Most or all birds collectively referred to as fowl belong to one of two orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl (Anseriformes). Interestingly, studies of anatomical and molecular similarities suggest these two groups were close evolutionary relatives; together, they form the fowl clade which is scientifically known as Galloanserae (initially termed Galloanseri). This clade is also supported by morphological and DNA sequence data as well as retrotransposon presence/absence data.
As opposed to "fowl", "poultry
", on the other hand, is a term for any kind of domesticated
bird or bird captive-raised for meat or eggs; ostriches
for example are sometimes kept as poultry, but are neither gamefowl nor waterfowl. In colloquial speech, the term "fowl" is however often used near-synonymously with "poultry" or even "bird", 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.
Many birds that are eaten by humans are fowl, including poultry such as chickens or turkeys, game birds such as pheasants or partridges, other wildfowl like guineafowl or peafowl, and waterfowl such as ducks or geese.
While they are extremely 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 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.
Systematics and evolution
Fowl were the first neognath
lineages to evolve. From the limited fossils
that have to date been recovered, the conclusion that they were already widespread - indeed the predominant group of modern birds - by 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
, had formerly prompted some scientists to ally Anseriformes with Charadriiformes
instead (see also
"). 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.
Apart from the living members, the Gastornithiformes are probably a prehistoric member of the Galloanserae.
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- (1999): The Origin and Evolution of Birds, Second Edition. Yale University Press, New Haven.
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- (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
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