Thursday, June 30, 2011

Unringed adult Willow Warblers and Chiffchaffs turning up in the gardens (and therefore not our ringed breeding birds) are further indication that autumn is on its way. As is the dispersal of young Whitethroats, phylloscs and Stonechats across the island, some of which no doubt arose from the nearby mainland. A juvenile Blackcap in the heligoland this morning was not of Bardsey origin either. Also not of these parts is a Barnacle Goose x Canada Goose hybrid which has spent the last two days exploring the coast. At sea another dark adult Arctic Skua drifted past and Black-headed Gulls are now daily. The Curlew flock has reached 30 and four Redshank have arrived. The highlight has again not been an avian one...

Giselle found the first Hummingbird Hawkmoth of the year on the 28th. There were then at least five yesterday. These fantastic moths arrive to the UK from Southern France before feeding up on nectar rich flowers such as this Fuchsia. They then lay eggs on Lady's Bedstraw (present on Bardsey in abundance) and produce a second generation later in the summer. These adults may attempt to over-winter (I had one hibernate at my window on Skomer) but they rarely survive (the Skomer individual was dead by March). The 28th also saw the first Rusty-dot Pearl of the year, another immigrant to Britain. (c) Richard Brown

Another surprise yesterday was a second Poplar Hawkmoth caterpillar which hatched on Willow leaves brought in to feed the one remaining Puss Moth and the first Poplar Hawk (the first confirmed Bardsey breeding record). (c) Richard Brown

Tuesday, June 28, 2011

We can't help but think that autumn is just around the corner as, despite the fact that it's still pretty quiet at the moment, a few birds are starting to move away from their breeding grounds. Yesterday we saw a small passage of Swifts, as well as an Arctic Skua, two Sandwich Terns and another Arctic Tern, whilst today a few Willow Warblers and Chiffchaffs had arrived. Although there has been a distinct lack of rarities and scarcities (this month last year saw White-throated Sparrow and Greenish Warbler) it's nice to have a bit more diversity on the morning census!

An adult Arctic Skua headed past the South End this morning and kept spirits high that something good may be lurking around the corner... (c) Richard Brown

...there wasn't, but we probably take these fantastic birds for granted! The West Coast Chough have fledged three chicks that were colour ringed at the beginning of the month. The juveniles already show the black glossy plumage of the adults but their yellowish bills, paler legs and clumsy flight easily sets them apart. (c) Richard Brown

The Puss Moth Caterpillars have all pupated now, and have each made a fantastically disguised chrysalis adorned with chewed up bits of bark and wood. There are seven in total on this chunk of dead wood. (c) Richard Brown

Close-ups of the pupae show just how camouflaged these little critters are. They will now over-winter in this state, emerging as adult Puss Moths in May 2012. (c) Richard Brown

Friday, June 24, 2011

It's eerily quiet on Bardsey with very few migrants around. Three Lapwing were the highlight of yesterday and Curlew numbers are starting to build up, with 19 recorded on the West Coast. Elsewhere on the wader-front the Ringed Plover chicks have fledged, taking their first flights around the Solfach shore-line. The adults were still alarming, which seemed strange when the chicks were flying around elsewhere. A closer look on the shingle, however, revealed another clutch of three eggs, laid in the same scrape as before. The anti-gull cage over the nest site is clearly proving popular with this pair.

An Arctic Tern graced us with its presence yesterday morning, perching on the South End boulders before giving Rich some impressive fly-bys. This is a rather unseasonal record, the bird possibly being a failed breeder. 

Arctic Terns complete what is by far the longest known regular migration of any animal. This individual will be planning a trip down to the Antarctic Oceans for the winter. (c) Richard Brown

The lack of migrants gave us the ideal opportunity to finish the Oystercatcher monitoring. The chicks are getting quite big now and are surprisingly difficult to spot as they hunch down low in rock crevasses. This individual has already started to develop an orange bill, although it has the dark tip typical of a juvenile. As we approached the South End we walked into a strange weather phenomenon...

There was clearly a lot of static in the air... (c) Giselle Eagle

All but two of the Puss Moth caterpillars have pupated, but we are still bringing in fresh Willow for the remaining boys. Eagle-eyed Giselle spotted an intruder in their tank...

Feeding on the same food plant, this caterpillar appears to be that of a Poplar Hawkmoth! This is the first confirmed breeding record of this species on the island. (c) Richard Brown

Monday, June 20, 2011

It has been a little over four weeks since the first of the Puss Moth Caterpillars hatched. We've been struggling to keep up with their willow-cravings, having to bring in larger and larger branches just to see them through the night, and as a result, they've grown exponentially!

The larger they get the pinker their face surrounds become (top), and they also seem to lose interest in their extendible defensive tail. Perhaps they know now that most passing birds would be biting off far more than they could chew. Their rear feet now act as impressively strong suckers and it's almost impossible to move them from a leaf if they don't consent to it. Their brown saddles are unique to each caterpillar, varying in colour and length, and at this stage their fantastic white spots are really well defined. Measuring about 3" long, as modelled by Rich's finger (bottom), surely it wouldn't be much longer before they began to pupate...

...And it wasn't! This is the first of the boys to begin pupation. It's a fascinating act to watch as they spin a dark silky hammock to rest in before chewing off bits of bark to adorn their cocoon in a brilliantly successful attempt at camouflage. It took this caterpillar a good few hours to complete it's disguise. (c) Richard Brown

Continuing with the lepid-love, Six-spot Burnets are now on the wing and jewelling the main track with iridescent metallic greens and reds. Yesterday's transect survey counted a minimum of 177 individuals on the wing, by far the most ever recorded on Bardsey.

No sooner do they hatch, they find a mate and begin creating the next batch of Six-spot Burnets. The eggs will hatch this year and over-winter as larvae. Their vivid colours, like many lepidoptera, serve as a defence mechanism to deter predators from eating them...

...but this male Whitethroat clearly isn't fooled, particularly as he has a brood of hungry chicks to keep quiet. (c) Richard Brown

Rich left at 5am this morning to begin the last whole island census of the year. This Skylark is one of the parent birds of the brood we ringed yesterday and is clearly finding plenty food amongst the fields of the West Coast. (c) Richard Brown

At least 13 fledgling Wheatears are now chacking around the island. (c) Richard Brown

Sunday, June 19, 2011

Single Spotted Flycatcher and Blackcap, along with two Sand Martins, gave a glimmer of hope that some birds were moving, but nothing else materialised. A further 31 Swallow pulli were ringed, as were the first Skylarks of the year.

The clutch of five will all have hatched within eight hours of each other. The young are fed almost immediately by the incubating female and the male brings food within the first two hours. The blind chicks open their wide black and yellow gapes in response to a feeding call given by the adults. Their eyes open on the fourth day from when the chicks also begin to call for food. On the fifth day the chicks will leave the nest to collect food from the incoming parent but will always return to the nest. Over the next couple of days they venture further from the nest but return to roost. After about eight or nine days the young will spontaneously leave the nest, although sometimes lured by calls from the adults. (c) Richard Brown

The chicks are amazingly well camouflaged, but this is not the only way that they avoid bringing unwanted attention to themselves. They produce convenient faecal sacks so as to not litter the nest area with their bright white poo. The adults will actually eat these sacks when the chicks are small! As the chicks, and sacks, get larger the adults begin to collect the deposits and fly them away from the nest area. (c) Richard Brown

Friday, June 17, 2011

Yet another run of migrant free days has really made it feel like spring is over, but we are still very busy monitoring our breeding birds. Six young Blue Tits are in the Obs garden (since the Obs was founded in 1953 only one Blue Tit has fledged, at Nant in 1989) and fledged Willow Warbler are in Cristin Withy, the Obs garden and at Nant (this species has only bred nine times in the same period). The severity of last winter must have played a big part in the decline in numbers of our commoner breeding landbirds but productivity seems to be very good in the most-part and the gardens are alive with the calls of young Dunnocks, Wrens, Pied Wagtails, Robins, Chaffinches and Blackbirds. Elsewhere fledged Meadow Pipits, LinnetsWheatears and Stonechats are conspicuous. The first fledged Peregrines and Chough have now joined the fledgling Ravens on the thermals above the mountain. A few of our landbirds are yet to fledge young but it is looking like this wont be the case for long...

Both Whitethroats and Sedge Warblers are currently feeding young. There are more pairs of Sedge Warbler breeding than ever before and Whitethroats are back up to four pairs after a few lean years. (c) Richard Brown

Gannets, the largest indigenous seabirds in the Western Palearctic, do not breed on Bardsey, indeed the closest colony is probably Grassholm in Pembrokeshire where about 30,000 pairs breed. But we do see them in varying numbers virtually every day around our shoreline. Today they were fishing close inshore whilst we were counting Oystercatcher territories. (c) Richard Brown

It was great to spend time watching the Gannets fish. They were working in a short circuit, doubling back after a dive to scan what was proving a productive area of sea. It was obvious when a bird had spotted its target, their heads fixing a point in the water as they flew. Gannets have their eyes positioned far enough forward on their faces to give them binocular vision which helps to accurately judge the distance to their prey. After fixing a target, their heads remained near motionless as their bodies cartwheeled around above them to start the dive. (c) Richard Brown

Gannets can dive from up to 30m above sea-level and reach speeds of up to 100km/h as they strike the water. They have special adaptations to deal with this fishing technique including air sacs positioned under the skin of their face and chest which act as a cushion when they impact the water and an absence of external nostrils to stop water from being forced into their lungs. (c) Richard Brown

Wednesday, June 15, 2011

On Monday we decided to take a brief break from traversing the steep and rocky East Side for seabirds and made the most of the warm, sunny weather by beginning the annual Swallow monitoring on the island. 

Creeping around in barns and old pig sties was worth it with 19 pairs recorded in total. Of those 19 two had lined nests but not yet laid, leaving a count of 34 eggs and 27+ young from the remaining 17 pairs. Upon arriving back from their South African wintering grounds, Swallows make repairs to old nests, before lining them with straw, feathers and wool in which to lay their eggs (above). Most of the chicks we recorded were just hatched and therefore too small to ring (middle), but one pair at the farm must have started earlier than the rest and four suitably sized chicks were ringed (bottom). The ringing of chicks has shown that most British Swallows set up territories within 30km of where they themselves hatched. (c) Richard Brown

Oystercatcher chicks have started to hatch all over the island. The parent bird's alarm calls cause the chicks to crouch low to the ground, under or near vegetation. Some are easier to find than others and we couldn't help but wonder if this one thought that it was well hidden because it had its head covered. (c) Richard Brown

A visit to Seal Cave, our largest Razorbill colony, proved fruitful with about 80 birds ringed. Productivity seems to be acceptable but at least one pair of Herring Gulls are specialising in taking the helpless chicks. The breeding season has been quite protracted this year with many adults still incubating eggs, several recently hatched young (such as the one above), but also many chicks which have already fledged (at about 18 days old). (c) Richard Brown

A Collared Dove taken in the Cristin Heligoland became the 69th species to be ringed this year. Despite the daily occurrence of flocks numbering up to ten individuals at the moment, this species continues to prove very difficult to catch. Indeed this was only the 51st to be ringed in the 58 year history of the Obs. These wandering birds, of which the majority are birds which have fledged this year, are most likely visitors from the farms of the nearby mainland where they are numerous. Collared Doves can breed in the year in which they hatch, so these fledged young, already moulting their wings and body feathers so that they are indistinguishable from older birds, may be nesting soon. Collared Doves have only nested once on Bardsey, an attempt which soon failed. (c) Richard Brown

Giselle found this July Belle whilst we were searching for Oystercatcher chicks among the Gorse of the South End, which was not much of a surprise as Gorse is the larval foodplant. More of a surprise is that it is only the second Bardsey record since 1999. (c) Giselle Eagle

Sunday, June 12, 2011

A fantastic calm and sunny day yesterday meant that we could get around the steep north and east sides of the island to continue the seabird monitoring. The gull colonies were first on our hit list, with Herring Gull chicks plentiful and easy to locate on the rocky outcrops. It became more of a challenge as we entered the Lesser Black-backed Gull colony as they tend to hide their chicks amongst the dense bracken and nettle beds. Lesser Black-backed Gulls form monogamous pairs and, although nesting colonially, defend their territory fiercely. It's important, therefore, that there is sufficient vegetative cover within each territory as exposed wandering chicks will often be pecked to death by neighbouring adults. Parent birds have a series of key-calls that act as commands to their chicks. A 'Kaw' call causes the chick to run and hide in cover, whereas a 'Mew' call summons the chick to come out and feed and a 'Kowp' call summons the chick to return to the nest to be brooded.

This Lesser Black-backed Gull has just finished an exhausting hatching session. It will initially take food from inside its parents' bill by pecking at the red bill-spot, but when older it will usually eat food off the ground when brought in by parent birds. (c) Richard Brown

Where Herring Gull and Lesser Black-backed Gull colonies overlap it can be difficult to differentiate between young chicks of the two species due to their similar size and almost identical downy patterning. A chick only a few days old (above) cannot be accurately identified until it's primaries have started to grow (below). A Herring Gull at this stage would show pale inner primaries, a key feature when separating fledged juveniles in flight. (c) Richard Brown

We continued on our gull-fest with perhaps the most docile of gull species. The adults are fantastic in the hand and upon release return immediately to their nest ledges. Kittiwakes begin nesting much later than Lesser Black-backed Gulls so it will be a couple of weeks before we can get in to ring the chicks. 
(c) Richard Brown

 Razorbills and Guillemots nest together in the boulder fields of the East Side and the chicks are often to be found side by side. They're easily identifiable, however, with Razorbills almost immediately showing the diagnostic white facial stripe of the adult. Guillemot chicks (above) have dark heads with paler flecks to the ends of their down whereas Razorbill chicks (below) have pale silvery heads. (c) Giselle Eagle

Razorbills fledge at only 18 days old while still flightless. Fledging usually occurs in the evening, when the adult bird leads the chick out of the boulders. Before this, the chick may have moved no more than 30cm away from its nest site. They call excitedly to each other, and the chick follows the parent bird (almost invariably the male) dropping down across boulders before eventually entering the sea. Once in the water the chick swims close to the side of the adult and together they swim silently out to sea. This chick, photographed only yesterday, will probably fledge this evening. (c) Richard Brown

Another update on the boys! Most of them have undergone their final moult before pupation. They've developed stunning white circles along their flanks, huge bright pink head surrounds with fake eyes, fantastically striped feet and their adapted legs have developed black spots (below), squirting out huge red warning streamers when under threat. Their moulted skins are left as a white papery deposit on the leaf on which they moult (above) and we have seen one of the lads eating the skin. (c) Richard Brown