Friday, 6 July 2018

The mysterious life of a Guillemot field worker

In 1972 Tim Birkhead (now a professor at Sheffield University) came to Skomer to study the Guillemots (Uria aalge) for his doctoral studies. Back then the Guillemot population on Skomer had declined dramatically from around 100,000 pairs in the 1930s to just 2,000 pairs in the 1970s (likely due to oil spills during WWII). Tim initially set out to understand the dynamics of the declining Guillemot population on Skomer.

Each year a Guillemot field worker arrives on Skomer in April to continue the project. These elusive creatures spend most of their time at the Amos in the company of around 2,500 Guillemots. The season begins with re-sighting of individually colour ringed Guillemots to enable estimates of annual survival. Then as breeding pairs start to form, a sample of around 100 breeding sites are mapped and their progress monitored throughout the season. This includes recording the timing of egg laying, chick hatching, fledging and breeding success.

A Guillemot with Sand Eel
Now over 40 years later, and what started as a three year doctoral study has become an incredibly valuable long-term monitoring project. The Guillemot population on Skomer is now around 25,000 individuals and the main aims of the project are: 1) to understand the population biology of Guillemots and, 2) to provide a robust monitoring system to document population changes.

A Guillemot field worker in her natural habitat

Once the chicks have hatched their diet is recorded over a 13 day period by identifying fish in the adults’ bill before it is fed to a chick. The grand finale of the season occurs in late June and involves the arrival of Tim, his ringing team and lots of climbing gear. This means it’s time to abseil onto the Amos where we colour ring around 300 Guillemot chicks and collect fish samples.

The Guillemot colony at the Amos

This year was a slow start with fog, wind and rain but gradually the Guillemots arrived and faithfully returned to their respective breeding ledges. The first egg of the season was seen on 1st May. When drawing comparisons we use the median lay date as this is a more accurate representation of what’s going on. This year the median lay date was 11th May which is 6 days later than in 2017. Often the first egg is an outlier and tends to be lost, however, this year it survived to yield the first chick which was seen on 31st May. The median hatch date was 13th June which is 7 days later than in 2017. In comparison to last year, chicks were fed more sprat and but fewer sandeels and Gadids (cod). This is a promising finding as sprats are a much higher quality prey.

The ringing team

A Guillemot chick
Long-term studies, like the Guillemot project, are highly valuable because they enable us to study individuals throughout their lifetime (the oldest Guillemot in the study is 33 years old) and investigate questions that weren’t even considered when the project started. Importantly, long-term studies enable us to investigate how populations respond to change before the change has occurred so we get the full picture.

Unfortunately in 2014, the funding for this project was cut and it has since relied upon donations. To find out more and help secure the future of this invaluable study please visit:

By Hannah Meinertzhagen – Guillemot field worker

Tuesday, 19 June 2018

Whole Island Seabird Counts and Shearwater Census

I am on Skomer for three weeks now. June is the busiest month on the island with visitors and breeding birds. As Seabird Volunteer I am an extra help for the main breeding season.

My name is Magdalena (Magda). I am from the northern part of Germany and currently studying Biology at the University of Hamburg. For my master’s thesis I analyse the foraging behaviour of two different wader species in the Wadden Sea: the Dunlin and the Red Knot.

I always wanted to go to an Island for a longer period to get inside on what is required to keep a place like Skomer running. Normally you must stay for at least three months. Being on Skomer as the Seabird Volunteer is a nice opportunity for me to live on an Island for five weeks, to learn more about monitoring birds and to get experience in practical conservation.

South Haven: Bluebells and Red Campion on South Plateau

When I first arrived on Skomer the Bluebells and the Red Campion were forming a blue pinkish carpet on the whole Island. Many butterflies and moths can be found and, of course, there are the birds!I am involved in everything which is connected to the whole island seabird counts - including counts from a boat, counts from land, the Manx Shearwater census and data entry. But of course, there are more things were help is needed e.g. chicks of many bird species get ringed.

Seabird boat counts with perfect weather

The Manx Shearwater census has a special addition this year. Apart from the annual census there is a whole island census, which recently came to an end. The whole island census had about 300 plots and there were six people who spend one to three weeks on the Island only for the census. In total they invested about 500 men hours crawling over the Island in all weathers.

How does the Manx Shearwater census work?

For the annual census there are 18 plots which we use each year. To find them they are marked with a metal cane and a GPS point. We use 25 m ropes. With the first rope we mark North and each person uses one rope to walk from the cane outwards forming many pie-like pieces.
We work clock wise and, using MP3-players, we play a territorial call of the Manx Shearwater for 10 seconds down every burrow, waiting another 10 seconds for the bird to respond. We use two different clickers - one for a positive response and another one for a negative response. As for burrows, we only count those which have a real breeding chamber and are not only a tunnel. We must make sure that we count burrows with two entrances only as one. Another difficulty is a double response. When there are two birds calling you must find out whether there are two burrows or two birds in one burrow.
Having finished all 18 plots it’s no surprise that some of us can mimic a Manxie call almost perfectly. Or is it because my “hutmate” Dulcie and I hear them all day AND all night...? 

Doing the Shearwater Plots everyone searches their “slice” for burrows

Keeping the motivation up, even when getting soaked

Our evening hobby is Oystercatcher ringing. There are many Oystercatcher breeding pairs on the Island, which all have chicks in a ring-able or almost ring-able age by now. The chicks must be big enough so that the rings don’t go off and if they are to big they might be able to fly and impossible to catch. That’s why the age of one to two weeks is perfect for ringing. But it is very difficult to find them. As soon as they hatch they are relatively mobile and hide under high vegetation. When we see a bird, we must be very fast, if we are to slow they will run and hide otherwise they will crouch. And then we must find the perfectly camouflaged chick, which is impossible if we haven’t seen were it went. Until today we managed to find six of them. All have got new shiny orange and metal bracelets.

Oystercatcher chick with his new rings

There are only two weeks left until I will return to Germany. I am looking forward to the rest of my stay.

Magdalena Behrens (Seabird Volunteer)