It wasn't a rock or a birds flew in the night

Hi!  I'm sorry, I normaly speak french, so I hope I will be clear in the way for you to undestand.
 Two of my friends and me were at my friend's place and decided to sleep outside in the backyard, on air beds, directly on the grass.  It was a beautiful summer night, no clouds, no wind, and no people awake, in this (little) suburbs of Montreal. At a moment, we were just kiding and laughing, you know, like any young people can do, and suddendly, my friend said to look up in the sky the strange thing.
 It was dark-brown, like a big rock (shape of an egg maybe), with rough appearence, you see? It was completely quiet, and was floating at about 150 meters from the ground. It's very particular, the way it was going : I don't think that there was any engine in the object, the propulsion was very weird, like if it was just gently glide, but fast!  I don't know how to explain it in another way (in french it would be easier). It was going like something floating firmly in a particular way (to the west).
 I saw it for 5-10 seconds (don't know exactly), it finaly disappeared.  Not disappear by gogin further. Disappear like "pop", one second we see it, one other second we don't see it.  It was night and there was no lights on the object, so maybe I missed something, but that is what I remember.
 I think the object made 100 meters by the moment we observe it before it disappeared. It was going from east to west. Just over us. We all see it (but one of us, now, think it was birds).
 What I remember the most about this event, is the strange feeling of "something weird", you know.  It wasn't a birds flew, because at the end, those should go scatter, not disappear. A meteor would burn and fall. I don't know what is was.
Thank you!
Witness indicates that the date of the incident is approximate.  PD