The season is terning...

Monday, 30 August

By now many of the terns which bred at Hayling Oysterbeds and in Langstone Harbour will have started on their annual migration back to wintering quarters in Africa. Others will hang around in British waters before they also leave. Whatever the status or location of these birds they have all departed their nesting areas. Well all but one pair that is. A very late nesting pair of Common Tern is still feeding two young on the north island of the Oysterbeds lagoon. They hatched their eggs on 08 August so the young are now almost three weeks old. I find it remarkable they have survived the last week of rainy and (at times) windy weather but they have. I visited the reserve last Friday and found them begging for food from their parents. The fact that the parents haven’t given up in the recent weather is admirable. Well, perhaps it’s more hormonally-led behaviour. A similarly late pair of Common Terns in 2006 eventually successfully fledged there two young in early September so this late nesting isn’t without precedent. The previous fledglings which I referred to in my previous post were finally led away from the lagoon on 16 August. I was lucky, and felt privileged, to witness their departure. One of the adults came in and fed one of its two young and then, without any calling that I could hear, started on its way back to the main harbour. As it got ten metres or so away from the lagoon islands one and then both youngsters flew up and followed it out. One was a bit smaller and blunter-winged than the other but, as a family group, they disappeared tentatively into the distance. They increased the total of fledged Common Terns from the reserve this year by two…. it currently stands at 82.

I’ve not been out much since last week but in sunnier conditions earlier this month there were a lot of hoverflies to be seen. I managed to get images of some of them, and even had a go at identifying a few. Having spent some time wandering around with a previous warden at Farlington Marshes in years gone by, someone who specialized in surveying and identifying these creatures, some of the identification stuff has rubbed off on me (I emphasize the “some” there!). Hoverflies I CAN get into, I suppose because many of them are very colourful and are a good subject for macro-photography. I even remembered some of the Latin names (most insects do not have common names, so you HAVE to learn the Latin). The key to locating the commoner species is to find some late-summer flowering plants, and look for them nectaring (and wait for the sun to come back out...not necessarily in that order….). Here’s a couple that I saw at the Oysterbeds, taking nectar from the yellow lowering Common Ragwort, an important source of nectar for many insects in the summer:

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Sphaerophoria scripta......................................Scaeva pyrastri

My visit to the reserve last Friday also coincided with a high spring tide and a good selection of autumn passage migrants. Along with several hundred Dunlin, Ringed Plovers, Redshanks and Turnstone a nice group of five juvenile Curlew Sandpipers and a Ruff had dropped in. The continued presence of an Osprey in the harbour had shifted the main roost of Oystercatchers in the harbour from the main harbour islands to the outer embankment of the Oysterbeds, with a total of 1276 counted. Quite impressive. A smaller number of Grey Plover (38) and Knot (3) were also seen. Seven Whimbrels, two Greenshanks and three Common Sandpipers completed the list of waders. Also of note were seven Little Terns with the gathering of Common Terns on the shingle spit just to the south of the lagoon, while single juvenile Black and Arctic Terns dropped in or flew past. Finally, the first returning Black-necked Grebe of the season was in the main harbour channel on the falling tide. Later I dropped by the Wildlife Trust reserve at Southmoor where at least 70 Yellow Wagtails had gathered to feed amongst the cattle. A Redstart and a couple of Wheatears were also here (four of the latter were also seen earlier at the Oysterbeds), while nearby three late Swifts were feeding over the pools at Budds Sewage Farm along with fifty or so Swallows and Sand Martins.

Still going....

Thursday, 05 August

Well, it’s almost the end of the breeding season for the sea birds at Hayling Oysterbeds but not quite! Currently the pair of Common Terns that I featured in my last update still has two half-grown young, while two other pairs are incubating eggs still… Three more young Black-headed Gulls have just made it onto the final total for fledging by this species as they can now fly around. They are of course still begging for food on the lagoon islands, but eventually as the adults bring in food less regularly they will learn to feed for themselves and move on (or follow their parents out to the main harbour).

During the last set of high daytime tides up to 300 Common Terns and 11 Little Terns gathered on the lagoon islands, making for a spectacular site especially when they all wheeled around in response to a passing Peregrine or distant soaring Buzzard. A few Sandwich Terns appeared more occasionally, while a few evenings ago an Arctic Skua flew through the reserve putting everything into temporary flight. These are rare visitors to the harbour (the nearest breeding grounds are in northern Scotland) and in five seasons of being one of the wardens at the Oysterbeds I have never seen one here in the summer. They feed by kleptoparasitism (literally, parasitism by theft). Typically they chase terns and gulls to force them to drop or disgorge their food, their agile and swift flight combined with larger size (compared with the smaller terns) aiding their success rate. The bird at the Oysterbeds was quickly pursued by one of two of the local gulls, and quickly continued on its way over the harbour.

Interestingly it has been suggested that young Oystercatchers can engage in intraspecific kleptoparasitism, steeling food from adults. However, I wonder if some of this can actually be attributed to observations of juveniles staying in the same vicinity as their parents for weeks if not months after their fledging and the loose family group still functioning in terms of the adults still supporting the youngsters? Certainly family groups can still be identified early in the autumn long after fledging has taken place, with the juveniles often begging for food from the adults, often successfully. At first the juveniles will feed exclusively on worms, but many will learn the adult skills of locating and cracking into the shells of crabs, cockles and mussels.

Late display from the Common Terns continues and I managed to capture the following images of some of the posturing the adults get involved in when courting.

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The next update, as the season finishes, may start deviating away from the breeding sea birds so what better way to start than to introduce a good place for seeing our smallest species of owl? The Little Owl is a scarce but well distributed resident breeding species on Hayling Island that can be seen hunting both day and night in the summer. Several pairs occur along the west side of the island, and the billyline track just inland and opposite the Oysterbeds is a good place to look for them. Currently the most regular place for easy views is from the gate on the east side of the track opposite (and just north of) the oysterbeds lagoon. Birds have recently been seen perched in adjacent trees and on the pile of old telegraph poles just in front of the gate. Look more distantly from the track before approaching the gate, as it is easy to flush birds off the lying poles before you see them there!

End of breeding season almost in sight

22 July, 2010

Having missed an update last week I have to report on rather a lot so will try to be as succinct as possible. The major event recently was the strong winds and high tides of 14th and 15th July. The overnight tide and gales during the early hours of 15th July threw waves across the top of some of both South and North Islands in the lagoon and wiped out a total of three broods and seven nests of Common Tern, plus a few very late Black-headed Gull nests. The combined height of the tide and waves reached over 5.4 metres in places, and is unprecedented during the last five years of our wardening. All of the ‘top’ areas of both islands are over 5.2 metres (most are considerably higher, notably the new shingle recharge area) and would not have been inundated under any of the high spring tides that I have recorded in recent years. The timing of the stormy conditions could have been a lot worse of course, as an earlier event could have wiped out many more small tern and gull chicks and nests. Overall it has already been a very good season for Common Tern and Black-headed Gull breeding success. Exact numbers will follow in due course but it is likely to be at least 1:1 productivity (i.e. averaging at least one fledged young per breeding pair) for each species.

Predation of tern chicks has continued and sadly two broods that survived the storms of last week have now disappeared. Continued predation by Mediterranean Gull is the likely cause. One brood has appeared since then, at the southern end of South Island. These are likely to be the last new chicks we see on the reserve this summer. As is typical the first egg hatched a day before the second and until the second egg hatched the female looked very uncomfortable trying to incubate egg and brood chick at the same time. The male soon came in, passed a tiny fish to the female. She then fed the new chick for the first time.





Various other very late attempts at re-nesting will probably come to nothing as the colony begins to break up. In recent days I have counted up to 130 adult and 60 juvenile Common Terns on the reserve, many of the juveniles still being fed by their parents but still returning occasionally to their nesting territory on the islands. As time moves on more will remain in the harbour, some on the shingle spit to the south of the lagoon, before finally dispersing more widely. In the meantime the recent increase in display and territorial activity by some of the adults provides an opportunity to observe all stages of the breeding cycle in one quick scan with binoculars! I might add that the sheer spectacle of watching terns flying within metres of you as they pass between harbour and lagoon continues to be a delight to watch. The photographic opportunities are limitless too (the images below were taken with an 85mm macro lens!!).

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Apart from a few newly fledging juvenile Black-headed Gulls, and some older juveniles remaining on the islands, there are now only three smaller gull chicks left. I will continue watching these to (hopefully) add them to the overall figures when they too fledge. There's been a noticeable recent increase in territorial activity with some of the remaining adult gulls re-affirming territories for next year I, with the camera capturing some interesting freeze-frame motion shots of their posturing!

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It’s not been so good a season for Oystercatcher or Ringed Plovers, with the latter failing to fledge any youngsters and the former only one. This is the latest image of the juvenile Oystercatcher; it is still being fed worms by its parents, but for the last couple of weeks it has learnt to wash them free of mud for itself (previously the adults were only presenting it with pre-washed worms!).

As the season also draws to a close out on the main Langstone Harbour islands the success of the Little Terns out there is being indicated by the regular appearance of small numbers of juveniles accompanying some adults at the Oysterbeds. Encouragingly these birds have “found” the new shingle area at the north end of the reserve and are currently using it as a loafing site at high tide. I counted a maximum of seven juveniles and four adults the other day. Just in case there is any doubt as to the differences between juvenile Little and Common Terns two instructional images appear below. In fresh plumage juvenile Little Terns have bold dark inner markings on their pale upperpart feathers (much like juvenile Sandwich Terns do) whereas Common Terns, although more variable, have narrower and more regular “sub-terminal” markings and buffy edges to the same slightly darker feathers. Of course, size is an indicator too, with Little Terns really being…. little!

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Hungry fledglings (and Med Gulls)

Tuesday, 06 July

As June passed into July I had been continually busy with recording numbers of young birds fledging on the reserve. Overall it looks like a good year but with a sting in the tail. I was hoping that the later nesters now hatching young would do as well as the early nesters and make it an excellent year for breeding productivity, but this is not going to be the case. The disappearance of small chicks on the island in the lagoon continues, with both Mediterranean and Lesser Black-backed Gulls the culprits. They predate the chicks to eat them (enough said…as it does get a bit gruesome) and are both efficient and persistent. On Sunday, as the wind speed increased to a fresh south-westerly, a Lesser Black-backed Gull tucked into the colony like it was fast food station, clearing out three broods of Black-headed Gulls during the afternoon. Unfortunately (for the small tern chicks) I have established that there are at least two adult Mediterranean Gulls predating. Yesterday both were patrolling (read ‘hunting’ there) the islands at the same time. One took an egg as well as a chick or two…

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Adult Med Gull patrolling over South Island looking for food. You would think that more of the nesting terns would drive them away (like the tern already in flight the second image is about to do).

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Fortunately most of the tern chicks are either fledged or very nearly and are very hungry as one of the images below indicates! Their first proper feathers vary quite a bit in colour between individuals; this sometimes becomes helpful for me tracking individual broods. They all stay to the same relatively small area during their first three to four weeks of life which also helps. I saw my first one taking flight on the first day of the month and yesterday many were trying out their wings as they rose into the air above the island. At one stage they looked like dozens of jack-in-the-boxes exploding from their homes! A couple ventured southwards over the main harbour waters while others flapped about over the lagoon. Many will leave the site soon. A few images below:

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Black-headed Gulls fledglings are also at the leaving stage, or have already left, and yet again this summer I left it to the last minute to count them before they disperse. There are more to come but so far almost 500 have fledged. The remainder are still hungry and their high pitched begging calls can be heard all around the lagoon.

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A few Black-headed Gulls and Common Terns (images below) are still on nests, either failed breeders from earlier in the season having another try or very late starters. Courtship activity can be seen from both of these species at the moment.

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And last but not least…. the Oystercatchers. It has been another week of swings and roundabouts on the reserve for this species. As one of the other pairs on North Island lost their two very small recently-hatched chicks over the weekend, the pair on South Island has been busy feeding their fast-growing youngster. Both parents, especially the male, can frequently be seen bringing in worms from the harbour to the lagoon. At other times the youngster shadows the male as he finds food around the edge of South Island and is quick to make sure that anything found is eaten!

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The nice and the nasty

Tuesday, 29 June

Spending time watching a sea bird colony gives me the chance to see some fascinating and incredible behaviour. I have mentioned before the predation of tern chicks by Mediterranean Gulls and, right at the end of a long and hot weekend at Hayling Oysterbeds, I witnessed yet another predation event. The same returning adult male Med Gull took under ten minutes of patrolling over the islands in the lagoon on Sunday evening to nab a small Common Tern chick. The deadly act all happened, as usual, in the blink of an eye, and for the most part went undetected by the other birds. Even the terns themselves seemed mostly oblivious to the overhead menace, excepting one of two which drove the gull away from their own young. Perhaps these are the wise ones. But most are not.

The Med Gull, with its beak full of stolen booty, landed quite close to me at the northeast end of the ‘northwest embankment’ near to the main weir. It was here that I was able to make a few short digiscoped video recordings. These show how the gull mashes and squishes the corpse into a package more suitable for swallowing by bashing it against the rocks. It attempts several times to swallow it whole, and will eventually succeed, but on this occasion I was unable to record it as it was chased off by a Black-headed Gull. Still, the poor dead chick was already halfway swallowed…

Sadly, this gull has almost certainly been responsible for more deaths of tern chicks than I have witnessed. Last Friday I watched it patrolling over the islands for a long time before I took a break from the lagoon area. On returning I found it sat on the water with a rather large (tern chick-sized) lump in its throat! Most of the tern chicks are now too large for Med Gulls to predate, but there are several new broods of small chicks, just the ‘right’ size for predatory Med Gulls, appearing on South Island. Hopefully this Med Gull will go away before it has more impact on the breeding productivity of the terns this summer.

Prior to the above incident I had been taking pictures of the Common Terns in flight, and managed a couple of pleasing shots (bear in mind these are heavily cropped images):

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There seemed to be lots of fish in the lagoon (or perhaps they were just more visible, coming to the edge and the surface in the hot weather) and one particular Common Tern was taking advantage of it. Many times it came back to the same spot in the lagoon, hovered, plunge-dived, emerged with a small silvery fish, and flew straight back to feed its hungry chick on South Island. Most of the terns fish elsewhere in the harbours. Some obviously go as far as the south end of Chichester Harbour or the sea off Hayling Bay and return overland across Hayling Island to the breeding colony at the Oysterbeds, a round trip of perhaps five or six miles. Prey species appears very variable. And it’s not just fish either. Shore crabs are currently being bought in by many of the adults, the young not having quite the trouble in swallowing them as they were a week or so ago. What look like tiny shrimps are also being bought back to feed the young. If there’s anyone (perhaps a student) out there particularly interested in marine biology then there is opportunity for lots of observation-based field work here, as I reckon that most of the items being bought in by the terns could be identified to near-species (or species) level with the aid of a telescope.

Good weather is helping the birds

Tuesday, 22 June

It’s not really too surprising that the fine weather this summer is currently helping the sea birds to do well at the Oysterbeds. Since my last update yet more Common Tern young have hatched and, just in the last couple of days or so, several new incoming pairs have set up territory and have begun nesting. These are perhaps likely to be pairs that have failed on there first breeding attempt on the main Langstone Harbour islands. In fact, I strongly suspect that, as well as the attraction of the new shingle on South Island this year, the increase in the numbers of breeding Common Terns at the Oysterbeds this summer is also been a function of their higher breeding success here. Although second attempts are often not as successful as first attempts some have gone on to raise young on the reserve late in the season here during recent years. My guess is that ALL of the successful breeders quickly return in the next spring to the site they were last successful on, which helps to attract in all the others (at the Oysterbeds this has all been helped by the improved habitat, of course!). Like Little Terns, the provision of viable breeding sites for Common Terns is now important in Langstone Harbour, bearing in mind that the harbour, including the Oysterbeds, support over 1% of the UK breeding population of this species.

OK, so you’re bored with the stats.... Moving on swiftly, some of the tern chicks are now a fortnight old. During next week some will be taking their virgin flights. In the meantime they are jostling for position on the islands. South Island is positively bristling with hungry chicks! Inevitably there are a few squabbles and fracases, mostly minor but sometimes more violent. Most days I spend at least some time watching the terns closely and have witnessed quite a few attacks on chicks from adults. Most of them appear to involve neighbouring adults and chicks, the latter getting too close and wandering into a neighbours territory. But it does seem that a few Common Terns are much more prone to unprovoked attacks on chicks, and I have seen adults attacking small home-alone chicks still at the nest site while the parents are away. It’s not always entirely clear if these more aggressive attacks are made by adults with their own chicks or not.

Those who have visited the reserve recently (wot, you mean you haven’t visited yet?!) will have seen the strange wooden structures on the South Island. As noted in the previous post they are “chick shelters” and specially placed! I have been really pleased to see that many of the chicks are using them for a variety of reasons. Mostly they use them for shade during the heat of the day, or as a wind break. Others are using them as a hiding place from unwanted attention from neighbouring adults. A slightly comical video clip can be seen below...



Predation of chicks from incoming aerial predators is a real risk but so far it has been largely absent. I have chosen my words carefully, as this evening two tern chicks were taken in quick succession by a hungry adult male Mediterranean Gull. Maybe he is the same bird which predated chicks for a couple of weeks last summer. After his chick feast he flew to South Binness Island in the main Langstone Harbour where some 400 pairs of Mediterranean Gulls are nesting. The tern chicks need to grow up fast! Earlier this month I had seen a Mediterranean Gull take eggs from the colony, on each occasion apparently stray eggs from the bare shingle (of which there are a scattering, if you look really closely through a telescope). On Saturday I watched an visiting adult Lesser Black-backed Gull take two Black-headed Gull chicks from the colony.

The young Black-headed Gulls have grown fast, and the first one has already fledged. The following images show how developed some of the larger fledglings are (click on each one to enlarge them). The one in the first image is looking out over the lagoon waters just prior to taking its first fluttery flight on Sunday.



Many more young will have fledged by this time next week. But, as there are still a few birds still on eggs, and a few very small chicks, the fledging season will be protracted. Already more and more broods are moving away from the lagoon islands and ending up around the edge of the lagoon or in the sheltered bay just to the south.

For a complete picture story of the progress of the various species on the Oysterbeds this summer please visit Peter Drury's excellent photo gallery.

Just a little bit of bad news for the Oystercatchers. One of the three pairs nesting on the North Island has failed within 48 hours of successfully hatching one chick. Exact cause unknown, but a similar thing happened to this pair last year. There are two pairs still on eggs. The pair on South Island still have their one youngster, which has already got into the high tide roosting habit of its parents (rather than trying to snuggle under the wings or body of mum!).

A tern for the better

Tuesday, 15 June 2010

Sorry, I couldn't resist the media-like headline! But it does sum it up quite well. The weekend was a success for the birds at the Oysterbeds. More of the clutches of Common Tern eggs hatched and, up until late yesterday evening, all of the adults that had hatched young still had some or all of their family. There are plenty of broods of two and three young. In fact, Sunday gave me an opportunity to count pretty much all of the young chicks as the adults kept coming and going to feed them. The final tallies were: 80 pairs nesting; 46 pairs with young; at least 104 young including 16 broods of three. It was too windy yesterday to establish comparative numbers after another 24 hours but at least three more clutches had hatched.

From a predators viewpoint all these chicks are potential food packages. In effect, the islands in the lagoon are currently a natural fast-food restaurant ready to be turned into a take away by any hungry predator! One worrying aspect of the weather at the moment is the wind strength. This makes finding food for the terns more difficult, and both adults will more often leave the chicks 'home alone' to find food for them, this exposing them to increased chances of avian predation (in this case, gulls). Once again, as one day last week, I noticed that in the moderate breeze of yesterday more of the food items being bought back to the colony and fed to the chicks were tiny flat fish rather than slender (and easier-to-swallow) silvery fish.

I have provided some artificial shelters for the chicks. These are just simple constructions of wood that were placed close to individual nests. Already by Sunday several of these shelters (there are nine in all) were being used by tern chicks. I watched one chick disappear into the darkness of one (an upturned V-shaped shelter with a peak of about 20 centimeters) only to scamper out, like a starving clockwork Gremlin, when it saw that its siblings were being fed by dad!

Mediterranean Gulls continue to provide a threat to the chicks, and yesterday evening I witnessed, for a third time recently, an adult patrol the colony and leave with a stray gull egg. It could easily have been a tern chick. They need to grow fast to reduce their risk of predation from Med Gulls.

The Oystercatchers on South Island lost one of their chicks last Thursday night/Friday morning. I'm not sure why, but a proportion of wader chicks do seem to die in their third day of life. This may be because they never learn to feed properly and, once their post-hatching energy resources are used up, they perish. The remaining chick seems to be doing well. Oystercatchers are very good attentive parents and bring in fresh food for their young. This is unusual for a species of wader. Most wader chicks learn to feed for themselves within hours of hatching. Oystercatchers learn very slowly, and are fed right up until and often after fledging by both parents, predominantly the male to begin with. As well as feeding on worms, they feed on crustaceans and shellfish such as crabs, cockles and clams. The skills needed to crack the shell of a cockle and prize the contents out are learned. I have seen juveniles, fledged in August, still begging for food from their parents in October. Worms form the staple diet of these younger, inexperienced birds.