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Waterfowl Breeding Biology
A. Major breeding concentrations in
North America
1. Arctic Tundra
2. Boreal Forest
3. Prairie Wetlands
a. Prairie Parkland ecotone
b. Potholes (small ponds)
4. Western basins
5. Great Lakes
6. Coastal Wetlands
Tundra: Treeless plain
Tundra Wetlands
Snow Geese
Eiders
Some ground-nestiong divers
Boreal Forest
Cavity-nesting & other divers
Canada Geese
Dabblers common too
Minnedosa pothole
region of Manitoba:
prime duck nesting
habitat
Dabblers highly
concentrated here
THE most important
waterfowl breeding area
Some divers too
Parkland Ecotone
Dabblers important
More-stable wetlands (less drought)
Cavity-nesting divers too
Western Basin
A. Divers; especially redheads
(no photo yet)
Great Lakes and Northern Lakes Region
A. Mergansers
B. Some Divers
C. Wood Ducks
Coastal habitats
Eiders, Harlequin, etc.
Anserinae vs. Anatinae
Characteristic
Geese
Ducks
pair bond
Life
<1 yr
Age of maturity
2+
1
Plumage
Sex ratio
Sexes alike
Plain
Goslings 1 color
Nearly 50:50
Sex. Dimorphism
elaborate colors
2-tone ducklings
More males
Parental care
Both male and fe.
Only female
Nest defense
Especially males
Female; only some
Courtship
Only “triumph “
Elaborate displays
Waterfowl are Precocial vs. altricial
have a high degree of independence from birth
Waterfowl are nidifugous vs. nidicolous
leave the nest soon after hatching
Pairing
Geese: mate in winter or spring at age 2+
Male follows female to her natal area
Ducks: mate each spring at age 1+
Nest failure and renesting often requires repairing
Extra males are available for renesting females
Excess males may stimulate breeding behavior
Age of maturity example for Canada Geese
Age
Male
Female
Another
study
1st year
10%
0%
0%
2nd year
90%
70%
30%
3rd year
99+%
99+%
99+%
Sex ratio:
More males in all species of waterfowl
Geese: sex ratio is closer to 50:50
Ducks: sex ratio is sometimes very skewed
toward males (e.g., 70% + documented in
some years in Canvasbacks)
Ritualized breeding displays, esp. in ducks
Copulation in waterfowl is called “treading”
Almost always occurs on water
Male penis is evolved to penetrate
(sheathed penis; unlike other birds)
Copulation, continued
Hawaiian goose copulates on land
Is usually initiated by the male
Female may incite by swimming with a
low, flat body posture
Typical ceremony:
Male swims high in the water
Male head dipping
Neck and head into the water then up
to vertical
Female copies
Copulation ceremony, continued
Female may swim low at this point to
cooperate or incite copulation
Male scrambles onto females back
This forces her to sink down into the
water further
He grabs the back of her neck with his
bill as if to keep her head above water
Copulation lasts only 5-10 seconds
Post-copulatory behavior
Male opens wings slightly\
Male and female raise up in the water
Both paddle vigorously and call
Male flaps wings
Male and female both preen
Copulation is more frequent than necessary
to fertilize eggs
May serve to strengthen pair bond
Several North American species are more
promiscuous than once thought
Mallard for example
Extra-pair copulations
Pair bond is non-existent in some
waterfowl species outside of North America
Muscovy for example
Nesting
Waterfowl eggs are never spotted
Color varies, depending on evolutionary
factors
Characteristics of cavity vs. open nests
CAVITY
OPEN
WHITE EGGS
GREEN-BROWN EGGS
WHITE DOWN
COLORED DOWN
{pulled from Breast and placed in nest}
"DUMP" NESTS
FEWER DUMP NESTS
FEMALE HISS
LESS HISSING
{like a snake}
EXAMPLE
COMMON MERGANSER
RED-BREASTED MERGANSER
LIGHT DOWN
DARK DOWN
PALE IVORY EGGS
OLIVE-GREEN EGGS
Many species will lay their eggs in other
species nests
Not common but not rare either (uncommon)
Not the primary reproductive strategy as it is
in some species outside North America
South American black-headed duck
Uses “nest parasitism” regularly
Eggs dropped in other species nests or
those of the same species
Often infertile
Often by first-year birds
Ducks and geese lack the instinct to carry nest
material
Cavity nests for example have only material
found in the cavity plus down pulled from the
breast
Open nesters will pull in nearby vegetation
Otherwise, ground nest is usually a scrape
on the ground, with down added as the clutch
nears completion
Eggs are laid once a day; may skip a day
Larger species may lay every other day
Female incubates 20-44 days (usu. 26-28)
Incubation period varies among species
More northern species have shorter
incubation period
Larger species have longer incubation
period
Male incubates only in the whistling ducks
and a few other non-North-American species
Female brood patch is exposed by pulling
down used to insulate the nest
Used to cover the nest when she’s away
Nesting behavior
Incubation begins about the time the last egg
is laid
Hen may leave the nest during incubation
Only for a few minutes each day
Less and less as eggs near hatch
She may need to drink, bathe, or even feed
Will moisten breast feathers to transfer
moisture to the eggs
Eggs are turned at least once a day
Nesting behavior, continued
Female is less-likely to flee the nest as
incubation proceeds
Can use this behavior to capture females
on the nest
When frightened, 58 species of waterfowl
(worldwide) will feign a broken wing as a
nest defense
Some will hiss; sounds like a snake
Mostly seen in cavity nesters
Eiders and some others will deficate on
the eggs when frightened
Nesting behavior, continued
Deficating on the eggs may be
camouflage or may give the eggs a foul
(fowl?) odor or taste
Female continues to increase the amount of
down in the nest for first several days of
incubation
Young hatch within a few hours of each
other by “pipping” through the egg with the
egg “tooth”
Female will brood them until they dry,
usually within 16-18 hours
Nesting behavior, continued
She will call them from the nest with special
call
She immediately leads them to water for
safety from predators
Yes, they can swim right away
Feed on their own; not fed by parent
Mother’s gentle call maintains brood
cohesion (audio-imprinting)
May brood young under her wings, but they
do not ever return to the nest once fledged
Nesting/fledging behavior, continued
If young hatch late in the day, they may
remain the nest until morning (i.e., more than
18 hours)
Precocial young develop very rapidly
Can fly within 40-75 days for North
American species
Smaller and more-northern species
develop most rapidly
Critical timing for arctic-nesting species!
Select a nest site
2 days
Lay clutch of eggs
6 days
Incubation
28 days
Grow to flight stage
40 days
Total
76 days
Snow-free days in a
typical arctic summer
75 days!
Annual weather fluctuations are critical to
arctic breeders
Conditions in the prairies or other migratory
stop-over areas are critical to arctic breeders
too
No food when they arrive in arctic
Don’t feed significantly until hatch
Breed on snow-free ridges in tundra
Synchronous breeding in arctic species
Essentially all the geese and eiders are
hatching within the same 5 days each season
Breeding - Continued
A. While nesting in the high arctic tundra is
synchronized within a 5-day period and
renesting is not an option once incubation
has begun, more temperate breeders nest
over a 50-day period, with many of the
late nest being renesting by birds that lost
their first nest
Nest predators
A. Arctic
1. Waterfowl prefer islands where some protection
from mammalian predators (e.g., arctic fox) is
offered
2. Gulls, ravens, jays, and jaegers are common
predators, not deterred by islands
3. Eskimo and Samoyede natives collect eggs and
flightless adults
a. Protected by treaty where use is for subsistence
b. Can hurt colonies in some years
4. Except for some geese and eiders, nesting is
scattered and not gregarious
Nest predators, continued
B. Temperate areas
1. Man is the worst “predator” on nests
a. Egg collecting, disturbance, mowing and other
farm operations
1) Indeed, this may be why such a large percentage of
waterfowl nest in the more-northern prairie marshes (ie,
they have survived there in larger numbers than further
south where man has a stronger presence)
2. Open nesters:
a. Mink, foxes, coyotes, raccoons, snakes, crows
and gulls, large turtles, others
b. Cats and dogs
Nest predators, continued
3. Cavity nesters:
a. Snakes are number 1
b. Other cavity-nesting birds (e.g., starlings,
woodpeckers)
c. Raccoons
C. Adaptations to avoid predation
1. Nest in colonies:
a. Large numbers of birds may deter predators
b. Predators in a small area “swamped” by so much
food (greater % avoid predators
2. Scattered nests to avoid detection
Adaptations to avoid predation, continued
a. Some data suggest predation is higher in the
prairies when ducks are forced to nest at higher
densities due to drought or reduction in area of
nesting habitat due to agriculture
a. Predators have a smaller area in which to search
3. Selection of dense nesting cover by most
ground-nesters and female remaining on nest
when approached
4. Selection of islands and tree cavities
Other nesting problems
A. Flooding
1. May be why so many ground-nesters move upland,
often more than 100 meters
2. Even in cavity-nesting species
a. Wood ducks along the Ohio river, etc.
3. Geese, especially brant because they nest so close
to shore, may be wiped out by high seas
a. Significant losses in some years
1. Female’s body condition
1. She may have to abandon nest if her reserves fall
too low
2. Some snow geese die on the nest when weight
drops too low
3. Clutch sizes are smaller for waterfowl in poor
condition
Overall nest success
A. Hatching success high for eggs incubated full
term
1. Fertility rate of 95-99% is typical
2. Some embryo mortality during development
a. May be related to cold spells and disturbance during
incubation
B. Competition for tree cavities is often high
1. Large percentage of dump nests
2. Many females do not nest at all
3. Probably about 20% of female wood ducks
successfully nest in any given year!
1. Combined effects of flooding, predation, and competition
Nest success, continued
C. Losses of goose nests in the arctic due to
predators are typically less than 10%
1. May be as high as 90% when lemming
population cycles are at a low and foxes
switch to eggs
D. Severe weather such as drought may
cause extremes in reduced nest success
1. In one severe drought year, less than 5% of
lesser scaup nested in the North American
prairies
Canada Goose Data from Western Kentucky
Fate of Nests
47 Nests
Mean clutch size = 5.3
12 Unsuccessful
3 depredated
1 hen died
2 "displaced"
3 deserted
3 failed
35 Successful
111
banded
8 weeks
later
Fate of Eggs
248
Eggs
147 hatched
5 died
in nest
142 left
nest
111 banded
8 weeks
later
46% of
neckbands
seen later
101 unhatched
26 broken
or missing
33
infertile
42
died in
development
Nest success, continued
A. Renesting:
1. In a Manitoba study, 50% of mallards that lost
their nest renested
a. Of those, 40% hatched broods
2. A third attempt when the 2nd clutch is
destroyed is exceptional but can happen
3. Renesting is unknown in swans and rare in
geese
4. The interval between nest destruction and
renesting increases with incubation stage of
the first nest
a. Renesting may be impossible when the nest is
lost late in incubation
Post-hatch
A. Common predators are mink, fox, hawks and
other birds, coyote, dogs, cats, turtles, and
large fish
1. pike may kill 10%
2. Most loss is in the first 2 weeks
3. 40% survival is probably typical of hatched ducklings
B. Lake and pond breeding geese often move
upland soon after hatch and return to the water
each evening
C. Arctic geese travel the tundra valleys, grazing
areas heavily
D. Duckling seek invertebrate foods for rapid
development of muscles and feathers
Post-hatch, continued
A. Adults are typically flightless (molting)
while young are growing
1. Late in the flightless period is an ideal time to
band waterfowl since the adults can be
captured easily and the young are big
enough to put permanent leg bands on
2. They can be herded into pens or netted on
the water
Post-fledging
A. Once waterfowl leave the breeding
grounds, survival of young is probably still
lower than that of adults
1. They have not attained full adult weight
2. Body fat reserves are lower
3. There is probably a density-dependent
migration and over-winter mortality
4. The importance of these factors can be
evaluated with banding data
5. Otherwise, post-fledging mortality is lumped
with adult mortality
The “post-breeding” period
A. By the fall flight from breeding to wintering
areas, there are typically 1-2 young for
every adult in most waterfowl populations
1. If populations remain stable from year to
year, what is the total post-breeding mortality
rate?
a. If you said 50% or more, you’re probably about
right
b. Varies among species
c. For the more-popular hunted species, most of that
mortality is due to hunters