SECURITIES & EXCHANGE COMMISSION
                             Washington, D.C. 20549
                             ----------------------

                                 SCHEDULE 13G/A
                                 (Rule 13d-102)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
           TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                              PURSUANT TO 13d-2(b)

                               (Amendment No. 2)*

                         MAGELLAN HEALTH SERVICES, INC.
                                (Name of Issuer)

                          Common Stock, $.01 Par Value
                         (Title of Class of Securities)

                                    559079207
                                 (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:

     [ ]  Rule 13d-1(b)
     [x]  Rule 13d-1(c)
     [ ]  Rule 13d-1(d)





                           (Page 1 of 5 Pages)
---------------
     *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 purposes 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. 559079207                13G/A            Page 2 of 5 Pages

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     (1)    NAMES OF REPORTING PERSONS
            I.R.S. IDENTIFICATION NO.
            OF ABOVE PERSONS (ENTITIES ONLY)

            JANA PARTNERS LLC

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     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP **
            (a) [ ]
            (b) [ ]
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     (3)    SEC USE ONLY
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     (4)    CITIZENSHIP OR PLACE OF ORGANIZATION

            DELAWARE
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NUMBER OF      (5)  SOLE VOTING POWER
                            0
SHARES         --------------------------------------------------------------

BENEFICIALLY   (6)  SHARED VOTING POWER
                            0
OWNED BY       --------------------------------------------------------------

EACH           (7)  SOLE DISPOSITIVE POWER
                            0
REPORTING      --------------------------------------------------------------

PERSON WITH    (8)  SHARED DISPOSITIVE POWER
                            0
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     (9)     AGGREGATE AMOUNT BENEFICIALLY OWNED
             BY EACH REPORTING PERSON
                            0
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     (10)    CHECK BOX IF THE AGGREGATE AMOUNT
             IN ROW (9) EXCLUDES CERTAIN SHARES **                       [ ]
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     (11)    PERCENT OF CLASS REPRESENTED
             BY AMOUNT IN ROW (9)
                          0.0%
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     (12)    TYPE OF REPORTING PERSON **
                           IA
-----------------------------------------------------------------------------
                    ** SEE INSTRUCTIONS BEFORE FILLING OUT!







CUSIP No. 559079207                 13G/A            Page 3 of 5 Pages
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Item 1(a).     Name of Issuer: Magellan Health Services, Inc.

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

               16 Munson Road
               Farmington, CT 06032

Item 2(a).     Name of Person Filing:  JANA Partners LLC

Item 2(b).     Address of Principal Business Office or, if None, Residence:

               200 Park Avenue, Suite 3300, New York, New York 10166

Item 2(c).     Citizenship:

               This Statement is filed by JANA Partners LLC, a Delaware
               limited liability company. JANA Partners LLC is a private
               money management firm which holds the Common Stock of the
               Issuer in various accounts under its management and
               control. The principals of JANA Partners LLC, Barry
               Rosenstein and Gary Claar, are U.S. citizens.

Item 2(d).     Title of Class of Securities:

               Common Stock

Item 2(e).     CUSIP Number: 559079207


Item 3.  If this statement is filed pursuant to Rules 13d-1(b) or 13d-2(b) or
(c), check whether the person filing is a: Not applicable

          (a) [ ] Broker or dealer registered under Section 15 of the Act,

          (b) [ ] Bank as defined in Section 3(a)(6) of the Act,

          (c) [ ] Insurance Company as defined in Section 3(a)(19) of the
                  Act,

          (d) [ ] Investment Company registered under Section 8 of the
                  Investment Company Act of 1940,

          (e) [ ] Investment Adviser in accordance with Rule
                  13d-1(b)(1)(ii)(E),

          (f) [ ] Employee Benefit Plan or Endowment Fund in accordance
                  with Rule 13d-1(b)(1)(ii)(F),

          (g) [ ] Parent Holding Company or control person in accordance
                  with Rule 13d-1(b)(1)(ii)(G),

          (h) [ ] Savings Association as defined in Section 3(b) of the
                  Federal Deposit Insurance Act,





CUSIP No. 559079207                 13G/A            Page 4 of 5 Pages

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          (i) [ ] Church Plan that is excluded from the definition of an
                  investment company under Section 3(c)(14) of the Investment
                  Company Act of 1940,

          (j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to 13d-1(c), check this box:  [x]


Item 4.       Ownership.

          (a)  Amount beneficially owned: 0
          (b) Percent of class: 0%
          (c)  Number of shares as to which JANA Partners LLC has:
                 (i) Sole power to vote or direct the vote: 0
                (ii) Shared power to vote or direct the vote: 0
               (iii) Sole power to dispose or direct the disposition: 0
                (iv) Shared power to dispose or direct the disposition: 0


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

              If this statement is being filed to report the fact that as of
              the date hereof the reporting person has ceased to be the
              beneficial owner of more than five percent of the class of
              securities, check the following [X].

Item 6.       Ownership of More than Five Percent on Behalf of Another Person.
              Not applicable

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







CUSIP No. 559079207                 13G/A            Page 5 of 5 Pages

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Item 10.  Certification.

Each of the Reporting Persons hereby makes the following certification:

By signing below I certify that, to the best of my knowledge and belief, the
securities referred to above 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.


                                    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.


DATED:  February 10, 2006


                                    JANA PARTNERS LLC

                                    /s/ Barry Rosenstein
                                    -------------------------------------
                                    Barry Rosenstein
                                    Managing Partner


                                    /s/ Gary Claar
                                    -------------------------------------
                                    Gary Claar
                                    Managing Director