San Francisco Bay NWR Complex
Pacific Southwest Region

The Murre Maniac
The Common Murre Project Update July 2009

End of the Breeding Season

In July we witnessed the end of the Common Murre breeding season. The breeding season ended earlier than in previous years, with the last breeding birds on the rock gone by 13 July. In 2007 and 2008 birds were seen on the rock as late as 6 and 8 August. It has been an unsuccessful breeding season for the Common Murres on Devil’s Slide Rock and Mainland areas. At the mainland colony we saw a complete failure of breeding with no eggs hatching out of 32 eggs laid. There were 157 breeding sites monitored in our plots this year and only 11 chicks hatched. None of the chicks survived long enough to be considered fledged.

There are many possible reasons for such low breeding success in Common Murres this year. As discussed last month the murres may be traveling farther to find food, which makes it difficult to spend time incubating an egg or feeding a chick. As more and more murres leave the rock after abandoning an egg, some do not return at all, those that do come back do not spend as much time on the rock throughout the day. This leaves the murres that are still incubating eggs or brooding chicks more susceptible to the weather and predation because there are less murres around to help protect them. This is the first year since 1996 that no murre chicks have fledged from the rock.

July 2009 Colony Counts of Devil’s Slide Rock
Date #Murres   Date #Murres
July 2
July 16
July 4
July 18
July 6
July 20
July 8
July 22
July 10
July 24
July 12
July 26
July 14
July 29

*Compiled by Jonathan Shore


Last updated: September 1, 2011