Wednesday, 11 October 2017

Sooty Tern and Brown Booby breeding event

Recently we flew to New Caledonia for a three-week sailing trip, which included the Isle of Pines in the south and then east across to Ouvea at the northern end of the Loyalty Islands group.

We spent a couple of days at the Atoll de Beautemps-Beaupre (1), the northern most atoll of Ouvea, where we found a nesting colony of Sooty Tern (Onychoprion fuscatus) and a smaller nesting colony of Brown Booby (Sula leucogaster).  I also found a surprise pair of Peregrine Falcons, Falco peregrinus sub species nesiotes, which are found only in Vanuatu and New Caledonia - where they are uncommon - and in Fiji, where they are rare.

We anchored off the only coral cay island on the Atoll de Beautemps-Beaupre.

Please click on photos to enlarge.

Alchemy 1 anchored off the coral cay island in the Beaupre Atoll.

The uninhabited island is about 1 km long and is based on an ancient coral reef with overlying coral sands which support the dominant Coconut Palms plus a small variety of other tree species including Pandanus Palms.

Access to the breeding colonies on the island is difficult due an eroded coral rock shoreline which is undercut due to sea erosion of the old coral reef. However, for breeding sea birds, the rocky shoreline does provide some protection from visiting seafarers who anchor at the opposite end of the island.  Access over much of the island is also difficult due to thick palms and other understory vegetation. After a failed attempt to walk to the colonies I accessed them by water in Alchemy 1’s dingy.

The understory made walking on the island near impossible – the Coconut Palms would have once been managed for copra by the locals. However they now look to be long neglected.

The undercut ancient coral reef is typical of many of the coral cay islands of New Caledonia. Obviously, this coral was built in a time when sea levels were two to three metres higher than the present level.

The Brown Boobies were nesting and resting on a bare section of old coral reef at the far end of the island from our anchorage.

View from where I got ashore from the dingy along the exposed ancient coral reef towards the vegetated coral cay island.

My first task was to make my way slowly and carefully past the nesting Boobies taking some photos as I went. Most of the birds stayed on their nests and the few that flew soon returned when I had passed by. There were no predators to threaten the Boobies – the only other water bird I saw in the area, apart from the Sooty Terns, was one grey morph Reef Egret.

Male Brown Booby – note the blue face and bluish feet.
Same Booby as above in a different position.

Female Brown Booby – note the yellow face and feet.

There were approximately 30 Brown Booby nests. Many more birds were roosting or perhaps preparing to breed. There may have been even more Boobies roosting on the island overnight. Breeding had just begun as the nests I saw contained only eggs and all other nests had birds sitting with no chicks present as far as I could see.

Male Brown Booby on a nest incubating eggs.

Typical Brown Booby nest – there are usually 2 and rarely 3 eggs in a Brown Booby clutch so there still could be another egg added to this nest.

There were many more Brown Boobies present than were nesting at this stage. Some took briefly to the air allowing for a few flight shots.

Male Brown Booby in flight.
Female Brown Booby in flight.
Female Brown Booby – their forward-facing eyes no doubt aid prey capture as this species, like gannets, dive for their food. Their large webbed feet also help propel their dives to deeper depths in pursuit of prey.
This is an immature Brown Booby from a previous breeding event.  

Having passed through the Booby nesting area I came to the Sooty Terns, where large numbers of advanced juveniles were in many crèches spread along about 100 metres of the rocky shoreline. All up, by my conservative estimate there were probably 400-500 juveniles present. Given Sooty Terns only lay one egg there should be about 1,000 parent birds present. However there were nowhere near this many seen, so I assume most of the adult birds were out at sea hunting or perhaps they had moved on, leaving the young to fend for themselves?

Adult Sooty Tern – they are very like Bridled Terns.
Close-up photo of a juvenile Sooty Tern.
The juveniles have off-white under-wing coverts, lower belly and vent.
The young terns exercised their wings from time to time.
A small section of one of the juvenile Sooty Tern crèches – they mostly gathered close together for protection – but from what?
More young Sooty Terns sharing a rock area with Brown Boobies – some adults and juvenile Terns are in the air.

At this stage I reached the start of a section of shoreline with crèches of young spread along about 100 metres of rocky reef. To go any further would have unduly disturbed the young birds so I sat down on a rock and observed the activity.

I felt the birds seemed to be a little agitated especially the adult birds which flew in at speed wheeled around over the juvenile crèches and immediately zoomed away again without stopping to feed a young one. I was starting to think I must be the cause of their behaviour when I noticed a different bird in the air above me. A quick look with the bins revealed a Peregrine Falcon. It circled around and around calling as it went.

Peregrine Falcon circling the Sooty Tern crèches.
The Falcon called constantly as it circled.

After taking a few photos of the circling Falcon I picked up the call of a second Falcon which I soon found perched in a Coconut Palm before me and right above a couple of juvenile Sooty Tern crèches.

The female Falcon is perched in the tall palm leaning to the right just to the left of centre of the photo – the juveniles are on the rocks below.
The second Peregrine Falcon perched in a Coconut Palm almost directly above a couple of the tern crèches.

The second Falcon was noticeably larger than the circling bird so I decided this was a male-female pair. A later check of Guy Dutson’s Birds of Melanesia field guide revealed that this pair with a buff or rufous wash on their underparts were the sub species nesiotes which is uncommon in Vanuatu and New Caledonia where it breeds and is rare in Fiji where it has also been recorded breeding.

I was surprised to find Peregrines way out in the Pacific Ocean exploiting a temporary Sooty Tern breeding event on a remote coral cay island.  Here, picking up young chicks and juveniles would be very easy for these accomplished hunters. As the juvenile Sooty Terns were close to moving on, the Peregrine pair would also soon be needing to move on and find new prey to exploit.

I sat for 30 minutes or so looking to see if the Falcons took a young tern however the circling bird soon landed on a Coconut Palm a short distance away and the female remained perched in the palm above the tern crèches. I took a few flight shots of the terns while I sat observing. The terns were very fast for photos however I managed to capture a few passable images.

Juvenile in flight. 

It was soon time to return to Alchemy 1 for morning tea and then a snorkel on the reef.

My water taxi arriving to pick me up from my session with the Brown Boobies, Sooty Terns and the Peregrines.

What a privilege to visit such a remote and beautiful location and observe both sea birds above the atoll and sea life below.

(1) Named after a famous French Hydrographic Engineer and cartographer, Charles-Francois Beautemps-Beaupre 1766-1854.

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