Time to Jump! (2:2)

One of the highlights of the breeding season at Stora Karlsö is when the common murre chicks fledge and take to the sea in spectacular fashion: by jumping from their cliff nests to the beach below! We are now in the middle of the chick jumping period and therefore the end of the field season. The chick jumping is a bit of an event in Sweden and this year Swedish television (SVT) was here to film two programmes about it. So tune in to ‘Mitt I Naturen’ and ‘Djur med Julia’ to see the chicks in action!

But before I sign off for the season with cute pictures of chicks and suchlike, an update on the telemetry. As we have been able to recapture 4 (!) razorbills this season with time-depth recorder devices on them, we have been able to deploy 6 such devices on murres, with the intention of recapturing them next season and get both breeding season and over-wintering dive data.

Common murre with TDR device attached, ready to be released.

We have also deployed 15 GPS devices on the murres and retrieved 12, a very respectable recapture proportion. Fortuitously we have some tracks from when a storm hit the area and there is evidence for the murres moving to avoid the worst of it.

Bird recaptured and picture taken just prior to removing the GPS, thereby ending a three-day long deployment.

Overall, it’s been a good telemetry season, especially as regards recapture of razorbills from last year. Now it’s on to analyzing all the great data!

Finally, as promised, a picture from the ringing of murre chicks as they fledge on the beach. We take mass, as well as some feathers, and give them both a plastic and metal ring. Then we release them and hope they make it to their fathers waiting for them close to shore. And then of course we hope to read their rings again next year when they return as juveniles!

Me holding a newly ringed and weighed murre chick. Notice the realistic stains on its front, the price for cliff-nesting with lots of other birds!

Of course the murre chicks are not alone on the island, there are lots of other (cute) chicks to be seen this time of year. Easiest to see as a researcher in the artificial ledge (built in 2009 to study murres) are razorbill chicks that are hatching now and will fledge in a few weeks time, mostly after the murres are done. Since 2015 a few razorbills breed on the ledge and as of July 1 this year, we have a razorbill chick! This is exciting news as razorbills are more challenging to study (breeding mostly under boulders and rocks on Karlsö), and this opens a whole new suite of possibilities for research on this more enigmatic species.

The obligatory razorbill chick picture from inside the artificial ledge (aka Auk Lab). At this stage (a day old) they are still light grey/white, but will look a lot more like the adults by the time they fledge.

 And now all that remains is to sign off for this year! It’s been productive and busy, as it should be, and hopefully we will have gathered exciting data that will soon see the light of day in new papers. Until then, see you around!

The capture-and-handle adult murres team! From left to right: Natalie Isaksson (Lund University), Tom Evans (Lund University), Rebecca Young (Baltic Seabird Project).

   

/Natalie

Photo’s: Natalie

Return to the Island (1:2)

This season it’s back to the island of Stora Karlsö in the Baltic Sea to join the dedicated team of seabird researchers doing research on (you guessed it) seabirds!

Upon arriving at the island it was straight to work studying the diet and provisioning of common murre chicks by staring down a ledge with breeding individuals and recording size and species of fish brought to the chicks for an entire day (from 3:00 to 23:00). Time spent at the nest with chick and partner were also noted. This kind of study allows us to understand what the provisioning effort is to chicks and to see what parental strategies are most successful (e.g. raising the chick to fledging size). Behaviors such as not incubating the egg or not feeding the chick often enough, or even trampling the chick to death while bickering with a ledge neighbor are some examples of birds wasting the energy they invested in breeding this year. Typically, common murres lay one egg in the breeding season and it is rather rare for them to re-lay if they lose their egg.

Rebecca Young (left) and PA Berglund (right) entering data from the diet study on a sunny day.

This year we suspect, due to late laying dates and the fact that more experienced (e.g. older) individuals are electing not to breed, that it will be a ‘bad’ year. That is, we don’t expect as many chicks as usual to fledge and that therefore breeding success this year will be lower than in the past. In fact, when we checked the records, we saw that this year was the latest on average laying date in a decade! Too soon to say anything conclusive about why, but hypotheses we have floated so far include a bad winter (e.g. that the birds returning to breed do not have the energy to do so), low fish quantity or quality in the breeding area, and even abiotic factors.

There are several related monitoring type studies that take place concurrently on Stora Karlsö. One of these is ring resightings. Several different areas on the island are used and for 45 minutes a researcher reads the rings of common murres located in these areas, with the aid of a scope or binoculars of course. One such researcher who uses this kind of data is Blanca Sarzo, PhD student, who models common murre survival. 

Blanca Sarzo entering ring resighting data into one of two field computers.

The main reason that Tom Evans and I return to Stora Karlsö, however, is for collecting tracking data. This year we’re focusing on maintaining and laying groundwork for long-term annual tracking of common murres to take place on the island. This is feasible given the artificial ledge that allows us to be close to the birds without disturbing them, which in turn allows us to keep tabs on who is breeding with whom and whether they have had a tracking device on them in previous years. We aim to put devices on the same individuals as much as possible since this allows for individual repeatability studies and direct comparison between years.

Before you can track birds, however, you need to prepare the devices. This can mean anything from maintenance to configuration and (as we work with diving birds), waterproofing. It is essential to the mission, therefore, to set up a servicing station.  

On the left, the soldering and waterproofing station. Top right, a GPS device charging. Bottom right, 2 GPS devices that are ready to be put on a bird.

 

The next step is, of course, to catch a bird. Depending on the day and mood of the birds this can be quite a long period of waiting around for the right bird to sit on the chick. As we also bleed the birds for aging studies conducted by Rebecca Young (Baltic Seabird Project) we focus on birds that we know the exact age of and have had GPS devices on them previously. These are then caught by nose pole in the artificial ledge and processed there as well. We take several measurements, bleed them, collect feces and tick samples for a study conducted by Michelle Wille from Uppsala University, and lastly attach a GPS device using tesa tape to the back of the bird. After that it’s time to release the bird and check when it returns to the colony to attend its chick.

Aron Hejdström (right) taping a GPS device to the back of a common murre while I (Natalie Isaksson) hold the bird in position (left).

 Common murre with GPS device on its back outlined in red!

Last year we put TDR’s and GPS devices on several razorbills. There is no chance of recovering a GPS the following year as they are only attached to the back feathers with tesa tape and if the partner does not preen the device off eventually, they will moult it off after the breeding season. However, we attached TDR’s on the legs of the birds with plastic rings so it is possible to recover devices the next year in case the birds are not re-caught the previous year. It is therefore part of my work this year to as many of the razorbills as possible from last year and retrieve the TDR’s from them. A few days ago we successfully caught the first razorbill of the season and removed its’ device from last year. One down, five to go!

Tom Evans holding razorbill 8114406 with TDR still visible attached to the yellow plastic ring on its’ left leg. Rather unusually, this individual did not try to bite Tom’s fingers off.

Until next time!

/Natalie Isaksson

Photo: Natalie Isaksson

Half-time report from the nightjars

 

The author and the nightjar in the first morning light.

It was with great excitement we set out to the forests in NE Småland to retrieve the data loggers that we deployed in last year´s breeding season. The new (< 2 g) GPS-tags that we used were programmed to enable us to explore various aspects of the nightjars´ non-breeding movement. In addition, we would for the first time see the full migration track of a nightjar with high precision and without these annoying information gaps close to the equinoxes (due to the escalating uncertainty in the latitude component in geolocator-derived position data).

We have been very fortunate and up to now we have retrieved eight GPS-tags which are more than we expected and hoped for. Unfortunately the tags´ batteries did not last as long as anticipated, which is probably to be expected when using cutting-edge miniaturized technology. We are of course very happy with the data provided and are looking forward to analyse it in detail during our long non-field season.

But first we will spend a few more weeks among the nightjars, ringing more birds and deploy new tags!

 A nightjar, plenty of coffee and a laptop are crucial components for a successful fieldwork. The latter is used to keep track of all the ringed birds. While many birds stick to their breeding territory and are re-trapped in more or less the same place, others roam around 10s of km. Hence, it is crucial to pick the right bird if you want to get your device back!

This is how a nightjar ringed in Italy looks like. After trapping and approximately 500 nightjars in the last couple of years without any recoveries of birds ringed abroad we were surprised to find a bird with an Italian ring and one male with a German ring within just two weeks.

After a full night of field work I struggled to figure out what was wrong with this ring – it did not look like our Swedish rings used to do. Note the comb-like claw on the middle tow – a structure which function still has not been thoroughly described.  

 

/Gabriel Norevik