ROTH, J.E., SYDEMAN, W.J. & MARTIN, P.L. 2005. Xantus’s Murrelet breeding relative to prey abundance and oceanographic conditions in the southern California bight. Marine Ornithology 33: 115-121.

We investigated the effects of temporal variability in prey abundance and oceanographic conditions on Xantus’s Murrelet Synthliboramphus hypoleucus breeding on Santa Barbara Island, California, USA from 1983 – 2001. We used estimates of prey abundance from California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys. We focused on known murrelet prey, including larval northern anchovy Engraulis mordax, larval Pacific saury Cololabis saira, larval rockfish Sebastes spp., and mesozooplankton (including euphausiids). We obtained data on upwelling and sea surface temperature (SST) from the National Oceanic and Atmospheric Administration (NOAA) to characterize oceanographic conditions. Average clutch initiation date was earlier in years with abundant mesozooplankton, stronger upwelling, and lower SST. Average clutch size was higher in years with abundant larval saury and mesozooplankton and lower SST. These results suggest that murrelets in the Southern California Bight (SCB) are influenced by “bottom-up” processes in which variability in oceanographic conditions affects breeding through effects on prey abundance.

Key words: Xantus’s Murrelet, breeding biology, prey abundance, oceanographic conditions, Santa Barbara Island, Southern California Bight