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

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 habitatsEiders, Harlequin, etc.

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