Godin, The Humps, Herm

11 July 2014

Catherine definitely won the title this year for the most creative excuse for withdrawing from a Seabird Monitoring Trip - an Earthquake! Bizarrely it was true too…less than an hour before we were due to leave the harbour our house shook and there was a loud bang. Thinking it was a supersonic aircraft passing overhead I ignored it and carried on getting ready…but soon Catherine’s phone lit up and that was effectively the end of her trip. It was in fact the largest earthquake recorded in the Island for more than a hundred years, with an epicentre just SW of Jersey and a rating of 4.6 on the Richter Scale.

This trip was to be an enjoyable climax to the season on The Humps monitoring the breeding success of the c 40 pairs of Common Terns. Sea Fisheries (Dave Wilkinson and Amy Critchlow) very kindly took Phil Alexander and me out in the RIB, and all looked well as we approached Godin with adult Common Terns calling overhead. However, as soon as we had landed and walked up into the colony it was obvious that the terns had failed. Despite a thorough search of the colony we could not find a single chick, and apart from one intact nest of three eggs, there were only a few eggs which had been gathered together out of the nest scrapes. Most of the eggs had been broken…by rough piercing...but not all the yolks had been eaten. In some eggs there were also remains of chicks…and there was one dead chick in the same area (dead for at least a week to ten days).

My first thought was corvid predation (perhaps a Magpie)…but on reflection this seems most unlikely as in this case the eggs would have been broken open (split eggshells) and the contents devoured. Rat predation seems most unlikely on The Humps and again the manner of the predation/destruction did not resemble rats feeding on the eggs. When shown photographs Chris Mourant commented that he had seen similar type predation of chicken eggs by Hedgehogs…but again this seems most unlikely on such a tiny islet as Godin. Jan Dockerill subsequently sent me a 2011 paper on predation of Common and Roseate Terns by European starlings in the Azores, which may conceivably explain what we saw. I e-mailed the lead author with photos of our visit to see if what we saw is consistent with such predation, but the scene did not resemble predation by starlings either.

If this is not avian or mammalian predation it leaves human interference as a possibility…and this cannot be ruled out. The Common Tern colony on Les Ecrehous, Jersey is known to have suffered human interference from visiting boat owners (believed to be non-local) some years back. Whether many eggs were taken for food and just a few left…or whether this may have been mischievous destruction by youngsters while their parents were moored in the lagoon is of course not known…and in some ways it is best not to speculate on such matters. What is clear, however, is that following a successful first year in 2013, the Common Tern colony on Godin (which had doubled in size this year) has failed. Whether this puts off these notoriously fickle birds from returning to the islet next year remains to be seen.

There were still a few large unfledged Great Cormorants and Great Black-backed Gulls on Godin, but Phil and I restricted this visit to the tern colony as the other seabirds were too large to be able to capture safely for ringing.

Both Phil and I returned to the RIB rather depressed. This was not the happy ending to the 2014 Herm Seabird monitoring that we had imagined. Once again though it does show the importance of monitoring what is happening with our seabirds. Over the next few weeks we will consult seabird experts outside the Islands to see if we can learn anything further on the probable cause of the predation/destruction of tern eggs this year.

 

PKV

15 July 2014

PS We have subsequently learned that several tern species will use specially made nesting boxes...and so this must be worth considering to help improve protection of these beautiful seabirds around Herm.