CBS has reported that a path on the upper deck is being planned to enable bike riders to get across in both directions while a third traffic lane on the lower deck will ease congestion for drivers heading eastbound.

However, the discovery of a nest and egg in a tree has put work on a key part of the $70 million Richmond-San Rafael Bridge project on hold.

The species, Anna’s Hummingbird, is protected under the Migratory Bird Treaty Act that forbids the removal of the egg and offers other protections to birds.

The nest, about half the size of a fist, was discovered about a week ago when work was set to begin.

Randy Rentschler, from the Metropolitan Transportation Commission said: “In this particular case a bird’s nest was found. Hummingbirds are on the list so we followed the rules.”

“A single Hummingbird nest with an egg is going to cost us a couple of weeks,” Rentschler added.

Rentschler said he doesn’t know how much it will cost.

“At this point we think we can make the time up,” he said.

While stopping work for a single hummingbird egg may sound extreme, the bigger the project the bigger the odds that something like this will happen.

Rentschler said: “In all cases on major construction projects you can find a species of something that’s protected by somebody, the feds of the state.”