Reevaluating Marine Diets of Surf and White-Winged Scoters: Interspecific Differences and the Importance of Soft-Bodied Prey

Anderson, Eric M.; Lovvorn, James R.; Wilson, Matthew T.

doi:10.1525/cond.2008.8458

Cited by 23 publications

(14 citation statements)

References 35 publications

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“…Thus, we used gizzard contents to assess diet for these 2 samples of surf scoters. Both the sampling methods used for hunter-killed birds and the use of gizzard instead of esophagus contents mean that associated diet results likely underestimate the importance of soft-bodied prey (mainly crustaceans and polychaetes; Anderson et al 2008 Because the width of the intertidal zone in Penn Cove was relatively narrow and a large proportion of feeding by scoters occurred at subtidal elevations, we extended transects in that site to a water depth of 6 m at MLLW. Transect lengths were 0.12 km in Penn Cove and 4 km in Padilla Bay.…”

Section: Surf Scoter Dietsmentioning

confidence: 99%

Section: Surf Scoter Dietsmentioning

confidence: 99%

“…Vertical lines connect seasonal estimates for single sites; horizontal lines are median values spicillata, a declining yet widely distributed sea duck that feeds in marine habitats for most of the year. Although sea ducks consume a range of benthic macroinvertebrates, bivalve prey are often of high value to many sea duck species (Stott & Olson 1973, Goudie & Ankney 1986, Anderson et al 2008. Ac cordingly, the importance of marine foraging sites to sea ducks is commonly assessed in terms of the availability of bivalves in unvegetated habitats (Nilsson 1980, Nehls & Ketzenberg 2002, Sukhotin et al 2008.…”

Section: Introductionmentioning

confidence: 99%

“…data). We verified age class and sex and conducted all diet analyses as in Anderson et al (2008). So that diet estimates would correspond approximately to the peak periods during which each site was used (see 'Results'), we collected surf scoters in Penn Cove on 11 and 12 December 2005 (n = 9) and in Padilla Bay on 29 August 2005 (n = 9) and from 12 to 27 March 2006 (n = 10).…”

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confidence: 99%

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Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator

Anderson¹,

Lovvorn²

2012

Mar. Ecol. Prog. Ser.

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Foraging profitability can be strongly affected by the size structure of different prey, so that predator distributions are not a simple function of total prey biomass. For a bottom-feeding avian predator, the surf scoter Melanitta perspicillata, we assessed effects of prey size and other prey attributes on seasonal shifts in scoter use of 2 major foraging habitats in Puget Sound, Washington, USA. During early winter, many thousands of scoters fed at an unvegetated site where profitable prey appeared limited to mussels Mytilus trossulus of smaller sizes (2 to 30 mm) despite their much lower biomass relative to larger mussels and several other prey types. Accordingly, scoter numbers decreased at that site as small mussels declined over winter. During pre-migratory fattening in spring and feather molt in summer, > 8000 surf scoters aggregated at a seagrass site where they fed mainly on epifaunal crustaceans (50 to 73%) and gastropods (12 to 27%). Body sizes of most crustacean prey had increased substantially since winter. Thus, prey size had opposite effects on the profitability of unvegetated habitats that provide mainly mussels (smaller items likely reduce shell processing costs) versus seagrass crustaceans (larger items are likely more visible and yield greater energy per prey item, although relative mobility of prey can alter their value). Total prey biomass, and prey distributions relative to water and sediment depths, appeared less important than prey size to shifts in scoter diets and numbers. Our synthesis of past studies indicates that biomass and production of mussel beds are typically an order of magnitude greater than for entire assemblages of seagrass macroinvertebrates. However, because of seasonal shifts in prey size structure, seagrass sites can be an important complement to mussel beds when the narrow size fraction of mussels that are profitable to scoters declines. KEY WORDS: Epifauna · Foraging profitability · Marine habitat · Melanitta perspicillata · Prey biomass · Size selection of prey · Surf scoter Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 467: [219][220][221][222][223][224][225][226][227][228][229][230][231][232] 2012 Predators usually select prey based on their relative profitability (energy gain minus cost), which is affected by a range of factors before and after prey capture. Before prey capture, profitability depends largely on the density and dispersion of prey, as well as the ability of prey to evade predators by being cryptic or highly mobile (Christensen 1996, Lovvorn & Gillingham 1996, Sih & Christensen 2001. Also important before prey capture is the ability of predators to detect and access prey, which is often related to the structural complexity of the feeding habitat (Crowder & Cooper 1982, Lundvall et al. 1999. After prey capture, profitability depends on the nutrient and energy content of prey and on factors that affect processing rate such as relative composition of indigestible material (e.g. shell, bone; ...

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Section: Surf Scoter Dietsmentioning

confidence: 99%

Section: Surf Scoter Dietsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator

Anderson¹,

Lovvorn²

2012

Mar. Ecol. Prog. Ser.

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“…Differential digestibility of consumed prey items (e.g., marine and terrestrial invertebrates, plant material) and associated potential biases in dietary studies has been documented in a variety of birds, including waterfowl (Briggs et al, 1985;Bourget et al, 2007;Anderson et al, 2008), corvids (Berrow et al, 1992), blackbirds (Williams and Jackson, 1981) and passerines (Dillery, 1965;Custer and Pitelka, 1975). We suspect this is also true of invertebrates eaten by gulls.…”

Section: Discussionmentioning

confidence: 83%

Temporal Variation in Terrestrial Invertebrate Consumption by Laughing Gulls in New York

Bernhardt

Kutschbach-Brohl

Washburn

et al. 2010

The American Midland Naturalist

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ABSTRACT.-Laughing gulls (Larus atricilla) are commonly found in many areas of North America and little is known about their diet, particularly in coastal-urban interfaces where gull-aircraft collisions can be a serious concern. The objective of this study was to describe and quantify the consumption of terrestrial invertebrates by laughing gulls at a coastal-urban interface in the northeastern United States. We examined the stomach contents of laughing gulls (n 5 1053) collected during wildlife damage management operations at John F. Kennedy International Airport during the summers of 2003 and 2004. Terrestrial invertebrates consumed by laughing gulls represented 2 taxonomic phyla, 4 classes, 15 orders and 40 families. Beetles (Coleoptera) and ants (Hymenoptera) were the most common terrestrial invertebrates consumed by laughing gulls. We found evidence of temporal (i.e., monthly) variation in the frequency of occurrence of terrestrial insects in laughing gull diets. Laughing gull gender and age did not influence the frequency of occurrence of terrestrial insects in gull diets. Terrestrial environments (e.g., areas of turfgrass) appear to provide important foraging locations and food resources for laughing gulls in coastal-urban areas. This information is important for developing effective management approaches to reduce human-gull conflicts, such as gull-aircraft collisions at coastal airports.

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Spatial ecology of long‐tailed ducks and white‐winged scoters wintering on Nantucket Shoals

White

Veit

2020

Ecosphere

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We examine the long-term co-occurrence of long-tailed ducks (Clangula hyemalis) and whitewinged scoters (Melanitta fusca) wintering at the Nantucket Shoals off Massachusetts, USA, and ask: (1) What oceanographic features attract these aggregations? (2) How are distributions of prey and sea ducks related to one another? and (3) What is the explanation for the spatial association between these two species? A winter concentration of long-tailed ducks on the order of 3 9 10 5 birds have been present near Nantucket Island and the Nantucket Shoals since the 1970s, and there is evidence of some concentration there since the late 1800s. Despite the difference in diet, the two duck species overlap in spatial distribution in relation to a prominent tidal front on the west side of Nantucket Shoals where nested swarms of pelagic amphipods and massive clam beds occur in persistent broadscale concentrations. Gammarid amphipods were collected seasonally by bongo tows over 39 yr , and Atlantic surf clams and ocean quahogs were collected by hydraulic dredge over a 34-yr timescale . Long-tailed ducks and whitewinged scoters were counted during systematic low-level aerial surveys. Both long-tailed ducks and white-winged scoters associated with amphipod and clam aggregations at similar scales, and tracked amphipod and clam concentrations at larger spatial scales, up to~30 km. These multi-scalar nested associations suggest that the sea ducks foraged within a hierarchical patch system structured by the tidal regime, and concentrated in areas of spatially anchored recurring prey, with highest densities in southwest areas. Enhanced concentrations of prey within a relatively narrow zone on Nantucket Shoals provide a predictable food resource to wintering sea ducks whose populations are in decline. As supported by our generalized additive models, we propose that the positive spatial associations among these species are at least partly explained by local enhancement or facilitation, whereby each species of duck derives foraging benefit from noting the location of aggregations of the other. This interaction will be important to the designation of marine protected areas.

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Reevaluating Marine Diets of Surf and White-Winged Scoters: Interspecific Differences and the Importance of Soft-Bodied Prey

Cited by 23 publications

References 35 publications

Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator

Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator

Temporal Variation in Terrestrial Invertebrate Consumption by Laughing Gulls in New York

Spatial ecology of long‐tailed ducks and white‐winged scoters wintering on Nantucket Shoals

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