WHEN hawks clamor to abolish talons and beaks - or nuclear warheads - owls and even doves should worry. Either the hawks don't know what's good for them, or they are mounting a massive deception. Soviet and United States leaders appear to be searching for a formula to reverse the mad momentum of the arms buildup, but their visions of perfection could be the enemy of the good. The superpowers and most other states could gain from significant cuts in their nuclear arsenals, but international stability does not benefit from loose talk about eliminating all nuclear arms within 10 years.
Reducing Soviet and US nuclear arsenals by 50 percent over five years is probably a feasible and useful goal. Moreover, steep reductions in Soviet and US forces would contribute to pressures on France, Britain, and China to limit their nuclear arsenals and would facilitate tough measures to prevent acquisition of nuclear arms by other countries.
Both sides should eliminate weapons especially suited for a first strike; weapons difficult to verify; and those that are accident prone. Cuts should include missiles with multiple warheads; weapons whose accuracy threatens missile silos and command centers; weapons whose short flying time could pressure the other side to launch on warning; and weapons whose vulnerability tempts their owners to ``use 'em or lose 'em.''
Pershing 2 missiles could reach Soviet targets in less than 10 minutes and are vulnerable to a Kremlin first strike. All medium- and intermediate-range missiles and bombers deployed against targets in Europe and western Russia should be eliminated. NATO will also want reductions in Soviet short-range missiles based in East Germany and Czechoslovakia, although Moscow could then ask for curbs on French and British missiles.
Certainly halving the strategic arsenals of Moscow and Washington should leave both superpowers with ample margins of deterrent capacity against all comers. Forces of 6,000 nuclear weapons on both sides are far greater than the minimum or ``existential'' deterrent proposed by Robert S. McNamara and some other strategists. But to eliminate all nuclear arms (or, as President Reagan seems to have proposed in Iceland, all ballistic missiles) in a decade could make the world a more dangerous place. Without the Damocles sword of nuclear retaliation, one or both superpowers might be tempted to initiate a conventional war. The losing side in a conventional war might then let loose whatever other weapons of mass destruction it retained.
Many instabilities are possible - even likely - in a world where Moscow and Washington pledged to eliminate their nuclear arms. Not only would the West feel more vulnerable to Soviet conventional forces, but the USSR would be more sensitive to the weight of Chinese mass. The clout of India, Brazil, and of course Japan would also soar in a world without nuclear arms. What if some desperate country - Pakistan, Taiwan, Israel - created and maintained a fistful of nuclear arms? It could be the dictator of a new era.
Another possibility is that one of the existing nuclear powers manages to cache a few dozen nuclear weapons in violation of the disarmament pledge. Cheating at the margins would probably not yield much influence. But if one superpower had disarmed while the other secreted a small arsenal, the cheat could dictate without fear of reprisal.
Last but not least is the issue of new and exotic technologies. If all nuclear arms were destroyed, rival governments would seek to develop and deploy new weapons not yet prohibited by treaty. These incentives already exist, but they would not be greatly increased if both superpowers retained thousands of nuclear arms. But if one government produced, say, efficient, directed-energy weapons after the other had surrendered its engines of mass destruction, there might be only one superpower.
The bottom line is that both the US and USSR could benefit from reducing their strategic arsenals by half - perhaps even by two-thirds or three-fourths. But there is a threshold below which nuclear disarmament could be a danger.
If superpower arsenals were cut by 50 percent, the task of a strategic defense system would be smaller but still overwhelming. America's security would be on a stronger footing by strategic arms control and d'etente than by a shaky defense system, unrestrained offensive weapons buildup, and a spirit of East-West confrontation. Halving strategic arsenals and forgoing strategic defenses is an approach to which both superpowers should say ``yes.''
Walter C. Clemens Jr. is professor of political science at Boston University and adjunct research fellow at the Harvard Center for Science and International Affairs.