CreepyPasta译：我知道我儿时的朋友为什么会失踪了(5)

It was an unusually warm November afternoon, right after Ava's 7th birthday. My family bought her a small cake the day before. Now I can't help but think it was our fault she had a swollen, purplish face that day. 
"Ava, you're okay? What happened?" I worried to see her like that. 
"I just fell from the stwairs," she said. Her mouth was so severely beaten up she couldn't even pronounce some phonemes. 
But I believed her and accepted the answer, soon turning my attention to something else. I'm so sorry, Ava. 

We decided to use the warm day to bird watch, which I was very into in the last few weeks, since my parents gave me some binoculars. For that reason, we entered the forest a little deeper than usual. We found a beautiful nest of Junco, full of chicks. 
I was focused on the birds, when Ava had a distant, intrigued look on her face. 
"Are you listening? (sigh)… what a beautiful song." Ava was marveling at something, but I couldn't hear it. So I kind of ignored it. 
After a few minutes, she started walking deeper into the woods, presumably trying to find the source of the beautiful song. I still heard nothing but our footsteps crunching leaves on the ground and distant chirping.