Future of tropicbirds up in the air

Wednesday, 11 January 2023

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Future of tropicbirds up in the air

Change to status of Red-tailed Tropicbird considered

The spectacle of a gleaming white tropicbird contrasting against the tropical, aquamarine water and the dramatic landscape of Christmas Island is certainly one to savour, but, sadly, it’s one that is less common than it was just a few years ago.

Populations of the subspecies of the Red-tailed Tropicbird which breeds on Australian territories in the Indian Ocean have declined by more than a third in recent years. That’s an alarming drop, one that has been noted by the Threatened Species Commission and has given its members cause to reconsider the bird’s current conservation status.

Christmas Island is the key breeding site for this subspecies of the Red-tailed Tropicbird. They lay their eggs on the bare ground in cavities in the island’s coastal cliffs, and when the island was predator free, it was a haven for the birds.

However, with introduced predators now rife on Christmas Island — particularly cats, and rats and Yellow Crazy Ants to a lesser extent — nesting tropicbirds, as well as their eggs and chicks, are regularly preyed upon, and this has caused the steep decline recorded over the last thirty years. Now there are thought to be only 3350 of the birds surviving.

There is currently an eradication program being undertaken and, if successful, it will rid Christmas Island of all of its cats by 2025. Introduced Yellow Crazy Ants are also being controlled, while rodent control has, apparently, largely been left to the island’s voracious population of red crabs. The more existential issue of climate change, with its increasing frequency and severity of cyclones will also increasingly affect the island’s birds.

Although this subspecies of the Red-tailed Tropicbird breeds at other Indian Ocean nesting sites on the Cocos–Keeling Islands, Ashmore Reef and Rowley Shoals, their breeding populations are all small, and pale into insignificance when compared with the numbers breeding on Christmas Island. These tropicbirds also once bred much farther south, formerly nesting in very small numbers on the Houtman Abrolhos as well as on Sugarloaf Rock off Cape Naturaliste (and, historically, a handful of other south-western islands), but these sites were deserted some years ago.

The Threatened Species Commission has yet to make a decision on the conservation status of these spectacular birds. Whatever that decision may be, it will play a role in shaping the future of the Indian Ocean’s Red-tailed Tropicbirds.