around. They tend to get feeding out the way early as well. Many birds leave the Medway to fish elsewhere; in first hour after dawn good counts can be obtained from Queenborough as birds depart out into the greater Thames. At the same time anywhere along the southern stretch an odd bird or three might well be heading inland to feed and several also make their way into the tidal river via Chatham.

Some feed in my stretch, the southern Medway estuary. The texts state they do not often hunt cooperatively, but as I started watching closely I thought they they did it quite often. It took me a little while to work out what was actually happening.

Watch Bartlett and South Yantlet Creeks on a dropping tide in the morning, and there is a good chance you will spot one of these 'feeding flocks'. Each usually around 10- 50 strong (but up to 60 recorded), they raft together and several will be diving together- fish have become concentrated in the creeks on the retreating tide and these birds follow them out.

But watch more closely, and the birds do not arrive as a flock; sometimes in handfuls certainly, but numbers usually build. Nor do they hunt cooperatively, by taking turns in a rolling formation with birds at the rear overflying to take a go at the front- it is simply a melee- nothing frantic, simply each to their own. They are individuals coming together for the food, nothing else.

Loafing or roosting?

Cormorants are diurnal. They migrate during the day, they feed during the day. They need a safe night roost. The 'roosts' we see during the day are loafing areas- haul out spots for the well fed. A place to get rid of the wet as well; Cormorant feathers soak up water to help overcome buoyancy issues, and need time to dry. These loafing sites are deserted at night for the safe roosts. (Logically, in winter most loafing sites will be under water for part of the tidal cycle.)

Loafing spots can be as simple as a marker tower (Pinup Reach off Copperhouse is a good example), discreet as a shallow sandbank (Bartlett, Bishop, Sharpness- tail feathers dry better on sand than wet mud), as obvious as a wreck (the caisson off of Motney) or as straightforward as the actual roost site.

There are two main roosts on the estuary, both viewable distantly from the southern shore. Technically, they are both north shore sites, but they are as easy to count from over here as over there- so it seemed a shame not to(!)

~ Bee Ness Jetty

In the ornithological literature you will find Oakham Jetty, Kingsnorth Jetty and Bees Ness Jetty all listed as roost sites. They refer to the same thing- Bee Ness Jetty. Anyone interested in a potted history of what was, at just over 2.5km, Britain's longest jetty can read about it here. The jetty was abandoned after the site closed in 1977 and so became a safe roost, especially after sizeable sections collapsed, or were removed for safety reasons.

The present roost (shown in red) is on a distant section out over Bee Ness itself.

~ Grain Tunnels

At first glance, this structure is often dismissed as a derelict pier, but actually sits above the twin cable tunnels linking Grain with Chetney (if anyone knows the exact purpose, I would love to know) and was never linked to the shore. The tunnels are 1.7 km in length, and 2.8 metres in diameter- workers do access them, at that size I certainly wouldn't like to(!) Aerial views courtesy of Google Earth also confirm the 'jetty' to have two large open spaces- all in all a perfect, safe remote roost site.

It seems this has been overlooked in literature, perhaps because this part of Grain is often overlooked by birders; most published counts for Medway have been simply for Bee Ness.

Birds from both roosts will disperse in all directions. Watch them often enough and you start to realise whilst more tend stay in the Medway when waters are low and feeding is easy, most will still head out into the Thames estuary to the north and east of Sheerness; Cormorants are known to travel routinely up to 15 kilometres to feed- so this sort of distance is just a short daily commute for the Medway's birds.

Numbers

Historic counts reflect the increase in overall numbers seen since Cormorants started breeding inland in the south-east of England during the 1980s, with the increase in early autumn numbers being down to dispersing young. Before that, peaks were always in winter, and were British birds, mainly Welsh, also Scottish and north of England. Wales might seem an odd source at first, but Cormorants are not routinely pelagic- they like to stay in sight of land, so overland dispersal is just as routine as coastal.

Kent has rather more overseas ringing reports than neighbouring Essex and Sussex, which makes sense and hints towards the possible small but regular arrival of the subspecies sinensis from increasing numbers breeding on the near continent in the 1980s being the source of the new colonies.

Put simply, sinensis favours fresher water and breeds inland in trees, whilst carbo favours saltwater and the coast. I never really bother to assign to race here. They are usually way too far out to play with assessing gular patch angles (which in any event overlap slightly) and, besides, work on brood DNA in the new inland colonies has shown carbo to have got themselves caught up in small numbers. They just go down as Cormorant.

You can, however, record fairly easily the slow drop in numbers of young as they continue to disperse, and are replaced by more adults arriving to winter. Or seemingly winter. The term in 'BWP' is individual nomadism. Birds can and will continue to change sites during the winter. Some years see more birds than others, which is down to prey availability. Cormorants are fickle.

There has been a small collapse in numbers during the present decade, mainly down to small collapses out along that final kilometre of the Bee Ness Jetty. The safe roost capacity has been shrinking. It will be interesting to see what happens in the next few years. Historically, a jettyload was up to around 350 birds, 400 tops. During the past four years my roost counts (dusk/dawn) have never really moved much above the 200 mark, and the favoured stretch has been packed. (Grain has remained steady at around the 50 to 80 mark.)

If the crumbling continues, could they switch elsewhere? Probably not that easily. One or two alaready loaf on Kingsnorth Jetty, but that is usually atop the old lamp posts- Kingsnorth has been all too regularly disturbed by security patrols in the past. The patrols could be tolerated by gulls, which would rise and return when the danger was gone, so the handrails beyond Oakham island were claimed as a regular roost for Common Gulls when the power station was in operation.

Counting

Being diurnal, roosting Cormorants tend to congregate in number as dusk begins, and only a few stragglers leave returning until the final fifteen minutes before sunset. They do seem to start to leave at the first traces of dawn, and can be missed- a morning count following an evening add-up have tends to be down by about 10-20%.

Counts of the roost during other times of the day can be misleading. Counts in discreet areas of the estuary can seem not as useful at first glance- but do confirm feeding areas and can be hugely entertaining. In early November this year, on an uncovering tide just after dawn, I watched a number of Cormorants leaving the Bee Ness Jetty roost and ending up on the edge of Bartlett Spit as it began to uncover.

My notebook read as follows:

0 @ 06:50
14 @ 06:55- flew in together to land on mudflat edge.
19 @ 07:05- a further 5 flight in
32 @ 07:10- further arrivals take group to 32. Most are near to each other in loose gathering, one c. 50 metres away.
32 @ 07:23- first five enter water, rest stay on mudflat. Fishing commences.
1 @ 07:27- female Marsh Harrier crosses estuary from Bayford, keeps some distance from Cormorants over Bishop Ooze. Panicking waders cause all Cormorants (bar the individual) to take to air and drop into South Yantlet Creek out of sight behind Nor/Friars Saltings.
47 @ 07:30- 40, then a 3 and a 4, drift back out (clearly more had been loafing out of sight), none are feeding.
0 @ 07:31- all back into South Yantlet Creek as Marsh Harrier reappears, with a Buzzard for company.
16 @ 07:33- 14 and 2 back out, fishing.
34 @ 07:39- 27 swim back and haul out, another 5 remain in creek, 3 individuals, 2 close together, starting to dive. 2 more fly in onto flat.
34 @ 07:41- female Marsh Harrier passes back along South Yantlet Creek- 1 Cormorant takes flight from water and is harried for a short distance before MH gives up.
43 @ 07:42- 9 more swim in from behind Friars, to haul out some 60 metres west of main group.
42 @ 07:54- 1 from main group takes off and heads inland.
42 @ 08:02- all but two enter water, many starting to dive.
56 @ 08:04- the Marsh Harrier returns and 39  birds leave water for mudflat. At same time numbers on water are boosted by more birds arriving from behind Friars- 17 now swimming together.
56 @08:05- Marsh Harrier flights at group, all bar 12 enter the water and start to head behind Friars.
0 @ 08:07- remainder enter water and disappear behind Friars- waders also panic and flight. Marsh Harrier now seen to have claimed fish, and drops onto flat to eat. The Cormorants do not return.


All good stuff, but if I had simply counted and moved on I could have had any figure between 0 and 56 down as present:

Of course, each total would have been right for that exact minute, but it wouldn't have told the story.

Why, if you can spare the time, always worth staying and watching a spot for as long as you possibly can. I know most of us like to use the term 'birder' nowadays, but being a 'birdwatcher' can still be fun.

At the moment I have one burning Cormorant-related question. When you scan Bee Ness, it appears that birds are sometimes in pairs. Years ago it was thought that behaviour might be pairing up prior to returning to the breeding grounds, but that was dismissed in more recent texts- display and pair formation happens back at the colonies. So what is this apparent pairing all about? Answers on an electronic postcard, please...

Where to start?

Every estuary has a Head. A starting point, where the river opens up to mudflats, often extensive in nature. The Medway is no exception. For the sake of a boundary to my recording area, I looked to a specific cut-off line between Lower Upnor and St. Mary's Island. While extensive mudflats on the southern shore start a little further downriver, the northern flats open up from here on Cockham Reach, and for several centuries stone marker posts at Lower Upnor have shown the limit of the jurisdiction on fishing rights for the old City of London. The City purchased these rights from the Crown in 1197, and marker stones were erected (and on the Thames at Yantlet).

What was a good enough cut off for King and London is good enough for me. Certainly heading upriver from here the Medway has the look of a narrowing tidal river- whilst still tidal until Allington, the increasing mix of fresh to salt water now favours a different community, and it is often only in extreme winter weather that many waders ever venture further inland.

I always enjoy birding here, but my prime motive is studying the intertidal movements around the estuary, and this is certainly not the most productive spot for that. Even the growing mudflats at the head, from Lower Upnor down to the Strand are not usually busy for waders and wildfowl, which is probably down to the 'salt wedge'. Salt water sinks. Fresh water runs in over the top and then slowly mixes- the salinity of an estuary only reaches its highest at the mouth. During these past three winters I have only found any notable number of waders along Cockham Reach and Short Reach when the weather has been cold. Then, pressure elsewhere will move Dunlin and Redshank up the Head, with a scattering of Oystercatcher and Curlew. On a day like today, mild and damp, I always scan the northern flats from here with not a little envy.

To lessen the load I always include a visit to the three Basins of the old Dockyard, which separate St. Mary's from the mainland. Today the Great Northern Diver was still in residence on No 2, with Shags there and on No 3. It actualy turned out I was most impressed by the water levels today- it is not often low enough to reveal the mussel beds and a little bit of the hidden concologist in me comes out for a while.

My personal guide to birding St. Mary's Island has now just gone live on another page of this blog, which I hope might be useful to some. The intention is to upload guides for the whole of the southern shoreline during the course of the year.

After St Mary's, I then usually make a fleeting visit to Gillingham Pier. This remains a quiet spot outside of any adverse weather but some reason is a lure to both Little Grebe and Mute Swan.

Looking east from Gillingham Pier

Little Egret, big ship (the LV21 lightship, Gillingham Pier)

Finally, as something of a reward, I call in at The Strand. One of the Medway Unitary Authority's main leisure parks, the main river channel is close inshore and now heads due east just below the first of the main islands, Hoo Island. I always make a note of any birds on its southern flank, the Middle Bank. Although the wrong side of the main channel, the island is a barrier between the Bank and the north shore birds- birds usually swap between the Bank and Gillingham and Cinque Port Marshes. Again, close to the Head this can still be hit and miss, and while I have more good sessions than bad, today wasn't what you could call a good one. Still, I could feel virtuous for having covering the Head once more, and leave the more exciting bits for another day. (Can you tell it was just starting to rain at this point?)

Many of the roads on St. Mary's Island
have bird names.
 I think this might be Phalarope Way?