Cannibalism witnessed in UAE cormorant colony

Biologists in Umm Al Quwain have documented young Socotra cormorants eating their siblings.
Siniya island is home to the country's biggest colony of Socotra cormorants, with around 15,500 breeding pairs. But that number has been dwindling and used to be three times as great. Photos courtesy Rob Gubiani
Siniya island is home to the country's biggest colony of Socotra cormorants, with around 15,500 breeding pairs. But that number has been dwindling and used to be three times as great. Photos courtesy Rob Gubiani

UMM AL QUWAIN // Lazy, hungry, obnoxious and reluctant to leave home - young Socotra cormorants bear all the hallmarks of any other teenager.

It is the result, in part, of some extremely tough love from their parents. When the chicks are six weeks old, their parents take a somewhat extreme step to "encourage" them to start flying: they stop feeding them.

Sometimes, the hungry fledglings respond to this in the manner intended, taking to the wing in search of food. But often, they take an extreme retaliatory step, making a snack out of their younger neighbours.

Rob Gubiani, a biologist at UAE University, has seen it several times. One teenage bird, he says, "grabbed the pink chick, newly born, tilted its head back and swallowed it whole."

Phalacrocorax nigrogularis is not much to look at. A graceless black bird endemic to the Gulf, it is hated by fishermen, who see it as a threat to their stock.

In part, the birds are their own worst enemy. They throw up food when they're scared, and are such poor flyers that they have been known to impale themselves on the acacia's long thorns when they fly off in a fright.

What's worse is their smell - a crime for which at least one colony, in western Abu Dhabi, was completely destroyed.

But they are poorly understood. "We really don't know much about any of these seabirds here," says Dr Sabir Muzaffar, the UAEU professor who heads a project to study them, "in terms of biology, how frequently they feed, how quickly their chicks grow."

From August to April, Siniya island, just off the coast of Umm Al Quwain, is home to the UAE's largest remaining colony, comprising around 15,500 breeding pairs - around a sixth of the global population.

Funded through the National Research Foundation, the Mohammed Bin Zayed Species Conservation Fund and in collaboration with the Environment Agency-Abu Dhabi and the Marine Environmenal Research Centre, the scientists studied 14 plots - each containing about 15 nests - at the edge and in the middle of the Siniya colony during the peak mating season, from September to December.

Even their nesting sites held a surprise. While the cormorants usually live on unshaded sandy islands, on Siniya they have taken to nesting under planted acacia trees.

"A large proportion of the birds were using trees for shade, which is something we've never seen before," Mr Gubiani says.

"At this point we can't say definitively that they're actively choosing trees but it's still a trait we hadn't noticed before."

He suspects it might be an attempt by the parents to conserve energy, allowing them to concentrate their efforts on finding food rather than shading the eggs themselves. The result, he says, has been bigger than normal eggs.

Each female lays three or four eggs. Typically two hatch, and the chicks stay in the nest for around a fortnight. After that, says Dr Muzaffar, "they start wandering around and they form these creches".

The creches are huge gatherings of around 5,000 chicks of different ages. That in itself is unusual, according to Keith Wilson, the marine programme director for Emirates Marine Environmental Group (EMEG), who has been cataloguing a colony of Socotra cormorants on Umm Al Qasar, off the coast of Abu Dhabi more than 150km west of the capital, for three years.

"[It] sounds as though the feeding is not as good as it used to be," he says. "Normally if they don't have disturbance they would [creche] in a phased way, so they wouldn't be eating each other because they'd all be the same size."

But on Siniya, as elsewhere in the Gulf, he says, "there's so much disturbance that they're all over the place. That's unnatural, it wouldn't happen normally."

That disturbance appears to be a combination of construction work and industrial work, including oil drilling.

And the result, never before documented in cormorants, is cannibalism. Older chicks - typically seven weeks old - prey on their younger brethren.

The behaviour has been seen nine times so far.

"I would say the level of cannibalism they've got in Siniya is mainly due to disturbance," Mr Wilson says. But he points to similar occurrences in other species, such as gulls, ospreys, hawks and ravens. "To a certain extent it would be natural but it's exacerbated by disturbance."

The team hopes, too, to disprove the popular belief that the cormorants are a threat to fishermen. Already they have seen that adults eat a diet of flying fish when their chicks are young, indicating a possible link between the breeding cycle of flying fish (which are not an important species for fishermen) and the breeding cycle of the cormorants.

"It's a good argument to support the fact that they aren't competing directly with the fish industry," Mr Gubiani says. "That's a misconception."

While the birds themselves are unloved, their eggs are popular with feral cats and foxes which swim at low tide across the 80-150 metre channel from the mainland.

The eggs have human fans, too. Instances have been reported of people taking the eggs from entire colonies. And while the birds themselves are now protected under UAE hunting laws, the eggs are not.

That, as well as a general decline in habitat, is hurting the population. Despite the impressive flock that circles Siniya, its numbers are in rapid decline, and it is listed as vulnerable by the International Union for Conservation of Nature (IUCN).

EMEG reports that Abu Dhabi's 12 colonies have dwindled to six, home to a third of the global population. At least seven of the UAE's 20 colonies have gone extinct since 2006.

On Siniya, the population has fallen from an estimated 50,000 breeding pairs to just 15,500. There are now an estimated 38,000 in the entire country.

"There have been places where apparently they were looking at over 50,000 breeding pairs and those colonies are completely gone now," Dr Muzaffar says.

"There have been substantial declines over the years and we're just hoping we can hold onto the ones we have now."

Mr Wilson is hopeful that further study can persuade UAE and IUCN authorities to list the species as endangered.

"The birds have been sort of moving around from island to island," he says. "Now that there's a lot of development in the Gulf, the oil is taking over, the islands are being developed and the number of islands [with colonies] is plummeting. It should be listed as threatened. This is the closest that you're going to get to an endemic bird in the region, and yet it's the only one that's not protected and it's the only one that should be protected because it's the only place in the world where it lives."


Published: March 3, 2012 04:00 AM


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