Black-necked Swan
Cygnus melancoryphus
The black-necked swan is the only member of its genus that breeds in the neotropics and is the largest waterfowl native to South America. Adults are 102 to 124 cm (40 to 49 in) long with a wingspan of 135 to 177 cm (53 to 70 in). Males weigh 4.6 to 8.7 kg (10 to 19 lb) and females 3.5 to 4.4 kg (7.7 to 9.7 lb). The sexes are alike. Adults' body plumage is white and the neck and head black; the latter usually has a white stripe behind the eye. They have a prominent red knob at the base of their bill. Juveniles are grayish rather than white and lack the knob until their third or fourth year. Voice: The black-necked swan is mostly silent outside the breeding season. During that time, both sexes give a "soft, musical 'Whee-whee-whee' with the accent on the initial syllable", repeating it to challenge intruders. The call is also used to maintain contact between members of a pair. Males also give "a musical 'hooee-hoo-hoo'."
ID text from Wikipedia, CC BY-SA 4.0
Black Swan
Cygnus atratus
Black swans are black-feathered birds, with white flight feathers. The bill is bright red, with a pale bar and tip; and legs and feet are greyish-black. Cobs (males) are slightly larger than pens (females), with a longer and straighter bill. Cygnets (immature birds) are a greyish-brown with pale-edged feathers. Mature black swans measure between 110 and 142 centimetres (43 and 56 in) in length and weigh 3.7–9 kilograms (8.2–19.8 lb). Their wingspan is between 1.6 and 2 metres (5.2 and 6.6 ft). The neck is long (relatively the longest neck among the swans) and curved in an "S"-shape.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Black-necked Swan and Black Swan.