The hikers spotted a red-tailed pheasant.
In this case the hyphen is necessary because it indicated that the tail is red, not the pheasant. The hyphen attaches the color red to tail. Red-tailed is a compound adjective that identify the pheasant.
A hyphen is not needed in twentieth century because it is a common phrase that readers know go together. The hyphen between tall and dark is incorrect. Tall and dark both describe the man, rather than each other. The same is true for long-winding. Long and winding describe the road. Long does not describe the winding.
