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Study: Nest boxes boost Roseate Tern numbers

Roseate Tern
A Roseate Tern emerges from its nest box. Photo by Brian Burke

For many years, conservationists working to protect endangered Roseate Terns have provided nest boxes for the birds on their breeding islands in Ireland, the northeastern U.S. and eastern Canada. A new study published this week by the British Ecological Society shows that the boxes make a big difference for the birds’ breeding success.

That wasn’t always clear, however. In a 2020 summary from Birds of the World, the authors noted that “Roseate Terns readily adopt these artificial sites and at some colonies appear to prefer them to all natural sites. Although these artificial nest sites probably allow more pairs to nest at some colonies than could do so in their absence, this has not been demonstrated in a controlled study and it is not clear whether they augment breeding success or simply accommodate pairs that would have bred successfully in natural sites.”

Today, conservationists and scientists from BirdWatch Ireland, Trinity College Dublin, and University College Dublin say that nest boxes greatly assist in the extraordinary success of Roseate Terns on Rockabill Island, off the coast of Dublin. 

Ireland is home to the majority of Europe’s Roseate Terns, and tiny Rockabill, which is about the size of a soccer pitch (1.5 to 2 acres), hosts 85% of the European population. The number of breeding pairs is now 10 times what it was when the project started in 1989, and chicks that hatched and fledged on Rockabill have gone on to boost other important colonies in Wexford and England. 

And every year for the past 33 years, BirdWatch Ireland conservation wardens have been placing hundreds of wooden nest boxes out on Rockabill Island, in effect providing the terns with secure little houses to nest in. 


Roseate Tern numbers up, but perils remain

Like most seabirds, Roseate Terns nest on the ground, but whereas most tern species prefer open areas to lay their eggs, Roseates nest in sheltered spots – usually under vegetation or beside rocky overhangs or in crevices. They like their nests to be hidden from above and from a distance to protect them from predators and poor weather. 

Life can be tough for a warden on Rockabill Island. Photo by Brian Burke

The scientists hoped the nest boxes would provide additional shelter, but by analyzing 15 years of data comparing the impact of traditional open nests with nests in the nest boxes, they found their strategy was having an even bigger positive effect.

Their analyses show that the nest boxes helped the Roseate Terns have much more success in raising their young: More eggs hatched, and more chicks survived to fledge into juveniles when they were born in the nest boxes.

This suggests the nest boxes help protect the terns from bad weather, predators, and even from squabbles with their neighbors, while also making the best use of limited space on this tiny island by allowing for a much higher density of nests.


“It is fantastic to have found that over three decades of a hard manual slog by BirdWatch Ireland wardens – during which time they put out hundreds of nest boxes on the island each year – was more than worth it,” says Darren O’Connell, a co-author of the article and a Research Fellow at University College Dublin. “What seems like a simple conservation strategy is proving to be very effective by having a really positive impact on Roseate Tern breeding.” 

Co-author Brian Burke, Scientific Officer with BirdWatch Ireland, added: “It’s great to now have the science to back up what we’ve been doing, and hopefully other conservation projects can learn from this.”

The nest boxes deployed by the wardens are cheap and easy to make, and on another positive note, many have been made and colorfully decorated by students in the local Balbriggan Community College, helping to open young eyes to the importance of conserving our precious biodiversity. 


Thanks to Trinity College Dublin for providing this news.

Watch a video about Roseate Terns using nest boxes in Ireland

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