Waterfowl Breeding Biology

Waterfowl Breeding Biology • Major breeding concentrations in North America • Arctic Tundra • Boreal Forest • Prairie Wetlands • Prairie Parkland ecotone • Potholes (small ponds) • Western basins • Great Lakes • 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 • Divers; especially redheads (no photo yet)

Great Lakes and Northern Lakes Region • Mergansers • Some Divers • Wood Ducks

Coastal habitats Eiders, Harlequin, etc.

Anserinae vs. Anatinae

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

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 CAVITYOPEN 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 MERGANSERRED-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!

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 • 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 • Arctic • Waterfowl prefer islands where some protection from mammalian predators (e.g., arctic fox) is offered • Gulls, ravens, jays, and jaegers are common predators, not deterred by islands • Eskimo and Samoyede natives collect eggs and flightless adults • Protected by treaty where use is for subsistence • Can hurt colonies in some years • Except for some geese and eiders, nesting is scattered and not gregarious

Nest predators, continued • Temperate areas • Man is the worst “predator” on nests • Egg collecting, disturbance, mowing and other farm operations • 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) • Open nesters: • Mink, foxes, coyotes, raccoons, snakes, crows and gulls, large turtles, others • Cats and dogs

Nest predators, continued • Cavity nesters: • Snakes are number 1 • Other cavity-nesting birds (e.g., starlings, woodpeckers) • Raccoons • Adaptations to avoid predation • Nest in colonies: • Large numbers of birds may deter predators • Predators in a small area “swamped” by so much food (greater % avoid predators • Scattered nests to avoid detection

Adaptations to avoid predation, continued • 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 • Predators have a smaller area in which to search • Selection of dense nesting cover by most ground-nesters and female remaining on nest when approached • Selection of islands and tree cavities

Other nesting problems • Flooding • May be why so many ground-nesters move upland, often more than 100 meters • Even in cavity-nesting species • Wood ducks along the Ohio river, etc. • Geese, especially brant because they nest so close to shore, may be wiped out by high seas • Significant losses in some years • Female’s body condition • She may have to abandon nest if her reserves fall too low • Some snow geese die on the nest when weight drops too low • Clutch sizes are smaller for waterfowl in poor condition

Overall nest success • Hatching success high for eggs incubated full term • Fertility rate of 95-99% is typical • Some embryo mortality during development • May be related to cold spells and disturbance during incubation • Competition for tree cavities is often high • Large percentage of dump nests • Many females do not nest at all • Probably about 20% of female wood ducks successfully nest in any given year! • Combined effects of flooding, predation, and competition

Nest success, continued • Losses of goose nests in the arctic due to predators are typically less than 10% • May be as high as 90% when lemming population cycles are at a low and foxes switch to eggs • Severe weather such as drought may cause extremes in reduced nest success • In one severe drought year, less than 5% of lesser scaup nested in the North American prairies

47 Nests Mean clutch size = 5.3 12 Unsuccessful 35 Successful 111 3 depredated 1 hen died banded 2 "displaced" 3 deserted 8 weeks later 3 failed Canada Goose Data from Western Kentucky Fate of Nests

Fate of Eggs 248 Eggs 147 hatched 101 unhatched 5 died 142 left 26 broken 33 42 in nest nest or missing infertile died in development 111 banded 8 weeks later 46% of neckbands seen later

Nest success, continued • Renesting: • In a Manitoba study, 50% of mallards that lost their nest renested • Of those, 40% hatched broods • A third attempt when the 2nd clutch is destroyed is exceptional but can happen • Renesting is unknown in swans and rare in geese • The interval between nest destruction and renesting increases with incubation stage of the first nest • Renesting may be impossible when the nest is lost late in incubation

Post-hatch • Common predators are mink, fox, hawks and other birds, coyote, dogs, cats, turtles, and large fish • pike may kill 10% • Most loss is in the first 2 weeks • 40% survival is probably typical of hatched ducklings • Lake and pond breeding geese often move upland soon after hatch and return to the water each evening • Arctic geese travel the tundra valleys, grazing areas heavily • Duckling seek invertebrate foods for rapid development of muscles and feathers

Post-hatch, continued • Adults are typically flightless (molting) while young are growing • 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 • They can be herded into pens or netted on the water

Post-fledging • Once waterfowl leave the breeding grounds, survival of young is probably still lower than that of adults • They have not attained full adult weight • Body fat reserves are lower • There is probably a density-dependent migration and over-winter mortality • The importance of these factors can be evaluated with banding data • Otherwise, post-fledging mortality is lumped with adult mortality

The “post-breeding” period • By the fall flight from breeding to wintering areas, there are typically 1-2 young for every adult in most waterfowl populations • If populations remain stable from year to year, what is the total post-breeding mortality rate? • If you said 50% or more, you’re probably about right • Varies among species • For the more-popular hunted species, most of that mortality is due to hunters

Waterfowl Breeding Biology