Reproductive success of planktivorous seabirds in the North Pacific is related to ocean climate on decadal scales

Abstract

Growing evidence indicates relationships between seabird demography and both largeand small-scale variation in climate and oceanography, yet few studies have examined multiple species and locations simultaneously. As secondary consumers, least, whiskered, and crested auklets (Aethia pusilla, A. pygmaea, and A. cristatella, respectively), congeneric planktivorous seabirds endemic to the Bering and Okhotsk seas, are expected to respond to changes in ocean climate due to their low trophic positioning. From 1990 to 2008, we measured reproductive success (productivity) and breeding phenology (mean hatching date) of auklets on Buldir, Kiska, and Kasatochi, 3 islands spanning 585 km across the Aleutian Islands, Alaska, USA. A model including Island, Species, and Winter Aleutian Low Pressure Index (ALPI) best explained productivity, with reproductive success decreasing among all species with increasing ALPI (β = -0.273 ± 0.0263 [SE]), likely through control of water temperature and prey (zooplankton) availability. Auklet productivity also increased with increasing winter sea surface temperature (SST) in the western North Pacific and western Bering Sea (and correspondingly decreased with increasing SST in the Gulf of Alaska), and was correlated negatively with spring sea-level air pressure in the North Pacific. These responses are reflective of positive values of the Aleutian low pressure system. Though our datasets cover only 19 yr or less, we found similar correlations between climate and auklet productivity among all species and islands. Together, our results suggest that ocean climatic conditions and reproductive success of planktivorous auklets are significantly related.KEY WORDS: Productivity · Oceanography · Demography · Aethia spp. · Least auklet · Crested auklet · Whiskered auklet · Aleutian Islands 424: 205-218, 2011 Pacific and Bering Sea, this shift resulted in greater climatic variability (Bond et al. 2003, Hunt & Elliott 2004, Rodionov et al. 2005, greater stratification of the water column, and increased primary productivity (Trenberth & Hurrell 1994, Iida & Saitoh 2007. Other purported ecosystem shifts have occurred in 1989-1990 and 1998-1999, but these putative shifts in system state have not been well documented (Overland et al. 1999, Hare & Mantua 2000, Mueter et al. 2007. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerSeabirds, as conspicuous, generally unexploited, secondary and tertiary consumers in marine systems, provide a unique opportunity to investigate coupled climate-ecosystem variation (Durant et al. 2009). Indeed, the relationship between ocean climate, ranging from direct measures of SST to multivariate climate indices, e.g. Pacific Decadal Oscillation (PDO) (Mantua & Hare 2002), and seabird breeding performance has been investigated frequently in the North Pacific (e.g. Gjerdrum et al. 2003, Abraham & Sydeman 2004) and elsewhere (e.g. Harris et al. 2005, Durant et al. 2006, Møller et al. 2006, Lavers et al. 2008, Jenouvrier et ...

Stability of a Seabird Population in the Presence of an Introduced Predator

“…At Kiska volcano, major eruptions in the 1960s produced virtually unlimited numbers of auklet breeding sites in the vast dome of porous lava at Sirius Point, where near complete breeding failure occurred in 2001 and 2002 in the presence of abundant introduced rats (Major et al 2006). Such failure has never occurred on any island except Kiska (Bond et al 2011). Thus, although the forecasted declines in auklet populations at Kasatochi and Buldir islands can be related to North Pacific-wide ocean productivity issues affecting all islands, or perhaps unknown local factors, such as gull predation or vegetation encroachment, the major demographic issue is limited to Kiska and is coincident with rats (Major et al 2006).…”

“…Because Least Auklets apparently experience very similar environmental conditions across the Aleutian Islands (Bond et al 2011(Bond et al , 2012 The auklet colony at Kiska Island encompasses an area of approximately 2 km² and is situated on two lava domes, one recent (1960s), the other older and from the 19th century (Coats et al 1961, Simkin et al 1981, Major et al 2006. Although there are a very large number of birds breeding here and there are areas with encroaching vegetation, available habitat is presumably not limiting (authors' personal observations).…”

“…The additive effects of increased climate variability and introduced rats at Kiska Island may make this population extremely vulnerable. Furthermore, auklet demography at all three islands is affected by ocean climate and oceanography that forces North Pacific ocean productivity, and could explain population dynamics at all islands (Jones et al 2002, Bond et al 2011. Among the three islands included in this study, Kasatochi volcano erupted in 2008, following at least 100 years of dormancy, covering the colony site with a thick layer of ash and blocking most auklet crevices (Williams et al 2010).…”

“…Recent studies have linked oceanographic indices with seabird reproductive success and survival (Jones et al 2002, 2007, Hipfner 2008, Wolf et al 2009, Bond et al 2011. As global climate changes, extremes in oceanographic conditions may become more frequent (Timmermann et al 1999).…”

“…Data on Least Auklet reproductive success, i.e., number of chicks fledged per pair per year, and adult survival from 1990-2010 at Buldir Island, 1996-2007at Kasatochi Island, and 2001-2010 at Kiska Island, were collected during ongoing, long-term monitoring programs supported by AMNWR (Bond and Jones 2008, Buchheit and Ford 2008, Payne 2008, Tucker et al 2010, Bond et al 2011 Reproductive success, i.e., recruitment to the juvenile stage through adult reproduction, was estimated by locating, marking, and monitoring Least Auklet breeding crevices once every four to seven days from late May through early August (Bond et al 2011). Each nest was assigned a fate after fledging, and reproductive success was calculated as the proportion of total eggs laid that resulted in a fledged chick.…”