Matches and mismatches: ocean climate, prey phenology and breeding success in a zooplanktivorous seabird

Abstract

In the marine environment, climatic changes are asymmetrically altering the phenologies of species at different trophic levels, causing an increase in the severity of mismatching between predators and their prey. At Triangle Island (British Columbia, Canada), the zooplanktivorous seabird Cassin's auklet Ptychoramphus aleuticus breeds less successfully in warm-water years than in coldwater years. Previous researchers hypothesized that this occurred because, in warm years, there is less temporal overlap between the auklets' nestling-provisioning period and the period when the copepod Neocalanus cristatus, an important prey item, is available to the birds in near-surface waters. I tested this hypothesis with data collected between 1996 and 2006. As predicted by the match-mismatch hypothesis, the copepods became scarce in nestling diets 2 to 3 wk earlier in warmer than in colder years, and were less prevalent overall in warm years. The auklets' offspring were more likely to survive from hatching to fledging, and were heavier in mass at fledging, in years in which their diets were richer in N. cristatus. Information-theoretic approaches indicated that this effect of diet, a direct consequence of spring ocean temperature, outweighed other indirect influences of ocean temperature on offspring performance. Comparison with independent data on the timing and magnitude of local annual zooplankton biomass peaks indicated that prey timing, rather than prey abundance, was the key factor determining seasonal prevalence of the copepod in nestling diets. This study adds to a growing body of evidence showing that climate-driven phenological mismatches can alter critical trophic interactions, with potentially deleterious demographic consequences for predators. KEY WORDS: Match-mismatch · Ocean climate · Auklet · Copepod Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 368: [295][296][297][298][299][300][301][302][303][304] 2008 ( Reid et al. 2006), strong temporal matching between their breeding period and the annual peak in the availability of key prey species can be vital to successful population processes (Regehr & Montevecchi 1997, Durant et al. 2003, Suryan et al. 2006.At Triangle Island (British Columbia, Canada), previous research showed that in cold, phenologically late years, when compared with warm, phenologically early years, offspring of the seabird Cassin's auklet Ptychoramphus aleuticus grew more quickly on diets that remained richer in the copepod Neocalanus cristatus until later in the season (Bertram et al. 2001, Hedd et al. 2002. Invoking the match-mismatch hypothesis, these authors proposed that the relationship was causal: in cold, late years, the period of maximal biomass of late-stage copepodites in surface waters begins late and ends late, matching well with the birds' energetically demanding chick-provisioning period (which is comparatively fixed), while in warm years, the peak occurs too early and spans too narrow a window of time for the birds. H...

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