Exposed! Seabirds at Sea Team's fieldwork on red-throated divers

 

The red-throated diver is listed on Annex I of the EU Birds Directive as a rare or vulnerable species. In the UK the species breeds only in Scotland and Northern Ireland, with strongholds in Shetland, Orkney and the Hebrides. They mainly breed on small lochans (pools) in open peat moors, but “commute” to forage for small fish at sea.The purpose of this work was to collect information to support the identification of important marine areas for the species during the breeding season, to be put forward as possible Special Protection Areas (SPAs) within the European marine Natura 2000 site network. The survey work involved radio tracking and visual observations of breeding birds, as well as at-sea surveys, and was conducted in collaboration with Scottish Natural Heritage.

 

The advance party (Mark and Neil) spend the week walking through the bogach, scouring the island for birds successfully breeding on small lochans. Even at this early stage, it’s apparent that 2007 is not going to be a good breeding season for the species. Nevertheless, we find a reasonable number of possible breeding pairs to work on.

 

The rest of the team arrive and we move into our main base for the work: a house in Solas with room for the six of us and all our kit. We begin to catch birds to carry radio transmitters; the procedure requires military planning, patience, skill, luck, and calm dry weather. During several days waiting under camouflage nets in tick and midge infested heather, we manage to catch and tag six breeding adults (under license). We only tag birds once they have hatched chicks as they are less likely to abandon the nest; this year many of our possible pairs are still sitting on eggs, so six is pretty good going. We celebrate our success so far with an evening at sea, fishing for mackerel.

 

The only week that the house we rented is not available, so we decamp to two B&Bs next door. Many of our remaining untagged birds on small lochans are failing to hatch eggs and after a couple more attempts it is clear that we’re unlikely to deploy more tags. Still, six would normally be enough to work with and we begin tracking the tagged birds at sea. We start to collect useful data, although one bird has managed to damage its tag, reducing the range of the signal.

 

We return to the house in Solas and a break from the fry-ups! The problems of a poor breeding season are now obvious; lots of pairs are losing chicks to starvation or predation, including most of our tagged birds. We actually witness an otter chomping down one of our chicks! We begin “Plan B” - using visual tracking of birds from large lochs to supplement radio tracking data; this is difficult to achieve, but we know from experience that it can yield results. “Sollas week”; the local week of festivities, provides a welcome distraction in the form of a night down on the machair with the locals, a BBQ, and an impromptu ceilidh.

 

All our tagged birds have now either failed, or fledged their chicks, but we continue to collect visual observations of foraging flights for other pairs. We’re now racing to collect as much data as possible before the season ends! The final part of the work is a survey of diver numbers and distribution in surrounding inshore waters. We have a brilliant final day at sea and in addition to completing our survey, we have fantastic sightings of white-tailed sea eagles, a black-throated diver, minke whales, and a family of otters - probably well fed on diver chicks! Thanks to everyone’s hard work we’ve managed to overcome the difficulties of a really poor breeding season and come away with some useful data. Just time for a celebratory feast at the Tigh Dearg Hotel, before we head home…