Tuesday, 23 September 2014

Familiar Faces

As the Dublin Bay Birds Project approaches its second winter, we are getting reacquainted with our colour-ringed waders. As well as getting to know the individuals, their haunts and habits in Dublin Bay, we are also beginning to see the real benefit of our ringing efforts. Our birds have been reported from as far away as Scotland, Iceland and Norway.

Bird ringing is not a new technique by any means, but it is a hugely effective tool in the conservationist’s tool kit. Not only does it allow us to build a picture of bird movements locally and internationally, but when we catch (or re-catch) birds, it allows us to collect biometric data and assess their body condition, which aids our understanding of the species, and ultimately leads to more effective conservation.

While colour-ringing (and subsequent re-sightings) generate valuable data, we are also fitting a subset of the birds with radio-transmitters in order to get a finer level of detail. The first of the radio-transmitters were deployed last January , and a mammoth radio-tracking effort followed. We collected some high resolution data on eleven radio-tagged birds, both by day and by night, during high and low tides.

 Radio-tracking continued into the spring, and by early April, we could no longer pick up the signals from any of the Oystercatchers or Bar-Tailed Godwits. The last of the Redshanks stuck around until the last week in April, before heading north into the unknown. 

Helen and Niall Radio tracking last winter

Out of sight, but never out of mind, we focused on terns for the summer months. But the colour-ringed and radio-tagged birds were never far from our minds: where were they breeding; had a winter feeding on Sandymount Strand allowed them to get into breeding condition; did they breed successfully; when would they arrive back in Dublin again?

Oystercatcher re-sighting locations (red)
Oystercatchers ringed as Pulli in Scotland and colour ringed in Dublin (green)
Ringing location (blue)

We checked emails eagerly, waiting for news from birders and researchers from far away with unpronounceable names. With time, the emails trickled in from far off places…

Among the jet setters were Redshank "BH", who was re-sighted in Iceland’s western fjords  on the 18th May, and Bar-tailed Godwit “DH", who was re-sighted in Finnmark, Norway a day later, on May 19th. Oystercatcher “CU” was seen (on a traffic island!) in Stokksetri in Iceland. His mate was subsequently colour-ringed as part of an Icelandic study. Who knows where she will spend the winter?

Redshank "BH" (yellow), Bar-Tailed Godwit "DH" (green) re-sighting locations
Ringing location (blue)

The database has almost reached 1,000 re-sightings, which is fantastic, and we’d like to sincerely thank everyone who has submitted records to date. These re-sightings are the life-blood of the project.
Of the 151 Oystercatchers that we ringed, 89% have been re-sighted at least once, and 66% of have been seen three times or more. Ten of them have been seen outside Ireland. Oystercatcher “FI" has been re-sighted in Dublin 23 times, and takes the crown for most regularly recorded colour-ringed bird. "FU" and "BC" come in at a close second, with 21 re-sightings each.

Redshank "AN" ringed and radio tagged John Fox

We were delighted to catch up with Oystercatchers, "NA" and "CH," and Redshanks, "AN" and "AP" in recent weeks. These guys have played a pivotal role in our data collection, as they carried radio-transmitters for us last winter. Great to see them back in Dublin again!

We are looking forward to the coming months and getting out and re-sighting more and more of our birds. We will continue to build a picture of their movements both within the bay and further afield. As always, we would love to hear from you and integrate your re-sightings into our growing database. It’s a great way to spend an autumnal day, and anyone can do it (but a scope or camera helps). If you do manage to get out and about, you can submit your sightings here.

Monday, 1 September 2014

Sandymount Spectacle

Annually, from mid-August onwards, Dublin Bay plays host to the avian spectacle that is the post-breeding tern aggregations. Sandymount Strand is a roosting hotspot for thousands of terns from four species. Common, Arctic and Roseate Terns make up the bulk, with Common Terns accounting for the vast majority. Most evenings, Sandwich Terns can also be observed too: you may not manage to pick one out from the crowd, but you'll most likely hear the loud grating kerrick kerrick calls of Sambos (to give them their cool name!) in flight. 

Sandwich Tern in breeding plumage Dick Coombes

It's not just birds that have bred in Dublin that are attracted to the Strand, but birds from the UK and further afield too. The fact that a small number of Black Terns, whose nearest breeding colony is in The Netherlands, are seen in the roost every year confirms that it's not just local birds that the roost supports. 

Mixed tern flock on Sandymount Strand John Fox

Dublin Bay provides an excellent food resource, in the form of small fish, in order to sustain the big numbers during this staging period. After feeding off-shore all day, the terns converge on Sandymount Strand in their thousands each evening. The numbers at the roost builds from mid-August to mid-September, until Mother Nature prompts them to set off southwards to spend the winter in west African waters, and even further to Antarctica, in the case of many of the Arctic Terns. 

Arctic Tern in breeding plumage Andrew Kelly

To avoid predation and disturbance, most terns tend to breed in out of reach places, such as off-shore islands, so this post-breeding aggregation offers a great chance to observe these beautifully delicate seabirds up close. The sheer numbers allow a fantastic opportunity to really appreciate these birds and to work on your ID skills! The best time to watch this spectacle is about an hour or so before sunset; and the higher tide the better, as the birds are pushed further up the beach.

Several roost censuses during this period allow us to determine the peak numbers and the species composition, and gives us an opportunity to assess the trends from year to year. So, if you see a couple of windswept guys staring in the direction of a large group of terns in the coming weeks, it's probably the Dublin Bay Birds Project team. Come say hello - we'd be happy to point out what's about and hear about what you've seen.