10 October 2017

The Big Biggleswade Starling RAS

Denise Cooper-Kiddle and Derek Gruar write:

The BTO Breeding Bird Survey survey has recorded a 49% decline in Starlings across the UK since 1995. Why numbers have dropped so dramatically is not fully known. Retrapping Adults for Survival (RAS) projects are helping find out whether adult mortality is a possible cause.

Adult Starling. Photo by John Harding

My back garden in Biggleswade, Bedfordshire gets more than its fair share of Starlings (4,446 ringed here since 2010). Three years ago, the BTO suggested I should start a RAS project. As well as a unique metal ring I also add a colour ring to every adult bird caught between 1 April and 31 August each year. Since then I’ve colour ringed 634 adults. My RAS uses red rings with a white letter/number code starting with a P or a K and are unique to each Starling throughout Europe.

Starling roost. Photo by Laura Kuselska

What makes the Biggleswade RAS exceptional is the volume of data it produces. In June 2015, two months after the start of my first RAS season, I was contacted by a retired couple living a few streets away. They had started seeing Starlings with red rings in their garden and a leaflet they picked up in a local shop (1,000 had been distributed around the area) told them about the project. Brian and Viv took on Starling spotting as almost a ‘day job’ and Brian, an ex data manager, decided to set up and manage a complete project database. Every red-ringed bird is added into the database and every day on which that bird is sighted is recorded. This shows that an ‘amateur’ ringer and some absolute hero volunteers can provide a lot of information about a declining species.

So far the database contains 7,382 confirmed day sightings (ring code seen clearly among the mass of Starlings rushing around feeding). Looking at when individual birds were sighted shows that some birds are only seen during the breeding season and some are seen all year round.

Click to enlarge

Staying around or not, can make a lot of difference regarding the number of days on which a bird is sighted. Take two of the ‘regulars’ that have been seen on over 150 days since they were colour ringed. PIF has been seen on 158 days since being colour ringed on 4 May 2015. PVC has been seen 163 times, but wasn’t colour ringed until 14 June 2016. The difference is that PIF disappears for months at a time outside the RAS season and PVC has been seen on at least two days in every month since being colour ringed.

I did consider colour ringing the juveniles I catch as well, but decided against it as so few return as breeding adults the following year: of the 271 adults I have red ringed in 2017 only 52 had been metal ringed here as juveniles in 2016 (about 5% of the total of 980 juveniles ringed here in 2016). A lot will not have survived their first winter, but hopefully quite a few will simply have dispersed and gone elsewhere. It does look as if some birds return at some point because three Starlings metal ringed here in 2011 or 2012, and never seen or retrapped since 2012, suddenly turned up this year to ‘collect’ their red rings.

Juvenile Starling. Photo by Christine Matthews

Where do Starlings ringed in Biggleswade go? A number of recoveries and controls of birds within a 40 km radius suggests they disperse over a reasonable area. Two recoveries have been very noteworthy - a juvenile ringed here in August 2014 was found dead in Capel-Sylen, Carmarthen in March 2015 and an adult ringed here in November 2016 was found dead just outside Bunschoten-Spakenburg in the Netherlands in August 2017. This was especially interesting for me as I lived in Bunschoten-Spakenburg for 11 years; just one of those quirks of fate when investigating these fascinating birds.



With the 2017 RAS season now finished and the data entered into the database, who knows what the results will show us in the next few years. If you do see a red colour ringed Starling starting with the letters P or K, feel free to contact me on Info@denisecooper-kiddle.com.