waterfowl breeding biology a.major breeding concentrations in north america 1.arctic tundra 2.boreal...
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Waterfowl Breeding BiologyA. Major breeding concentrations in
North America1. Arctic Tundra2. Boreal Forest3. Prairie Wetlands
a. Prairie Parkland ecotoneb. Potholes (small ponds)
4. Western basins5. Great Lakes6. Coastal Wetlands
Minnedosa pothole region of Manitoba: prime duck nesting
habitat
Dabblers highly concentrated here
THE most important waterfowl breeding area
Some divers too
Anserinae vs. Anatinae
Characteristic Geese Ducks
pair bond Life <1 yr
Age of maturity 2+ 1
Plumage Sexes alike
Plain
Goslings 1 color
Sex. Dimorphism
elaborate colors
2-tone ducklings
Sex ratio Nearly 50:50 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 predatorsA. 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 areas1. Man is the worst “predator” on nests
a. Egg collecting, disturbance, mowing and other farm operations1) 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, continued3. Cavity nesters:
a. Snakes are number 1
b. Other cavity-nesting birds (e.g., starlings, woodpeckers)
c. Raccoons
C. Adaptations to avoid predation1. 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 agriculturea. 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 problemsA. Flooding
1. May be why so many ground-nesters move upland, often more than 100 meters
2. Even in cavity-nesting speciesa. 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 condition1. She may have to abandon nest if her reserves fall too
low2. Some snow geese die on the nest when weight drops
too low3. Clutch sizes are smaller for waterfowl in poor condition
Overall nest successA. Hatching success high for eggs incubated full
term1. Fertility rate of 95-99% is typical
2. Some embryo mortality during developmenta. May be related to cold spells and disturbance during
incubation
B. Competition for tree cavities is often high1. 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
3 depredated 1 hen died
2 "displaced" 3 deserted
3 failed
12 Unsuccessful
111banded8 weeks
later
35 Successful
47 NestsMean clutch size = 5.3
46% ofneckbandsseen later
111 banded8 weeks
later
5 diedin nest
142 leftnest
26 brokenor missing
33infertile
42died in
development
147 hatched 101 unhatched
Fate of Eggs
248Eggs
Nest success, continuedA. Renesting:
1. In a Manitoba study, 50% of mallards that lost their nest renesteda. 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 nesta. Renesting may be impossible when the nest is lost
late in incubation
Post-hatchA. 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 weeks3. 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-fledgingA. Once waterfowl leave the breeding
grounds, survival of young is probably still lower than that of adults
1. They have not attained full adult weight2. Body fat reserves are lower3. There is probably a density-dependent
migration and over-winter mortality4. The importance of these factors can be
evaluated with banding data5. 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
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