The Red-sided Eclectus originates from the large island of New Guinea. It was first described by Scopoli in 1786 and was the first subspecies to be described. This was only ten years after the nominate Grand was described. Although this subspecies is slightly larger than the Grand and slightly smaller than the Vosmaeri subspecies, these are individual birds that appear larger than the Vosmaeri. Remember that the Red-sided look-alikes, the Australian subspecies is very large and the Solomon Islands subspecies are much smaller. In aviculture there can easily be quite a variance in size.
The Red-sided Eclectus male is a deep forest green color with a bluish tint. This is more noticeable in the head and neck areas. Its green body plumage has a yellowish ting compared to the Grand Eclectus that is very similar to the Red-sided male. The Red-sided is slightly larger in overall size compared to the Grand Eclectus. The Red-sided Eclectus has dark blue primary coverts and its primaries have distinct green edging to the outer webs. They have a wide band of pale light yellow edging on its tail. This band is especially visual from beneath being about one half inch in width. This yellowish tail band is even wider than that of the male Vosmaeri. Its iris is orange-red in color.
The Red-sided female is distinctly known for its brilliant royal blue breast, mantle and lower belly feather coloration. This royal blue coloration forms a very distinct bib that shows a well-defined line between it and the red neck and head feathers. In some individual birds this blue bib may show a light tint of purple in it. Those females that are darker blue breast coloration tend to have a narrower blue eye ring. The intense red feathers on its head and neck extend down to the bird’s breast-bone shows a very sharp contrast to the brilliant blue bib. This bib is low on the breast almost cutting the bird visually in half. The brilliant blue bib does not flow on the body over the wing bend area when the wings are closed. This is very different to those subspecies (Vosmaeri and Grand) with lavender or purple in them. A brilliant bluish-purple bib that flows over the closed wing bend is almost for sure a hybrid.
The Red-sided female has an eye ring of tiny blue feathers that completely surround the eye. This blue eye ring usually appears after the bird’s first molt but may not be observed until the bird is over one year of age. This blue eye ring is also evident in the Solomon Islands, Aruensis, Biaki and Macgillivary’s subspecies. Its iris is whitish-yellow in color.
The Red-sided female has a dark red (reddish-maroon) back, upper tail coverts and thigh feathers. Some of the wing feathers show green on the inside, which is covered by the outer portion of the next feather. Some of her back feathers also may show a green (closest to the body) that is overlapped by the next feather.
The Red-sided tail is reddish-maroon colored at the base and becomes a bright red toward the center and ends with a pinkish-red coloration that is often tinged in orange.