Characteristics
While they are quite diverse ecologically and consequently, in an adaptation to their different lifestyles, also morphologically and ethologically, there are still some features which unite water- and landfowl. Many of these, however, are plesiomorphic for Neornithes as a whole, and are also shared with paleognaths.
- Galloanserae are very prolific; they regularly produce clutches of more than 5 or even more than 10 eggs, which is a lot for such sizeable birds. For example birds of prey and pigeons rarely lay more than two eggs.
- While most living birds are monogamous, at least for a breeding season, many Galloanserae are notoriously polygynous or polygamous. To ornithologists, this is particularly well known in dabbling ducks, where the males literally band together occasionally to "gang rape" unwilling females. The general public is probably most familiar with the polygynous habits of domestic chicken, where usually one or two roosters are kept with a whole flock of females.
- Hybridization is extremely frequent in Galloanserae, and genera, not usually known to produce viable hybrids in birds, can be brought to interbreed with comparative ease. Guineafowl have successfully produced hybrids with domestic fowl and Blue Peafowl, to which they are not particularly closely related as Galliformes go. This is an important factor complicating mtDNA sequence-based research on their relationships. The Mallards of North America, for example, are apparently mostly derived from some males which arrived from Siberia, settled down, and mated with American Black Duck ancestors. See also Gamebird hybrids.
- Galloanserae young are remarkably precocious. Anseriform young are able to swim and dive a few hours after hatching, and the hatchlings of mound-builders are fully feathered and even able to fly for prolonged distances as soon as they emerge from the nest mound.
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