UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G


                    Under the Securities Exchange Act of 1934

                               (Amendment No.  3  )*
                                             -----

                              Glacier Bancorp, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    37637Q105
                                -----------------
                                 (CUSIP Number)


                                December 31, 2005
              -----------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


      Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:

                                [X] Rule 13d-1(b)

                                [ ] Rule 13d-1(c)

                                [ ] Rule 13d-1(d)


*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).




CUSIP No. 37637Q105                    13G
         -------------------

--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        Columbia Wanger Asset Management, L.P. 04-3519872
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                        (a)  [_]
                                                                        (b)  [_]
        Not Applicable
--------------------------------------------------------------------------------
3    SEC USE ONLY



--------------------------------------------------------------------------------
4    CITIZENSHIP OR PLACE OF ORGANIZATION


        Delaware
--------------------------------------------------------------------------------
  NUMBER OF    5    SOLE VOTING POWER

   SHARES              2,755,000
               -----------------------------------------------------------------
BENEFICIALLY   6    SHARED VOTING POWER

  OWNED BY             0
               -----------------------------------------------------------------
    EACH       7    SOLE DISPOSITIVE POWER

  REPORTING            2,755,000
               -----------------------------------------------------------------
   PERSON      8    SHARED DISPOSITIVE POWER

    WITH               0
--------------------------------------------------------------------------------
9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON


        2,755,000
--------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                                                                             [_]
        Not Applicable
--------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9


        8.6%
--------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*


        IA
--------------------------------------------------------------------------------




CUSIP No. 37637Q105                    13G
         -------------------

--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

        WAM Acquisition GP, Inc.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                        (a)  [_]
                                                                        (b)  [_]
        Not Applicable
--------------------------------------------------------------------------------
3    SEC USE ONLY



--------------------------------------------------------------------------------
4    CITIZENSHIP OR PLACE OF ORGANIZATION


        Delaware
--------------------------------------------------------------------------------
  NUMBER OF    5    SOLE VOTING POWER

   SHARES              0
               -----------------------------------------------------------------
BENEFICIALLY   6    SHARED VOTING POWER

  OWNED BY             2,755,000
               -----------------------------------------------------------------
    EACH       7    SOLE DISPOSITIVE POWER

  REPORTING            0
               -----------------------------------------------------------------
   PERSON      8    SHARED DISPOSITIVE POWER

    WITH               2,755,000
--------------------------------------------------------------------------------
9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON


        2,755,000
--------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                                                                             [_]
        Not Applicable
--------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9


        8.6%
--------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*


        CO
--------------------------------------------------------------------------------




Item 1(a)   Name of Issuer:

               Glacier Bancorp, Inc.
            --------------------------------------------------------------------

Item 1(b)   Address of Issuer's Principal Executive Offices:

               49 Commons Loop
               Kalispell, MT  59901
            --------------------------------------------------------------------

Item 2(a)   Name of Person Filing:

               Columbia Wanger Asset Management, L.P. ("WAM")
               WAM Acquisition GP, Inc., the general partner of WAM ("WAM GP")
            --------------------------------------------------------------------

Item 2(b)   Address of Principal Business Office:

               WAM and WAM GP are located at:

               227 West Monroe Street, Suite 3000
               Chicago, Illinois 60606
            --------------------------------------------------------------------

Item 2(c)   Citizenship:

               WAM is a Delaware limited partnership; WAM GP is a Delaware
               corporation.
            --------------------------------------------------------------------

Item 2(d)   Title of Class of Securities:

               Common Stock
            --------------------------------------------------------------------

Item 2(e)   CUSIP Number:

               37637Q105
            --------------------------------------------------------------------

Item 3      Type of Person:

               (e)  WAM is an Investment Adviser registered under section 203 of
                    the Investment Advisers Act of 1940; WAM GP is the General
                    Partner of the Investment Adviser.
               -----------------------------------------------------------------

                               Page 4 of 10 pages




Item 4      Ownership (at December 31, 2005):

               (a)  Amount owned "beneficially" within the meaning of rule
                    13d-3:

                    (i) WAM:          2,755,000
                    (ii) WAM GP:      2,755,000
               -----------------------------------------------------------------

               (b)  Percent of class:

                    (i) WAM:          8.6%

                    (ii) WAM GP:      8.6%
               -----------------------------------------------------------------

               (c)  Number of shares as to which such person has:

                         (1)  sole power to vote or to direct the vote:

                              (i) WAM:         2,755,000
                              (ii) WAM GP:     0

                         (2)  shared power to vote or to direct the vote:

                              (i) WAM:         0
                              (ii) WAM GP:     2,755,000

                         (3)  sole power to dispose or to direct the disposition
                              of:

                              (i) WAM:         2,755,000
                              (ii) WAM GP:     0

                         (4)  shared power to dispose or to direct disposition
                              of:

                              (i) WAM:         0
                              (ii) WAM GP:     2,755,000
               -----------------------------------------------------------------

Item 5      Ownership of Five Percent or Less of a Class:

               Not Applicable
            --------------------------------------------------------------------

Item 6      Ownership of More than Five Percent on Behalf of Another Person:

               The shares reported herein include the shares held by Columbia
               Acorn Trust (CAT), a Massachusetts business trust that is advised
               by WAM, a Delaware limited partnership. CAT holds 8.5% shares of
               the Issuer's shares.
            --------------------------------------------------------------------

                               Page 5 of 10 Pages




Item 7      Identification and Classification of the Subsidiary Which Acquired
            the Security Being Reported on by the Parent Holding Company:

               Not Applicable
            --------------------------------------------------------------------

Item 8      Identification and Classification of Members of the Group:

               Not Applicable
            --------------------------------------------------------------------

Item 9      Notice of Dissolution of Group:

               Not Applicable
            --------------------------------------------------------------------

Item 10     Certification:

               By signing below I certify that, to the best of my knowledge and
               belief, the securities referred to above were acquired and are
               held in the ordinary course of business and were not acquired and
               are not held for the purpose of or with the effect of changing or
               influencing the control of the issuer of the securities and were
               not acquired and are not held in connection with or as a
               participant in any transaction having that purpose or effect.

            Disclaimer

               In accordance with Rule 13d-4 of the Securities Exchange Act of
               1934, each of the persons filing this statement expressly
               disclaim the beneficial ownership of the securities covered by
               this statement and the filing of this report shall not be
               construed as an admission by such persons that they are the
               beneficial owners of such securities.
            --------------------------------------------------------------------

                               Page 6 of 10 Pages




                                    SIGNATURE

      After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


Date: February 13, 2006

                    The undersigned corporation, on the date above written,
                    agrees and consents to the joint filing on its behalf of
                    this Schedule 13G in connection with its beneficial
                    ownership of the security reported herein.


                                     WAM Acquisition GP, Inc.
                                       for itself and as general partner of
                                       COLUMBIA WANGER ASSET MANAGEMENT, L.P.


                                     By:    /s/ Bruce H. Lauer
                                         ---------------------------------------
                                            Bruce H. Lauer
                                            Senior Vice President and Secretary

I.

                               Page 7 of 10 Pages




II. Exhibit Index


Exhibit 1           Joint Filing Agreement dated as of February 13, 2006
                    by and among Columbia Wanger Asset Management, L.P., WAM
                    Acquisition GP, Inc. and Columbia Acorn Trust.

                               Page 8 of 10 Pages




                                                                       EXHIBIT 1

                             JOINT FILING AGREEMENT

The undersigned hereby agree to the joint filing of the Schedule 13G to which
this Agreement is attached.


               Dated: February 13, 2006


                                     WAM Acquisition GP, Inc.
                                       for itself and as general partner of
                                       COLUMBIA WANGER ASSET MANAGEMENT, L.P.


                                     By:    /s/ Bruce H. Lauer
                                         ---------------------------------------
                                            Bruce H. Lauer
                                            Senior Vice President and Secretary


                                     COLUMBIA ACORN TRUST


                                     By:    /s/ Bruce H. Lauer
                                         ---------------------------------------
                                            Bruce H. Lauer
                                            Vice President, Treasurer and
                                            Secretary

                               Page 9 of 10 Pages