It is easy to see how it gets its name; the heads of the males are black, front and back, just as if they are wearing black cowls covering their heads, chests, and part of their backs. Their tails are black, as are their wings except for their wrists which have a yellow patch. There are no bars on their wings. The rest of the belly and back are bright yellow. One interesting feature of their beak is that at least 1/3rd of the bottom beak at the base is bluish.
They love to feed on the abundant hibiscus flowers, and often hang upside down to get to the nectar.Some, but not all, females don’t have the full black cowl of the male. Instead the crown and back of the head of the female is a yellowish-olive color. In the collage below a female is gathering a strand from a palm leaf while the male looks on from an upper palm leaf. You can easily see the bluish color at the base of the lower beak on both males and females.
They also feed on palm flowers, as you can see from the photos below.