Chasing Terns

BEES MSc student Tony Murray writes from the Sunny Southeast:

The plight of roseate terns (Sterna dougallii) has been well documented over the last number of years. The NPWS have been involved in wardening the largest ternery in Ireland at Lady’s Island Lake, Co. Wexford for many years now, and since my move from Mayo to Wexford in 2004 it fell under my responsibility as the Wildlife Ranger for South Wexford.

This site, situated in the extreme south-east of Ireland, is comprised of a shallow, brackish coastal lagoon separated from the sea by a sand and shingle barrier. The lagoon habitat within the site is an excellent example of a sedimentary lagoon with a sand/shingle barrier. It is by far the largest and best example of this type of lagoon in the country and is in a relatively natural condition, despite regular breaching of the gravel barrier

The annual tern wardening project of the colony generally involves management of the site, predator control and monitoring, deployment of nestboxes and ringing and ring reading as has been done at other Irish, UK and French Roseate Tern colonies. Recording of all nesting species, numbers nesting, clutch sizes, etc. is also under taken for all species.

Under the supervision of Professor John O’Halloran and Dr. Tom Kelly at the School of BEES, UCC and as part of a research MSc I decided to take a closer look at both roseate tern and sandwich tern (Sterna sandivensis).

My main aims are to identify a section of both roseate tern and sandwich tern colonies and study each through the season. With nearly all roseate terns ringed over the years, I wanted to try and see if pairs returned to same part of the colony? Do they stay in the same pairs from one year to another?

Roseate Tern Copulation

A big task was to try and sex the individuals and see during provisioning watches what parent is doing most of the fishing and provisionin.

Sexing terns is not easy and they are not sexually dimorphic, so it involves long watches waiting for spring provisioning by males or copulation to see who’s who….

Fortunately this involves long hours recording nothing waiting for their intimate moment then getting the ring numbers to log them as a pair, their particular nestbox and most importantly which one is male and which one the female.

I am then monitoring the nests through the season recording chick wing growth and weight as regularly as the weather allows, in tandem feeding watches on both species is identifying prey types, prey size and frequency of provision.

As I write the second year is about to kick off with Sandwich Tern chicks expected to hatch this week and roseates continuing to put down their broods earlier and at a much faster rate than last year….. Hopefully the weather will hold and we’ll have another great season!

A special thanks to Christopher Wilson and David Daly.

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