Masked Booby makes first appearance in Tubbataha in 20 years

On May 11, 2016, in the grey early morning light on a remote coralline isle in the middle of the Sulu Sea, a group of researchers and marine park rangers saw an animal that no one has seen in the area for more than 20 years.

It was a Masked Booby (Sula dactylatra), a large and strikingly plumaged seabird, that was last seen on Bird Islet in the North Atoll of the Tubbataha Reefs Natural Park (TRNP), Palawan, in 1995.

The Masked Booby, which is the biggest and heaviest of the six surviving booby species in the bird family Sulidae, was observed on the mornings of May 11 and 12 by a survey team led by environment and natural resources management specialist Arne Jensen, who has studied the seabirds in Tubbataha for more than 25 years and is chief consultant of the Tubbataha Management Office on the management of seabirds.

The team was on Bird Islet, which is about 170 kilometers southeast of Puerto Princesa, to conduct a census of seabirds and their breeding areas in TRNP. The team has held several surveys over the past years but this is the first time that it has recorded the Masked Booby.

The Wild Bird Club of the Philippines Checklist of Birds of the Philippines 2016 declares the Masked Booby as “Extirpated,” with the last sighting of a resident bird from “North Islet, Tubbataha Reefs, Palawan (1995).” The checklist notes one sub-adult documented “off Babuyan Islands, Cagayan (2003).” With the Philippine population believed to be gone, any new sighting is presumed to be of individuals that have strayed from abroad.

The team observed the lone Masked Booby standing and walking among Brown Booby (Sula leucogaster) and Greater Crested Tern (Thalasseus bergii), which, along with Brown Noddy (Anous stolidus), Black Noddy (Anous minutus), Sooty Tern (Onychoprion fuscatus), and Red-footed Booby (Sula sula), roost and nest in dense colonies on the uninhabited islet.

The Masked Booby superficially resembles the smaller Red-footed Booby but it has a dark facial skin, yellow bill and iris, and a black tail. Like other sulids, it is a superb flier that hunts by plunge-diving for fish in deep waters.

Boobies got their name after European sailors stumbled on to them on land and thought that the trusting and guileless seabirds were stupid for letting themselves be approached and killed without a struggle.

Bird Islet: An important nesting place for seabirds in Tubbataha

Bird Islet in Tubbataha is the Masked Booby’s last known nesting place in the Philippines but unabated egg poaching until 1996, and other human activities have contributed to wiping out the population, according to Jensen.

Seabirds need uninhabited islets for nesting. They have no natural defense against humans and the non-native predators and pests that are associated with human settlements: dogs, cats, and rats.

“The only reason why so many seabirds breed in Tubbataha is because the protected area remains free of these predators. However, the risk remains that they may accidentally be introduced,” Jensen said.

Up until 1988 when Bird Islet was declared off-limits to humans—except for the annual census, which has strict rules to ensure the safety of the resident seabirds and marine life—itinerant fishermen have looted eggs and chicks from the site. Poachers also used the islet to sun-dry strips of meat from turtles and other marine animals they have caught in the surrounding waters.

The presence of exotic plants on the islet may also have contributed to the demise of the Masked Booby.

The central area of the islet was overgrown with ipil-ipil and other exotic plants at the time when the Masked Booby population died out, said Juan Carlos T. Gonzalez, director of the Museum of Natural History at the University of the Philippines-Los Baños and professor of zoology at the UPLB Institute of Biological Sciences.

Fishermen had planted the trees to use as a navigational aid, and a source of firewood when they spent time there.

The Masked Booby is a ground nester and the trees meant it had to compete with other ground nesters such as Brown Booby and Greater Crested Tern over valuable nesting space on the small island, said Gonzalez, who was part of the survey team.

Over the years, the marine park rangers have uprooted the exotic plants at the site, easing the pressure on ground-nesters to compete for space.

Historical records of the Masked Booby in the Philippines

The first documented sighting of Masked Booby on Bird Islet was in 1911 by American explorer and zoologist Dean Worcester, who visited the area. (Worcester, who became Secretary of the Philippine Government Commission, was a controversial public official and was convinced that he was the subject of a scathing editorial in the newspaper El Renacimiento entitled “Aves de Rapiña” in 1908.)

In 1982, ornithologist Robert S. Kennedy reported seeing about 150 adult Masked Boobies on the islet.  By 1992, Jensen found only a single pair of adults and three sub-adults. In 1995, just one pair was found and photographed on the islet. Those two birds were the last of the species seen on the islet for twenty-one years.

Data from e-Bird, an online bird checklist program run by Cornell Lab of Ornithology and National Audubon Society, show the same trend of declining numbers over the years.

A birder reported in e-Bird of four immatures and one adult “sitting on anchor buoys” at the “Santiago oil exploration temporary platform” about 40 kilometers off the west coast of Palawan on June 30, 1980. The same observer reported the same number of birds on June 29, four immatures on June 27, and three immatures on June 26.

On June 13, 1981, the same reporter recorded two females and one immature at Bird Islet. The next day, he reported seeing “several flying at sea” but none roosting on the small island.

There is an e-Bird report dated July 24, 2007 of a single Masked Booby at “South China Sea, Ilocos Sur,” but report details are sparse and no photograph is available.

On March 2002, one was photographed flying over the Babuyan Channel in northern Luzon. This is the last photographic evidence of Masked Booby in the country prior to May 11, 2016.

Other reports from nearby countries in the past few years are a sighting of two birds in Indonesia, in November 13, 2012; and one each in February 26, 2015, August 30, 2015, and October 14, 2015, in Taiwan.

The value of monitoring seabird populations

Keeping track of seabird populations is important because “birds are fast-responding indicators to changes in the environment,” said Jensen, who is also outgoing country representative and international associate expert of Wetlands International.

“In the case of Tubbataha, the presence of a large number of a diverse number of seabird species mirrors the excellent condition of the marine environment, especially the abundance of fish and squid which is the main food source for the seabirds,” he added.

“The monitoring of seabirds is also part of the overall park monitoring scheme detecting human disturbances in the area,” Jensen said.

“The presence of the Masked Booby suggests that “the conditions for the seabirds in the area are optimal again and that the recovery of the populations of seabirds after nearly a generation of devastating human activities such as collections of eggs and chicks and a massive, general human disturbance,” he added.

“The increase in the seabird population from about 5,000 breeding seabirds in 1998 to nearly 40,000 individuals in 2016 shows how well TRNP is being managed,” Jensen said.

Will the Masked Booby breed again in Tubbataha?

The sighting of a lone booby does not guarantee that the species is making a comeback, but it is a hopeful sign, said Gonzalez.

A return to the islet of the Masked Booby “may indicate that the detrimental conditions that caused its extirpation in the Philippines have been addressed, if not resolved, due to effective management of the marine protected area," he stated.

Jensen believes the likelihood of the species nesting again on the islet “is there but it is very slim.”

“The nearest colonies in Indonesia and northwestern Australia are all very small and in decline. So there is a recruitment problem because of the scarcity of Masked Booby individuals,” he said.

“In addition, about 40% of the preferred booby breeding area in Tubbataha has been lost due to a combination of the rise in sea levels, and more and stronger storms hitting Bird Islet and causing erosion,” he stated. 

Survey data show that the islet’s land area has shrunk by 21% since 2004.

The shrinking land area is “creating a housing problem” for the Brown Booby, which has a very high breeding density. This means the Masked Booby will therefore have to compete for access to the prime breeding areas it prefers, Jensen explained.

Plastic pollution is an emerging threat in the area, he noted. Every year, the team comes upon a number of dead seabirds that are entangled in abandoned fishing gear.

There are also signs that seabirds may be are ingesting bits of plastic because they mistake them for food. There is still no evidence that this is happening in Tubbataha but the team is watching the situation, he added.

When the survey team departed Bird Islet on the morning of May 12, the Masked Booby was still there, standing on its preferred spot on the northeastern portion of the islet, looking around, and practicing courtship moves such as picking up twigs and feathers from the ground.

Perhaps one day, an unpaired individual of the opposite sex would come along to share its scrap of sand. But for now, among the thousands and thousands of seabirds on the coralline islet, it is the only one of its kind. — TJD, GMA News