Mayzie might just be the light to Horton's heavy. Seems pretty obvious, right? She's a tiny bird, light enough to fly. But Shmoop takes nothing for granted, so let's dig deep.
Compared to Horton, Mayzie displays very few emotions. We see dissatisfaction, contentment, and then, for just a moment (when she decides she wants the egg back), anger. Is she a shallow, emotional lightweight who doesn't feel things deeply? Or is she covering deeper emotions with her flighty, fickle front?
As a single, unwed bird in 1940, Mayzie might be getting a lot of flak from society. Her parents might have pressured her into going off to Palm Beach so they didn't have to face the scorn of the community. Or she might have internalized the idea that as a single mom, she wouldn't make a good parent. Maybe she's experiencing guilt, shame, and desire for a fresh start.
Can we forgive Mayzie? After all, she definitely feels some kind of emotion toward the egg. Otherwise, she wouldn't have asked Horton to watch it, and she wouldn't be so freaked when she sees it with Horton.
Peter Costello argues that because Mayzie is such a liar, and she never redeems herself, "she's one of the most reprehensible characters in the Seuss canon" (source, 95). Yowza.
He kind of has a point, though. Think of the extraordinarily un-motherly lie she tells when she finds Horton and the egg at the circus:
"But it's MINE!" screamed the bird, when she heard the egg crack.
(The work was all done. Now she wanted it back.)
"It's MY egg!" she sputtered. "You stole it from me!
Get off of my nest and get out of my tree! (191-193)
Luckily, Horton has some witnesses (read: us).