Orchard Road and bird crap have become largely synonymous over the years.

This is the result of thousands upon thousands of birds descending upon the trees lining the prime shopping district every day -- mostly in the evenings and when it is not raining -- as the smug avian creatures eat, chirp and poop all over the trendy hairless apes below that roam the streets there thinking they have made it in life because they are at Orchard Road.

And if you have ever been crapped upon by one of these feathery fellows, well, now you know why, according to Man Vs Birds, a 30-minute documentary that will be showing on TV soon.

Here's the official explanation from the documentary's trailer:

"Though heavily urbanised, Singapore is located in one of the most biologically-diversed regions of the world. For the birds migrating on the East Asian-Australasian flyway, this island is a vital refuelling stop."

"So when moving between forest patches a lot of these birds have to move through urban spaces like Orchard Road, flanked by Botanic Gardens, Dempsey Hill, The Southern Ridges. And these are places you have migratory birds and forest birds as well."

"There are four species of birds you can find at Orchard Road. The Asian Glossy Starling, the Javan Myna, the house crow and the rock pigeon."

"So the birds have rather cleverly partitioned Orchard Road into three tiers. The highly intelligent crows would perch highly in the tree canopy. In the middle you usually have the starlings, the mynas would hang around there but they're usually further down on the ground as well. But the ground level is mostly dominated by the pigeons bobbing their heads."

"It seems like quite and efficient system, probably one of the reasons why all these species can be so abundant in Orchard Road."

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Man Vs Birds is directed by Kylie Tan and Priscilla Goh, both 25 years old. It took six months to shoot and is one of five documentaries in the Discovery Channel series Singapore Stories.

The documentary trails Steven Goh, executive director of the Orchard Road Business Association, who is expending a lot of effort and resources to keep the 2km tree-lined shopping boulevard clean.

For example, every night, 3,000 litres of high-pressured water is used to clean the streets to rid it of bird droppings.

A screening of the documentary will be held on July 11 at at People's Park Complex. (Details here.)

Alternatively, you can catch the documentary when it is shown on Discovery Channel (StarHub TV Channel 422) on July 16.