The bird that you may have heard is not the aswang but the "tik-tik". We have encountered aswangs in the province and they are always accompanied by this bird. According to Philippine folklore, the tik-tik is the aswang's familiar - much like black cats are to witches in Western folklore. When you hear a tik-tik on the West side of your house, that means the aswang is on the east side of your roof. When you hear the tik-tik at the south, the aswang is positioned on the North.
I actually saw one in Mindoro. It was summer then, me and my friends, we rent a room in big house of the said resort. On our last night, after nang dinner namin we are planning to go out and swim "sana".. but since katatapos lang namin magdinner that time, umakyat ulet muna kame sa room namin kung saan may terrace, we are on the 2nd floor of the big house.
It was 10pm, me and my friend having a chit-chat while smoking outside of the room at the terrace, we saw something which we thought was an incredibly huge bird following a smaller bird. But when it landed on the roof of the house in front of the big house which we are rented, we really saw it was a dark woman with really large bird wings. Good thing our light in the room was off because the it was full moon and we want to experience talking under the moon at the beach.
At 1st we couldn't move and react, we didnt even got the chance to shout, we stayed there for a about a minute or so...then my friend who is inside saw it also she didnt waste any time but grabbed us and dragged us inside the room. and shut the Terrace door and all the window and curtain. We sat on the floor and we prayed so hard, and we didnt even move or even talking.
After a couple of minute, narinig naming parang lumipad na at dumaan sa bubong namin, hinila nalang namin mga beddings sa sahig at doon na kaming natulog...the next morning, we found out that meron palang pregnant woman doon sa tapat ng big house na inupahan namin. We told about the "tik-tik" sa may ari ng bahay and she said palagi daw yun pumupunta sa bahay na un dahil doon sa buntis.
Good thing last night na namin sa resort na un or else sobrang nasira tlaga ang bakasyon namin.