BIRDS OF a feather flock together, to coin a phrase. To coin another, less quotable one, when inclement weather impends, birds fly south in search of sunshine and a more pleasant limb to sit on.

Like birds, Harvard protesters like nothing more than to flock together. Those featherless campus aviants like the sunshine, too.

The sun has stopped shining on the divestment issue, and activist birds have flown away to a new issue, the unionization of campus clerical and technical workers. Although both issues are, of course, important, it is discouraging to see that protesters think they must move en masse, and that interest in a newer and more chic cause can leave another vital one unattended.

LAST SPRING, activists virulently protested Harvard's holdings in companies that do business in South Africa. The protesters insisted that it was wrong for Harvard to lend support to a far-away regime that mandated the legal separation of its Black citizens from its white ones.

And University officials recognized the power of their claims. University Hall eventually began to make concessions to try to quell the storm. In the spring of 1986, as shanties stood in the Yard and hundreds of students flocked to meetings of the South African Solidarity Committee (SASC), Harvard dumped nearly half of its South African holdings.

Last year, the movement limped along aimlessly after the shanties disappeared over the summer. SASC members could do little more than respond to the various jibes that started to come from the community, the most pointed of which came from the campus's conservative community, which invited racists like South African Vice Consul Duke Kent-Brown to campus.

When SASC members returned to campus this year, they found that many of their leaders of exceptional charisma or moral vigor had graduated. They heard no news from South Africa because of the media blackout there and could see no shanties on other campuses nationwide.

Simultaneously, they found an issue of greater attractiveness: the attempt unionize Harvard's clerical and techinical workers.

The unionization issue was ideal, a chance to help poor workers take on Big Bad Harvard. And, better yet, its not a very time-consuming endeavor. You only have to work on it for an hour or two between classes, while at other times paid staffers work do the dirty work. "It is hard to work on issues like South Africa, which is so far away, when there are things like unionization that are so close to home," one former SASC member quipped.

It is hard to understand how protesters of purportedly deep moral conviction could so quickly drop their beliefs. That when one vital branch of protest gets chilly, they can so quickly fly to another.

It's strange to harp back to those sunny spring days when protesters acted on their sympathy with the plight of Black South Africans by sitting in their mock shanties. It is astoudning how quickly such allegedly selfless moralists can forget about the bloodshed and oppression that continues there.

Spring has surely passed for the divestment movement. The plunder of South Africa goes on.