Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Abstract

Ongoing climate change is altering Arctic marine ecosystems with major consequences for food-webs. Seabirds, by foraging over large marine areas but returning regularly to their breeding colonies, provide a good medium for tracking such changes. We studied the prey delivered to nestling thick-billed murres Uria lomvia at a colony in northern Hudson Bay, Canada, over the period 1981−2013. During that period, ice conditions in the region altered substantially, with earlier break-up and clearance. This change was not gradual but mainly occurred in the mid1990s. Breeding chronology also advanced, but not as fast as early summer ice clearance advanced. Ice conditions strongly affected diet, presumably reflecting the change in the timing of breeding relative to ice clearance. Of the dominant species in the diet, the proportion of Arctic cod Boreogadus saida decreased and the proportion of capelin Mallotus villosus increased over the 33 yr period, even after ice effects were taken into account, suggesting a progressive and cumulative effect of environmental change on the marine community. Those cumulative changes were manifested primarily in the diet representation of the most frequent taxa (cod and capelin), with variation in secondary diet components being driven by the availability of the dominant taxa. Diet diversity, representing an increase in the proportion of benthic fish (stichaeids, zoarcids, pholids and sculpins) and invertebrates (squid, amphipods and crustaceans), increased when ice cover was low, and hatching was late relative to ice break-up. Chick growth rates were low when the proportion of benthic fish was high. Hence, although it appears that growth rates are influenced by diet composition, it is more likely that they reflect the availability of the dominant schooling prey species, rather than any nutritional deficiency in benthic species.KEY WORDS: Ice cover · Climate change · Forage fish · Thick-billed murre · Uria lomvia Resale or republication not permitted without written consent of the publisher

Increased sea ice concentration worsens fledging condition and juvenile survival in a pagophilic seabird, the snow petrel

“…Based on multi-decadal time series, we showed that snow petrel body condition at fledging and juvenile survival were related to SIC and large-scale Antarctic atmospheric circulation. In the Arctic, sea ice conditions are known to affect diet of marine predators, and since sympagic fishes are expected to lose habitat due to sea ice decrease, this will affect their predators like seabirds and marine mammals [21].…”

Black-legged kittiwakes as messengers of Atlantification in the Arctic

“…Many surface feeding seabirds forage in the pelagic ecosystem and can therefore act as bioindicators of changes in pelagic communities. Diet samples collected from these birds can be used as ecosystem data from locations that are otherwise difficult to access 14 – 16 . Black-legged kittiwakes ( Rissa tridactyla , Linnaeus 1758), referred to as “kittiwakes” hereafter, are small colonial gulls with a circumpolar distribution and especially well-suited for such studies.…”

“…79° N 12° E), a glacially-influenced fjord on the west coast of Spitsbergen, kittiwakes exhibit relatively predictable foraging behavior during the breeding period and almost all feeding occurs within the fjord 19 – 21 . Consequently, the incubation and chick-rearing diet of kittiwakes in Kongsfjorden primarily reflects prey availability within the fjord, and, thus, the composition of diet samples may be used as an indicator of ecosystem changes in this area 15 , 16 .…”

Changes in the diet composition of Common GuillemotUria aalgechicks on Skomer Island, Wales, between 1973 and 2017

“…Guillemot chick diet varies geographically (Barrett , Wilhelm & Storey , Gaston & Elliott ), with Sandeels being more important in northern British colonies than southern colonies (Heubeck , Anderson et al . ).…”

“…Researchers have recently attempted to collect data from different studies and different time periods to explore geographical and temporal relationships in prey composition. This can generate large, often heterogeneous datasets which may contain gaps, primarily because some years are unrepresented due to variable effort, different methodology and different sampling frequencies (Gaston & Elliott , Green et al . ).…”