Wednesday, 10 May 2017

2017 Tern Season is Here

The longer the days get the fewer waterbirds we see in Dublin Bay. The Brent Geese are all but gone and we look forward to their return this autumn! But there's little time to reminisce on the winter season past as it's time to gear up for the immanent return of our breeding terns.  

The ESB Dolphin, 
Dublin's largest Common Tern breeding colony Helen Boland

As I write Dublin Bay is seeing more and more terns arrive in from the West-African coast after migrating north to breed on the Irish coastline and at coastal areas throughout Europe. Common Terns Sterna hirundo and Arctic Terns Sterna paradisaea breed within Dublin Bay. Further south Little Terns Sterna Albifrons breed along the North-Wicklow coast and not far off Dublin's coast, north-west Europe's largest Roseate Tern Sterna dougallii breeding colony exists at Rockabill Island. The earliest birds are already prospecting nest sites at these colonies and the first eggs will be laid before long. 

An Adult Common Tern offers his mate a Sand eel Neil Harmey

With eggs expected in late May, our first census visits will take place in the last days of the month. During the census visits, nests (slight depression in the shingle) and eggs are counted and we check for any signs of predation. 

Common Tern eggs in "the nest" Ricky Whelan

Predated Common Tern egg
found during the 2014 breeding season
Niall Tierney

To make things a little tougher for would-be predators, terns have no real nest structure and eggs are cryptically marked so the task of finding them all during census visits can be a little tricky. Once you get your "eye in" the operation runs smoothly! 

A tern nest in an old Dublin Port life buoy Richard Nairn

As the season progresses we return to the colonies to asses what the success rate has been and to colour ring the chicks. The ringing allows us to see if and when birds return to breed at the colony, if they move between colonies as well as where migration might take them each autumn.

Common Tern chicks "fluffies"
 with a bit left to go before fledgling Ricky Whelan
Chicks in the box ready to be ringed Ricky Whelan

Dr Stephen Newton and Helen Boland ringing Common Tern chicks
during the 2014 breeding season
Ricky Whelan

With severe weather, predators and disturbance being the main factors potentially dictating the success of the breeding terns its can be a short but tough few months in Dublin. Despite all the potential risks we know from our long term monitoring that the Dublin Bay colonies have been doing well and the population numbers have remained stable over time. 

Colour-ringed newly fledged Common Tern "PAT" on railings
close to Dublin Port, 2016
John Fox 
This past year our tern colour ringing has paid dividends with multiple reported re-sightings from Namibia on the West-African coast and elsewhere. We want to hear about all re-sightings be it from Courtown, Coruna or Cape Town, so please let us know if you spot any colour ringed terns. Our birds have a metal ring on one leg and a yellow or blue colour-ring on the other. The key info we need is the colour and the alpha-numeric code on inscription on the ring i.e. "PAT". For full details on the scheme and to submit your re-sighting Click Here.

Tern colour ring re-sighting reporting page BirdWatch Ireland

Be sure to visit the blog over the summer months to hear about progress over the breeding season. If you require any more info or just want to get in touch you can email us at: