Why is a stork called "Chasidah"?
Rashi: Because it performs acts of kindness with its friends.
Moshav Zekenim, citing R. Eliezer of Garmaiza: It gives Ma'aser 1 from its children. This is why the angels (Chayos) are called on its name - "Kenaf Renanim
Sefer ha'Itur (Shechitah 45b): Some call it Gita, for it casts them off (like Gerushin). Pane'ach Raza - this is why in Devarim, it is next to "Aser Ta'aser" (verse 14:18; Chasidah is four verses before this).
Why is "ha'Anafah" written without a Vov in front of it?
Moshav Zekenim: When a stork (written before this) is Mezanah with its friends, it immediately immerses in water lest its 'husband' smell [the semen]. If it does not do so, if the male smells it, he will act like an Anafah, which is irritatable and Mezanah, and it flies and breaks [the female's] neck with a father in its wings.
QUESTIONS ON RASHI
Rashi writes that Chasidah does Chesed with its friends. If so, why is it among the Tamei birds?
Mishneh Halachos (6:124, citing the Ba'al Shem Tov), Daf Al ha'Daf (Chulin 63a citing the Beis Yisrael): The proper Midah is to do Chesed with all, and not only with friends.