At 26-29cm the Mistle Thrush is one of the larger thrushes, being slightly larger than a Blackbird and noticeably larger than the Song Thrush. As well as its larger size, the Mistle Thrush often appears more plump-bellied than its smaller relative and it has a proportionally longer tail. When on the ground the Mistle Thrush often adopts an upright stance that further emphasises its size.
The upperparts are a pale grey-brown (colder in tone than those seen in the Song Thrush) and the white underparts are heavily spotted with brown spots. These spots do not form lines on the flank but may form a necklace pattern around the throat. The underwings are white, which contrasts with the colour seen in Song Thrush. The long tail has distinctive white tips to the outer feathers. The legs are a pale yellow-brown.
Mistle Thrushes can utter a series of harsh chattering notes (a rattling call), particularly when alarmed or disturbed. The loud song consists of a series of short phrases, rich in nature and of a tonal quality similar to the blackbird. This song is usually delivered from a high perch and is characteristic of early spring or even late winter, often in strong winds, hence its country name ‘Storm Cock’.
Mistle Thrushes are familiar garden birds, either seen alone, in pairs or in family groups, Often seen in the open, they are rather more boisterous than the Song Thrush. Longer flights tend to involve an undulating action as the bird closes its wings briefly between some wing beats.
Mistle Thrush nests are large and untidy, sometimes including odd materials such as waste paper and plastic. Many nests are built in late February, with a typical site in woodland being 30ft up on the top of a snapped-off tree. Each pair raises two or occasionally three broods and they may sometimes use the same nest. The nests can be very well concealed and each has a mud layer sandwiched between the ragged outside finish and the ample inside lining of fine grasses.
One of the most interesting behaviours displayed by Mistle Thrushes in gardens is resource guarding. This is when one or sometimes two birds defend a food source, such as a holly or yew. This is defended against all-comers, the vigilant bird trying to ensure that food resources are maintained for itself throughout the winter. It has been shown that resource guarding birds have bigger and earlier clutches than birds that do not do it.