New Years Explosions

I only manage to get a few hours of sleep, but it's rejuvenating nonetheless. I'm on last watch, Charlie waking me up at about four in the morning. I'm sitting awake now, leaning my back against the wall behind me, my eyes picking out patterns from the cracks in the walls the pass the time. My sight comes to the edge of what used to be a window, glancing out of it to see if anything's there, and catch a glimpse of deep redish-purple.
I stand, taking a few steps towards the empty square in the wall, and smile. Even though the world as we knew it has ended, strange mutant creatures threaten our existence, our life has been reduced to literal rubble, and we struggle to survive, we still have this. The sun rising over the horizon, setting the dark, ashy sky a beautiful golden-pink hue.
I never got to see this before now. My hospital room was on the wrong side of the building to see the sun rising or setting. It's really quite amazing. I think about waking the others, but they've probably seen this a thousand times before, and they deserve as much rest as they can.
A couple of hours later Charlie stirs, waking Cale (who is rather unhappy about being woken this early). We run through some plans on how we're going to advance, what to look for, where to go.
"We still need to find more food," Cale puts in, playing idly with the dirt and stones littering the floor.
"That's a given. But where? How long would it take? Who knows how little supplies there would be," Charlie says, scowling.
"Such a pessimist... It doesn't matter how long it would take, as long as we don't die of hunger before then. How long would that take again? Three days?"
"Three to five, depending on level of activity and weather conditions," I mutter softly.
He nods. "Right. So we have that long to find something, which shouldn't be hard given I found some on the first day."
"Could have just been lucky..." she murmurs angrily.
"Hey! If you call nearly getting killed by two mutant zombie thing-a-majigs over a can of fruit 'lucky', then there's something wrong with you."
"I'm not the one that has problems."
He puffs up angrily, then sighs. "We need to focus. Can't fight them if we're fighting each other. Speaking of... What are we going to do about those bird-things?"
"Find them, fight them, destroy them. Simple."
"Yeah, but how are we going to do that? Wait until another one tries to kill us, hide from it, then follow it back to its nest? Good luck with that!"
"We could kill them off one by one. Work our way through their numbers, however many that would be."
"How many do you suppose there are?"
"I don't know. Twenty or so?"
"I think it would be more than that. Fifty, maybe seventy..."
"Both of you are way off."
They stop and stare at me, Charlie with her usual, wary gaze and Cale with a bemused look. "Why would you say that? How would you know how many of them are out there?" he chides, crossing his arms.
I sigh, thinking back over my 'autopsy' of the thing. There was one thing I didn't tell them, one thing I kept back. I wasn't sure what to make of it, but now that I've thought it through, now would be a good time to break the bad news. No, not bad news, terrifying news.
"None of them are 'its'. The one we fought, it was... male," I tell them quietly.
"So?" Cale says, frowning, not really getting it.
"Hold on a sec. You're saying they have genders?" I give a small nod. "But would that mean..."
Cale's eyes widen minutely, showing he now understands. "No way," he breaths.
"Yes," I say reluctantly. "They can reproduce."
Silence for the space of a few breaths bar the sound of the wind through the gaps in the walls. Then, Cale moans, "Well, fuck."
I'm reluctant, not wanting to have to talk about this, but they should know the facts. "Depending on how fast they breed, how many there were to start with... Let's say they had twenty to begin with, and they breed like regular birds, say... A magpie. If half of them mated when they were first created, that would leave us with five mutant offspring, which would jack the total to twenty-five. If there were fifty to begin with, we would have sixty five. Seventy, to eighty-seven. One hundred, to one-twenty-five..."
"That isn't too bad a rate, right...?" Charlie asks, shrugging.
I sigh softly. "Given the power of these creatures, we would be in trouble even if they could not reproduce. We had trouble just taking down one, on its own."
"Whatever," Charlie scoffs, looking away. "All that matters is that we live. So we should work on that for the time being."
"Good thinking. What's the plan?" Cale asks, and I just shrug.
"We'll cover more ground if we split."
"Split? No, no, no, haven't you ever seen a horror movie? Bad things happen if they split up. Our life is like that now. Besides, as much as i know Charles here can take care of herself, we still shouldn't leave her alone," he says, not quite a pathetic excuse but close.
Charlie frowns. "This isn't a movie. It's real. Not all the stupid cliche's apply."
"Says the one who believes in aliens taking over..."
I hold up a hand, and they look at me weirdly and with a hint of annoyance. "I agree with both of you. We can try it this way -I'll go with Charlie, since I don't have as many physical skills as Cale, who will head out a different direction. You are apparently better at finding edible substances than us, so you can do that, while we try to find anything else that could be of use to us. How's that?"
They think about it, then she scoffs, crossing her arms. "I don't see why I need you with me, but whatever."
Cale shakes his head. "It still isn't a good idea, but... Unless we go together, which would take longer, I don't see anything else we could do." He stands up, stretching. "Let's get goin', then."