The only way to force them to attack your fortress in any game is to make them babysnatchers.
I'd prefer that they aren't but I will keep this in mind if nothing else works.
Otherwise you can change their ethics and religion to be the opposite of dwarves, which makes it more likely they'll be at war with at least one dwarven civilization.
They're ethics are largely opposite. Over the past ten or so worlds gened, only one (a pocket map) had dwarves at war with them. So I don't believe this is not much of an option.
Or make them unable to speak.
This is strange, they don't have the [CAN_SPEAK] tag, but in the arena, they speak anyway.
[CREATURE:OWLMAN]
[DESCRIPTION:A tall winged owl-like creature fond of attacking surrounding civilizations for food.]
[NAME:owlman:owlmen:owlman]
[CASTE_NAME:owlman:owlmen:owlman]
[CREATURE_TILE:153][COLOR:6:0:0]
[CREATURE_SOLDIER_TILE:153]
[INTELLIGENT]
[BENIGN]
[CANOPENDOORS]
[FLIER]
[PREFSTRING:horrifying shrieks]
[BODY:HUMANOID:2WINGS:2EYES:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:SPINE:BRAIN:SKULL:5FINGERS:4TOES:BEAK:
RIBCAGE]
[BODY_DETAIL_PLAN:STANDARD_MATERIALS]
[REMOVE_MATERIAL:HAIR]
[USE_MATERIAL_TEMPLATE:FEATHER:FEATHER_TEMPLATE]
[BODY_DETAIL_PLAN:STANDARD_TISSUES]
[REMOVE_TISSUE:HAIR]
[USE_TISSUE_TEMPLATE:FEATHER:FEATHER_TEMPLATE]
[BODY_DETAIL_PLAN:VERTEBRATE_TISSUE_LAYERS:SKIN:FAT:MUSCLE:BONE:CARTILAGE]
[BODY_DETAIL_PLAN:BODY_HAIR_TISSUE_LAYERS:FEATHER]
[USE_MATERIAL_TEMPLATE:TALON:NAIL_TEMPLATE]
[USE_TISSUE_TEMPLATE:TALON:TALON_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:TOE:TALON:FRONT]
[SELECT_TISSUE_LAYER:HEART:BY_CATEGORY:HEART]
[PLUS_TISSUE_LAYER:SKIN:BY_CATEGORY:THROAT]
[TL_MAJOR_ARTERIES]
[BODY_DETAIL_PLAN:STANDARD_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RIBCAGE_POSITIONS]
[USE_MATERIAL_TEMPLATE:SINEW:SINEW_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD:BLOOD_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD:LIQUID]
[CREATURE_CLASS:GENERAL_POISON]
[GETS_WOUND_INFECTIONS]
[GETS_INFECTIONS_FROM_ROT]
[USE_MATERIAL_TEMPLATE:PUS:PUS_TEMPLATE]
[PUS:LOCAL_CREATURE_MAT:PUS:LIQUID]
[PHYS_ATT_RANGE:STRENGTH:450:950:1150:1250:1350:1550:2250] +
[PHYS_ATT_RANGE:AGILITY:150:600:800:900:1000:1100:1500] ++
[PHYS_ATT_RANGE:TOUGHNESS:450:950:1150:1250:1350:1550:2250] -
[MENT_ATT_RANGE:ANALYTICAL_ABILITY:450:950:1150:1250:1350:1550:2250] --
[MENT_ATT_RANGE:FOCUS:700:1200:1400:1500:1600:1800:2500] +
[MENT_ATT_RANGE:CREATIVITY:450:950:1150:1250:1350:1550:2250] -
[MENT_ATT_RANGE:PATIENCE:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:MEMORY:450:950:1150:1250:1350:1550:2250] ++
[MENT_ATT_RANGE:SPATIAL_SENSE:700:1200:1400:1500:1600:1800:2500] +
[BODY_SIZE:0:0:4000]
[BODY_SIZE:1:168:17500]
[BODY_SIZE:12:0:70000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[BODY_APPEARANCE_MODIFIER:BROADNESS:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[SET_BP_GROUP:BY_CATEGORY:EYE]
[BP_APPEARANCE_MODIFIER:CLOSE_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:DEEP_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:ROUND_VS_NARROW:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:LARGE_IRIS:25:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[SET_BP_GROUP:BY_CATEGORY:SKULL]
[BP_APPEARANCE_MODIFIER:HIGH_CHEEKBONES:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:BROAD_CHIN:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:JUTTING_CHIN:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:SQUARE_CHIN:0:70:90:100:110:130:200]
[SET_BP_GROUP:BY_CATEGORY:HEAD]
[BP_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[BP_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[MAXAGE:80:100]
[ATTACK:BITE:BODYPART:BY_CATEGORY:BEAK]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:bite:bites]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_CANLATCH]
[ATTACK:PUNCH:BODYPART:BY_TYPE:GRASP]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:punch:punches]
[ATTACK_CONTACT_PERC:100]
[ATTACK_FLAG_WITH]
[ATTACK_PRIORITY:MAIN]
[ATTACK:SCRATCH:CHILD_TISSUE_LAYER_GROUP:BY_TYPE:STANCE:BY_CATEGORY:ALL:TALON]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:snatch at:snatches at]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_WITH]
[CAN_LEARN]
[BABY:1]
[GENERAL_BABY_NAME:owlman hatchling:owlmen hatchlings]
[BABYNAME:owlman hatchling:owlmen hatchlings]
[CHILD:6]
[GENERAL_CHILD_NAME:owlmen child:owlmen children]
[CHILDNAME:owlmen child:owlmen children]
[EQUIPS]
[DIURNAL]
[HOMEOTHERM:10067]
[SWIMS_LEARNED][SWIM_SPEED:2500]
[CASTE:FEMALE]
[FEMALE]
[CASTE:MALE]
[MALE]
[SELECT_CASTE:ALL]
[SET_TL_GROUP:BY_CATEGORY:ALL:FEATHER]
[TL_COLOR_MODIFIER:BROWN:1]
[TLCM_NOUN:feathers:PLURAL]
[SET_TL_GROUP:BY_CATEGORY:ALL:SKIN]
[TL_COLOR_MODIFIER:BROWN:1:BURNT_UMBER:1:CINNAMON:1:COPPER:1:DARK_BROWN:1:DARK_PEACH:1:DARK_TAN:1:ECRU:1:PALE_BROWN:1:P
ALE_CHESTNUT:1:PALE_PINK:1:PEACH:1:PINK:1:RAW_UMBER:1:SEPIA:1:TAN:1:TAUPE_PALE:1:TAUPE_SANDY:1]
[TLCM_NOUN:skin:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:BLACK:1]