Male birds are singing to attract a mate and it is beautiful to hear. Richard Kuehn and Dean Schuler took a walk yesterday and found these birds - a Pacific Wren [formally called Winter Wren] and a Wilson's Warbler.
To hear the sound of a Pacific Wren, here is the link to the Cornell Lab of Ornithology: http://www.allaboutbirds.org/guide/Pacific_Wren/sounds. And to hear the Wilson's Warbler, here is the link: http://www.allaboutbirds.org/guide/Wilsons_Warbler/sounds
Thanks to Rich for allowing me to share his photos with you here.