Burhou, Alderney

19 – 21 July 2014

For the first time in six years we were going to Burhou to try to assess Storm Petrel numbers on the island. With only three qualified ringers (Chris Mourant, Ian Buxton and PKV), one trainee (Phil Alexander) and two AWT staff (Tim Morley and Nicci Cox) we could not replicate the work of previous visits when eight 18 metre nets had been operated on two consecutive nights. However, we planned to set four nets per night, all at the north-eastern end of the island.

Chris Mourant, Phil Alexander and I caught the Bumblebee ferry service to Alderney leaving St Peter Port at 0730 on the Saturday morning. The crossing was very smooth and we were soon in Alderney, where members of AWT met us and stored our gear. This then enabled a breakfast at the mobile café on the harbour. Here we learned that the AWT boat (Sula of Braye) had suffered an engine problem the day before, and alternative arrangements were going to have to be made to get us out to Burhou. This meant that we had most of the day in Alderney.

This was in effect a bit of a bonus for me as it enabled some ring reading of the gull flocks on Crabby Beach, although the high tide and early part of the day meant that the flocks were always quite small. Nevertheless a very valuable 33 colour ring reads were taken, with another five added at a field just behind Platte Saline Beach. The majority of reads were Lesser Black-backed Gulls (LBBGs), but it was very satisfying to record the Lithuanian-ringed Black-headed Gull Black P547 back on Alderney for at least its fourth autumn/winter.

After a hot lunch on Alderney (another bonus!) there was time for some more ring reading at Crabby (another 16 gull reads), before we set off in the harbour RIB at 4 p.m. It was a quick blast across the Swinge to Burhou, where we were able to pull up along the gulley and unload in some comfort!

Once settled in to the hut, and after a quick brew of tea, I set off to record more ring reads from the gulls on Burhou. There is little point in colour ringing gulls unless effort is put in to record them, and it is particularly valuable to be able to read rings at the birds’ nesting colonies. This is why, unlike the first few years of the gull colour ringing on Burhou when all the effort was put in to ringing new birds, I always ensure that I spend a good amount of time reading rings of the nesting birds. My efforts were richly rewarded with 83 gull colour rings – the vast majority of which were LBBGs, but the total did include 14 Herring Gulls!

During tea breaks we ringed our first four well-grown LBBG chicks near the hut garden. Just before dusk we set off to erect the four nets. Initially we planned to put them on the eastern side of the north gulley…but given the remarkably calm conditions we decided to run the nets in a SE direction from the north-east end of the island.

Just on dusk Chris checked the nets and when he came back with a bird I assumed it to be a Rock Pipit. He passed the bag to me…and I got a really pleasant surprise when I extracted a juvenile Grasshopper Warbler…clearly the post-juvenile dispersal/migration has started! By 10.30 p.m. it was well dark (with the crescent moon not yet risen in the night sky). Our first round of the nets produced the first few Storm Petrels…but there was little time to spend admiring them, as very soon the petrels were coming in thick and fast.

The team was working flat out to keep pace with the birds being caught in the four nets. It was marvellous to see so much Storm Petrel activity on Burhou. Clearly the petrels are still doing very well on this island!

It proved to be a very hard night’s work for the whole team…but because we were so busy time flew by…and before we knew it we had caught over 300 petrels (251 new and c 50 retraps including four French and four British-ringed birds!). By 3.00 a.m. we noticed that several of the birds ringed earlier in the night were getting re-caught as they attempted to come ashore. In view of this we furled the nets and packed up for the night…extremely contented with an amazing night’s ringing! I don’t think any of us had even dreamed of catching so many Storm Petrels. It beggars belief how many birds we would have caught if we’d been able to take a full team of qualified ringers and operated the usual eight 18 metre nets!

After a very short night’s sleep we were all up for breakfast and (more importantly) several cups of tea. Having seen quite a few large un-ringed LBBG chicks running around, we took a decision to very carefully enter the LBBG colony again to see if there was a decent number of chicks still to ring. The previous weekend we had ringed 209 LBBG chicks, many of which had been very advanced.

It was considerably easier work with a team of six people (as opposed to the usual  three), and it was soon evident that not only could we safely re-enter the colonies, but there were enough unringed chicks in them to make this a sensible thing to do. It took around half a day to work the main parts of the colonies, but in the process we ringed another 67 LBBG chicks (bringing the 2014 grand total of chicks for Burhou to 276, only a few birds short of the number ringed in the very good year of 2009). Only one chick was too small to take a metal ring.

Although we found a reasonable number of chicks we had ringed the previous week, there were many birds (c 100?) that we never found on this trip. Undoubtedly some of these had fledged (as fledged LBBGs were seen flying well on both Burhou and Alderney…and indeed across the Swinge in between), but there must have been other ringed birds that we simply did not find despite the larger team this time. Whatever…having the bonus of the Storm Petrel trip as well this year (with its later timing and larger team) did also produce some very valuable bonuses for the LBBG studies (in terms of additional chicks ringed and colour ring reads taken).

The only disappointing aspect of the gull work this time was the surprising failure of the cage trap to catch fully-grown gulls. In fact despite baiting and setting the trap three times we only caught one LBBG in it…despite having 150+ gulls feeding all around it (and indeed in it when it was not set). Considering the effort involved in getting this trap to Burhou it questions whether we should simply revert to nest trapping again during a single visit next late May, as it is important for the study to ring a reasonable sample (c 50) of adults in the colony each year.

In the early evening, while Tim Morley and Nicci Cox of AWT went over to Little Burhou to check on the rat sticks (to assess whether any mammals are resident on the islet), Ian Buxton and I joined them to see if there were any gull chicks to ring. We managed to locate and ring three Herring Gull chicks and two Great Black-backed Gull chicks, but all were virtually fledged. Single chicks of each species were found which were too large even to try to capture.

With more breeze for the second night, but still dry and dark conditions, we decided to erect only three nets for the Storm Petrels. These were set running up the gulley at the north-east end of the island. We ringed right through until 3 a.m. again, but with the wind rising and the nets beginning to blow to an uncomfortable level we furled and went back for some tea. On this night we caught 99 new Storm Petrels and several more retraps (including another British-ringed bird).

The grand total of Storm Petrels ringed with just four nets on the first night and three on the second was 451 birds (350 new, 92 retraps and nine foreign controls). At least one of the retraps was 20 years old, and several were 13 years or older. This really was an amazing level of success, and bodes very well for the Storm Petrel population on the island. Hopefully the data we obtained on this trip will enable Phil Atkinson of the BTO to put the figures through a population model to gain some insight in to the current population levels on Burhou. Phil’s last assessment of the population in 2008 using capture/recapture of ringed birds was 2,800 birds. This is certainly a lot more representative of the true population than the 40 pairs recorded by tape playback methods.

Before the boat picked us up at mid-day the following day there was time for me to get some more ring reading completed (another 36 reads including an old adult LBBG from Suffolk, which was originally ringed as a chick in July 2000). Ian, Chris and Tim managed to ring then last three Shag pulli left on Burhou, before we packed up and returned to Alderney.

Back on the mainland there was time for some well-earned drinks and a hot lunch, before some more ring reading at Crabby Beach and the ploughed field just behind Platte Saline Beach. With another 33 ring reads in the book, it was time to return to Alderney airport for our 17.20 flight home.

This had been a very successful trip to Burhou and Alderney on several important fronts…and it was indeed a most fitting way to conclude a very long and strenuous season of seabird monitoring and ringing.

 

PKV

24 July 2014