Notes on the Feeding Behavior of the Common Merganser (Mergus merganser)

The Condor ◽  
1974 ◽  
Vol 76 (4) ◽  
pp. 472
Author(s):  
Bertin W. Anderson ◽  
Michael G. Reeder ◽  
Richard L. Timken
Keyword(s):  
Feeding Behavior ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. II: Predation of Stream-Resident Juvenile Salmon by Merganser Broods

1987 ◽  
Vol 44 (5) ◽  
pp. 950-959 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Body Weight ◽  
Census Data ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Vancouver Island ◽  
Juvenile Salmonids ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of stream-resident juvenile salmonids by broods of the common merganser (Mergus merganser) was investigated in three streams on eastern Vancouver Island from 1980 to 1982. Daily fish consumption by merganser ducklings was estimated to range from 80% of body weight for ducklings at 10 d of age to 40% of body weight for those at 40 d of age. Merganser ducklings were never observed to eat juvenile salmonids on tidal waters, but did eat them on the freshwater reaches of streams studied. Typically, broods inhabited only the freshwater reaches of their natal stream while young, but spent progressively more time foraging on tidal waters as they grew older. The biomass of broods (and hence potential consumption) on fresh water was estimated by reconstructing the history of individual broods from census data. These results suggest that merganser broods consumed on the order of 82 000–131 000 coho salmon (Oncorhynchus kisutch) fry in the Big Qualicum River between June 10 and August 25. This is equivalent to 24–65% of the observed wild smolt production from this system, assuming that these fry would otherwise have survived as well as uneaten fry.

Food-searching behaviour of the common merganser (Mergus merganser) II: Choice of foraging location

1985 ◽  
Vol 63 (6) ◽  
pp. 1271-1279 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Coho Salmon ◽  
Search Pattern ◽  
Flock Size ◽  
Searching Behaviour ◽  
Natural Stream ◽  
Mergus Merganser ◽  
Visit Duration ◽  
The Common ◽  
Common Merganser ◽  
Time Required

Factors influencing the choice of foraging location by the common merganser (Mergus merganser) were investigated by baiting three adjacent, enclosed sections of a natural stream with various densities of juvenile coho salmon (Oncorhynchus kisutch). Merganser abundance within 1 km of the enclosure site increased from < 3 to > 10 birds within 1 week of stocking the enclosures with 43-g coho smolt. Although abundance declined gradually thereafter (as expected from seasonal trends on other nearby streams), the frequency of visits to the enclosure site continued to increase for 22 d until the enclosures were stocked predominately with smaller (2-g) coho fry. Visits were more frequent when other mergansers were already present at the site. Also, the proportion of mergansers flying overhead that landed near a decoy "flock" increased with decoy flock size. In general, the duration of visits to the site was not affected by the number of birds present. Visit duration increased exponentially with increasing fish density and decreased with searching time required until first capture. Mergansers spent more time searching in the most profitable enclosure. Allocation of searching time among the enclosures was not consistent with a "giving up time" decision rule; however, mergansers appeared to follow an area-restricted search pattern both within and among the enclosures.

Food-searching behaviour of the common merganser (Mergus merganser) I: Functional responses to prey and predator density

1985 ◽  
Vol 63 (6) ◽  
pp. 1260-1270 ◽  
Author(s):  
C. C. Wood ◽  
C. M. Hand
Keyword(s):  
Coho Salmon ◽  
Flock Size ◽  
Previous Exposure ◽  
Functional Responses ◽  
Experimental Conditions ◽  
Natural Stream ◽  
Daily Food ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

The hunting performance of the common merganser (Mergus merganser) was evaluated in relation to prey density and merganser flock size by stocking three enclosed sections of a natural stream with known densities of juvenile coho salmon (Oncorhynchus kisutch). Two size classes of coho were stocked: smolt averaging 43 g at densities of 0.02–0.65/m2, fry averaging 2 g at 0.08–1.6/m2 and various mixtures of smolt and fry at a combined density of 0.65/m2. The stream enclosures differed in the amount of cover available to fish. Mergansers were less successful at capturing coho smolt or fry in the enclosures wth cover from undercut banks. Smolt exposed to mergansers earlier that day were less vulnerable than smolt with no previous exposure. The feeding success of individual mergansers was not significantly affected by flock size for flocks of 25 birds or less. A smoothly asymptotic functional response (type II) was observed under all experimental conditions. Coho smolt were selected over coho fry. It is concluded that a merganser's average daily food requirement (ca. 400 g) can be satisfied at smolt densities of 0.02–0.30/m2 depending on the availability of cover for smolt and their previous exposure to mergansers.

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. I: Predation during the Seaward Migration

1987 ◽  
Vol 44 (5) ◽  
pp. 941-949 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Mortality Rate ◽  
Prey Size ◽  
Pacific Salmon ◽  
Size Selection ◽  
Juvenile Salmonids ◽  
Seaward Migration ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of juvenile salmonids by the common merganser (Mergus merganser) was investigated during the period of seaward migration in two streams where fish populations are enhanced by spawning channels and hatcheries. Observation of foraging behaviour and crop-gullet contents indicated that, during this period, mergansers foraging on freshwater reaches of the streams ate juvenile salmonids almost exclusively whereas those foraging on tidal waters rarely ate salmonids. Maximum rates of salmonid mortality were estimated by assessing merganser abundance and the pattern of foraging activity on fresh versus tidal waters. Maximum mortality rate declined as fish abundance increased (i.e. mortality was depensatory) in all cases where the effects of prey size-selection could be ignored owing to an overwhelming abundance of one prey species. Bounds on maximum mortality rate by species for the entire migration period were computed under different hypotheses about the prey size-selection habits of mergansers; maximum mortality rate did not exceed 10% for any salmonid species over the entire seaward migration.

Dispersion of common merganser (Mergus merganser) breeding pairs in relation to the availability of juvenile Pacific salmon in Vancouver Island streams

1986 ◽  
Vol 64 (3) ◽  
pp. 756-765 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Pacific Salmon ◽  
Prey Availability ◽  
Vancouver Island ◽  
Egg Laying ◽  
Breeding Pair ◽  
Juvenile Salmon ◽  
Mergus Merganser ◽  
Juvenile Pacific Salmon ◽  
Stream Size ◽  
Common Merganser

Common merganser (Mergus merganser) breeding pairs and broods were censused on eight coastal streams on Vancouver Island to evaluate the relative importance of the number of potential breeding pairs, stream size, and the availability of juvenile Pacific salmon in limiting merganser breeding density. The number of potential breeding pairs did not limit nesting density on at least one stream where juvenile salmon populations were enhanced by a hatchery and spawning channel. At distances > 1 km above tidal influence, breeding pairs were evenly dispersed along the streams during the peak egg-laying and incubation period at maximum densities of 0.4–1.4 pairs/km. Maximum breeding pair counts were higher and more variable among streams on the lower kilometer of freshwater (1–9 pairs) and on tidal waters near the stream outlets (4–9 pairs). Stream size accounted for only a part of the variation in breeding pair counts. The estimated number of broods produced on each stream was highly correlated (r = 0.95) with both drainage area and juvenile salmon production, including production from hatcheries. Possible mechanisms relating the dispersion of breeding pairs to the availability of juvenile salmon are discussed. A "food assessment" hypothesis, whereby breeding pairs choose a nesting stream on the basis of prey availability during the nesting season, could not be rejected on the basis of predictions about hatching dates and duckling survival. This hypothesis has serious implications for mortality of wild salmonids in hatchery-enhanced streams.

Feeding-Behavior and Diet of the Common Ringtail Possum, Pseudocheirus-Peregrinus, in Eucalyptus Woodlands and Leptospermum Thickets in Southern Victoria

1987 ◽  
Vol 35 (5) ◽  
pp. 487 ◽  
Author(s):  
LI Pahl
Keyword(s):  
Feeding Behavior ◽  
Food Selection ◽  
Species Trees ◽  
Flower Buds ◽  
Pseudocheirus Peregrinus ◽  
Different Populations ◽  
The Common ◽  
Four Levels ◽  
Eucalyptus Maculata ◽  
Ringtail Possum

The foliage of Eucalyptus spp. contributed 61-98% of the annual diet of ringtails at sites dominated by Eucalyptus spp. or prickly teatree, Leptospermum juniperinum. Up to 45% of the Eucalyptus foliage consumed was young, and young foliage was mostly eaten during spring and summer. The remainder of the diet consisted of foliage of several species of shrub and significant proportions of the diet of one population consisted of flowers and/or flower buds of Eucalyptus maculata during winter. The proportion of shrub foliage eaten was generally highest at sites dominated by less preferred Eucalyptus spp., such as E. tereticornis, E. camaldulensis and E. botryoides, compared to sites dominated by the favoured species, E. ovata, E. dives, and E. maculata. Ringtails in thickets of coast teatree, L. laevigatum, fed predominantly on foliage of that species. The proportions of Eucalyptus and shrub foliage eaten by different populations did not appear to be correlated with availability, suggesting that ringtails fed selectively from the foods available. Food selection was practised at four levels: between species, trees, leaves and leaf parts. Partly digested leaf material appeared to have been consumed by pouch young before they had begun to feed on foliage.

scholarly journals Transient definitive host presence is sufficient to sustain avian schistosome populations

2021 ◽  
Author(s):  
Sydney P Rudko ◽  
Brooke A McPhail ◽  
Ronald L Reimink ◽  
Kelsey Froelich ◽  
Alyssa Turnbull ◽  
...  
Keyword(s):  
Definitive Host ◽  
Snail Host ◽  
Effective Control ◽  
Lake Ecosystem ◽  
Infection Prevalence ◽  
Control Effort ◽  
Swimmer’S Itch ◽  
The Common ◽  
Common Merganser ◽  
Swimmer's Itch

To control swimmer's itch in northern Michigan inland lakes, one species of bird, the common merganser (Mergus merganser), has been relocated from several lakes since 2015. Relocation efforts are driven by a desire to reduce the prevalence of the swimmer's itch-causing parasite Trichobilharzia stagnicolae. The intention of this state-sponsored control effort was to interrupt the life cycle of T. stagnicolae and reduce parasite egg contribution into the environment from summer resident mergansers such that infections of the intermediate snail host Stagnicola emarginata declined. Reduced snail infection prevalence was expected to greatly reduce abundance of the swimmer's itch-causing cercarial stage of the parasite in water. With no official program in place to assess the success of this relocation effort, we sought to study the effectiveness and impact of the removal of a single definitive host from a location with high definitive host and parasite diversity. This was assessed through a comprehensive, lake-wide monitoring study measuring longitudinal changes in the abundance of three species of avian schistosome cercariae in four inland Michigan lakes. Environmental measurements were also taken at these lakes to understand how they can affect swimmer's itch incidence. Results from this study demonstrate that the diversity of avian schistosomes at the study lakes would likely make targeting of a single species of swimmer's itch-causing parasite meaningless from a swimmer's itch control perspective. Our data also suggest that removal of the common merganser is not an effective control strategy for the T. stagnicolae parasite, likely due to parasite contributions of migratory birds in the fall and spring. This suggests that only minimal contact time between the definitive host and the lake ecosystem is required to contribute sufficient parasite numbers to maintain a thriving population of parasite species with a high host-specificity.

Specificity of a Black Fly, Simulium euryadminiculum Davies, toward its Host, the Common Loon

1964 ◽  
Vol 96 (6) ◽  
pp. 911-913 ◽  
Author(s):  
J. K. Lowther ◽  
D. M. Wood
Keyword(s):  
Head And Neck ◽  
Host Location ◽  
Herring Gull ◽  
Gavia Immer ◽  
Common Loon ◽  
Black Fly ◽  
Large Numbers ◽  
The Common ◽  
Common Merganser

AbstractThe attraction of large numbers of the ornithophilic black fly, Simulium euryadminiculum Davies, to its host, the common loon, Gavia immer (Brünnich), to the place where the loon skin had been washed, and to a dried museum skin of the loon, is described. The fly was not attracted to museum skins of a pied-billed grebe, common merganser and herring gull. The data suggest a system of olfaction in host location, probably involving volatile, air-borne substances. It is possible that the colour or pattern on the head and neck of the loon serves to attract the fly to this area of the host.

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