EricEng - I don't believe bond income is a capital gain, but is instead always taxed at ordinary income tax rates. Could you be confusing bonds with how stock dividends are treated?
@rokel - Have you visited your brokerage account's "cost basis" page? Look for your bond index fund there, under "unrealized capital gains". That's money you could be taxed on if you sold. That should tell you the tax impact of selling the bonds - the gain you will report on your taxes if you sell.
Another approach is to sell the taxable bonds, but purchase "tax-exempt" bonds. I prefer ETFs, so I like "Vanguard Tax-Exempt Bond ETF" (VTEB), which pays interest that is exempt from Federal (IRS) taxes (but you pay state tax on the interest).