In contrast, some species in Taihu, China, such as mallard Anas platyrhynchos, northern pintail Anas acuta, gadwall Anas strepera
, greater scaup Aythya marila, smew Mergellus albellus and falcated duck Anas falcata have been reported to exhibit a female-skewed sex ratio in one year, and a balanced ratio in another year.
Mae nifer o wahanol hwyaid i'w gweld yma gan gynnwys yr hwyaden lydanbig (Spatula clypeata; Shoveler), yr hwyaden lwyd (Anas strepera
; Gadwall) a'r hwyaden bengoch (Aythya ferina; Pochard), ac mae'r tair hwyaden yma'n nythu yma.
Aythya fuligula (Tufted Duck), Aythya nyroca (Ferruginous Pochard), Netta rufina (Red-Crested Pochard), Aythya ferina (Common Pochard), Anas strepera
(Gadwall), Tadorna ferruginea (Ruddy Shelduck), and Anas acuta (Northern Pintail).
Gaston (1991) studied the effect of hunting on body condition of gadwalls Anas strepera
. His results showed that lipid reserves increased when hunting was suspended, but he also concluded that such simple relationships alone are inadequate tests and that other factors like temperature also have an influence.
3 E aregonensis (extinct shelduck) Anas crecca (Green-winged Teal) 7 M, W Anas plat yrhynchos/diazi 16 M, R, W (Mallard or Mexican Mallard) Anas acula (Northern Pintail) 6 M, W Anas strepera
(Gadwall) 1 M, W Anas clypeata (Northern 2 M, W Shoveler) Anas discors/cyanoptera 7 M, W (Blue-winged or Cinnamon Teal) [Anas sp.
Relative intensity of predation also was: 1) high but variable on relatively rare, migrant belted kingfishers in both segments; 2) more variable on species that sustained lower relative intensity of predation in the usually turbid segment; and 3) zero on some species that were relatively abundant during pre-nesting or nesting periods, such as gadwalls (Anas strepera
), buffleheads (Bucephalus albeola), and spotted sandpipers (Actitis macularia), respectively (Tables 1 and 2).
Number of bones Number of bones Loye Miller counts 1931 A.Miller Species LACM SBMNH 1932 Pelecanus occidentalis 0 0 Ciconia maltha 14 3 Chen caeulescens (Chen?) 1 0 Anas platyrhynchos 2 1 Anas strepera
0 0 Anas americana 0 0 Anas crecca 0 0 Cathartes aura 1 3 Gymnogyps amplus (californianus) 4 5 Coragyps (Catharista) occidentalis 2 0 Teratornis merriami 6 3 Haliaetus leucocephalus 0 7 Circus cyaneus (hudsonius) 0 1 Accipiter striates (velox) 0 I Accipiter cooperi 2 3 Accipiter gentilis (Astur atricapillus) 7 0 Buteogallus (Geranoaetus) fragilis 5 1?
ducks with clinical signs Common name (taxonomic name), n = 8 each Mild Severe Tufted duck (Aythya fuligula) ([dagger]) 4 3 Eurasian pochard (Aythya ferina) ([dagger]) 3 1 Mallard (Anas platyrhynchos) 0 0 Common teal (Anas crecca) 0 0 Eurasian wigeon (Anas penelope) 0 0 Gadwall (Anas strepera
) 0 0 Total 7 4 No.
A total of 14 species were inventoried during the study period: White-headed Duck, Garganey Anas querquedula, Eurasian Teal Anas crecca, Tufted Duck Aythya fuligula, Ferruginous Duck, Mallard Anas platyrhyncos, Northern Shoveler Anas clypeata, Gadwall Anas strepera
, Eurasian Wigeon Anas penelope, Northern Pintail Anas acuta, and Common Pochard Aythya ferina (Anatidae); and Common Coot Fulica atra, Common Moorhen Gallinula chloropus, and Purple Swamphen Porphyrio porphyrio (Rallidae).
It is noted that during the period of wintering, the ducks mallard cohabit with other aquatic species such as the Gadwall (Anas strepera
) birds, the Eurasian Coot (Fulica atra), the Great Cormorant (Phalacrocorax carbo), the Eurasian Teal (Anas crecca), the Common Moorhen (Gallinula chloropus), the Great Crested Grebe (Podiceps cristatus) and the Little Grebe (Tachybaptus ruficollis).
The species included in the analysis are the following: Anas acuta, Anser albifrons, Anser anser, Anser brachyrhynchus, Anas clypeata, Anas crecca, Anser erythropus, Anser fabalis, Aythya ferina, Aythya fuligula, Aythya marila, Aythya nyroca, Anas penelope, Anas platyrhynchos, Anas querquedula, Anas strepera
, Branta bernicla, Bucephala clangula, Branta leucopsis, Branta ruficollis, Cygnus columbianus, Cygnus cygnus, Clangula hyemalis, Cygnus olor, Mergellus albellus, Marmaronetta angustirostris, Melanitta fusca, Mergus merganser, Melanitta nigra, Mergus serrator, Netta rufina, Oxyura leucocephala, Polysticta stelleri, Somateria mollissima, Tadorna ferruginea, Tadorna tadorna.