Thursday, 29 March 2012

Reverse migration of 'west Atlantic' Brent to Ireland

Following reports of an odd double-metal ring combination on a pair of Brent in Dublin, observations of which were made several times, Graham managed to get to the bottom of the mystery thanks to our Canadian colleagues Sean Boyd and Kathy Dickson.
These birds appeared to have a metal (steel) ring on one leg and an aluminium ring on the opposite leg which made them unusual.
The birds were observed at several Dublin locations between 20th November 2011 and 28th March 2012 and it turns out they were probably banded on Baffin Island.

Canadian biologists have been studying this "Atlantic" population which breed in low-arctic Canada and winter on the eastern seaboard of the US (example the 'banana-eating Brent at Queen's New York in the previous blog post'), banding birds on the Great Plain of the Koukdjuak, Baffin Island, or on Southampton Island further west in the Foxe Basin. The fact that the birds appeared to be a pair makes it most likely they were banded on Baffin Island, where pairs and family groups are the target of banding activities (at the Southampton site the majority of birds are non-breeder moulters, but may also include failed breeders).

Lest you think that fitting two metal rings was an accident (and it sometimes happens!) we are advised that 'double-banding' Brent at these two sites has been done intentionally as part of a study to determine band loss rates by comparing regular aluminum bands to stainless steel.

Thanks to all keen-eyed observers involved, the diligence of getting to the bottom of the story (Graham) and the information from Sean and Kathy. As Sean says we can all sleep easy now :-)

And here is a picture from Cian which apparently he is embarrased about. It would take an exceptionally good picture to be able to distinguish these 'Atlantic' Brent from our 'Irish' birds but the rings give the game away - it would be interesting to know how many and how frequently low Canadian Arctic birds head across the Atlantic in the winter. We certainly know now that it does occur!

Wednesday, 28 March 2012

What's yellow and lies on the beach?

We all know that Brent Geese prefer inter-tidal foods where available in sufficient quality and quantity. It's certainly the food of choice in terms of its digestibility and nutritional quality. But not all inter-tidal food is green and slimy. Check this out:

which is a description and more pictures showing this!

But is it a banana or is it something else?

It's not all about geese

Last weekend part of the IBGRG catching group, ringers and the newly converted Highland Brent Team ascended on western Clare for some wader action. It pays to maintain familiarity with lesser species but nonetheless impressive migrants.
Catches of Oystercatcher, Turnstone, Sanderling effectively rounded up about every bird that was on the beach - the plan expertly executed by Brian, Kerry, Ron and Simon and a jolly good time was had by all.
The blog here would be a very good spot to post some of the video and still pictures taken from the day. I, in particular, would like to see the picture of BE falling in the maggoty weed. Nice.
We were trying to recover geolocators from Purple Sandpipers but nobody told them about the catching party and they failed to show. So we made the best of a bad job.

This is not a Brent Goose

First Brent arrivals in Iceland

This period of fine weather has no doubt accelerated the annual exodus of Brent (and other geese) northwards. By all accounts Barnacles, Greenland White-fronted and Brent are existing Irish airspace and I watched a flock of Whoopers fly out into the Atlantic about 10 days ago.
On 25th Gudmundur reported the first observations from western Iceland - 5 birds without rings. No doubt the numbers are well up on that by now.
A picture of Gudmundur's two dogs attached. They were the first to spot the birds and are looking forward to many hours of their guardian abandoning them in the house or the boot of the jeep now that 'Brent season' is upon us.
Note that 'Tina' (on the left) is all geared up for feeding labrador puppies....

Monday, 19 March 2012

Dark-bellied Brent Geese in Dublin

Just a quick post on tonight seeing as I haven't added anything for a while...

Prompted by an ID query I cam across on the internet earlier this evening thought I'd right something about one of the other races of brent geese that occasionally can be seen in Dublin in the winter. There were at least 3 (the true figure is probably far higher) dark-bellied brent geese wintering in North Dublin this winter and I saw them fairly regularly during the course of my work. Normally dark-bellied brents winter elsewhere in Europe - they are common for example back in the south east of England where I grew up. To start with they can often look surprisingly similar to the light-bellied in certain light, but after weeks of looking at brent geese telling them apart soon becomes second nature! Below are some pics I took at Red Arches at the end of February.

Picture 1: Note how much darker the underparts and flanks are, and how the dark area extends further towards the belly and up the flanks

Picture 2: This picture shows another useful feature quite well. The back colour of dark-bellied brents is subtly different to that of light-bellies being more slate-grey. Additionally the colour of the back tends to be a bit more solid, lacking the narrow pale fringes that are more common on light-bellues

Picture 3: Note the dark smudgy area that extends beyond the legs on the otherwise white belly. I think this is the easiest feature to split the two subspecies - its particularly obvious when ring reading!

I'll try to add some more stuff about the science soon when work is keeping me a bit less busy!

Sunday, 11 March 2012

My research in Dublin - Colour Rings and Social Networks

I've just spent 5 weeks in Dublin and during that time resighted nearly 500 of our colour-ringed brent geese over 3000 times - but a big question is what can we learn from all this information?

My research is focussed on looking at patterns of social interactions in the population, so that we can improve our understanding of what causes them and the impacts that they can have on the individuals themselves. In order to do this I'm using a method known as social network analysis, which I'll attempt to introduce and explain briefly below. It is using this approach that requires such a huge amount of data on where and when we've seen each individual goose.

Part of a flock of brent geese in Kilbarrack containing 2 colour-ringed birds

By resighting colour-ringed individuals in flocks together on many occasions over a short period of time, we can build up a picture of which individuals are found together most often, and whether an individual is always seen with the same other ringed birds or whether it moves between flocks and is seen with lots of other colour-ringed birds. This picture can be represented using a diagram known as a social network. This is a graph where each individual is a point on the graph and lines between the individuals represent whether they have been seen together a set number of times. A simple example is illustrated below.

Part of a Brent Goose social Network. Each red square is a different individual (labelled by its ring code). Lines join individuals that have been seen together 3 times or more

Using social networks you can consider the interactions of an individual within a wider context. You can calculate a number of characteristics of an individual that gives you an idea of the number of associates it has, the strength of these associations, how important an individual is to the structure of the network as a whole. Additionally you look at the overall properties of the network itself, in particular whether individuals occur in little clusters of "friends" or whether all individuals are well connected to each other or not.

All of this can provide us with some very interesting and useful information on the structure of social interactions in the population, and I'll go into more detail on each of these applications in future posts.

Thursday, 8 March 2012

Why did the brent goose cross the road?

The geese in Dublin seem very comfortable with an urban lifestyle now! After all, the grass is always that little bit greener on the other side....

Friday, 2 March 2012

Researching Brent Geese in Dublin

There's no better place to get up close and personal with light-bellied brent geese than Dublin. This morning I was sat watching a family crossing the road in front of my car!! The geese here spend most of the winter feeding in parks, on sports pitches and even on small patches of grass in housing estates and have learnt that people don't really represent any threat. This means that they can be approached to within only a few metres.

 Juvenile light-bellied brent goose, Old Yellow Walls, Malahide 

All this means that finding ringed geese and reading their rings can be pretty easy - sometimes you can even do it even without binoculars! This is one important reason why Dublin is the main study site for our current research efforts. After all my job at the moment involves resighting as many colour-ringed birds each day as I can, so that we can begin to understand how their social structure works and to what extent individual birds tend to remain in distinct social groups.

PFYY at Portmarnock Park (the metal ring on the bird's right leg shows it was
ringed in Iceland)

There is another reason, why Dublin makes a great place for my research. Birds feeding in the parks are often disturbed (over enthusiastic dogs are often the cause!) and groups often split up or join together as they move between different parks and grassy areas. This means it is possible for group membership to change many times in one day and allows me to collect data much faster than I could in many other places. All this disturbance can be very frustrating though if it happens just after you've found a flock!

Lots more about the brent geese of Dublin, and how our research in the capital is going will be added shortly!