What's the difference between redstart and redtail?

Redstart

Definition:

(n.) A small, handsome European singing bird (Ruticilla phoenicurus), allied to the nightingale; -- called also redtail, brantail, fireflirt, firetail. The black redstart is P.tithys. The name is also applied to several other species of Ruticilla amnd allied genera, native of India.
(n.) An American fly-catching warbler (Setophaga ruticilla). The male is black, with large patches of orange-red on the sides, wings, and tail. The female is olive, with yellow patches.

Example Sentences:

(1) Look out for peregrine falcons and ravens riding the cliffupdraughts, and in spring listen for the tinkling songs of redstarts.
(2) Unlike the supremely adapted swallow aeronauts that skimmed the grass in the pastures and would shortly be migrating, the redstart merely flitted between perches on broad wings that seem better suited to following the erratic flight of an insect than to long-distance travel.
(3) When he wrote that "Redstarts flew from tree to tree, taking the line a slack rope would take slung between them; economy in flight is what makes it graceful", it is the economy of the prose which makes the observation graceful.
(4) The ancient Greek philosopher Aristotle was one of the first to speculate on these annual movements, proposing that the redstart – a summer visitor to Europe from Africa – transformed each autumn into the robin, and that swallows hibernated under water or in caves.
(5) We had the briefest of glimpses of a redstart along this footpath on several occasions during the summer, but never a view as clear as this.
(6) It’s difficult to pin down the exact hue of a redstart’s chest and tail; it lies somewhere in the last incandescent embers of a dying fire, as do its ash-coloured wings and charcoal black face mask.

Definition:

Example Sentences:

(1) The redtail monkeys of the Kibale Forest, W. Uganda, live in social groups of about 35 members with only one adult male.
(2) The foci is apparently maintained on account of the rising number of the redtailed Libyan jird.