Eagle loss

Okay, so tell me,” Percy said, “why is it bad to be in the Fifth Cohort? You guys are great.”
The compliment made Hazel’s toes tingle. “It’s... complicated. Aside from being Pluto’s kid, I want to ride horses.”
“That’s why you use a cavalry sword?”
She nodded. “It’s stupid, I guess. Wishful thinking. There’s only one pegasus at camp — Reyna’s. The unicorns are just kept for medicine, because the shavings off their horns cure poison and stuff. Anyway, Roman fighting is always done on foot. Cavalry. ..they kind of look down on that. So they look down on me.”
“Their loss,” Percy said. “What about you, Frank?”
“Archery,” he muttered. “They don’t like that either, unless you’re a child of Apollo. Then you’ve got an excuse. I hope my dad is Apollo, but I don’t know. I can’t do poetry very well. And I’m not sure I want to be related to Octavian.”
“Can’t blame you,” Percy said. “But you’re excellent with the bow — the way you pegged those gorgons? Forget what other people think.”
Frank’s face turned as red as Dakota’s Kool-Aid. “Wish I could. They all think I should be a sword fighter because I’m big and bulky.” He looked down at his body, like he couldn’t quite believe it was his. “They say I’m too stocky for an archer. Maybe if my dad would ever claim me...”
They ate in silence for a few minutes. A dad who wouldn’t claim you... Hazel knew that feeling. She sensed Percy could relate, too.
“You asked about the Fifth,” she said at last. “Why it’s the worst cohort. That actually started way before us.”

The eagle,” Percy said.
Hazel was stunned. "How’d you know?”
Percy shrugged. “Vitellius was talking about how the legion lost its eagle a long time ago — the first time, he said. He acted like it was a huge disgrace. I’m guessing that’s what’s missing. And from the way you and Reyna were talking earlier, I’m guessing your eagle got lost a second time, more recently, and it had something to do with the Fifth Cohort.”
Hazel made a mental note not to underestimate Percy again. When he’d first arrived, she’d thought he was a little goofy from the questions he’d asked — about the Feast of Tuna and all — but clearly he was smarter than he let on.
“You’re right,” she said. “That’s exactly what happened.”

SoN ch.8