The yellow-breasted boatbill (Machaerirhynchus flaviventer) is a species of bird found in New Guinea and Far North Queensland, Australia. The yellow-breasted boatbill is a species of bird belonging to the Machaerirhynchidae family, of the genus Machaerirhynchus. The yellow-breasted boatbill is a common avian animal, and it is well known within communities of ornithologists. Its natural habitat is primarily that of subtropical or tropical regions, particularly moist forests; the yellow-breasted boatbill has no preference for altitude within its environment and can be found abundantly in its natural habitat.
The yellow-breasted boatbill is a distinctive bird that is small in size and stature ranging from 11 to 12.5 cm. On average they weigh around 9-10g. Its black bill is large relative to its body and is wide, long and flat resembling the shape of a boat, hence the bird’s name. The tip of the bird's beak is hooked, similar in shape to other bird species, especially those in the same machaerirhynchidae family. It also has a distinctive keel which serves to highlight the underside of the yellow-breasted boatbill, which is a distinguishingly bright yellow, leading all the way up the bird's body until its breast. This physical characteristic expectedly pertains to the bird's common name. The underside of the yellow-breasted boatbill's beak area is white, covering the region where its neck would be. The bird has large round eyes with stark black pupils. It also has a yellow stripe running across its forehead in an area akin to eyebrows. The upper top side of the boatbill is black for males, and a lighter olive colour for the females. Aside from that, there are no many other notable differences between the genders. The bird has white stripes across the base of their wings, which are more commonly called wing bars. The yellow-breasted boatbill has a long black tail relative to their small bodies. The end of their tails is rounded, and they are often documented as being stiff, pointing upwards. The yellow-breasted boatbill has average sized legs with small talons at the end of a four toed foot, including the birds rear metatarsals.