Amid shareholders’ mounting rage over what they see as wantonly excessive compensation for underperforming executives, defenders of high pay have had one steadfast rebuttal: It’s needed to retain top management talent.

But corporate boards, it seems, aren’t buying it. In a survey of board members released Tuesday by consulting firm Watson Wyatt, relatively few of the 85 participants were worked up over the prospect of losing company leaders. Only 31% expressed significant or great concern about management retention; the rest registered moderate, small, or no concern.

Yet 63% agreed or strongly agreed that American companies in general should change their executive compensation plans in response to pressures from the financial crisis and the new pay regulations for government-aided companies, which indeed seem to be spilling over to the corporate community at large. Only 22% disagreed that such changes are warranted.

Thirty-four percent said their companies have already reduced executive salaries, target bonuses, or long-term incentive awards. But the survey asked participants separately whether they believe pay opportunities will decline over the next two years from where they are now, and 70% said they will.

The question is whether board attitudes will shift again as the recession slackens. Right now, said Ira Kay, Watson Wyatt’s global director of executive compensation, there is very little voluntary turnover at the executive level, so throttling down pay levels is a fairly easy decision. “Directors are being pragmatic, saying they’ll worry about turnover when it happens,” Kay told CFO.com.

For most companies, placing a low priority on executive retention makes sense for another reason, suggested Keith Hall, a former CFO of Lending Tree who sits on the boards of two public and three private companies, two compensation committees and one governance committee. “Executives are like the general population — there is a distribution curve,” he said. “There is a big blip of people in the middle who are average. The ones who are excellent are in the little tail off to the right. Those are the ones you should be concerned about losing.”

For example, about Jack Welch, who created tremendous shareholder wealth during his 20 years at the helm of General Electric, Hall said, “He was paid extremely handsomely, and I would not deny him one penny.” Hall’s chief concern, he added, is that, because of the allegedly undeserved windfalls many executives have enjoyed, some of those who deserve high rewards will see their pay slashed too.

Indeed, even performance-based compensation is not in line for a big surge, according to board members who responded to the Watson Wyatt survey. Only 18% said they think such pay opportunities will rise significantly or greatly over the next two years, while 54% see them improving to a small extent or not at all.

That’s not because board members don’t think there should be a link between pay and performance, Kay suggested, but rather because most believe that link is already strongly established at their companies. “They think the public reaction to what’s going on in Corporate America is wrong, and that there is already a great deal of pay for performance,” he said, citing previous research by the consulting firm.

But another factor driving the low expectations for adding pay-for-performance metrics — which can have the effect of limiting compensation — is that making changes simply will take time, Hall suggested. The inflation in pay took place over many years during which companies got into the habit of comparing their executives’ earnings to those of their counterparts at similar-sized companies, without much regard to whether those people in fact deserved what they were getting, he observed.

“There’s got to be a shake-out period,” Hall said. “Fighting back against that trend and reeling things back down to reality will take a while, with boards sucking it up and trying to make the right decisions.” In some cases shareholder votes will serve as wake-up calls, “but CEOs also have to wake up and redefine what’s fair, and that’s got to be tied more to long-term value creation and not what the guy down the street is getting paid.”