Allen's Gallinule
Porphyrio alleni
They are similar in size to the only slightly larger water rail. The Allen's gallinule has a short red bill, greenish back and purple upperparts. They have red legs with long toes, and a short tail which is white with a dark central bar underneath. Breeding males have a blue frontal shield, which is green in the female. Immature Allen's gallinules are sandy brown with a buff undertail. The downy chicks are black, as with all rails. They nod their heads as they swim.
ID text from Wikipedia, CC BY-SA 4.0
Purple Gallinule
Porphyrio martinica
The purple gallinule is a medium-sized rail, measuring 26–37 cm (10–15 in) in length, spanning 50–61 cm (20–24 in) across the wings and weighing 141–305 g (5.0–10.8 oz). Males, averaging 257 g (9.1 oz) in mass, are slightly larger than females, at 215 g (7.6 oz) on average. An adult purple gallinule has purple-blue plumage that will shine green and turquoise when in good lighting. Adults also have a pale blue shield on their forehead, which connects with the red and yellow bill.
ID text from Wikipedia, CC BY-SA 4.0

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