Ducks exhibit sexual dimorphism in vocal anatomy. Asymmetrical ossification of the syrinx (bulla syringealis) is discernable at about 10 days of age in male Pekin duck (Anas platyrhynchos domestica) embryos, but information is lacking on the early development of the bulla in wild ducks. To evaluate the reliability of this characteristic for sexing developing embryos, we examined the syrinx of dead embryos and compared results with molecular sexing techniques in high arctic nesting Common Eiders (Somateria mollissima). Embryos 8 days or older were accurately (100%) sexed based on the presence/absence of a bulla, 2 days earlier than Pekin duck. The use of the tracheal bulla can be a valuable technique when sex identification of embryos or young ducklings is required.
BagliaccaM., PaciG., and MarzoniM. (2005) Effect of egg weight categories, storage time and storage temperature on incubation length in duck eggs (Cairina moschata L. and Anas platyrhynchos domestica L.). J. Poul. Sci., 42, 205–214.
2.
BellroseF. C., ScottT. G., HawkinsA. S., and LowJ. B. (1961) Sex ratios and age ratios in North American ducks. Illinois Natural History Survey Bulletin, 27, 391–474.
3.
BeerJ. V. (1963) The rapid sexing of downy Anatidae by the structure of the syrinx. Wildfowl Trust Annual Report, 14, 160–162.
4.
BlumsP., and MednisA. (1996) Secondary sex ratio in Anatinae. AUK, 113, 505–511.
5.
BoulandA. J., WhiteA. E., LonabaughK. P., Varian-RamosC. W., and CristolD. A. (2012) Female-biased offspring sex ratios in birds at a mercury-contaminated river. J. Avian Biol., 43, 244–251.
6.
BromanI. (1942) Über die embryonalentwicklung der entensyrinx. Anat. Anz., 93, 241–251.
7.
DenkA. G. (2005) Male and female reproductive tactics in Mallards (Anas platyrhynchos L.): sperm competition and cryptic female choice. PhD thesis, Max-Planck-Institute for Ornithology, Starnberg.
8.
GirardG. L. (1941) The Mallard: its management in western Montana. J. Wildl. Manage., 5, 223–259.
9.
GriffithsR., DoubleM. C., OrrK., and DawsonR. J. G. (1998) A DNA test to sex most birds. Mol. Ecol., 7, 1071–1075.
10.
GowatyP. A. (1993) Differential dispersal, local resource competition, and sex-ratio variation in birds. Am. Nat., 141, 263–280.
11.
HandelC. M., PajotL. M., TalbotS. L., and SageG. K. (2006) Use of buccal swabs for sampling DNA from nestling and adult birds. Wildl. Soc. Bull., 34, 1094–1100.
12.
HaramisG.M., GoldsberryJ. R., McAuleyD. G., and DerlethE. L. (1985) An aerial photographic census of Chesapeake Bay and North Carolina Canvasbacks. J. Wildl. Manage., 49, 449–454.
13.
KamarG. A. R., and YamaniK. A. (1962) Sexing day old duckling by testing the swollen larynx. Poul. Sci., 41, 1357–1358.
14.
KellettD. K., AlisauskasR. T., MehlK. R., DrakeK. L., TraylorJ. T., and LawsonS. L. (2005) Body mass of Long-tailed Ducks (Clangula hyemalis) during incubation. AUK, 122, 313–318.
15.
KingA. S. (1989) Functional anatomy of the syrinx. In: KingA.S., and McLellandJ. (eds), Form and function in birds, vol. 4, pp. 105–192. Academic Press, London.
16.
JohnsgardP. A. (1961) Tracheal anatomy of the Anatidae and its taxonomic significance. Wildfowl Trust Ann. Rep., 12, 58–69.
17.
LehikoinenA., ÖstM., HollménT., and KilpiM. (2008) Does sex-specific duckling mortality contribute to male bias in adult Common Eiders?Condor, 110, 574–578.
18.
LemonsP. R., SedingerJ. S., NicolaiC. A., and OringL. W. (2012) Sexual dimorphism, survival, and parental investment in relation to offspring sex in a precocial bird. J. Avian Biol., 43, 445–453.
19.
LivezeyB. C. (1991) A phylogenetic analysis and classification of recent dabbling ducks (Tribe Anatini) based on comparative morphology. AUK, 108, 471–507.
20.
LivezeyB. C. (1995) Phylogeny and evolutionary ecology of Modern Seaducks (Anatidae: Mergini). Condor, 97, 233–255.
21.
LocknerF. R., and YoungrenO. M. (1976) Functional syringeal anatomy of the mallard. I. in situ electromyograms during ESB elicited calling. AUK, 93, 324–342.
22.
MickelsonP. G. (1973) Breeding biology of the Cackling Geese (Branta canadensis minima Ridgway) and associated species on the Yukon-Kuskokwim Delta, Alaska. PhD thesis, University of Michigan, Ann Arbor.
23.
MillerE. H., WilliamsJ., JamiesonS. E., GilchristH. G., and MalloryM. L. (2007) Allometry, bilateral asymmetry and sexual differences in the vocal tract of Common Eiders Somateria mollissima and King Eiders S. spectabilis.J. Avian Biol., 38, 224–233.
24.
OringM., and DixM. (1986) Sex ratios in some common British wintering ducks. Wildfowl, 37, 104–112.
25.
ParmeleeD. F., StephensH. A., and SchmidtR. H. (1967) The birds of southeastern Victoria Island and adjacent small islands. Nat. Mus. Can. Bull.222.
26.
PrykeS. R., and RollinsL. A. (2012) Mothers adjust offspring sex to match the quality of rearing environment. Proc. Roy. Soc. B, 29, 4051–4057.
27.
ReiterM. E., and AndersonD. E. (2008) Comparison of the egg flotation and egg candling techniques for estimating incubation day of Canada Goose nests. J. Field Ornithol., 79, 429–437.
28.
SchamelD. L. (1974) The breeding biology of the Pacific Eider (Somateria mollissima v-nigra Bonaparte) on a barrier island in the Beaufort Sea, Alaska. MSc thesis, University of Alaska, Fairbanks, AK.
29.
SuydamR. S. (2000) King Eider (Somateria spectabilis). The birds of North America. Number 491.
30.
TakahashiM. M., and NoumuraT. (1987) Sexually dimorphic and laterally asymmetric development of the embryonic duck syrinx: effect of estrogen on the in vitro cell proliferation and chondrogenesis. Dev. Biol., 121, 417–422.
31.
WellerM. W. (1956) A simple field candler for waterfowl eggs. J. Wildl. Manage., 20, 111–113.
