hmm probably u may want to talk about, recieving a love token from your gf/bf, which is a locket.Upon hearing a couple of bird chirping loudly, repeatedly from some distance away from you which doesn't sound like the usual brid chirping. You saw some kids tried by all means to knock a bird nest off from a tree.
Since you have only 150words to spare, probably u may want to focus mainly on the mischiefs of those kids.Probably not common acts, like throwing stones. But maybe throwing lighted match sticks? its up to your imagination.
You tried to stop them, and soon realised your efforts were futile. Somehow, u may want to have an ending which involves you losing your locket in an attempt to help it, be it a good or bad ending.
The bird realises your kindness and somehow found your locket. It returned the locket back to you, before dieing right before your eyes due to injuries and fatique.
lol something like that? =P You could find inspirations from here anyway if it doesn't suit to your liking lol. you may not want to add the other 2 triggers in, as said, you have only 150 words lol.
wish you luck in your competition.

lol