PORTLAND, Maine — Endowments at Maine’s colleges and universities have lost close to half a billion dollars in value as the economy and stock markets falter, forcing them to cut positions, freeze wages and delay construction projects.

With investments tanking, Bowdoin, Colby and Bates colleges, which have the largest endowments, saw their funds fall a combined $373 million in the final months of 2008 — a drop of some 22 percent.

And that doesn’t include this year’s continued slide in investment markets.

The free fall is leaving less investment income to run the schools.

“The term ‘unprecedented’ is overused, but I think it applies to the current circumstance,” said Douglas Terp, Colby’s treasurer and vice president for administration.

Colleges and universities get their operating funds from a variety of sources, including tuition, endowments and annual gifts. Public schools also get taxpayer-funded appropriations.

Endowments operate like savings and investment portfolios, where money is invested and grows over time. The schools spend a small percentage, typically around 5 percent, on operations each year.

Nonprofits of all sorts — schools, museums, symphonies, research laboratories — have seen their endowments get hammered.

The losses at colleges and universities are staggering. Endowments for U.S. and Canadian colleges and universities totaled $522 billion at the end of last June, according to a survey of 796 institutions by college business officers in conjunction with TIAA-CREF Asset Management.

In a follow-up survey of 435 of those institutions, the funds fell in value by an average of 23 percent for the five-month period from July through November, wiping some $120 billion off the books.

That’s double the largest previous decline — 11.5 percent in 1974, said Ken Redd, director of research and policy analysis for the National Association of College and University Business Officers.

If the current slide continues, colleges will have to take drastic measures to make up for their investment losses and prepare themselves for a surge in student aid applications because of the economic slump, he said.

Maine’s private schools are particularly hard hit because they rely heavily on endowment funds. Bowdoin got 24 percent of last year’s operating budget from its endowment; Colby is getting 18 percent of this year’s operating budget from its endowment; at Bates, about 14 percent of this year’s budget comes from its endowment.

At Colby, endowment losses alone will mean a $1.2 million hit for the coming fiscal year. The decline, along with a drop in fundraising, is prompting the school to cut back departmental operating budgets, defer construction projects, reduce or eliminate salary increases, and hold positions open, Terp said.

Bowdoin has frozen faculty and staff salaries for two years and deferred some maintenance and capital projects. It is also considering increasing enrollment to bring in more revenue.

In an open letter to the Bowdoin community, President Barry Mills said the school is assuming a 20 percent drop in the value of its endowment this fiscal year — a paper loss of more than $165 million. It is projecting zero percent returns for 2010 and 2011, and 7 percent returns in subsequent years.

After factoring endowment and gift projections, as well as reductions in other revenue sources, Mills said the college could have annual budget shortfalls of $2 million to $17 million from 2010 to 2014.

By comparison, the University of Maine System’s endowment amounts to less than 1 percent of the system’s overall operating budget. Still, the endowment decline — it fell from $115 million to $88.4 million the last six months of last year — is painful.

It provided $5.9 million to the state’s seven universities last year, but will produce only $4.2 million next year. That leaves $1.7 million less in endowment money for scholarships and operations next year than this year. With scholarship cuts, some students may have to drop out.

“You certainly could argue that for our students, the economy is hitting them very hard,” said Rebecca Wyke, vice chancellor for finance and administration for the University of Maine System. “This economy is the difference between whether they can stay in school or not.”

Higher education endowments have enjoyed healthy returns in recent years. Between 2002 and 2007, endowments averaged an annual 11.3 percent return, according to NACUBO and TIAA-CREF.

In Maine, Bowdoin’s endowment rose from $407 million to $831 million between 1999 and 2008, and Colby’s grew from $290 million to $600 million.

The endowments have weathered tough times as well. At Colby, the endowment value fell each year between 2001 and 2003, but not nearly as much as it has the past year.

The difference this time around was that virtually all sectors — domestic and international equities, energy, timber, venture capital, real estate, hedge funds — got pummeled in the market downturn.

“Everything went down,” Terp said. “Diversification meant very little.”