Saturday, 21 August 2010

A fortuitous date with Risso's

Having fled Mousa on Thursday afternoon due to the severe weather that was forecast, I was relieved to wake up to a bright, calm and even sunny (!) morning on Friday, enabling a return to Mousa. However, I rapidly began to get anxious and frustrated, when, having arrived at the boat for a 10.30am departure, we were still sat on the boat at the pier after 11am waiting for a cruise-boat load of tourists to arrive. Fortunately though, this turned in our favour as news came in of a pod of Risso’s dolphins in Mousa Sound making their way north – in our direction. Having just received a call to say the tourists would still not be there for another half an hour, Tom, the Mousa Ferry operator, very kindly took us out into the Sound in search of the pod. Within just 5 minutes, we had spotted and caught up with the animals. There were between 20 and 30 individuals, including at least 3 calves. It was hard to tell quite how many there were in total as they were all quite loosely aggregated across a wide area. We observed several individuals half-breaching out of the water and some tail-slapping too. All in all, it was a stunning display and more than worth a belated return to Mousa. Thanks very much to Tom, and his right-hand man Willie, for taking us out to enjoy these spectacular animals in such a responsible manner.

Adult Risso's dolphin with calf in Mousa Sound (Rob Fray)

Radio Gaga

Due to the challenges associated with studying birds that only return to land at night and nest out of sight in cavities, we know little about the extent and frequency of movements of breeding birds around the colony. Do birds fly directly to their nest-site on return to the colony? Or, do they range more widely throughout the colony? Storm-petrels typically undertake incubation shifts of 3-5 days’ duration and, it is assumed during this time, the off-duty partner remains far out at sea, foraging; however, might birds sometimes forage more locally and return to the colony on nights when change-overs do not occur? When incubating an egg or brooding a chick, does the bird ever leave the nest during each shift or does it sit tight for that whole time?

Radio-tags have been deployed on 6 adult birds in a trial project to help to start to answer some of these questions. Radio-tags consist of a small battery (10x4x3mm) with an attached antenna. Each tag is programmed to emit a radio pulse at a set frequency. By attaching tags of different frequencies to different birds, individuals can be detected and recorded using aerials mounted on posts within the colony and automated recording units. The units constantly search for the frequencies of the 6 tags that have been deployed; when one is detected, this is recorded, along with the time and date and signal strength, which is relative to the distance the bird is from the tracking system.

Radio-tags - the aerial on one has been cut down to a reduced length, ready for deployment on a stormie

The remote recording unit is attached to a power supply and an aerial (Biotrack Ltd)

Each tag weighs less than 0.6g and was mounted at the base of the four central tail feathers using Tesa© tape. A tag of such a small size will have minimal impact on the flight capability of a bird. The aerial was cut down to less than 7cm reducing any chance of snagging on rocks and limiting the detection range of a tag to less than 100m from a recording unit. Following repeated contact with salt water, the tape will gradually lose adhesion and detach over the course of a few weeks.

Attaching a radio-tag to the tail feathers (Hannah Watson)

Tags were deployed to birds whose nest locations are known, allowing us to monitor chick growth rate and subsequent breeding success to verify that the tags do not have any significant impact on birds. The current aims are to trial the equipment, determine how long tags last for and verify that there are no significant effects of the tags on birds. Next year, it is hoped that more tags will be deployed earlier in the season, during incubation, to obtain more detailed information about patterns of movement of breeding stormies within the colony.

Stormie with radio-tag attached (Hannah Watson)

Tuesday, 17 August 2010

A slight diversion...

A rare sighting was reported, this weekend, of a storm-petrel researcher, not only leaving the island of Mousa, but venturing further north than Lerwick! Two lovely days were enjoyed exploring the isle of Unst, the most northerly part of the UK. Unfortunately, I didn’t reveal any rare sightings of my own, not that I was really trying very hard at all, but a leisurely time was had involving a spot of botanising at the Keen of Hamar, marvelling at thousands of gannets at Hermaness, eating garlic-soaked langoustines and dipping cafes and brewerys. Sightings were limited but included Edmonston’s Chickweed, 2 Great Northern Divers (one in stunning summer plumage) and a sleeping otter (which my mum almost stood on!) on Ham Beach (by Muness Castle), 25+ Ruff feeding in fields around Muness Castle, and 1 Black-tailed Godwit on beach on Uyeasound.

Mousa escapee

Keen of Hamar

Slender St John's Wort Hypericum pulchrum

Edmonstons Chickweed Cerastium nigrescens, endemic to Unst

Field Gentian Gentianella campestris

Hermaness - the UK's most northerly nature reserve

Muckle Flugga - home to the UK's most northerly lighthouse - and just a few gannets on the adjacent rocks

Sundew Drosera rotundifolia

Peacefully sleeping otter, Ham Beach, Muness

Sunday, 15 August 2010

Joke of a July

Wet and wild...that pretty much sums up July on Mousa. So much for it being summer. And, everyone keeps telling me how wonderful last summer in Shetland was. Funnily, that doesn’t make me feel any better. While this has not necessarily affected data collection, it has made work pretty miserable at times. Very few additional nests were added to the study sample since the end of June; when you rely on sound to find nests, relentless wind and rain is somewhat of a impediment.

North-easterly winds and relentless rain pound the east coast of Mousa 

Unsurprisingly, much of July was spent holed up our small stone bothy – the only means of shelter on the island. And, what else is there to do but much on crisps, chocolate and cheese (the foods of choice on Mousa) and warm the red wine on the stove (it’s far from ideal drinking temperature otherwise).
Another consequence of the atrocious weather has also been long stints on the island without a break and days on end without seeing another soul. It’s a good thing the stormie “team” (this term used loosely since it’s just the two of us) get on so well and share the same tastes in food, drink and music. Tom, the ferry operator, might expect to lose a couple of days here and there due to weather in July; in the first 17 days of the month, however, he only made it over on 7 of those days. Things picked up a little bit in the latter half of July, but there were still many days where the weather prevented him from making the journey over.

Making the most of it...huddling in the relative warmth and comfort of the bothy, with a beer in hand, 
while gazing out into the fog

When we finally made it off for just a day and a night, it was such a rush to get back that we managed to forget bread, butter and wine! Then stranded again, we feared we may have to call in the coastguard to do an emergency drop. Though, I’m not quite sure any of those items would quite constitute an emergency in their eyes.

Dark skies gather over the mainland
The tents were abandoned long ago for fear of being blown to Norway and instead we sought refuge in the bothy and have not ventured to erect tents again since. At least in here, we have shelter from the howling wind and the lashing rain. Or so we thought, until one morning I woke up in a pool of water! Perhaps someone would be so kind to come and fit some new doors to the bothy, which don’t have several inches between the bottom of the door and the ground? And, another mattress would be nice too...wink wink.

Julie wrings out the rather soggy cushions that constituted my bed!

Monday, 9 August 2010

The last 48 hours has seen us consumed by a vast swathe of midges, zero geolocators deployed on stormies (boo), 6 radio-tags deployed on stormies (hurrah), Han consume a bowl of cereal using a spoon with a 60cm-long handle (which had previously been used for removing storm-petrel chicks from nests), our first deceased stormie chick (sniff sniff), Julie tell a joke to a sheep (it didn't laugh, but I did when she recounted it - at both the joke and the tale), 1 Whimbrel, 1 otter fishing in West Ham and 2 hooded crows creating a racket at God knows what hour of the morning! And, very little case that wasn't obvious. Needless to say, we have now escaped the island for a much-needed break. An update on the radio-tagging to follow shortly...

Wednesday, 4 August 2010

A glimmer of hope

With a change in the weather today and even a hint of sunshine, I decided to take my bins out to work with me for once. The first sighting of the day was a whopping 7 tents sprawled across the grassy plain just to the north of the broch! So much for having the island all to myself, while my field assistant is on the mainland and the boat is out of the water undergoing repairs. Later, I spotted 14 kayakers hugging the east shore of the island and put two and two together. I’ve been permanently looking over my shoulder the rest of the day, never knowing who might be watching me. Aside from breeding birds, all I could knock up was the spectacular array of 5 Redshank, 4 Turnstone, 1 Rock Dove, 19 Greylag Geese and 3 Hooded Crows! Surely something a little more interesting has got to rock up sometime soon? At least Turnstone is a new one for the garden list.

Oh well, I’ve retired to the bothy with a beer, awaiting darkness and the vague possibility of a glimpse of the Aurora Borealis. I’ve heard on the grapevine that there could be a good chance of catching sight of it from Shetland tonight...

Monday, 2 August 2010

Latest sightings

It's been fairly quiet for birds and, given that the stormie team spend most of their lives flat on the ground staring into crevices in walls, the chances of seeing anything are fairly slim anyway! Knot, sanderling and dunlin were all seen on the West Pool last week (though not by any of us!) and the grey heron was re-sighted on the Mid Loch.
Cetacean sightings have been disappointingly few and far between. Though, the weather has not exactly been amenable over the last month for sea-watching. The odd porpoises are sighted with reasonable regularity and a Minke whale was seen from the Mousa Ferry in Mousa Sound last week (again, of course, none of us saw it!). Orcas have been pretty regular further north, in Yell Sound, throughout July, but no such luck down here. Still waiting to get it on the garden list.

No otters have been seen in the garden (i.e. West Ham) for a couple of weeks, but I was able to get a photo of one the last time we sighted one. Not the greatest photo, but not bad given a small lens and the typical shyness of otters.

Otter feeding on the rocks in front of the bothy (Hannah Watson)

Alamootie update

Out of 165 nest sites that were identified with singing birds in at the beginning of the season, 67 have had an egg laid in them and 25 of those have hatched in the last 2 weeks. About 10 eggs have been lost, so there are hopefully around another 30 eggs waiting to hatch. Chicks that have been left alone by the parents so far, have weighed in at between 13 and 22 g and the tarsus measuring between 13.6 and 17.7 mm long. These chicks have been between 7 and 14 days old. Since chicks don't fledge until they are at least 50 days old (and possibly even until around 70 days old!), the first chicks will not fledge until the beginning of September at the very earliest. It's certainly a long season for the stormies and anyone studying them!

Sunday, 1 August 2010

Chicks Ahoy

The number of chicks is growing daily at the moment, with typically one or two new hatches each day. The chicks are born covered in a layer of down and, unusually, replace this with a second set of downy feathers, before the true feathers begin to grow. Having two sets of down is a unique characteristic of tubenoses and penguins. The bill is well-developed already and the ‘tubes’ (nostrils) on top of the bill are a distinctive characteristic of the tubenoses.

Downy-feathered chick at about 10 days old 
 Due to the poor visibility and accessibility of many stormie nests, detecting a hatch is often not easy. The adult sits tightly on the chick for the first few days. The hatched egg shell may be visible, providing evidence that a chick has hatched. Typically a chick can be heard calling before it is seen.

Chicks are brooded by an adult for maybe 7 to 10 days; after this, the chick is left alone while both parents spend the majority of their time feeding offshore. Once a chick is left alone for the first time, the chick is removed the chick from the nest to weigh and measure it. This will be repeated every 5 days allowing us to monitor chick growth and development. The rate of development can indicate the environmental conditions that the parents or chick are experiencing; for example, slow growth may reflect low food availability or could be related to disturbance experienced by the chick in the nest.

Retrieving a chick from a nest site in a dry-stone wall

Weighing a chick
 A chick may be fed only every 2-3 nights, so its weight fluctuates dramatically depending on when it received its last feed. Weight can thus not tell us as much about growth, so, at first, the length of the tarsus (knee to ankle) is measured which reflects skeletal growth. Once the skeleton is fully grown, at about 30 days old, the feathers will be beginning to grow in and the wing chord will be measured to monitor development further.