Habitat foraging niche of a High Arctic zooplanktivorous seabird in a changing environment

Abstract

Here, we model current and future distribution of a foraging Arctic endemic species, the little auk (Alle alle), a small zooplanktivorous Arctic seabird. We characterized environmental conditions [sea depth, sea surface temperature (SST), marginal sea ice zone (MIZ)] at foraging positions of GPS-tracked individuals from three breeding colonies in Svalbard: one located at the southern rim of the Arctic zone (hereafter ‘boreo-Arctic’) and two in the high-Arctic zone on Spitsbergen (‘high-Arctic’). The birds from one ‘high-Arctic’ colony, influenced by cold Arctic water, foraged in the shallow shelf zone near the colony. The birds from remaining colonies foraged in a wider range of depths, in a higher SST zone (‘boreo-Arctic’) or in the productive but distant MIZ (second ‘high-Arctic’ colony). Given this flexible foraging behaviour, little auks may be temporarily resilient to moderate climate changes. However, our fuzzy logic models of future distribution under scenarios of 1 °C and 2 °C SST increase predict losses of suitable foraging habitat for the majority of little auk colonies studied. Over longer time scales negative consequences of global warming are inevitable. The actual response of little auks to future environmental conditions will depend on the range of their plasticity and pace of ecosystem changes.

Dynamics of Calanus Copepodite Structure during Little Auks’ Breeding Seasons in Two Different Svalbard Locations

“…Therefore it is now of vital importance to study the match in time and space between the availability of older life stages of Calanus and little auks, because as was shown by this study, the development rate and the age structure of Calanus may differ significantly depending on the region, water temperature and time in the season. The issue is alarming not only because temperature warming has been shown to accelerate development of Calanus [65], but also because the altered phenology of many species is becoming an increasingly important problem for trophic interactions [31,64,66] and thus entire food webs. To date, disturbance in interactions between predators and prey (match/mismatch) have been observed in many groups of organisms, e.g., between fish and plankton [67,68], insects and plants [69], birds and insects [70][71][72] shorebirds and arthropods [73] or seabirds and zooplankton [33,74,75].…”

“…A similar trend was observed by LOPC measurements of Calanustype particles selected for the older life stages, with the predominance of the largest individuals The body size of individual copepodite stages (CI-CV) of Calanus differed clearly between the two investigated fjords, with smaller prosome length observed in warmer Kongsfjorden than in colder Hornsund. First of all, such a difference may be explained by expected differences in proportions of Calanus species (C. glacialis vs. C. finmarchicus), which is also of importance for little auks [66]. But the change in individual size within particular species has also to be taken into consideration.…”

Parental Coordination of Chick Provisioning in a Planktivorous Arctic Seabird Under Divergent Conditions on Foraging Grounds

“…The 48-h sessions (both observations and video recordings) were FIGURE 1 | Study area. Mean sea surface temperature (SST) values for July 2002-2017; the 242-m isobath represents the shelf break and boundary of the Arctic zooplankton community (Kwaśniewski et al, 2012), and the 60-km buffers around the studied colonies represent close foraging grounds of Little Auks (Jakubas et al, 2017). Two example sea ice extents are shown for the dates when Little Auks were food sampled in both colonies.…”

Peer Review #1 of "Trophic niches of a seabird assemblage in Bass Strait, south-eastern Australia (v0.1)"

“…Seabirds are major consumers of marine biomass, feeding on a variety of fish, cephalopods and crustaceans (Ridoux 1994, Brooke 2004). The foraging niche of seabirds is influenced by a range of factors, including environmental conditions (Waugh & Weimerskirch 2003, Amélineau et al 2016, Jakubas et al 2017, prey availability (Baird 1991, Camprasse et al 2017, morphological characteristics and their influence on flight performance (Phillips et al 2004, Navarro et al 2013, and interspecific competition (González-Solís et al 2008, Phillips et al 2008, Kokubun et al 2016. Competition is thought to promote foraging niche divergence since species occupying the same ecological niche cannot theoretically coexist through time (Schoener 1974).…”