Pigeons recognise friendly feeders - birds remember hostile people

The fluttering pigeons outside Gateway of India are as much a part of the tourists’ must-do lists as the coin throw at Rome’s Trevi Fountain.

But behind the light-hearted amusement of feeding pigeons may lie deep biological underpinnings that explain why the practice, as symbolised by Indian kabutarkhanas, has flourished down the centuries.

Pigeons can discriminate between friendly and hostile humans, an evolutionary advantage that may be one of the factors helping their populations thrive across urban centres at a time sparrows are in decline, scientists say.

Ornithologists have long observed what they believe is a rise in pigeon numbers in urban areas, a trend easy to sense in Indian cities with their traditional kabutarkhanas — public zones where pigeons congregrate to eat grain or other tidbits offered by humans. “Human benevolence is clearly among factors pushing pigeon populations upward,” said Mohammed Dilawar, an ornithologist tracking house sparrows for the Bombay Natural History Society, Mumbai.

“Pigeons also find it easier to bring up their little ones,” he said.

While newborn sparrows require an exclusive diet of insects, Dilawar said, young pigeons can survive on a liquid called “vegetable milk”, regurgitated by adult pigeons that feed on grain or other food that are always abundant from human feeders.

Now scientists in France have identified another facet of pigeon biology that probably help these birds in their search for friendly humans: pigeons appear to recognise individual people despite changes in clothing. In their experiments, Dalila Bovet and her colleagues at University of Paris asked two sets of people wearing different-coloured coats to feed pigeons in a Paris city centre park.

One set ignored the pigeons and allowed them to feed while other group chased the birds away preventing them from feeding. The pigeons appeared to recognise who was friendly and who was hostile, and were able to remember that information later.

The pigeons could recognise the hostile people even when they swapped their coloured coats with the friendly people. Even when hostile people changed stance and became friendly to pigeons, the birds continued to avoid them. “What is important — and surprising — is that the pigeons spontaneously used relevant characteristics of individuals instead of the most salient feature, which was the coloured coats,” said Bovet, associate professor at the laboratory for comparative ethology and cognition at the University of Paris.

“They seem to know that clothes are not a good way to tell humans apart,” Bovet told The Telegraph.

These findings, published earlier this year in the journal Animal Cognition, will be presented at a meeting of the Society for Experimental Biology in Glasgow on Sunday.

The scientists say the ability to discriminate between friendly and hostile humans is ecologically relevant because it could help the birds recognise a safe human feeder faster and save energy and time in gaining food. Overall, it is a combination of an abundance of food and nesting places as well as a decline in the population of natural predator birds that is contributing to rising pigeon populations, said Asad Rahmani, director of the Bombay Natural History Society.

Pigeons are what ornithologists call platform-nesters — birds that can build nests along ledges and corners of buildings.

“The population of predators such as peregrine falcons is low, and that is also helping pigeons,” Rahmani said.

“But any human-driven or unnatural rise in a species population can mean an ecological imbalance,” said Dilawar. “Pigeons are friendly birds, but they may also carry the risk of exacerbating respiratory infections.”

Posted by imran Monday, July 4, 2011


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