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.