Seasonal shift in the foraging niche of Atlantic puffins Fratercula arctica revealed by stable isotope (δ15N and δ13C) analyses

Abstract

We measured tissue stable nitrogen (δ 15 N) and carbon (δ 13 C) values to investigate the extent of seasonal and age-related variation in the foraging ecology of Atlantic puffins. For adults, there was considerable seasonal variation in the foraging niche. A generalized, lower trophic level (TL) diet during the winter moult was replaced by a highly specialized, higher TL diet during summer when birds were rearing chicks. The seasonal δ 15 N enrichment of 2.36 ‰ is consistent with an increase of 0.65 TL. Output from a 2-source single isotope (δ 15 N) mixing model suggested that adult diets were composed largely of zooplankton during winter with a switch to capelin (or other higher TL prey) in summer. A concurrent decrease in δ 15 N variability suggests that adult diets are more varied in winter. Trophic position of first-year birds was similar across summer and fall, as they went from being provisioned by parents at the colony to feeding independently. Both isotope mixing model and stomach contents analysis suggested that first-year birds relied largely (> 85%) on capelin (or other higher TL fish) in fall. In summer, the trophic position of adults was significantly higher than that of nestlings; however, greater δ 15 N variability suggested that nestling diet was mixed overall. Shipboard surveys indicated an offshore movement of puffins post-breeding; however, this distributional shift was not reflected in δ 13 C signatures of adults. The dietary shift and increased TL of adult Atlantic puffins from winter to summer is consistent with reports for puffin species in the Pacific, suggesting that puffins may undergo the most extensive seasonal trophic shift among the auk species.

Annual survival of adult Atlantic Puffins Fratercula arctica is positively correlated with Herring Clupea harengus availability

“…to krill as inferred by Hedd et al . (). Little is known about the winter distribution or diet of the Gulf of Maine Puffin population, but stable‐isotope (δ 15 N, δ 13 C) analysis of MSI chick and winter‐grown adult Puffin feathers shows neither the seasonal difference in diet described by Hedd et al .…”

A switch in the Atlantic Oscillation correlates with inter-annual changes in foraging location and food habits of Macaronesian shearwaters ( Puffinus baroli ) nesting on two islands of the sub-tropical Atlantic Ocean

“…The larger isotopic niche for both islands during the non-breeding season can be explained by the fact that birds, when not constrained by the duties of incubation and chick-rearing, adopt a wide range foraging strategy, often reflect in a larger isotopic niche width (Ceia et al, 2014;Hedd et al, 2010;Kowalczyl et al, 2013;, this study). There were marked differences in the occurrence of cephalopods in the diet between years, irrespective of island, likely revealing strong differences in the foraging ecology of Macaronesian shearwaters between the breeding seasons of 2011 and 2012.…”

“…3) Given the fact that carbon is enriched in coastal in relation to offshore predators (Hobson et al, 1994;Cherel et al, 2005), the presumably nearshore-foraging birds from Selvagem Grande are expected to have higher δ 13 C values than the more offshore-foraging birds from Porto Santo (Paiva et al, 2010a). 4) By foraging on both pelagic (around Selvagem Grande) and more coastal waters (Canary current system), birds from Selvagem Grande should show a broad isotopic niche (Bolnick et al, 2007;Hedd et al, 2010), but with a higher individual consistency in that niche (i.e. a greater variation among individuals than within individuals because some individuals may specialize to feed predominantly in coastal waters and other individuals in pelagic waters; Bearhop et al, 2006;Ceia et al, 2012;Votier et al, 2010).…”

Long-term decline in egg size of Atlantic puffins Fratercula arctica is related to changes in forage fish stocks and climate conditions

“…Thus, even if herring is important, this strongly suggests that other prey played a larger role in determining the puffin egg size. Recent stable-isotope studies (Davies et al 2009, Hedd et al 2010 have suggested that Atlantic puffins and their sibling species tufted puffins Fratercula cirrhata prey on zooplankton in winter and the early breeding season. Furthermore, Sorensen et al (2009) showed that pre-breeding female Cassin's auklets Ptychoramphus aleuticus that fed on energetically superior copepods laid earlier and larger eggs than those that fed on poorer juvenile rockfish Sebastes spp.…”