Winter pre-conditioning of seabird phenology in the California Current

Abstract

Climate change is predicted to affect the phasing and amplitude of upwelling in eastern boundary current marine ecosystems. Effects may be strongest during the spring or summer 'upwelling season,' but may also be influential during winter before the spring transition. We tested the hypothesis that wintertime environmental forcing 'pre-conditions' the ecosystem and affects the timing and success of breeding in 2 species of seabird, Cassin's auklet Ptychoramphus aleuticus and common murre Uria aalge, reproducing in the central California Current. Time series of the mean and variance of egg-laying dates were correlated with regional winds and sea surface temperature, which were used as proxies for the forcing and oceanic response of coastal upwelling, respectively. Winter proxies of upwelling were the most significant determinants of seabird reproductive phenology, with anomalously strong upwelling in January to March leading to earlier dates of egg-laying in both species. We hypothesized that anomalous (early) winter upwelling, even of weak magnitude or short duration, could seed the region with sufficient nutrients to enhance productivity and prey availability, leading to a healthier adult breeding population and an earlier start to the breeding season. The magnitude of the previous year's November winds were also positively correlated with the variance of egg-laying dates for the common murre, with upwelling-favorable winds leading to greater synchrony in egg-laying. We conclude that winter environmental conditions are important determinants of ecosystem dynamics in the California Current, and that seabird phenology is a particularly useful ecosystem indicator.

Winter ichthyoplankton biomass as a predictor of early summer prey fields and survival of juvenile salmon in the northern California Current

“…In the California Current, Schroeder et al (2009) indicated that productivity was enhanced even with modest upwelling in early winter and was followed by increased abundance of prey resources and earlier nesting phenology in seabirds. Additionally, rockfish growth and seabird reproductive success has been related to winter ocean conditions, particularly during February (Black et al 2010).…”

Climate-driven synchrony in otolith growth-increment chronologies for three Bering Sea flatfish species

“…Notably, chronologies did not relate to MEI, a measure of the ENSO, even when lagged. Though the impacts of ENSO have been widely observed in the north Pacific, especially in the California Current Ecosystem (Wells et al 2008, Schroeder et al 2009, the PDO appears to have much more relevance at higher latitudes.…”

Climate-forced seasonal mismatch between the hatching of rhinoceros auklets and the availability of anchovy

“…Although total snowfall in March was negatively correlated with temperature in the Teuri region, snow did not influence hatching date directly. Spring SST affects timing of breeding in several seabird species (Bertram et al 2001, Gjerdrum et al 2003, Frederiksen et al 2004, Thayer & Sydeman 2007, but wintertime conditions may also be influential (Schroeder et al 2009). The covariance between air temperature near the colony (AIRTEMP) and SST around the colony (LSST ) in March was significantly positive.…”

“…Inter-annual variation in the abundance and distribution of prey may similarly result in mismatches between food availability and predator needs, with substantial reproductive consequences (Anderson & Piatt 1999, Hunt & Stabeno 2002, Platt et al 2003, Edwards & Richardson 2004. In seabirds, the date of arrival at the breeding area or the egg-laying date depends on inter-annual variation in ocean climate (Durant et al 2004, Frederiksen et al 2004, Barbraud & Weimerskirch 2006, Schroeder et al 2009 this Theme Section). Biological determinants of breeding data have also been established.…”