Saturday, May 28, 2011

I can't remember the last calm day. But a few birds are still passing through the island, most notably a rather late Short-eared Owl which we found on the South End yesterday morning. A trickle of Sedge Warblers, Chiffchaffs and Spotted Flycatchers, along with a few flyover Redpolls and Swallows, are the only obvious migrants. So attention has turned to our breeding birds and we have been busy locating nests and ringing young. Yesterday we ringed a fantastic brood of three Peregrine chicks which were all a very good size. The masses of Manx Shearwater wings around the nest suggest that the adult birds are doing well at making the most of this abundant source of food.

 The breeding Oystercatcher and Chough were not impressed with the Short-eared Owl. (c) Richard Brown

One of several broods of Pied Wagtails which seem to be doing well in the outbuildings. (c) Richard Brown

Destined to become one of Britain's most hated birds, a robber of nests, a terroriser of bird tables, the subject of daft superstition and the nickname of the greatest Premier League football team. This magpie chick was one of three ringed from a gorse-top nest on the South End and the 59th species to be ringed this year. (c) Richard Brown

Another day, another Puss Moth update. The lads have started their second moult and are emerging with big faces and spotty flanks. (c) Richard Brown

  

Wednesday, May 25, 2011

We've been busy over the past couple of days doing a whole island Oystercatcher census. While walking the entire coastline to map territories and record clutch size, I (Giselle) took the opportunity to photograph a few nests. The amount of scrape lining varies markedly from nest to nest, but what's even more fascinating is the material used to line.


Short pieces of dead gorse twig were used in nests on the South End, where gorse is the predominant vegetation (top middle, bottom right). On the more rocky outcrops, nests were lined with small fragments of rock and shale (top right) and in areas where the sheep have been, a couple of pairs decided to waste not want not and lined their nests with sheep dottle (bottom middle). (c) Giselle Eagle

Some nests have very little lining at all, such as the four-clutcher (top left). A lot of pairs seem to locate their nest scrapes next to a prominent feature such as large boulders, but on a shingle beach, nest location may prove difficult, so one pair has cleverly built their scrape next to a large thrift plant (top middle). And finally, a conservation-irony in the bottom left - one pair that nests on the South of the island always chooses to line their scrape with snapped off pieces of Sharp Rush, a nationally scarce plant species and one of the features of the National Nature Reserve. (c) Giselle Eagle

The strong winds are still with us and landbirds are a little thin on the ground. Spotted Flycatchers remain the most abundant passerine migrant. (c) Richard Brown

Tuesday, May 24, 2011

The Woodchat Shrike seems to have taken up residence above Nant valley and we have been lucky enough to spend quite a lot of time watching it. It appears to be feeding in quite wide circuits, which has kept Rich on his toes trying to photograph it. Or rather off his toes and in a stealthy stomach-crawl through the gorse.

Woodchat Shrike amongst the gorse above Nant (c) Richard Brown

The bird is clearly feeding well and we've been trying to figure out what its been eating. It has taken a few bees and we've also watched it eat a Click Beetle. While Rich was crawling through the gorse, I (Giselle) spotted it coughing up a few pellets. We waited for it to leave its perch then crept in and collected a rather soggy, malformed pellet.

The remains of a Green Tiger Beetle and three grubs are obvious. The rest of the pellet seemed to consist of unidentified beetle remains, mostly legs and wing casings. (c) Richard Brown

Further evidence that the Shrike is feeding well. We wont be rushing to collect this sample. (c) Richard Brown

A quick update on the Puss Moth caterpillars. They're munching through a lot of willow leaves at the moment, and therefore getting much bigger. Since their first instar moult, they've started to turn greener on their flanks. And we still have all 13 of them!

 The rear legs of the Puss Moth Caterpillars have evolved into long whip-like appendages. When the caterpillars sense danger they flail their whips around to deter the predator. They also have the ability to spray formic acid from their heads if the threat remains. (c) Richard Brown

Monday, May 23, 2011

It's exactly a month since we discovered the Ringed Plover nest near Solfach. We covered the nest with a chicken wire cap to prevent the sheep from trampling the three eggs and to keep marauding gulls and crows out of reach of the nest. We left a gap at the bottom just large enough for the incubating adults to pass in and out of but hopefully too small for most predators. This technique proved very successful last year with two pairs fledging seven young from seven eggs. Today we checked the nest at 0830 and there were still three eggs, but when we checked at 1545 the three eggs were missing...

The Ringed Plover nest as we first found it, subtly decorated with scraps of shell. (c) Giselle Eagle

The view looking down through the protective chicken wire mesh this afternoon. Not a scrap of Ringed Plover egg remains. Instead three tiny chicks lay motionless. The adults remove hatched shell to avoid advertising the presence of young. (c) Giselle Eagle

The chicks are amazingly well camouflaged. It was best to find them today, still in the nest, as tomorrow the precocious young will have scurried away into the surrounding pebbles where they would be exceedingly difficult to locate. (c) Richard Brown

The three young were quickly ringed and replaced in the nest where they were immediately joined by both adults. Hopefully ringing these birds will enable us to understand how this little Bardsey population develops. Indeed the female of the pair would appear to be a returning bird from last year and several of last year's young have also revisited the island this spring. (c) Richard Brown 


Saturday, May 21, 2011

We recently received a fantastic letter from a viewer of this blog who lives in Aberdaron, a small village just over the treacherous Bardsey Sound. They had popped out of their garden studio and when they returned a Wryneck was flapping at the inside window. They rescued the bird but as they were returning it to the outdoors it made some bizarre head contortions which caused them to slacken their grip and the bird escaped off into the garden. What a fantastic experience. Wrynecks are a distinctive group of cryptically patterned Woodpeckers which lack the stiff tails that their cousins use when climbing trees.

video
A Wryneck caught on Bardsey a couple of years ago. The amazing head contortions are usually displayed when a bird is disturbed at the nest and act as a threat display. It would seem that the display also works well if the adult bird feels threatened, perhaps startling predators enough to facilitate escape. It has been suggested that this bizarre behaviour led to their use in witchcraft and that the name of their genus, Jynx, and that the act of putting a 'jinx' on someone, may be related. (c) Richard Brown

The Aberdaron record on the 19th of April is the only report from Gwynedd in 2011 and is one of only two Welsh records this year, the other being on Skomer on the 10th of April. 
Just a quick word on what our Little Owls are eating. Historically much has been made of the diet of Little Owls on Welsh Islands, with several papers highlighting the impact they have on species such as the Storm Petrel. A single pair of Little Owls on Skomer had a larder containing more than 100 Stormy corpses. Giselle had a little look at one of our three Little Owl territories and found evidence that they were taking a lot of large ground beatles (pellet in top photo) but also at least one Wheatear and what we think might be a Slow Worm (scales(?) in bottom photo). (c) Richard Brown
Strong winds have again hit the Island. The Woodchat Shrike, and 14 of the 28 Spotted Flycatcher recorded yesterday, remain. Two Reed Warblers and a Cuckoo seem to be the only birds new in.

We have made the most of the few gaps in the weather and managed to access some of the more treacherous areas of the Island. A bit of rope work and we managed to reach the first Chough chicks of the year. We access the nests each year in order to monitor productivity and colour ring the chicks to help ascertain the life histories of each bird. Each chick gets a unique colour combination which can be read in the field and therefore helps ornithologists deduce how birds within a population move and which areas and habitat types are important to conserve. (c) Richard Brown

 We also ringed the first ten Shag chicks of the year as part of our long term monitoring of seabird populations. (c) Richard Brown

Giselle has been caring for our fourteen Puss Moth caterpillars, well, thirteen of them as one mysteriously vanished. But the great news of yesterday and today is that, roughly five days after they hatched, the lads have started to moult into their second instars. This one is just out. (c) Richard Brown

Friday, May 20, 2011

Well it's been a little while coming, but today saw yet another fantastic bird added to what has already been a really satisfying spring. A first-summer female Woodchat Shrike was located in the Northwest Fields during the morning census and was soon twitched by everyone on the island. The bird was feeding well, with bees seeming to form the staple and at one point a massive bumblebee met its demise. It was clear that the bird was preferring a particular stretch of gorse covered wall and was feeding in a loop which frequently included this preferred section. So when the bird was elsewhere we slipped in a couple of spring traps and a box trap baited with juicy meal worms. As the bird returned to its favourite bush above the traps an excited hush fell on us all. Almost immediately the bird perched on top of the box trap, before dropping inside, the weight of the bird closing the door above it. The bird was processed quickly and was found to have good reserves of fat. It is now up on the hill above the Obs and seems to be enjoying the honeybees.

A stunning bird, the first Bardsey record since 2000 and only the 25th for the island! (c) Richard Brown

In the hand the worn brown flight feathers of a first year are distinctive. The buffish feathering in the brownish ear coverts and the dull brown grey mantle both suggest the sex. The extensive white in the wing, extending 13.5mm beyond the primary coverts, show this to be of the nominate race. (c) Richard Brown

It was fantastic to see this beautiful female Little Owl  in the hand. Little Owls have been well studied on Bardsey, with one venerable female being retrapped in 1988 at the age of 10 years 12 days. The oldest Little Owl recorded in Britain was 2 months and 15 days older! (c) Richard Brown

Happily three pairs of Stonechat, two more than last year, have taken up residence on Bardsey. Two pairs have already fledged five young apiece. (c) Richard Brown

Tuesday, May 17, 2011

Do you remember the Puss Moth that I (Gis) found at the beginning of the month? She appeared to be on her last legs, with very worn wings. Another clue that she wasn't very healthy was the fact that she'd laid several eggs on rushes, which aren't the food plant of this species.

Puss Moth with eggs. (c) Richard Brown

As the field was stocked with sheep, we decided to borrow a few of the eggs, to see if they would hatch. Rich had a theory that they might be sterile because he had once found a Northern Eggar, also on its way out, laying eggs in unsuitable habitat, and those eggs hadn't hatched. We took one rush with 14 eggs on, leaving around 30 in the field, and put them in a jam jar with some willow and left them alone. When they still hadn't hatched by the end of the week we were starting to think that Rich was right, but on Sunday morning, not one, not two but three caterpillars were creeping around the top of the jam jar!

 A newly emerged Puss Moth Caterpillar. The long red and orange tail streamers are used as a defence mechanism but take some time to dry and straighten out after they've hatched. Further up the stem is the head of another caterpillar about to hatch! (c) Richard Brown.

All 14 hatched successfully (with the last runty one needing a hand a day later because he had another hatched egg blocking his escape hole).  They're now all munching happily on willow leaves. They should eventually undergo a couple of skin shedding episodes, and turn into the classic green caterpillar off of the famous book 'The Very Hungry Caterpillar'. We wont be feeding pies or cheese to ours though. (c) Richard Brown

Avian wise on the island, it is another ridiculously quiet day, with the apparent highlight being a Yellowhammer at the farm. Yesterday was similar, but we did manage to catch a Moorhen, which was the 50th species to be ringed on the island this year!

I wore an old apron to ring it, as I had been warned that Moorhens have a tendency to leak. They also have a tendency to kick, so it was a refreshing change from the placid Willow Warblers that neither leak nor kick. This one was sexed as a male, based on its wing length and tarsus and toe measurement. It had evidence of juvenile plumage so had hatched sometime last year. (c) Richard Brown

We've had a good ringing year so far, and calm April days meant that many of the passage migrants could be easily mist-netted. A whopping 1143 new birds were ringed in April, with a current total of 1657 so far. Unfortunately the persistent wind at the beginning of May meant we couldn't open the nets, and so few birds were ringed. Now that the wind has died down, it seems there are no birds to catch. But as Rich always tells me, "Le Grande Un travels alone". As his French accent isn't the best, for months I thought he was saying "The Grand Urn Travels alone" and I didn't have the heart to ask what he was on about. Anyway, I digress. Watch this space because le Grande Un is coming!

Saturday, May 14, 2011

The last few days have seen things practically grind to a halt in terms of migrants. Whilst other locations are drooling over the likes of Collared Flycatcher and Trumpeter Finch, we have come down off our Coot-induced high and are left with the smallest of handfuls of common migrants, a single Grasshopper Warbler singing below the Obs probably being the best of the bunch. It's inevitable that, as we trudge away mile after birdless mile, that the eyes occasionally fall to the ground. So we've bumped into a few caterpillars.

Drinker (above) and Six-spot Burnet (below) caterpillars found whilst not finding any birds. The former feeds on a variety of grasses and reeds whilst the latter prefers Bird's-foot Trefoil and clovers. (c) Richard Brown

Eleven Turnstone, some of them rather dapper, arrived in Solfach this morning. Two Dunlin, 19 Whimbrel, a Curlew and the breeding Oiks and Ringed Plovers were the only other waders around. (c) Richard Brown

Spotted Flycatcher numbers have scraped double figures on a couple of days but only three remained during the morning census. (c) Richard Brown

Up to 355 Swallow have been recorded on each of the last few days. (c) Richard Brown

More caterpillars found whilst not finding birds. Northern Eggar (above) are usually found on Heather here, but also on Bramble and other woody shrubs, and a Yellow-tail (below) which will eat Blackthorn and other deciduous trees and shrubs. (c) Richard Brown

The reason we have had no birds attracted to the lighthouse. Despite some heavy rain during the day the nights have remained crystal clear. (c) Richard brown

There appear to be no records of Esperia sulphurella prior to this century, and possibly only one Bardsey record of this species common across the country. It has to be admitted that this is a little stunner, but things are getting desperate when this is the highlight of a morning survey. (c) Richard Brown

Wednesday, May 11, 2011

The big avian news of the day is only the seventh record for Bardsey. But as it was a Coot there is little else to say. We couldn't even string it as a yank. Much more impressive is the Turtle Dove at Nant which is present for its fourth day. Rare in Wales, Turtle Dove isn't too far off being a description species. Otherwise it's a rather quiet day with a few Lesser Redpoll and Goldfinch starting to move again and a reasonable passage of Swallows and House Martins.

Buffeted by the continuing strong winds, the Turtle Dove seems happy to stay low among the ruts in the old cow field. (c) Richard Brown

Now that the trees are all in leaf, Willows in particular are dripping with the silken tent nests of Lackey Moth caterpillars. While Lackey Moths are common across Southern Britain and Central Europe, they've only recently managed to form a stronghold on Bardsey. In 2006 there were only three adult Lackey Moths, all recorded in July, and they had not been noted for seven years previous to that. The first silk tent was found in Nant Withy in 1995. Since their single figure, erratic, occurrences in the late 90's, it seems the small arrival in 2006 was enough to form a colony on Bardsey and several tents were recorded in 2007. I (Giselle) did a count of the silk tents in the Obs Garden yesterday. There are at least 40 nests (that I can see from my height of 5'2) and double figure counts are also present in the Withies and in several of the gardens on the island.

These silken tents are woven by the caterpillars and are used to regulate their temperature, acting as a sort of sleeping bag for them to nestle into on cold days. On warm days they can be seen on top of their tents, basking in the sunshine. (c) Giselle Eagle

Lackey Moths themselves are dull and brown, but the caterpillars make up for this dullness with their fantastic array of blue, yellow and orange stripes. Their retro stripes are an obvious defence mechanism against the hungry passerines. They also have a fake face and have a tendency to wave around when disturbed, both of which must also go some way to deterring predators. It's not always a success, however, as the Golden Oriole was witnessed eating several of this species as it toured the Obs garden at the end of last week. (c) Richard Brown

Sunday, May 8, 2011

Heavy rain and an absent moon in the early hours led to a very dark spell at about 2am. Little in the way of small stuff seemed to be moving with only a Sedge Warbler, a Whitethroat and a Blackbird attracted. But 34 Manx Shearwater circled the tower and I managed to catch and roost 23 of them. The morning census yielded little in the way of new arrivals but the second Turtle Dove of the year toured the island and a few Swifts passed through. A Golden Oriole we found visiting the gardens this afternoon was presumably the bird from two days ago but without views of its right leg there was no way of being certain. Other scarcer visitors included a Pied Flycatcher, four Spotted Flycatcher and a couple of Tree Pipits and Garden Warblers. Two Cuckoos remain, one a singing male and one a probable female antagonising the Meadow Pipits.

The ageing and sexing of Golden Orioles is something that not too many ringers in Britain are lucky enough to have experience of. So this evening I've had time to sieve through the photographs of our recent bird and try to come up with an answer. Both adult and first-year Golden Orioles undergo a virtually full moult in their African wintering grounds. But the young birds are very unusual in that they moult into a plumage which is virtually identical to that which they left the nest with. Adult females can sometimes look similar to these spring birds but there are several features which can be used to identify a second calender-year bird. In the younger birds the greyish white underparts are distinctly streaked, grey on the breast, blacker on the belly (as can be seen on the photographs below); an adult female would typically have only faint streaking on the belly. The yellow along the outermost tail feather would also extend further than shown above if the bird were adult and the central tail feathers would be more rounded. The retained secondaries, although distinctive, are not an ageing criteria as both adults and second calender-years show this feature (although the retention is more frequent in younger birds). The percentages of retained secondaries noted by Jenni and Winkler are S6 25%, S5&6 35%, S4-6 15%, S3-6 15% and S3-7 10%, so our bird falls nicely into the typical pattern. The extensive, stepped, whitish tips to the primary coverts are much more typical of a male bird, but this sexing method is not thought to be 100% accurate. (c) Richard Brown

In the absence of a call, this Tree Pipit was identified on plumage and structure. Quite distinctive here are the short, well curved claws, different to the long, straighter claws of Meadow Pipit. The fine flank streaks are also distinctive, as is the contrast between white belly and buffish breast. The bill is relatively strong and the head pattern shows an eye-ring broken by a dark eye-stripe and a broad super extending behind the eye. There were lots of flies available in places out of the howling wind. (c) Richard Brown