Friday, 8 July 2016

Return On Investment

The Dublin Bay Birds Project team took the opportunity to colour-ring some adult common terns on Sandymount Strand, County Dublin last autumn and our efforts have already been rewarded!

We have blogged a number of times about ringing the tern chicks that are born at the Dublin Port breeding colonies. But did you know we have also managed to successfully catch and tag adult birds? Of course we don’t do this at the colonies or even within the nesting season as that could potentially disrupt adult birds incubating and feeding young for example.

Newly fledged Common Tern at Dublin Port
 with metal and colour ring (on left leg) on view
John Fox

Instead we carry out the tagging of adults at Sandymount Strand during the post breeding season (Late august – September). Terns of various species gather and roost here in the early autumn before migrating south for the winter. We know all the birds are not derived from the Dublin colonies from the numbers that accumulate and from the occasional presence of Sandwich Terns (who don’t breed in Dublin) and even Black Terns (which don’t breed in Ireland at all!) You can read all about this pre-migration mass roost at Sandymount Strand here.

A mixed tern flock arrives to roost at Sandymount Strand Dick Coombes

With the ringed chicks it can be three years or more before we would expect to see them on Irish shores once more as it will take this long at least for Common and Arctic Tern chicks to reach sexual maturity and return to the colonies to breed. Adults on the other hand if they survive the winter and migration will be back the following year and we could potentially spot them by re-sighting and reading the ring which in turn may tell us for example, what colony they are breeding and if they successfully rear young.

So we were pleased when our BirdWatch Ireland colleague Brian Burke got in touch from Rockabill Island in early June to ask us if we recognised a few colour ringed Common Terns he had managed to photograph! On inspection of the photos we could confirm our first resightings of the birds since been ringed in Autumn 2015. We also knew instantly that we had ringed them as adults as we place the colour ring on the right leg of adult birds (to avoid confusion as the same colour rings are used on both chicks and adults). 

3 colour-ringed adult Common Terns seen on Rockabill Island,
Brian Burke

We ringed "PFX" on August 26th, "PHL" on September 7th and "PKN" the very next evening on the 8th, all in 2015. You can see how they are getting on at Rockabill this year here.

We now look forward to the rest of the breeding season to see if any more of our colour ringed birds will show up in Dublin or elsewhere in Europe. The excitement builds as we approach the cusp of the breeding season when we can once more admire the big roosting flocks at Sandymount Strand (and maybe even catch and colour ring a few!).

A short trip for a Common Tern,
Rockabill (north) to Sandymount Strand (south), 

a little over 20 miles apart Google Maps

If you think you have seen one of our colour-ringed terns or any colour ringed bird in Dublin for that matter be sure to let us know at  

For more info on the colour ringing schemes in operation in Europe see here.


  1. Beautiful photos! Greetings from Montreal, Canada. :)

    1. Thank you Linda. Hello from all of us here in Dublin (and Ireland)

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