12 weeks of fieldwork along the Swedish coast

This years field season started May 1 and ran until mid-July. It was the result of collaboration with BirdLife Sweden. The main goal was to attach GPS loggers to Caspian terns and lesser black-backed gulls, both adults and juveniles.
The purpose?
To find out how/when/where they forage and migrate in order not only to increase our basic knowledge about these (in Sweden) endangered seabirds but also to better inform lawmakers on how and where to protect them. Some ‘bonus’ species where supplementary data was required from past years included great black-backed gull, herring gull, common and black guillemot, and razorbills. For this season I was based mainly in Fågelsundet, Uppland, Sweden but as the terns and gulls have colonies all over the country there were many long trips along the coast from Furö, Småland in the South to Rödkallen, Norrbotten, in the North.

The beginning of the season was spent brushing up on manuals for all the different loggers that are currently on birds and will be put on birds, manufacturing and mending traps, checking base station components, purchasing tools, etc. We got a shipment of over 45 GPS/GSM loggers in mid-May, all of which needed to be tested and prepped for deployment. I got some help with this from Martin Beal who was over for 2 weeks.

This seasons assortment of loggers, some old, some very new.

Fine-tuning harness attachment…who knew bananas would come in handy?

The first animals we caught and attached loggers to in May were some of the bonus species, great black-backed gull and herring gull as they are the earliest breeders of the bunch we work with. Great black-backed gulls are the largest birds I’ve ever worked with and I’m very grateful to Lennart Söderlund, local collaborator at Fågelsundet, who took the brunt of the blows delivered by their heavy beaks.      

One of this year’s bonus species, a great black-backed gull tagged and ready for release.

In late May it was time for the Caspian tern adults. This year 11 were caught in total on Furö, Långa Hållet, Fågelsundet, and Rödkallen. It was the first time adult Caspian terns were tagged with GPS loggers in Småland and Norrbotten and it will be very exciting to see where these Caspian terns spend their time foraging and what flyway(s) they use on migration. Here's a clip of a release of an adult Caspian tern with a logger.

 

Caspian tern in flight with logger.

Early to mid-June it was time for the lesser black-backed gull adults to be tagged. We had great success on Rödkallen, Norrbotten where 8 individuals (4 each of Caspian tern and lesser black-backed gulls) were caught on the same trip! This was the first time we were at this colony so this goes to show that inexperienced seabirds (i.e. never been caught before) are easier to catch than those that know what we’re up to.

Lars Harnemo, one of many collaborators, with adult lesser black-backed gull tagged on Rödkallen, Luleå.

In late June it was the Caspian tern chicks’ turn to get their loggers, at any rate the earliest ones. We want to tag the juveniles because we know so little about what they do when they leave the colony, whether they migrate to the same places and along the same routes as adults and where/when they are at their most vulnerable. 31 juveniles ended up being tagged. Last year most juveniles were predated before fledging so this year it will be interesting to see if survival is higher and where they end up going. At the very least we hope to see exactly which predator exerts the most pressure (most likely white-tailed sea eagle).

A Caspian tern chick just old enough for rings.

 

Claes Kyrk holding a juvenile Caspian tern old enough for rings and a logger, this time tagged on Furö, Småland.

Last but not least were common guillemots and razorbills on Gunnarstenarna, Stockholm. For these we had special GPS/GSM loggers capable of recording dives. They’re the last of the bunch and were tagged in July. Here we’re interested in their foraging movements during breeding, and whether both species use the same areas or partition the resources between them.

Mikael Odenstig on Gunnarstenarna with a common guillemot with GPS/GSM dive logger

As ever, the field season is full of surprises and helping out collaborators with their study species. Highlights included a Ural owl chick-ringing trip (I now understand why they’re called ‘slaguggla’ in Swedish) and the ringing of hundreds of starling chicks.

One of the perks of the field season is helping collaborators with their study species, here ringing of an arctic skua chick.

 

And here, a black guillemot chick.

So, to summarize, I spent 12 weeks in the field, applied 67 loggers of various sizes, shapes, capabilities and manufacturers to 6 species of seabird. It was a busy field season to say the least, and that is how it should be! Now all that remains is to kick back and, to paraphrase Dr. Seuss, see all the places they’ll go. 

//Natalie