Common Merganser (Mergus 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.

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

The Condor ◽

10.2307/1365825 ◽

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

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

Canadian Journal of Zoology ◽

10.1139/z86-112 ◽

1986 ◽

Vol 64 (3) ◽

pp. 756-765 ◽

Cited By ~ 5

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.

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

Canadian Journal of Zoology ◽

10.1139/z85-190 ◽

1985 ◽

Vol 63 (6) ◽

pp. 1271-1279 ◽

Cited By ~ 4

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.

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Mergus merganser Linnaeus. Common Merganser; Goosander. Harle bièvre.

The Birds of Africa ◽

10.5040/9781472926982.0182 ◽

2016 ◽

Keyword(s):

Mergus Merganser ◽

Common Merganser

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

Canadian Journal of Zoology ◽

10.1139/z85-189 ◽

1985 ◽

Vol 63 (6) ◽

pp. 1260-1270 ◽

Cited By ~ 32

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.

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