Atypical Feeding Behavior of Long-tailed Ducks in the Wake of a
Commercial Fishing Boat while Clamming
Matthew C. Perry, Peter C. Osenton, and Timothy P. White
Northeastern Naturalist, Volume 24, Issue 2 (2017): N19–N25
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2017 Northeastern Naturalist Notes Vol. 24, No. 2
M.C. Perry, P.C. Osenton, and T.P. White
Atypical Feeding Behavior of Long-tailed Ducks in the Wake of a
Commercial Fishing Boat while Clamming
Matthew C. Perry1,*, Peter C. Osenton1, and Timothy P. White2
Abstract - A foraging group of Clangula hyemalis (Long-tailed Duck) was observed on 10 February
2010 diving behind a commercial boat that was clamming near Monomoy Island, Nantucket Sound,
MA. We used a shotgun to collect 9 of the ducks, and our analyses of gizzard and gullet (esophagus
and proventriculus) revealed 37 food items in the gizzard and 16 in the gullet. Mollusca were the
dominant food in the gizzard (49%), whereas Crustacea were dominant in the gullet (57%). Crustacea
were the second most important food in the gizzard (38%), whereas Mollusca were the second most
important food in the gullet (31%). Relatively high volumes of the Amphipoda Caprella sp. (skeleton
shrimp) and the Decopoda Crangon septemspinosa (Sand Shrimp) were recorded in the gullet and
gizzard. Ensis directus (Atlantic Jackknife Clam) formed the greatest volume of Mollusca in the
gizzard (15%) and in the gullet (15%). Long-tailed Ducks had fed on this Bivalvia and several other
species of Mollusca that had no shell or broken shell when consumed. Many of the food organisms
were apparently dislodged and some damaged by the clamming operation creating an opportunistic
feeding strategy for the Long-tailed Ducks.
Marine birds are known to feed opportunistically on organisms captured by and discarded
from fishing vessels (Dare 1982, Furness and Monaghan 1987, Griffiths 1982, Hudson
and Furness 1988, Leopold 2002). Birds will also respond to natural prey made available
by the vessel’s propeller wash (Camphuysen 1996, Eades 1982, Perry 2012).
On 10 February 2010, we used a shotgun to collect (US Fish and Wildlife Permit
MB034670-1) a total of 9 Clangula hyemalis L. (Long-tailed Duck) that were diving in the
wake of a keeled clamming boat ~10 m (32 ft) long with an inboard motor. The boat was
clamming near Rodger’s Shoal, Nantucket Sound, MA, and ~1.6 km (1 mile) northwest of
Monomoy Point in water ~5 m (16 ft) deep. The clamming boat was using a dredge to most
likely obtain large clams, such as Mercenaria mercenaria (Northern Quahog) and Spisula
solidissima (Atlantic Surfclam). Smaller clams and other organisms are not collected by the
dredge, but are disturbed and damaged during the operation (G.M. Haramis, USGS Patuxent
Wildlife Research Center, Laurel, MD, 2006 pers. observ.)
There were ~50 ducks diving in the wake of the clamming boat with dredge, but we saw
no other ducks in the area of the clamming operation. Analyses of gizzard and gullet (esophagus
and proventriculus) using traditional techniques (Perry and Uhler 1988) revealed both
soft-and hard-bodied benthic organisms that may have been disturbed by the dredge.
We identified a large number of food items in the gizzard (37 items) and gullet (16
items) (Table 1). The high variability of prey items ingested by the 9 ducks supports previous
findings that Long-tailed Ducks use a flexible foraging strategy to locate food at sea
(Robertson and Savard 2002). Frequency of occurrences of the food organisms also had
high variability in the gizzard (11–100%) and in the gullet (14–100%). Amphipoda were
the only food organisms occurring in all gizzard and gullet samples. Mollusca were the
dominant food in the gizzard (49%), whereas Crustacea were dominant in the gullet (57%).
1USGS Patuxent Wildlife Research Center, 12100 Beech Forest Road, Laurel, MD 20708. 2Department
of the Interior, Bureau of Ocean Energy Management, Division of Environmental Sciences,
Branch of Biological and Social Sciences, 45600 Woodland Road, Sterling, VA 20166. *Corresponding
author - mperry1209@verizon.net.
Manuscript Editor: Jean-Pierre L. Savard
Notes of the Northeastern Naturalist, Issue 24/2, 2017
2017 Northeastern Naturalist Notes Vol. 24, No. 2
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M.C. Perry, P.C. Osenton, and T.P. White
Table 1. Prey items ingested by 9 Long-tailed Ducks feeding in the wake of a clamming boat, near Monomoy Island, Nantucket Sound, MA, 2010. All
organisms are maintained in the reference collection at USGS Patu xent Wildlife Research Center food habits laboratory.
Gizzard food (n = 9) Gullet food (n = 7)
Common name Scientific name Mean (SD) Freq. of occur. % Mean ( SD) Freq. of occur. %
Unknown crustacean Crustacea 15.77 (20.46) 67
Atlantic Jackknife Clam Ensis directus Conrad 15.40 (11.84) 78 14.72 (27.38) 71
Skeleton shrimp Caprella sp. 9.30 (27.89) 11 8.98 (23.77) 14
Unknown bivalve Bivalvia 6.10 (8.360 78
Atlantic Surfclam Spisula solidissima (Dillwyn) 5.85 (8.99) 67 1.31 (2.89) 29
Lunar Dovesnail Mitrella lunata (Say) 5.82 (8.40) 100 0.94 (2.36) 43
Atlantic Awningclam Solemya velum Say 5.68 (5.15) 78 2.23 (3.89) 57
Unknown amphipod Amphipoda 5.47 (5.44) 89 30.36 (23.42) 100
Detritus 4.89 (11.28) 78 0.41 (0.96) 29
Unknown fish Pisces 4.65 (13.88) 22 3.79 (10.03) 14
Sand Shrimp Crangon septemspinosa Say 3.74 (10.06) 78 12.6 (23.92) 71
Atlantic Nutclam Nucula proxima Say 3.11 (5.88) 78 0.02 (0.05) 14
Bloodworm species Glycera sp. 2.62 (6.28) 78 5.48 (9.40) 29
Unknown barnacle Cirrepedia 2.22 (4.70) 44
Miniature Moonsnail Tectonatica pusilla (Say) 1.69 (4.72) 56
Mounded-back Isopod Edotia triloba (Say) 1.23 (1.53) 78 4.93 (6.70) 86
False Quahog Pitar morrhuanus (Linsley) 1.05 (3.15) 11 0.03 (0.07) 14
Gould’s Pandora Pandora gouldiana Dall 0.87 (2.54) 22
Greedy Dovesnail Costoanachis avara (Say) 0.61 (1.75) 22
Northern Dwarf Tellin Tellina agilis Stimpson 0.60 (0.89) 44 1.19 (2.60) 57
Unknown crab Decopoda 0.48 (0.80) 56 0.08 (0.14) 29
Shark Eye Neverita duplicata (Say) 0.43 (1.30) 11
Unknown bivalve two Bivalvia 0.43 (1.30) 11
Northern Quahog Mercenaria mercenaria L. 0.29 (0.88) 11
Inornate Pandora Pandora inornata A.E. Verrill & Bush 0.26 (0.77) 11
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M.C. Perry, P.C. Osenton, and T.P. White
Table 1, continued.
Gizzard food (n = 9) Gullet food (n = 7)
Common name Scientific name Mean (SD) Freq. of occur. % Mean ( SD) Freq. of occur. %
Common Sand Dollar Echinarachnius parma (Lamarck) 0.26 (0.77) 11
Common Atlantic Slippersnail Crepidula fornicata (L.) 0.20 (0.33) 44
Glassy Lyonsia Lyonsia hyalina Conrad 0.20 (0.32) 44 0.44 (1.05) 29
Unknown hydroid Hydrozoa 0.17 (0.13) 67 0.41 (0.66) 57
Unknown gastropod Gastropoda 0.16 (0.13) 67 0.08 (0.12) 14
Yoldia species Yoldia sp. 0.15 (0.14) 56
Unknown mollusk Mollusca 0.13 (0.32) 22 10.28 (27.19) 14
Turbonille species Turbonilla sp. 0.07 (0.11) 33
Threelined Mudsnail Nassarius trivittatus (Say) 0.07 (0.10) 33
Transverse Ark Anadara transversa (Say) 0.07 (0.14) 22 0.04 (0.12) 14
Well-ribbed Dovesnail Costoanachis lafresnayi (P. Fischer & 0.06 (0.12) 22
Bernardi)
Channeled Barrel-bubble Acteocina canaliculata (Say) 0.05 (0.10) 22
Erichsonella Isopod Erichsonella filiformis (Say) 0.04 (0.11) 11
Pondweed species seed Potamogeton sp. 0.03 (0.08) 11
Unknown isopod Isopoda 0.03 (0.10) 11 0.25 (0.53) 29
Baltic Isopod Idotea balthica (Pallas) 0.02 (0.06) 11 0.04 (0.12) 14
Blue Mussel Mytilus edulis L. 0.02 (0.07) 11 0.04 (0.12) 14
Solitary Glassy-bubble Haminoea solitaria (Say) 0.02 (0.07) 11
Stout Tagelus Tagelus plebeius (Lightfoot) 0.02 (0.07) 11
Clamworm species Neanthes sp. 0.02 (0.07) 11 0.03 (0.10) 14
Nut clam species Nucula sp. 0.02 (0.07) 11
Toad crab species Hyas sp. 0.02 (0.05) 11
Unknown animal matter Animalia 0.95 (2.50) 14
Unknown sponge Porifera 0.22 (0.57) 14
One-pointed Isopod Idotea phosphorea Harger 0.10 (0.26) 14
Unknown vegetation Plantae 0.03 (0.07) 14
2017 Northeastern Naturalist Notes Vol. 24, No. 2
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M.C. Perry, P.C. Osenton, and T.P. White
Crustacea were the second most important food in the gizzard (38%), whereas Mollusca
were the second most important food in the gullet (31%). This reversal of observed quantities
of food itmes between the gizzard and gullet is most likely due to the bias created by
grinding of soft-bodied food in the gizzard (Swanson and Bartonek 1970).
Relatively high volumes of the Amphipoda Caprella sp. (skeleton shrimp), and the Decopoda
Crangon septemspinosa (Sand Shrimp) were recorded in the gullet (9% and 13%,
respectively) and gizzard (9% and 4%, respectively). The observed volumes of skeleton
shrimp and Sand Shrimp recorded in this sample were higher than those recorded in a previous
study (White et al. 2009). These species are believed to be mainly benthic organisms
and are not typically consumed by Long-tailed Ducks (White et al. 2009).
Skeleton shrimp were observed in some of the 35 Long-tailed Ducks analyzed in
Chesapeake Bay by the authors (M.C. Perry and P.C. Osenton, unpubl. data), but average
percentage was less than 1%. Cottam (1939) reported just over 1% by volume of skeleton
shrimp in his sample of Long-tailed Ducks. Sand Shrimp was not noted in the Chesapeake
Bay sample or in the Cottam (1939) sample.
Amphipods ingested by Long-tailed Ducks in fresh water of Lake Michigan included
Pontoporeia affinis Lindstrum and P. hoyi Smith (Lagler and Wienert 1948, Peterson and
Ellarson 1977). In salt water, Calliopius laeviusculus Kroyer, Gammarellus angulosus
Rathke, Onisimus glacialis Sars, Parathemisto spp., Gammarus spp., and Caprella spp.
are consistently documented diet items of Long-tailed Ducks (Cottam 1939, Goudie and
Ankney 1986, Jamieson et al. 2001, Johnson 1984).
Isopoda constituted 1% of the gizzard contents and 5% of the gullet contents. Edotia
triloba (Mounded-backed Isopod) and Idotea balthica (Baltic Isopod) were identified in
both the gizzard and gullet, but Idotea phosphorea (One-pointed Isopod) was found only in
the gullet. Baltic Isopod was determined to be an important food item for Long-tailed Ducks
in Newfoundland (Goudie and Ankney 1986).
We did not find Mysidacea (mysid shrimp) in the 9 birds in this sample. Mysid Shrimp
are bottom-dwelling organisms and therefore might have been expected in this group of
ducks as in other studies (Robertson and Savard 2002). Important mysid species in other
samples include Mysis litoralis (A.H. Banner), M. relicta Lovén, and Thysanoessa spp.
(Cottam 1939, Johnson 1984).
Decopoda other than Sand Shrimp that were found in this sample included Hyas sp.
(toad crab), which was in the gizzard. Other Decopoda eaten by Long-tailed Ducks in
other areas include crabs (Cancer spp., Panopeus herbstii H. Milne Edwards [Atlantic
Mud Crab], Dispanopeus sayi (S.I. Smith) [Say Mud Crab], Hexapanopeus angustifrons
(Benedict and Rathbun) [Smooth Mud Crab]), the fairy shrimp Lepidurus glacialis Packard,
Crago spp. shrimp, and Pandalus goniurus Stimpson (Humpy Shrimp) (Cottam 1939,
McGilvrey 1967, Sanger and Jones 1984).
Ensis directus (Atlantic Jackknife Clam) formed the greatest volume of Mollusca in
the gizzard (15%) and in the gullet (15%). Long-tailed Ducks had fed on this Bivalvia and
several other species of Mollusca that had no shell or broken shell in the gizzard or gullet.
Thus, most of the food found in both the gizzard and the gullet was meat that appeared to
be broken free of the shell during the clamming operation. The size of the clam meat in
some of the samples appeared to originate from clams larger than typically eaten by Longtailed
Ducks. The breaking of shells by the dredge makes for faster and energetically more
economical foraging by getting a larger quantity of meat without wasting energy grinding
shells (Wells-Berlin et al. 2015).
We found unidentified fish in the gizzard (5%) and the gullet (4%), and observed unidentified
vegetation in the gullet of 1 duck and seeds of Potamogeton sp. (pondweed species)
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2017 Northeastern Naturalist Notes Vol. 24, No. 2
M.C. Perry, P.C. Osenton, and T.P. White
in the gizzard of 1 duck. We observed an unidentified Hydrozoa (hydroid) in gizzards and
gullets of several ducks, but it comprised less than 1% of the average volume. We also noted
remains of Echinarachnius parma (Common Sand Dollar) in the gizzard of 1 duck, but not
in any of the gullets of the ducks.
Detritus constituted 5% of the material in the gizzards and less than 1% in the gullets.
The detritus was organic and included items such as unidentifiable twigs and pieces of wood
that were probably ingested because they had food items attached. In Chesapeake Bay, 2
Long-tailed Ducks were collected in the 1990s that had wire from a crab pot in their gizzard
that was most likely eaten due to the Cirrepedia (Barnacles) and other live organisms that
typically attach to old deserted crab pots (M.C. Perry, unpubl. data).
Several species of benthic organisms (e.g., One-pointed Isopod and Anachis avara
[Greedy Dovesnail]) were recorded that are not generally preyed on by Long-tailed Ducks.
These uncommon diet items are further evidence that many of the food organisms were apparently
dislodged by the clamming operation creating an opportunistic feeding strategy for
the Long-tailed Ducks.
This sample of ducks from the Monomoy Island area had high volumes of unidentified
Crustacea and unidentified Amphipoda in the gullets and gizzards of the ducks. It is most
likely that these unidentified food items were benthic Sand Shrimp or skeleton shrimp disturbed
and damaged by the clamming dredge. It is unlikely that the unidentified Crustacea
and Amphipoda were Gammarus annulatus S.I. Smith (a pelagic amphipod) as none of this
common mobile organism in the water column was identified in the gullet or gizzard of the
9 ducks. This organism has been commonly found in deeper water (15–23 m [50–75 ft]) in
the Atlantic Ocean south of Nantucket Island in dense concentrations, which is believed to
be the reason Long-tailed Ducks were making the long daily commute to the ocean in the
morning and then returning to Nantucket Sound at night (White et al. 2009).
We identified a total of 37 different types of food organisms in gizzards and16 in gullets
of the 9 ducks collected. All organisms found in the gullet were also found in the
gizzard except for Porifera (unknown sponge) and One-pointed Isopod. An average of
10.3 species was identified in gizzards and 3.5 species in gullets. The proportion of food
items that could not be identified to the species level of taxonomy amounted to 48% for
gizzard and 63% for gullet samples (tally from Table 1), so the overall species diversity
was likely higher. This dietary diversity is relatively high compared to other observations.
In Chesapeake Bay, a total of 22 different organisms were found in gizzards (n = 35) and 7
in gullets (n = 10) of Long-tailed Ducks analyzed for food by the authors (M.C. Perry and
P.C. Osenton, unpubl. data). Cottam (1939) reported an average of fewer than 6.5 species
per gizzard of 190 adult Long-tailed Ducks collected in 11 months of the year from several
areas of North America.
Feeding activity near the clam boat was similar to activity of Long-tailed Ducks observed
diving in the wake of the Nantucket ferry (Perry 2012), as we saw some flying to the
area and then immediately diving close to the dredging area. Our analysis of gizzards and
gullets confirms the presence of a large number of food organisms in the Nantucket Sound
area and a foraging strategy associated with human activity to access that food. In both
cases, the Long-tailed Ducks appeared to be ingesting food items that were readily available
due to the actions of the boats. Ingesting sponges, which are not commonly eaten by
Long-tailed Ducks, suggests that they are not specific of what they eat, but of what is readily
available and abundant, similar to what was reported by Robertson and Savard (2002). The
generalist nature of the feeding seems especially likely due to the foods being ingested in
an environment that had high turbidity from the dredging. This is another example of opportunistic
foraging by Long-tailed Ducks in Nantucket Sound (Perry 2012).
2017 Northeastern Naturalist Notes Vol. 24, No. 2
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M.C. Perry, P.C. Osenton, and T.P. White
Observations from the ground and air indicates that the vast majority of Long-tailed
Ducks in the Nantucket Island area are in Nantucket Sound at night, but depart daily and
feed in the ocean during the day (Davis 1997, Perkins 1988, White et al. 2009). It has been
hypothesized that this daily movement could have evolved from the presence of more
predators in the ocean than in Nantucket Sound (Perry et al. 2013). However, the observations
and analyses reported here indicate that some Long-tailed Ducks remain in Nantucket
Sound during the day and have adapted to human activity from a clamming boat, as reported
here, or the Nantucket ferry, as reported previously (Perry 2012). Long-tailed Ducks are
small-bodied ducks with a high metabolic rate; thus, they are predicted to maximize energy,
spending more time searching for and feeding upon soft-bodied prey than handling
and grinding shelled prey, especially in winter (Sanger and Jones 1984, Systad et al. 2000).
Clamming operations on Nantucket Sound may expose and aggregate energy-dense food
sources such as clams and crustaceans to smaller diving ducks that expend less time loafing
and more time searching for food than larger sea ducks. More observations and studies need
to be conducted to further document this connection between human activities and feeding
during the day in the Nantucket Sound by Long-tailed Ducks.
Acknowledgments. Technical and editorial comments were provided by T. Alison, A. Berlin, S.
Boyd, L. Garrett, J. Gonnelli, R. Kennedy, K. Laurent, V. Laux, G. Olsen, S. Perkins, and J.-P. Savard.
The use of trade, product, or firm names in this publication is for descriptive purposes only and does
not imply endorsement by the US Government.
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