Holding Court

Rockabill is alive with the sound of courting terns: shrill calls to mates, the helicopter-like warnings not to encroach on a particular tern's territory, females demanding to be fed... It's pretty loud!

Courtship in terns occurs in three main stages, with both sexes taking an active role in mate choice. The first stage takes place in the air, in circling displays above the colony. The aerial nature of this display may allow potential mates to size each other up, perhaps literally: there is some indication that the length of tail streamers in roseate terns is linked to reproductive quality, and may help terns decide on a suitable mate¹.

With wings spread wide and sunlight shining on them, terns can see how colourful each others flight feathers are. This may seem like an odd thing to say about a white/grey/black looking bird, but terns can see in the ultraviolet spectrum, and their newest flight feathers are covered in barbules which reflect this type of light. Terns are unusual in that they replace their flight feathers two and even three times a year. This happens slowly, and in overlapping stages, so that the second and third wave of feather growth can be seen at the same time. An abundance of new, “colourful” feathers may indicate good condition, and make that tern more attractive².

 Roseate terns strike a pose. Taken under NPWS license by Luíse Ní Dhonnabháin.

Terns pair off at the peak of this spiral, and after much displaying of the male's prized fish, he leads the female back to his nesting territory. Here after much synchronised posturing, the male hands over the fish to the female, after which they copulate for the first time (in common terns up to 50 copulations have been recorded for a single pair)³.

                   

Roseate tern pair mating. Taken under NPWS license by Luíse Ní Dhonnabháin.

In the second stage the pair head out to sea to feed, occasionally visiting the nesting territory.

In the final stage the female stays at the nest site while the male forages, bringing back food to the female while she lays the eggs. Some terns prefer to rob fish from their peers rather than head out fishing themselves. The time saved means that these terns can feed their mate more often, resulting in females with higher body masses and better outcomes for their fledglings. In spite of this, these kleptoparasites seem to make up only a small proportion of the colony's population⁴.

                                        

Roseate female wishes male would just hand it over. Taken under NPWS licence by Luíse Ní Dhonnabháin.

The arrival of the first eggs on Rockabill this week marks the end of the courtship period for the early birds, but there are still many more wooing away!

We hope you've been enjoying National Biodiversity Week, and made it to some of the programme's events. Until the next time!

Luíse Ní Dhonnabháin
& The Rockabill Team.

1 Palestis, B.G. et. al. (2012) 'Tail length and sexual selection in a monogamous, monomorphic species, the Roseate Tern Sterna dougallii' Journal of Ornithology , 153 (4).

2 Cabot D. and Nisbet I. (2013) Terns. HarperCollins:London.

3González-Solı́saf J., Sokolov E., Beckerd P.F. (2001) 'Courtship feedings, copulations and paternity in common terns, Sterna hirundo' Animal Behaviour, 61(6).

4 García, G.O., Becker P.H, Favero M. (2012) Kleptoparasitism during courtship in Sterna hirundo and its relationship with female reproductive performance.' Journal of Ornithology, 152(1).

Back in Action!

Hello everybody and welcome back to the Rockablog! A whole new season is currently just kicking off with a large flock of terns having arrived on the Rock on Thursday 3rd. It’s all hands on deck and the seasonal rush is upon us and we've deployed over 840 nest boxes around the island to accommodate all our guests! There are three of us wardening the island again this year Luíse O’Donovan, Heidi Acampora and myself, David Miley, returning for my second season on the Rock.

Lunch on the helipad. Photo Credit: Johnny Woodlock

We began work here 3 weeks ago with vegetation clearance of the thick mallow which covers many parts of the island, and requires thinning to make more space available for nesting Roseate, Common and Arctic Terns. We were massively assisted by Scout Leaders Declan de Freitas, Steven Stewart, Alan O' Kelly and Johnny Woodlock of Skerries Sea Scouts. Thanks a million, your hard work and sore backs are greatly appreciated gentlemen!

Scout Leaders Alan, Johnny and Steven enjoy the view after a hard days work, while Declan is still giving it socks, fair play Dec! Photo Credit: David Miley

Photo Credit: Johnny Woodlock

In rough weather some days there's only one way to get on the boat! Photo Credit: Johnny Woodlock

Dr. Stephen "The Ferryman" Newton our rower extraordinaire gets the lads onto the boat safe and mostly dry! Photo Credit: Johnny Woodlock

On Friday 4th of May we also received some very special guests from the mainland bearing very beautiful gifts for our Roseate Terns! Balbriggan Community College who have been producing nest boxes for the Rockabill Roseate Tern Scheme for the past 25 years and have produced over a 1,000 nest boxes, amazing work!!! 

Our student artisan crafts-people departing from Malahide for their trip to the Rock. Photo Credit: Sean Pierce.

Group photo time! Photo Credit: Sean Pierce.

That’s 25 years of present and past students, teachers and staff members that have been involved! Talk about making a difference to front-line conservation, their nest boxes have been present and providing shelters for nests and chicks of Roseate Terns for a quarter of a century as their numbers have soared from a meagre 189 pairs in 1989 to 1603 pairs in 2017. Below is the elegant and beautiful commemorative 25th Anniversary Box that Balbriggan Community College designed and produced:

"The Students of Balbriggan Community College have built and provided nestboxes for the terns on Rockabill since 1993." Photo Credit: Sean Pierce.

"Balbriggan Community College has co-operated with BirdWatch Ireland and has produced over 1,000 nestboxes for the Rockabill Project." Photo Credit: Sean Pierce.

"Many past pupils have been involved with the scheme organised by the school Woodwork Teachers: Mr. Harford 1993-2001, Mr. Macken 2001-2010, Mr. Boylan 2012-2018." Photo Credit: Sean Pierce.

"The huge increase in breeding numbers of Roseate Terns from 189 pairs in 1989 to 1600 in 2017, owes much of it's success to the nestboxes provided by the school." Photo Credit: Sean Pierce.

"Sponsored by Shearwater Sea Kayaking in 2018." Photo Credit: Sean Pierce.

Proudly waving the flag! Photo Credit: Sean Pierce.

Nestbox in the making! Photo Credit: Sean Pierce.

Final stop, Rockabill! Photo Credit: Sean Pierce.

Photo Credit: Sean Pierce.

Photo Credit: Sean Pierce.

Photo Credit: Sean Pierce.

A very special thank you to Balbriggan Community College for their continued and treasured support that they have provided for the Roseate Terns and the Rockabill Project over the years! Also a huge thanks to the 2nd Year Woodwork Class with Mr. Boylan, the Transition Year Art Class with Ms. Rossiter and Ms. Grant for design inputs. Beautiful boxes everyone ye really went the extra mile this year, we were really blown away by the creativity of this years boxes!

Things have been relatively quiet on the Tern front as the colony has been moving out sea and back onto the Rock on a number of occasions while they get settled, though they do seem to be really getting into the swing of things now with the colony starting to become very busy with at least 2,000-3,000 terns with us at the moment. We've yet to see our first egg on the island but I'm sure it'll only be a matter of days now.

Also folks there are numerous boats in the area out fishing, enjoying the weather and wildlife, a number which have attempted landings on the island, I'd like to inform people that landing is strictly limited to personnel authorised by The National Parks and Wildlife Services and The Council of Irish Lights and if fishing or taking photos around the island please refrain from landing or coming too close to shore that you cause disturbances to the Terns and Kittiwakes. That's all from us here on the Rock, we'll be back with more blog updates soon!

David Miley & The Rockabill Team