Thursday, 9 June 2016

The importance of Hide and Seek!

It's been a (mostly) sunny and calm couple of weeks on Rockabill and the majority of our Terns are now on nests. We'll be carrying out our whole island nest census very soon, and we should have our first chicks in the coming days!

One of the tasks that's been keeping us busy over the last couple of weeks has been ring reading - that is reading the small metal rings that have been put on the Terns over the years to get a better idea of 'who' exactly we have with us on Rockabill! The rings give us a way of knowing what age our birds are, and if they came from Rockabill originally or from a colony elsewhere - all important information to have for conservation management and future monitoring and planning. Our colleagues at Lady's Island and Coquet Island do the same, giving us a great insight into the Roseate Tern population in this part of the world. The birds don't even know they're wearing the rings - it's like when you forget you're wearing a watch!

Here's David ringing his first Roseate Tern. (Picture taken and ringing carried out under NPWS license)

We do most of our ring-reading from wooden hides placed around the island. This year we added a fourth hide to help us increase the amount of rings we can read and birds we can check in on. Big thanks to Jerry Wray for building what is our most comfortable hide to date! A great spot to sit down with a scope in front of you, listen to a few podcasts on your ipod, and read rings and just generally see what the birds get up to through the day!

Our new ring-reading hide, next to our new terracing and new nestboxes!

We've read the rings of over 600 Roseate Terns this season so far - that's almost a quarter of the Roseates we have here, which isn't bad if we do say so ourselves! It's getting harder to read the rings at the moment as most birds are either sitting tightly on their eggs or gone out fishing, but there'll be another window to read some more at the end of the season.

We ring our Roseates with a 'special' ring on their right leg (e.g. 44R2 above) and a  'normal' BTO ring on the left leg (picture taken under NPWS license)

From last year's ring-reading we know that >98% of our Roseate Terns were born on Rockabill. The Terns are very site-faithful and will prefer to come back to their natal colony in most cases, and return year after year as long as the island is hospitable (i.e. there's suitable habitat and no disturbance!). That other 2% were originally from Ladys Island, though the year before we had a couple of Coquet birds and a French Roseate breeding here too! The majority of breeding Roseate Terns are between 3-10 years old, and within that most are between 3 and 5 years old. We've had one Roseate Tern this year (and two last year) that were 23 years old though! To put that into context, our newest warden David is only 25 years old!

The ages of Roseate Terns recorded on Rockabill last year (2015). 

We've had a few interesting resightings in the last couple of years of Roseate and Common Terns with rings from an African ringing scheme, rather than from the BTO like the ones we use.

This year we have a nesting Roseate Tern that was originally ringed ringed on the coast of Senegal in April 2011, en route to Europe. Since we know where it's nesting now we can keep an eye out for it in future years! In my first year here in 2014 we also had a Common Tern ringed in the same area by the same ringer in April 2013.
Our Roseate Tern was originally ringed 5 years ago as an adult on the coast of Senegal!

And if you think that's impressive, we also have a Common Tern nesting here this year that was born on Rockabill in 1999 (17 years old!) that was subsequently caught in Namibia in February 2007! That's 8,700km away and even further when you keep in mind the Tern would have followed the coast  and sea rather than flying 'straight' there so it's likely to be at least 10,000km with that in mind. A fantastic reminder of the huge journeys our birds undertake every year! It's been seen on Rockabill in 2008, 2009, 2015 and again this year and has more than likely been here every year in between too!

Our Common Tern is 17 years old and was caught in Namibia in 2007 - it's covered a lot of mileage since 1999!

At the start of May a Roseate Tern was seen very far inland over in England, presumably having either been blown off course on migration or perhaps the challenges of long-distance migration had taken their tolls on it and made it disorientated. Unfortunately the bird didn't survive. Since it was in England we might assume it was trying to head to Coquet Island, but the ring on its leg revealed it to be a Rockabill bird, ringed here in 2010. Never assume anything when it comes to wildlife!

Picture of the Rockabill Roseate Tern at Tring Reservoir in England (Picture by Roy Hargeaves  via the Tring Reservoirs HMWT Nature Reserve facebook page)
Over the years we've had reports of Rockabill-ringed Roseate Terns from Iceland, Scotland, various parts of England and Wales, Spain, Denmark, Switzerland, the Azores and even Canada and America! Some of those resightings have been birds visiting other colonies, sometimes to breed, and others are birds either lost or doing some epic wandering!

Some research groups use colour-rings for the same reason we use 'special' rings on our Roseates - easy to see from a distance. We've spotted three Common Terns with yellow rings over the weekend and spent a good 24 hours looking into where they might have come from. They had BTO rings, which meant they were from the British Isles, and since there was two of them they couldn't be from too far away surely? (Don't call me Shirley!) 

'PFX' was seen on Rockabill this week, having originally been ringed in Sandymount. (picture taken under NPWS license)
'PKN' is currently sitting on three eggs out here on Rockabill. (picture taken under NPWS license)

...and 'PHL' is on two eggs out here at the moment! (picture taken under NPWS license)

Well the answer was no, they weren't from too far away at all! They were ringed at Sandymount on the other side of Dublin, where thousands of Terns gather each Autumn before beginning their migration in earnest. With that short distance in mind, the birds likely came from Rockabill in the first place! Not the most exciting of ring recoveries, but still, the more data the better! And I'm sure some yellow-ringed Common Terns will turn up at other colonies in the coming months and years, helping us learn more about the Terns that rely on it as a vital pit-stop before heading to Africa each year. 

We also found a broken blue colour ring earlier in the season , which were used by the Dublin Bay Birds team on their Common Terns last year. I'll let the lads from the Dublin Bay team tell you about that though... (I'm still laughing about it!). Last year we did have a record of a Common Tern ringed in Dublin Port out here, so we do have some evidence of movement between the two sites.

So there you have it - there's loads of information to be gathered from ring-reading at a big seabird colony like this, and lots to be learned! For more information about the value of bird ringing check out the links below!

1 comment:

  1. Keep up the great work lads. I am sure the birds appreciate it. We will visit of Rockabill when our boat Rockabill is fixed. She is named after a ship that cruised from Glasgow to Waterford. It was named after the lighthouse it regularly passed on its route. We see Rockabill from our house on Holmpatrick Terrace.