9/11 memorial lights trap thousands of small birds

Two beams emanating from Manhattan, known as the Tribute of Light, had to be turned off five times to allow the migrating birds to continue on their journey last week.

The birds were on their way from Canada to the warmer climate of the Caribbean and South America. They do not always fly over New York and the last time their migratory path coincided with September 11 was in 2004.

The Tribute of Light is turned on by the Municipal Art Society every year on the anniversary of the attacks.

Monitors from New York City Audubon, a conservation organisation, observed this year's tribute and alerted organisers to the confused birds.

An Audubon spokesmanu00a0 said, "We have a protocol in place in partnership with the Municipal Arts Society in case something happens like it did."

The lights were shut off for about 20 minutes each time to allow the birds to clear the area. An estimated 90,000 birds die each year after becoming disoriented by lights and crashing into skyscrapers in New York.