Female Shearwig

Up until Pikmin: Sinister Incinerator only male Shearwigs were ever encountered, the females said to be hiding underground. In the Mountain Springs, a Female Shearwig is encountered as the boss of the Pale Pit of Peril. It is much larger than the male shearwigs and in fact is surrounded by the bugs. It emerges from the ground and lumbers around very slowly, rearing back when it nears Pikmin and then slashing forwards, eating Pikmin. The backside is vulnerable and the attack can be easily sidestepped. The fight gets harder after it takes 50% damage because it will start flapping its wings occasionally to push over your Pikmin. During the entire fight you'll be pestered with male shearwigs as well, which will stop attacking after the female is defeated.

Trivia
The drastic increase in size between the female and male shearwig is similar to the size comparison between the female and male angler fish in real life.

Portal- Kombat

In Pikmin 4 The World to Free
Tikes notes Wow such a big size difference than the males. I found out that the females get treated almost like queens. However recent discovery, is that males only are over protective of their females, but the female just ain't a breeding device.... like Alice says that the females act kind of like a psychologist as well. They encourage, and do things to make the males happy. Their wings actually resemble to a spectaid, maybe they used to not have wings before an possible D.N.A imbalance occurred.

Alices notes I have to admit, these creatures match the three laws of my love meter. Nice charming personality, cute, gorgeous, and actually have a quite nice companionship. They also meet the tastes of a psychologist in many ways as well. If this creature actually spoke our language and was not a monster or the same gender, I will so tell her that shes the perfect type for me.

Captain Pikmin notes Try to kill of her little guardians first, also pay attention when she is underground. Make sure you place a rock were you think she's heading and slam into the pile, back into the air. She will get fatigue and slams into the ground. Swarm her with dignity when she is.

Pikmin: Gold/Silver/Bronze
The Female Shearwig is a key boss and it acts similar to PSI. The shearwigs it spawns can also swarm you.