Availability and consumption of food by common eiders wintering in the Gulf of St. Lawrence: evidence of prey depletion

1996 ◽  
Vol 74 (1) ◽  
pp. 32-38 ◽  
Author(s):  
Magella Gulllemette ◽  
John H. Himmelman ◽  
Austin Reed
Keyword(s):  
Prey Availability ◽  
Prey Selection ◽  
Sea Urchins ◽  
Stomach Contents ◽  
Somateria Mollissima ◽  
Eastern Canada ◽  
Common Eiders ◽  
Large Populations ◽  
Average Size ◽  
Density And Biomass

To quantify the influence of common eiders (Somateria mollissima) on their food supply in the Gulf of St. Lawrence, eastern Canada, we measured prey availability and patch utilization during two consecutive winters. In this region, eiders fed predominantly near submerged reefs where large populations of blue mussels (Mytilus edulis) and green sea urchins (Strongylocentrotus droebachienensis) were present. Density and biomass of mussels and urchins were estimated for two reefs at the beginning of the winter of 1985 – 1986 using SCUBA and quadrat sampling. Prey selection was assessed by comparing the size of prey from stomach contents of shot eiders with that of prey found in the habitat. Patch use was quantified from elevated blinds by regularly counting eiders from December to April. Mussels in the habitat were small (mean length 6.5 mm) and formed dense beds (mean density 25 398 individuals/m2), whereas urchins were large (mean diameter 35 mm) and occurred at lower densities (114 individuals/m2). However, the average biomass for these two prey species was similar, 2.8 and 3.1 kg wet mass/m2 for mussels and urchins, respectively. The mussels eaten by common eiders tended to be larger than the average size of those available. In contrast, urchins eaten were smaller than the average size present in the habitat. Depending on the reef, consumption of food by eiders ranged from 48 to 69% of the biomass for eiders feeding on mussels and from 3 to 6% of the biomass for urchins. We compared these estimates with those from similar studies and concluded that eiders substantially deplete mussel beds in winter, which in turn seems to affect their distribution.

Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

2021 ◽  
pp. 1-17
Author(s):  
Manuela Bassoi ◽  
Eduardo R. Secchi ◽  
Daniel Danilewicz ◽  
Ignacio B. Moreno ◽  
Roberta A. Santos ◽  
...  
Keyword(s):  
Sexual Maturity ◽  
Linear Models ◽  
Prey Species ◽  
Prey Availability ◽  
Prey Selection ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Brazilian Coast ◽  
Pontoporia Blainvillei ◽  
Franciscana Dolphin

Abstract The franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

Habitat selection by common eiders in winter and its interaction with flock size

1993 ◽  
Vol 71 (6) ◽  
pp. 1259-1266 ◽  
Author(s):  
Magella Guillemette ◽  
John H. Himmelman ◽  
Cyrille Barette ◽  
Austin Reed
Keyword(s):  
Habitat Selection ◽  
Shallow Water ◽  
Prey Density ◽  
Sea Urchins ◽  
Day Length ◽  
Antipredator Behaviour ◽  
Somateria Mollissima ◽  
Flock Size ◽  
Eastern Canada ◽  
Diving Depth

We studied habitat selection in relation to prey density and water depth in the common eider, Somateria mollissima L., wintering in the Gulf of St. Lawrence, eastern Canada. In this region, eiders are confronted with low temperatures, ice cover, and reduced day length. We predicted that they should select feeding habitats characterized by high prey density and shallow water to minimize the time and energy spent while diving. About 1000 flocks were localized by triangulation on our study site (20.5 km2). We inferred the diving depth and the habitat being used from the position of eiders on bathymetric and community maps. The highest density of prey occurred in shallow water reefs where there were patches of blue mussels, Mytilus edulis L., and green sea urchins, Strongylocentrotus droebachienensis (Müller). Despite the fact that eiders can dive to depths as great as 42 m to feed, they strongly aggregate in shallow water, and their distribution closely coincides with the highest density of prey. The degree of selection for the reef habitat varies with seasonal variations in the size of flocks and in the total number of eiders present. Although flocking as an antipredator behaviour cannot be rejected, we interpret the high degree of flocking by eiders in our study area as a strategy to facilitate feeding in winter.

scholarly journals Behavioral Responses to Decreasing Day Length in Wintering Sea Ducks

The Auk ◽  
2000 ◽  
Vol 117 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Geir H. Systad ◽  
Jan O. Bustnes ◽  
Kjell E. Erikstad
Keyword(s):  
Prey Availability ◽  
Day Length ◽  
The Arctic ◽  
Feeding Time ◽  
Somateria Mollissima ◽  
Sea Ducks ◽  
Light Intensities ◽  
Night Feeding ◽  
Common Eiders ◽  
Lower Light

Abstract Sea ducks generally are diurnal feeders, but large numbers winter above the Arctic Circle where day lengths decrease dramatically in winter. To determine how sea ducks cope with short day lengths, we studied different aspects of the behavior of three sympatric wintering species (Common Eider [Somateria mollissima], King Eider [S. spectabilis], and Oldsquaw [Clangula hyemalis]) at 70°N where day length is reduced to less than 4.5 h of twilight in midwinter. Numbers of both eider species remained fairly constant throughout winter, whereas Oldsquaws moved out of the area in midwinter. As day length decreased, eiders extended their feeding period into lower light intensities. Common Eiders and Oldsquaws spent a higher proportion of the day diving (underwater) when days were short, whereas King Eiders did not. As the days lengthened, King Eiders and Oldsquaws increased their total time diving at similar rates, which were faster than those of Common Eiders. Feeding at lower light intensities and increased proportions of time spent diving did not offset reduced feeding time in midwinter, and estimated time spent underwater during daylight on the shortest days was only 35% of that on the longest days in King Eiders, 51% in Common Eiders, and 39% in Oldsquaws. The ability to survive when days are short might be explained by use of stored nutrient reserves, night feeding, or high prey availability.

A large molluscivore bird (Common Eider, Somateria mollissima) is able to discriminate quality of blue mussels (Mytilus edulis) based on size and provenance

2015 ◽  
Vol 93 (8) ◽  
pp. 655-663 ◽  
Author(s):  
Elisabeth Varennes ◽  
Sveinn A. Hanssen ◽  
John C. Bonardelli ◽  
Magella Guillemette
Keyword(s):  
Energy Balance ◽  
Mytilus Edulis ◽  
Energy Intake ◽  
Prey Size ◽  
Prey Selection ◽  
Somateria Mollissima ◽  
Shell Material ◽  
Blue Mussels ◽  
Common Eiders

Molluscivore birds that forage on abundant but low-quality food have to ingest large quantities of food to achieve energy balance. Such a strategy is often associated with important digestive constraints limiting predator’s ingestion. Thus, these predators may use prey selection to ingest better-quality individuals among a generally low-quality prey population. Using captive Common Eiders (Somateria mollissima (L., 1758)) diving in a constant environment, we were able to examine their preferences for blue mussels (Mytilus edulis L., 1758) of varying qualities (different sizes or provenances). In addition, we studied the consequences prey selection had on Eiders’ energy intake rates and ingestion of flesh and shell material. Eiders selected 10–20 mm mussels and were able to discriminate and to select cultivated mussels from intertidal mussels. Prey selection allowed, in certain conditions of prey-size abundance, higher flesh and energy intake rates without increasing the ingestion of shell material. This study confirmed the energetic advantage that Eiders have when foraging in aquaculture sites, which explain the large depredation of preferred mussel sizes.

Influence of petroleum hydrocarbons on the endoparasitic helminths of the common eider, Somateria mollissima, from Newfoundland

2010 ◽  
Vol 85 (4) ◽  
pp. 430-434 ◽  
Author(s):  
R.A. Khan ◽  
C.V. Chandra ◽  
P.J. Earle ◽  
G.J. Robertson ◽  
P. Ryan ◽  
...  
Keyword(s):  
Newfoundland And Labrador ◽  
Petroleum Hydrocarbons ◽  
Intestinal Tract ◽  
Prey Availability ◽  
The Other ◽  
Somateria Mollissima ◽  
Metazoan Parasites ◽  
Illegal Hunting ◽  
Common Eiders ◽  
The Common

AbstractA comparison of commonly occurring metazoan parasites in the digestive tract was made between common eiders, Somateria mollissima, that were contaminated with oil and reference birds confiscated from illegal hunting. There was a greater number of commonly occurring parasites and their abundance in reference than in oiled eiders. Except for an acanthocephalan, Polymorphus botulus, which was embedded in the wall of the intestinal tract, most of the other taxa of parasites, including trematodes, cestodes and nematodes, were probably voided from the birds following ingestion of oil. Reference eiders harboured fewer species and a substantially lower mean abundance of parasites than those studied in Newfoundland and Labrador more than four decades ago; this may be a signal of a changing prey base or an increase in prey availability as winter ice cover continues to decline.

Blue mussel (Mytilus edulis) quality of preferred prey improves digestion in a molluscivore bird (Common Eider,Somateria mollissima)

2015 ◽  
Vol 93 (10) ◽  
pp. 783-789 ◽  
Author(s):  
Elisabeth Varennes ◽  
Sveinn A. Hanssen ◽  
John C. Bonardelli ◽  
Magella Guillemette
Keyword(s):  
Mytilus Edulis ◽  
Blue Mussel ◽  
Energy Content ◽  
Prey Selection ◽  
Somateria Mollissima ◽  
Sea Ducks ◽  
Common Eiders ◽  
Energy Assimilation ◽  
Digestive Processes

Benthivorous predators like sea ducks rely on abundant but low-quality food. Because they ingest whole blue mussels (Mytilus edulis L., 1758), including shells, they have to consume large quantities of food to maintain energy balance. Digestive processes may therefore limit energy assimilation in these predators, although selecting mussel types that minimize shell ingestion may improve foraging profitability. To test this prediction, we first quantified mussel quality from different sizes and habitats by measuring energy content and various features of mussel morphology. Then, we conducted digestive experiments on captive Common Eiders (Somateria mollissima (L., 1758)) fed with various mussel types to determine their impact on Eiders’ digestion. Aquacultured and small mussels were of better quality, because of higher energy content and less resistant shells. These mussel characteristics allowed faster digestive processes for an equal digestibility compared with large intertidal mussels. Previous studies showed that aquacultured and small mussels were generally preferred by sea ducks. Hence, prey-selection behaviours and digestive processes seem closely connected in these highly digestive-constrained predators.

Prey selection while diving by common eiders, Somateria mollissima

1992 ◽  
Vol 44 ◽  
pp. 417-426 ◽  
Author(s):  
Guy Beauchamp ◽  
Magella Guillemette ◽  
Ron Ydenberg
Keyword(s):  
Prey Selection ◽  
Somateria Mollissima ◽  
Common Eiders

Trophic position scales positively with body size within but not among four species of rocky reef predators

2020 ◽  
Vol 640 ◽  
pp. 189-200 ◽  
Author(s):  
AM Olson ◽  
A Frid ◽  
JBQ dos Santos ◽  
F Juanes
Keyword(s):  
Body Size ◽  
Trophic Position ◽  
Stomach Contents ◽  
Rocky Reef ◽  
Morphometric Traits ◽  
Predator Species ◽  
Predatory Fishes ◽  
Average Size ◽  
Interspecific Comparisons ◽  
Large Predators

Intra- and interspecifically, larger-bodied predators generally occupy higher trophic positions (TPs). With widespread declines in large predators, there is a need to understand their size-based trophic roles to predict ecosystem-level responses. In British Columbia, Canada, we examined size-based trophic interactions between predatory fishes—3 rockfish species (genus Sebastes) and lingcod Ophiodon elongatus—and their prey, converting predator δ15N signatures to TP and analyzing stomach contents. Intraspecifically, TP scaled positively with predator length and gape width, but the rates of change varied by species. Interspecifically, TP did not scale positively with the observed mean sizes or known maximum sizes of species. Lingcod TP was lower than that of yelloweye and quillback rockfishes, which were 51 and 37%, respectively, smaller than lingcod. Yellowtail rockfish had the smallest average size, yet their mean TP did not differ significantly from that of lingcod. Neither species differences in some morphometric traits known to influence body size-TP relationships nor phylogenetic history explained these results. Most prey consumed were <20% of the predator’s size, which might partially explain the lack of a size-based trophic hierarchy among species. Currently, large size classes of rockfishes are being lost due to fisheries and perhaps climate-driven changes. Our findings on intraspecific size-TP relationships indicate that fishery removals of large individuals may diminish trophic structures. Interspecific comparisons of TP suggest that, along with size, species remain an important factor in understanding trophic dynamics. In addition, smaller-bodied predator species may have significant ecological roles to be considered in ecosystem-based fisheries management.

scholarly journals Herd immunity drives the epidemic fadeout of avian cholera in Arctic-nesting seabirds

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jacintha G. B. van Dijk ◽  
Samuel A. Iverson ◽  
H. Grant Gilchrist ◽  
N. Jane Harms ◽  
Holly L. Hennin ◽  
...  
Keyword(s):  
Colony Size ◽  
Pasteurella Multocida ◽  
Herd Immunity ◽  
Reproductive Number ◽  
Somateria Mollissima ◽  
Common Eiders ◽  
Serological Status ◽  
Antibody Titers ◽  
Avian Cholera

AbstractAvian cholera, caused by the bacterium Pasteurella multocida, is a common and important infectious disease of wild birds in North America. Between 2005 and 2012, avian cholera caused annual mortality of widely varying magnitudes in Northern common eiders (Somateria mollissima borealis) breeding at the largest colony in the Canadian Arctic, Mitivik Island, Nunavut. Although herd immunity, in which a large proportion of the population acquires immunity to the disease, has been suggested to play a role in epidemic fadeout, immunological studies exploring this hypothesis have been missing. We investigated the role of three potential drivers of fadeout of avian cholera in eiders, including immunity, prevalence of infection, and colony size. Each potential driver was examined in relation to the annual real-time reproductive number (Rt) of P. multocida, previously calculated for eiders at Mitivik Island. Each year, colony size was estimated and eiders were closely monitored, and evaluated for infection and serological status. We demonstrate that acquired immunity approximated using antibody titers to P. multocida in both sexes was likely a key driver for the epidemic fadeout. This study exemplifies the importance of herd immunity in influencing the dynamics and fadeout of epidemics in a wildlife population.

Body and organ mass dynamics during remigial moult in a wing–foot-propelled diving sea duck: the Common Eider (Atlantic) (Somateria mollissima dresseri)

2015 ◽  
Vol 93 (10) ◽  
pp. 755-764 ◽  
Author(s):  
A. Viain ◽  
M. Guillemette ◽  
J.-P.L. Savard
Keyword(s):  
Muscle Mass ◽  
Body Mass ◽  
Flight Muscle ◽  
Somateria Mollissima ◽  
Dabbling Ducks ◽  
Diving Ducks ◽  
Common Eiders ◽  
Sea Duck ◽  
Remigial Moult ◽  
Atrophy Of The Heart

Body and organ dynamics, during remigial moult, have been mainly explored on geese, dabbling ducks, and foot-propelled diving ducks, but weakly on sea ducks. This study investigated the internal changes in a wing–foot-propelled sea duck to determine the adaptive strategies implemented. Forty-five male Common Eiders (Atlantic) (Somateria mollissima dresseri Sharpe, 1871), collected in the Gulf of St. Lawrence, were dissected; their body mass, muscle mass, and organ sizes were measured. We tested three hypotheses: (1) S. m. dresseri use a strategic reduction of body mass to reduce the flightlessness duration; (2) organs will exhibit changes consistent with a trade-off between function and maintenance to save and reallocate energy and proteins to feather growth; (3) S. m. dresseri would show lower flight muscle reduction than foot-propelled diving ducks. Somateria mollissima dresseri did not lose body mass, which does not support the first hypothesis. Atrophy of the heart followed by hypertrophy and opposite changes in leg muscle mass and gizzard mass are consistent with the second hypothesis. Flight muscle mass showed lower variations than in other ducks, validating the third hypothesis. We also suggest that the lipid depletion observed early in the moult could be a strategy to reduce foraging effort and minimize the risk of damaging the growing feathers.

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