Which components of diet quality affect retention time of digesta in seabirds?

Hilton, Geoff M.; Houston, David C.; Furness, Robert W.

doi:10.1046/j.1365-2435.1998.00267.x

Cited by 47 publications

(46 citation statements)

References 47 publications

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“…On the other hand, differential nutritional quality requirements of chicks may influence prey segregation between parents and offspring. Diet quality refers to several separately operating factors such as digestion time and nutritive value (Massias & Becker 1990, Hilton et al 1998. Firstly, it is known that retention times of digesta of fish are typically shorter than those of squid.…”

Section: Discussionmentioning

confidence: 99%

Food resource utilisation by the Magellanic penguin evaluated through stable-isotope analysis: segregation by sex and age and influence on offspring quality

Forero¹,

Hobson²,

Bortolotti³

et al. 2002

Mar. Ecol. Prog. Ser.

166

150

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the species in the study area, did not differ from other fish species (hake) in its δ 15 N value, we used it to represent a fish dietary alternative. Using a 2-source (anchovy and squid) isotopic mixing model, we determined that the mean proportion of anchovy in the diet was 49% for yearlings, 76% for chicks, and 69% and 67% for adult males and females, respectively. Sex and age differences in diet, as revealed by stable isotopes, may be the consequence of individual morphology (sexual size dimorphism) and reproductive constraints imposed by chick development since growing young require more nutritive prey than adults and yearlings. This reasoning would also explain the significant and positive correlation found between proportion of anchovy in the diet and body condition of chicks.

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Section: Discussionmentioning

confidence: 99%

Food resource utilisation by the Magellanic penguin evaluated through stable-isotope analysis: segregation by sex and age and influence on offspring quality

Forero¹,

Hobson²,

Bortolotti³

et al. 2002

Mar. Ecol. Prog. Ser.

166

150

View full text Add to dashboard Cite

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“…Mean retention time (MRT ) in the gut from mouth to anus was calculated as (4) where E i is the mass of excreta produced during the collection period i, t i is time since the trial feeding, and n is the number of collections (Jackson 1992, Hilton et al 2000. Absolute values of MRT can depend on how long sampling is continued beyond the time when most of a meal has been excreted (Hilton et al 1998). To ensure that this variation did not affect tests between Nuculana radiata and Macoma calcarea, MRT was compared between species for total collection durations of 12, 18, and 24 h after feeding.…”

Section: Methodsmentioning

confidence: 99%

Effects of clam species dominance on nutrient and energy acquisition by spectacled eiders in the Bering Sea

Richman¹,

Lovvorn²

2003

Mar. Ecol. Prog. Ser.

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The spectacled eider Somateria fischeri, a 'threatened' species, winters in pack ice of the Bering Sea. In dives of 40 to 70 m for benthic invertebrates, the high energy costs of foraging are offset by high benthic biomass. However, there is evidence that the dominant clam prey has changed from Macoma calcarea to Nuculana radiata, perhaps adversely affecting the foraging energetics of the eiders. We studied effects of differences in nutrient and energy content, crushing resistance of shells, digestibility, gut retention time, areal density, shell length, and depth in the sediments on the relative foraging value of M. calcarea versus N. radiata. To avoid using a 'threatened' species for experiments, we used common eiders Somateria mollissima for digestion studies and white-winged scoters Melanitta fusca (the same size as spectacled eiders) for foraging studies. For the prey size range comprising 93% of the eiders' diet (18 to 30 mm), M. calcarea including shells was lower in ash, and higher in nitrogen, lipid, and energy, than N. radiata. Digestibility was 76% for M. calcarea versus 67% for N. radiata, but gut retention time did not differ. In a tensometer, crushing resistance was much higher for N. radiata than M. calcarea for shells 18 to 24 mm long, but did not differ for 24 to 30 mm because shells of N. radiata were often severely abraded. For scoters foraging on freshly thawed Macoma balthica buried in sand in an aquarium 1.8 m deep, intake (no. s ) decreased by 31% when burial depth in the sediments was increased from 4 to 7 cm; most N. radiata are < 4 cm deep, and most M. balthica eaten by eiders are probably 7 to 10 cm deep. Considering energy content, digestibility, and intake rates at these burial depths for 1200 clams m -2 , energy assimilated was 14 to 19% higher for N. radiata than M. calcarea of the same length classes. However, larger M. calcarea yielded 58% higher intake of assimilable energy than smaller N. radiata. These patterns emphasize that relative foraging value depends strongly on size (age) structures of different prey populations, which vary with recruitment, growth, and mortality in different seasons and years. Our results show that impacts of long-term benthic change on eiders depend not only on shifts in total clam abundance, but also on species differences in digestibility, size structure, and size-dependent nutrient content and burial depth.

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“…The prey detected in scat samples is likely to reflect the most recent meal consumed by albatross, which is similar to stomach contents analysis. The digestion rates of seabirds are influenced by numerous variables, such as predator species, metabolic rate, meal size, food type, and feeding frequency (Hilton et al, 1998). In sooty albatross (Phoebetria fusca), the mean retention rate of prey ranged from 11 to 15 h, however some prey was still detected up to 50 h after eating (Jackson, 1992).…”

Section: Study Sites and Sample Collectionmentioning

confidence: 99%

DNA Metabarcoding as a Marine Conservation and Management Tool: A Circumpolar Examination of Fishery Discards in the Diet of Threatened Albatrosses

et al. 2017

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Almost all of the world's fisheries overlap spatially and temporally with foraging seabirds, with impacts that range from food supplementation (through scavenging behind vessels), to resource competition and incidental mortality. The nature and extent of interactions between seabirds and fisheries vary, as does the level and efficacy of management and mitigation. Seabird dietary studies provide information on prey diversity and often identify species that are also caught in fisheries, providing evidence of linkages which can be used to improve ecosystem based management of fisheries. However, species identification of fish can be difficult with conventional dietary techniques. The black-browed albatross (Thalassarche melanophris) has a circumpolar distribution and has suffered major population declines due primarily to incidental mortality in fisheries. We use DNA metabarcoding of black-browed albatross scats to investigate their fish prey during the breeding season at six sites across their range, over two seasons. We identify the spatial and temporal diversity of fish in their diets and overlaps with fisheries operating in adjacent waters. Across all sites, 51 fish species from 33 families were identified, with 23 species contributing >10% of the proportion of samples or sequences at any site. There was extensive geographic variation but little inter-annual variability in fish species consumed. Several fish species that are not easily accessible to albatross, but are commercially harvested or by-caught, were detected in the albatross diet during the breeding season. This was particularly evident at the Falkland Islands and Iles Kerguelen where higher fishery catch amounts (or discard amounts where known) corresponded to higher occurrence of these species in diet samples. This study indicates ongoing McInnes et al. Fishery Discards in Albatross Diets interactions with fisheries through consumption of fishery discards, increasing the risk of seabird mortality. Breeding success was higher at sites where fisheries discards were detected in the diet, highlighting the need to minimize discarding to reduce impacts on the ecosystem. DNA metabarcoding provides a valuable non-invasive tool for assessing the fish prey of seabirds across broad geographic ranges. This provides an avenue for fishery resource managers to assess compliance of fisheries with discard policies and the level of interaction with scavenging seabirds.

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Which components of diet quality affect retention time of digesta in seabirds?

Cited by 47 publications

References 47 publications

Food resource utilisation by the Magellanic penguin evaluated through stable-isotope analysis: segregation by sex and age and influence on offspring quality

Food resource utilisation by the Magellanic penguin evaluated through stable-isotope analysis: segregation by sex and age and influence on offspring quality

Effects of clam species dominance on nutrient and energy acquisition by spectacled eiders in the Bering Sea

DNA Metabarcoding as a Marine Conservation and Management Tool: A Circumpolar Examination of Fishery Discards in the Diet of Threatened Albatrosses

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