Friday, July 13, 2007

Fledging Murre Chicks take the Big Leap!

Late June into early July tends to be one of the most exciting times out here on Southeast Farallon Island because this is the time of year when our Common Murre chicks are fledging. Fledging is the term we use for when a chick is ready to leave the nest site and start its new life out on the open ocean. For the past four months, Murre parents have faithfully taken turns incubating their eggs and feeding their chicks. The adults must feed their chicks at the colony for approximately 25 days before they gain the sufficient size and grow in the appropriate feathers for life on the ocean. When the chicks are getting close to fledging, they begin exchanging intense vocalizations with their parents - almost as if they are discussing whether or not it is time to leave. Ultimately though, it appears to be the chick that makes the final decision and once the chick has decided to go there is no turning back.

For Murres, when the chick is ready to go, it is the father that takes the chick out to the sea and teaches them how to find and catch their own fish. Fledging, however, can be a difficult process. Chick and dad have to make their way through the entire colony of Murres (see diagram below) - which can be especially difficult seeing as how Common Murres have some of the most densely packed colonies of any bird in the world! Even after the father and the chick get through the colony (trying to avoid getting pecked by other territorial Murre adults), the chick still has to conquer the toughest part of its journey—the cliff jump. It is at this point, where the father flies down to the water below and calls to his chick to jump in. At some places on the island the chick has to jump off a ledge that is up to 150 feet high! That would be the equivalent of a human jumping off a building that was 1.5 times the height of the Eiffel Tower! Meanwhile they have to make sure they clear the rocks below and be cautious of the Western Gulls that are in the area and are always looking at them as an easy meal. This may seem like an unimaginable task for a chick that is only 20 days old, but they still manage to do it.

Route a typical murre chick takes to the ocean

Late evening (an hour or two before dusk) tends to be the time when most chicks begin their seaward journey and fledging continues throughout the night. It is to the chick’s advantage to fledge under low light conditions because it is more difficult for their predators to spot them at the cliff’s edge or in the water. As you can imagine watching this series of events take place can be quite exciting and is often one of the highlights of the seabird season for the biologists. On those nights that look good for chick "jumping"we often try to make dinner early so we can catch watch as many chicks fledge as possible.

It is always a memorable experience watching Murre chicks fledge because each chick’s journey is unique. Sometimes the chicks walk right down to the water's edge (as in the video above), sometimes they make a clean belly-flop into the water, and other times they belly-flop right onto the rocks below. The rocks don’t stop them though. They just get right back up, as if nothing happened, and continue on until they make it to the water, sometimes tumbling all the way down the cliff face and ploping butt end first into the crashing surf.

Once the chicks make it into the water they meet up with their dads and swim away from the island in search of food. Once on the water they are relatively safe from predators and will begin receiving their first fishing lesson. Murre dads continue to stay with and care for the chicks for about 2 months, but the chicks learn to feed themselves after only about a week on the water. With any luck these chicks will grow up fat and happy and return to the island in 5 to 6 years to find a mate and a territory of their own to call home.