As opposed to "fowl", "poultry" is a term for any kind of domesticated bird or bird captive-raised for meat, eggs, or feathers; ostriches, for example, are sometimes kept as poultry, but are neither gamefowl nor waterfowl. In colloquial speech, however, the term "fowl" is often used near-synonymously with "poultry," and many languages do not distinguish between "poultry" and "fowl". Nonetheless, the fact that Galliformes and Anseriformes most likely form a monophyletic group makes a distinction between "fowl" and "poultry" warranted.
The historic difference is due to the Germanic/Latin split word pairs characteristic of Middle English; the word 'fowl' is of Germanic origin (cf. Old English "Fugol", German Vogel, Danish Fugl), whilst poultry is of Latin via Norman French origin.
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.
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.
Systematics and evolution
From the limited fossils that have to date been recovered, the conclusion that the Galloanserae were already widespread—the predominant group of modern birds—by the end of the Cretaceous is generally accepted nowadays. Fossils such as Vegavis indicate that essentially modern waterfowl, albeit belonging to a nowadays extinct lineage, were contemporaries of the (non-avian) dinosaurs. As opposed to the morphologically fairly conservative Galliformes, the Anseriformes have adapted to filter-feeding and are characterized by a large number of autapomorphies related to this lifestyle. The extremely advanced feeding systems of the Anseriformes, together with similarities of the early anseriform Presbyornis to shorebirds, had formerly prompted some scientists to ally Anseriformes with Charadriiformes instead. However, as strong support for the Galloanserae has emerged in subsequent studies, the fowl clade continues to be accepted as a genuine evolutionary lineage by the vast majority of scientists.
Benson, D. (1999): Presbyornis isoni and other late Paleocene birds from North Dakota. Smithsonian Contributions to Paleobiology69: 253-266.
Chubb, A. (2004): New nuclear evidence for the oldest divergence among neognath birds: the phylogenetic utility of ZENK(i). Molecular Phylogenetics and Evolution30: 140-151
Feduccia, A. (1999): The Origin and Evolution of Birds, Second Edition. Yale University Press, New Haven.
Kriegs, Jan Ole; Matzke, Andreas; Churakov, Gennady; Kuritzin, Andrej; Mayr, Gerald; Brosius, Jürgen & Schmitz, Jürgen (2007): Waves of genomic hitchhikers shed light on the evolution of gamebirds (Aves: Galliformes). BMC Evolutionary Biology7: 190 (Fulltext).
Kulikova, Irina V.; Drovetski, S.V.; Gibson, D.D.; Harrigan, R.J.; Rohwer, S.; Sorenson, Michael D.; Winker, K.; Zhuravlev, Yury N. & McCracken, Kevin G. (2005): Phylogeography of the Mallard (Anas platyrhynchos): Hybridization, dispersal, and lineage sorting contribute to complex geographic structure. Auk 122 (3): 949-965. [English with Russian abstract] DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2 PDF fulltext. Erratum: Auk 122 (4): 1309. DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2
Sibley, C.G.; Ahlquist, J.E. & Monroe, B.L. (1988): A classification of the living birds of the world based on DNA-DNA hybridization studies. Auk105: 409-423.