HEADING TRACK POS DEV BY CL65 FLC DURING DEP PROC NOISE ABATEMENT PROC.

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WE HAD ARRIVED AT BOS ON RWY 32L -- IT BEING THE ONLY ONE CLR OF SNOW AT THE TIME. ON DEP CLRNC DELIVERY GAVE US RWY 33L; WHICH REQUIRED A TURN TO 315 DEGS AFTER FLYING RWY HEADING TO 2 DME. WHILE TAXIING OUTBOUND I NOTICED SNOW-CLRING VEHICLES ON TXWY C AT ITS INTXN WITH RWY 33L. AT THAT TIME TWR TOLD THE VEHICLES TO MOVE TO THE SIDE OF THE TXWY AND TOLD US TO CONTINUE ACROSS RWY 33L ON TXWY D AND TO EXPECT RWY 27 FOR OUR DEP. THE FO AND I HAD DISCUSSED THE SID WHEN WE FIRST RECEIVED RWY 33L AS OUR DEP RWY. AT THAT TIME I HAD SET THE HDG 'BUG' TO 315 DEGS. AFTER THE CHANGE TO RWY 27; THE FO AGAIN REFERRED TO THE SID ('LOGAN ONE') AND BRIEFED ME THAT THE NEW HEADING AT 2 DME OFF RWY 27 WOULD BE 235 DEGS. I ACKNOWLEDGED THAT; BUT BEING SOMEWHAT CONCERNED WITH THE CLRNC BTWN US AND THE SNOW-REMOVAL VEHICLES AS WE TAXIED PAST AND THE SNOW DRIFTING ACROSS THE TXWY; I FAILED TO CALL FOR THE FO TO RESET THE HEADING 'BUG' TO THE NEW HEADING. NOR DID THE FO SET THE 'BUG' ON HIS OWN VOLITION. AT 2 DME OFF RWY 27; I TURNED THE ACFT TO THE 'BUGGED' HDG OF 315 DEGS INSTEAD OF 235 DEGS AS I SHOULD HAVE. DEP CTL QUERIED US ABOUT OUR HEADING; WE ADMITTED OUR MISTAKE; AND THEY HAD US CONTINUE FURTHER R TO 350 DEGS. WE HAD LEFT OUR HOTEL IN TORONTO AT AB00 THAT DAY; DEPARTED FOR BOS AT AC00; DIVERTED TO MANCHESTER; NH; DUE TO LOW VISIBILITY AT BOS; HAVING HELD FOR ALMOST 2 HRS. WE LANDED AT MHT AT AF00; NEITHER WE (THE CREW) OR THE PAX WERE ALLOWED INSIDE THE TERMINAL OR EVEN OPS AREA (FOR THE CREW) DUE TO CUSTOMS CONSIDERATIONS. OUR DISPATCH FINALLY DISPATCHED US TO BOS AT AI35. AT BOS WE DID AS QUICK OF A TURNAROUND AS POSSIBLE. AT THE POINT WE TAXIED OUT FOR TKOF BACK TO TORONTO; NEITHER THE FO NOR I HAD HAD ANYTHING TO EAT THAT DAY EXCEPT PEANUTS AND CRACKERS FROM THE ACFT'S GALLEY. I BELIEVE THIS PROBABLY CONTRIBUTED TO OUR FAILURE TO COORDINATE RESETTING THE HEADING BUG FOR THE NEW DEP RWY. I HAVE NOTICED IN THE PAST; THAT LOW BLOOD-SUGAR LEVELS CONTRIBUTE TO FATIGUE AND APATHY.