Waterfowl Ecology & Management

WFS 464 (564)

Class Notes - Spring 2004

I. Waterfowl Taxonomy, Classification, & Characteristics

A. General Classification

1. The term waterfowl applies to 149-166 (4 recently extinct) species (depending upon the authority consulted) of ducks, geese, and swans. The term waterbird is often used to denote waterfowl, as well as other aquatic or wetland associated birds (e.g., coots, grebes, loons, cormorants, gulls).

2. All waterfowl belong to the class Aves (birds) and order Anseriformes.

a. Anseriformes is a primitive order within the class, and waterfowl usually appear near the first of most field guides.

b. Many authorities include only the family Anatidae as waterfowl, but some include the 3 screamers and the magpie goose also.

c. The number of accepted species differs greatly among authorities, with the “mallard group” being the most debated; in these notes, the “splitting” approach used by Baldassarre and Bolen (1994) is used.

d. The most recent taxonomic treatment was that of Livezey 1986 (Auk 103:737-754) who used 120 morphological characteristics to show relationships among forms; this system is presented in these notes, as well as refrences to the precious classification system.

3. There are 3 families within Anseriformes:

a. Anhimidae: screamers- 3 species of semi-aquatic, primitive birds that live in South America and resemble pheasants

b. Anseranatidae: Magpie Goose – very primitive, goose-like species of Australia.

c. Anatidae: ducks, geese, and swans.

4. The family Anatidae is divided into 7 subfamilies:

a. Dendrocyginae: Whistling Ducks

b. Thalassorninae: White-backed Duck – a primitive bird of Africa that resembles a Speckled Ruddy Duck.

c. Anserinae: Swans and Geese.

d. Stictonettinae: Freckled Duck – A primitive bird of Australia that resembles a black mallard with white speckles on its body.

e. Plectropterinae: Spur-winged Goose – A large bird of Africa that somewhat resembles a Magpie Goose.

f. Tadorinae: Shelducks & relatives – southern hemisphere ecological equivalents to many northern hemisphere forms.

g. Anatinae: Typical Ducks

5. Taxonomy of waterfowl is somewhat unique in that polytypic subfamilies are further divided into tribes:

Anserinae (Swans and Geese)
Tribe Cygnini (Swans)
Tribe Anserini (Geese)
Tadorninae (Shelducks & relatives)
Tribe Tadornini (Shelducks, Sheldgeese, Steamer Ducks, & relatives)
Tribe Sarkidiornini (Comb Duck)
Anatinae (Typical Ducks)
Tribe Anatini (Dabbling Ducks)
Tribe Aythyini (Bay Ducks, Diving Ducks, or Pochards)
Tribe Mergini (Sea Ducks)
Tribe Oxyurini (Stiff-tailed Ducks)

Note: Thalassorninae, Stictonettinae, and Plectropterinae consist of a sinfle species and are not divided into tribes; Dendrocygninae contains 8 species but it is uniform enough that the subfamily is not divided into tribes.

B. Taxa Characteristics

1. Family Anhimidae (Screamers) (3 spp. – South America)

1) Large size, but thin

2) Very long legs

3) Reticulate tarsus

4) Long neck

5) No osseus bulla (?)

6) Gray, black, and white

7) No sexual dimorphism

8) Single, annual body molt and gradual wing molt

9) Chicken-shaped bill

10) Large, palmate feet, only slightly webbed

11) Pairs for life

12) Matures in 2-4 years (2)

13) Males share in incubation

14) Herbivorous

Family Anseranatidae (Magpie Goose) (1 sp. – Australia)

1) Large size

2) Very long legs

3) Reticulate tarsus

4) Long neck

5) No osseus bulla, but a long, couled trachea

6) Black and white

7) No sexual dimorphism

8) Single, annual body molt and gradual wing molt

9) Odd bill shape with prominent nail

10) Large, palmate feet, webbed at the base

11) Pairs for life, but polygynous

12) Matures in 3-4 years

13) Males share in incubation

14) Herbivorous, primarily grazing or grubbing

15) Considered a subfamily (Anseranatinae) of the family Anatidae until recently

Subfamily Dendrocygninae (Whistling Ducks) – (8 spp. – circumtropical)

1) Small – medium size

2) Long legs (stand upright)

3) Reticulate tarsus

4) Medium necks (often furrowed)

5) No osseus bulla, but males have a slightly larger syrinx

6) Often with elaborate flank feathers

7) No sexual dimorphism

8) Single, annual body molt and synchronous wing molt

9) Pair for life

10) Mature in 1 year

11) Males share in incubation

12) Aquatic (often dive) or upland grazers

13) Considered a tribe (Dendrocygninae) of the subfamily Anserinae until recently

Subfamily Thalassorninae (White-backed Duck) – (1 sp. – Africa)

1) Small size

2) Short legs, attached far back

3) Scutellate tarsus

4) Short neck

5) No osseus bulla (?)

6) No sexual dimorphism

7) Single, annual body molt (?) and synchronous wing molt

8) Pair for life (?)

9) Mature in 1 year (?)

10) Male primary incubator

11) Aquatic form that has been difficult to classify; resembles Stiff-tailed ducks but more closely related to whistling ducks

12) Considered an aberrant member of Dendrocygnini until recently

Tribe Cygnini (Swans) – (8 spp. – Worldwide, except absent from Africa)

1) Large size

2) Short legs

3) Reticulate tarsus

4) Long necks (longer than body)

5) No osseua bulla

6) Mostly white (one black)

7) No sexual dimorphism

8) Single, annual body molt and synchronous wing molt

9) Lores without feathers and often colored

10) Pair for life

11) Mature in 2-4 years

12) Young carried on back of adult

13) Aquatic grazers

14) Not separated from geese until recently

6. Tribe Anserini (Geese) – (15 spp. Mostly North America, Europe, Asia; Cereopsis in Australia)

1) Small – large in size

2) Medium legs

3) Reticulate tarsus

4) Medium necks

5) No osseus bulla

6) No sexual dimorphism

7) Single, annual body molt and synchronous wing molt

8) Pair for life

9) Mature in 2-3 years

10) Upland grazers or grubbers

11) Not separated from swans until recently

7. Subfamily Stictonettinae (Freckled Duck) – (1 sp. – Australia)

1) Medium size

2) Short legs

3) Reticulate tarsus

4) Short neck

5) No osseus bulla, but a long, coiled trachea

6) Black with white “freckles”

7) Little sexual dimorphism (i.e., bill color and slight color fidderences)

8) Single, annual body molt (?) and synchronous wing molt

9) Pair for life (?)

10) Mature in 1 year (?)

11) Filter feeder (primarily algae), but sometimes dabbles

12) Superficially resembles some members of Anatini, but its closest living relatices are swans

13) Considered a tribe (Stictonettini) of the subfamily Anserinae until recently

8. Subfamily Plectropterinae (Spur-winged Goose) – (1 sp. – Africa)

1) Large size

2) Long legs, attached in middle

3) Scutellate tarsus

4) Long neck

5) No osseus bulla (?)

6) Little sexual dimorphism (bare skin and knob on male)

7) Single, annual body molt (?) and synchronous wing molt

8) Pair annually (?)

9) Mature in 2-3 years (?)

10) Upland grazer or graze in shallow water

11) Considered a member of the former tribe Cairinini (Perching Ducks) until recently

9. Tribe Sarkidiornini (Comb Duck) – (1 sp. – Africa, Asia, and South America)

1) Moderately large size

2) Moderately short legs, attached in middle

3) Scutellate tarsus

4) Medium necks

5) Osseus bulla (?)

6) Black, white and gray

7) Sexual dimorphism with large fleshy knob on bill of males

8) Single, annual body molt (?) and synchronous wing molt

9) Pair annually and polygynous

10) Mature in 1-2 years (?)

11) Dabble or graze at edge of water

12) Some researchers indicate that this species should be divided into two (Old World and New World species)

13) Considered a member of the former tribe Cairinini (Perching Ducks) until recently

10. Tribe Tadornini (Shelducks, Sheldgeese, Steamer Ducks, & Relatives) – (23 spp., 1 recently extinct – Mostly Africa, South America, Australia, and Asia)

Shelducks (7 spp., 1 extinct) and Sheldgeese (8 spp.)

1) Small-large size

2) Moderately long legs, attached in middle

3) Scutellate tarsus

4) Small (Shelducks) –medium (sheldgeese) necks

5) Osseus bulla in males

6) Often brightly colored with bright wing speculum

7) ½ sexual dimorphic species (mostly shelducks)

8) Single, annual body molt (?) and synchronous wing molt

9) Pair for life

10) Mature in 1-3 years

11) Aquatic or upland grazers, consume some animal material

12) Ecological equivalents to Northern Hemisphere Dabbling Ducks and Geese

Steamer Ducks (4 spp.) – South America

1) Moderately large size

2) Moderately short legs, far back on body

3) Scutellate tarsus

4) Short, thick necks

5) No osseus bulla

6) Gray, some white in wing

7) Minor sexual dimorphism (Mostly size and bill color)

8) Single, annual body molt (?) and synchronous wing molt

9) Pair for life

10) Mature in 2-3 years

11) Dabble or dive for mollusks or crustaceans

12) Extremely aggressive and fight to death

13) Ecological equivalents to Northern Hemisphere Eiders

14) Two flightless species

15) Considered a separate tribe (Tachyerini) until recently

Aberrant Species – These four forms were placed in various tribes in the past and are the most likely to be placed elsewhere in the future.

1) Pink-earred Duck: Filter feeder of Australia

2) Blue Duck: Mountain stream dweller of New Zealand

3) Torrent Duck: Mountain stream dweller of South America

4) Salvadori Duck: Mountain stream dweller of New Guinea

11. Tribe Anatini (Dabbling Ducks) – (59 spp. – worldwide

1) Includes most of the former tribe Cairinini (Perching Ducks), of which the North American wood duck was a member

2) Very small – medium size

3) Short legs, attached in middle

4) Scutellate tarsus

5) Medium necks

6) Osseus bulla in males

7) Metallic colors in wing

8) Most sexually dimorphic

9) Most have 2 annual body molts, and all have a synchronous wing molt

10) Most pair annually (exception island spp. and many previous Cairinini members)

11) Most mature in 1 year

12) Herbivorous or omnivorous dabblers

13) Can “spring” directly off the water

14) 1 flightless species (Auckland Island Teal)

12. Tribe Aythyini (Bay Ducks, Pochards, Diving Ducks) – (17 spp., 1 recently extinct – worldwide)

1) Very small – medium size

2) Short leg, attached far back

3) Scutellate tarsus

4) Medium necks

5) Osseus bulla in males

6) Dull colors in wing

7) Most sexually dimorphic

8) Most have 2 annual body molts, and all have a synchronous wing molt

9) Most pair annually

10) Most mature in 1 year

11) Herbivorous, omnivorous, or carnivorous divers

12) Must “take-off” from the water

13. Tribe Mergini (Sea Ducks) – (20 spp., 2 recently extinct – Mostly arctic or subarctic regions; mergansers also occur in South America and Asia, formerly Auckland Islands)

1) Very small – moderately large size

2) Short legs, attached far back

3) Scutellate tarsus

4) Short – medium necks

5) Osseus bulla in males (?)

6) Extensice white in wings of most species

7) Most sexually dimorphic

8) Most have 2-4 annal body molts, and all have a synchronous wing molt

9) Most pair annually (?)

10) Most mature in 2 years

11) Carnivorous divers, often diving to great depths

12) Must “take-off” from the water

14. Tribe Oxyurini (Stiff-tailed Ducks) – (8 spp. – All major continents bust mostly trobical or subtropical)

1) Small – medium size

2) Short legs with big feet, attached far back

3) Scutellate tarsus

4) Short necks, stocky build

5) No osseus bulla, enlarged trachea in males

6) Brown or rufus colors, dull wings

7) Most sexually dimorphic

8) (?) annual body molts, but all have a synchronous wing molt

9) Most pair annually

10) Most are “poor mothers”; 1 species is an obligate nest parasite

11) Most mature in 1 year

12) Omnivorous divers, usually diving in shallow water

C. Domesticated Waterfowl Species

1. Although most species of waterfowl are currently in captivity somewhere in the world, 4 species have been bred for meat or egg production long enough that domesticate varieties are now available that appear substantially different from their wild ancestors

2. The group of domesticated waterfowl includes 2 geese and 2 ducks.

Greylag Goose (Anserini)
White and brownish gray varieties, both with orange bills.
Often appear pot-bellied.

Swan Goose (Anserini)
Varieties that are white with orange billas and brownish with black bills.
More slender that Greylag derivatives, but often pot-bellied.
Usually have knobs above bills.

Mallard (Anatini)
Numerous varieties and color morphs (many white), highly variable in size (some are pot-bellied).
Males of most varieties have curls in their tails.

Muscovy Duck (Cairinini)
Several color varieties (most white, black, dark green or mottled).
Large, red, waddle-like structures on heads of most individuals (especially males).

3. Domesticated Greylag x Swan Goose and Mallard x Muscovy hybrids are common.

II. Molts and Plumages

A. Evolution of Plumages

1. Sexual Dimorphism vs. Sexual Monomorphism

Males of sexually monomorphic species usually assist in raising offspring and often pair for life.
Males of sexually dimorphic species usually desert females during early incubation and often pair annually.
Most current theories of sexual dimorphism predict that it either evolved through sexual selection (i.e., females select the most colorful males) or as species recognition patterns
Island forms probably were sexually dimorphic when they first colonized islands, but they became monomorphic with time (some biologists disagree and believe that they were monomorphic during colonization).
Proponents of the species recognition theory use this as support for their explanation of evolution of dimorphism (i.e., males of island species do not need to be brightly colored because fewer species are on islands, and there is less chance of species confusion).
Disadvantages in sexual dimorphism for island forms are necessary to explain sexual selection as the mechanism resulting in evolution of dimorphism (i.e., males on islands should be exposed to the same pressure as mainland forms if sexual selection is the force driving sexual selection).

2. Bright Plumages vs. Camouflaged Plumages

Sexually dimorphic species
Males of sexually dimorphic species generally are brightly colored, whereas females are dull and camouflaged.
Female camouflage is obviously important in concealing females while nesting and brooding to reduce the likelihood of nest predation and to increase brood survival following hatching.
Most males of dimorphic species also acquire dull plumages during the period that they are flightless, and they become more camouflaged during the time that they are most vulnerable to predation.
Some apparently brightly colored males are actually well camouflaged in their natural habitats (e.g., male wood ducks).

Sexually monomorphic species
Males of most sexually monomorphic species help in raising broods, and some actually help in incubation; consequently, being camouflaged is an advantage in reproducing successfully.
Most smaller monomorphic species are of dull coloration.
Some larger monomorphic species (e.g., Swans) are not camouflaged. For these species, predation may not be a serious threat; and bright plumages may serve a signal function (i.e., offspring that are extremely dependent upon their parents for a full year following hatching may better be able to locate white parents than camouflaged parents if they become separated).

3. Discrepancies between these trends and theories of dimorphism

a. Why are females not brightly colored during the nonbreeding season and camouflaged only when nesting? (conflicts with species recognition theory, but does not support sexual selection theory).