A B737-700 PILOT REPORTS OF HEARING AN ABNORMAL CRACKING SOUND IN THE COCKPIT. THE #4 EYEBROW WINDOW WAS FOUND CRACKED.

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WHILE ENRTE TO ZZZ FROM ZZZ1 AT CRUISE ALT FL360; THE PLT MONITORING HEARD AN ABNORMAL CRACKING SOUND IN THE COCKPIT. AFTER INVESTIGATING; THE PLT MONITORING (FO) NOTICED THAT THE #4 FO EYEBROW WINDOW APPEARED TO BE CRACKED. AFTER CAREFUL REMOVAL OF THE SUNSHIELD; IT WAS CONFIRMED. THE QRH WAS REFERENCED AND THE AFFECTED CRACKED WINDOW CHKLIST WAS COMPLETED. THE FLT CREW RELAYED THE EVENT TO COMPANY VIA COMRDO. THE FLT CONTINUED TO ZZZ1 WITH A HIGHER CABIN ALT SELECTED AS PER THE QRH. FLT LANDED WITHOUT INCIDENT AND NO FURTHER DAMAGE WAS DISCOVERED. AFTER LNDG AND DISCUSSING THE EVENT WITH MAINT AND OTHER FLT CREWS; IT WAS LEARNED THAT ACFT HAD A LOGGED BIRD STRIKE EARLIER NEAR THE AREA IN QUESTION. NO DAMAGE FROM THAT STRIKE COULD BE FOUND; CONFIRMED; OR LOGGED. I SUSPECT THAT THE WINDOW WAS WEAKENED BY THE STRIKE AND EVENTUALLY FAILED. THAT IS MY ASSUMPTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE SOUND WAS VERY DIFFERENT FROM NORMAL COCKPIT NOISE; ALMOST SIMILAR TO CRUNCHING UP A SHEET OF DRY NEWSPAPER. THE ABNORMAL SOUND LASTED ONLY A COUPLE OF SECONDS AND WAS GONE. HE HAS NOT HEARD FROM MAINT; WHICH SIDE OF THE WINDOW ACTUALLY CRACKED -- THE INNER OR OUTER PANE.