This name of this Shabbos is attributed to the fact that both the Parsha and Haftorah include a Shirah (song).
The congregation stands during the Shirah, facing the Sefer Torah.
When reading the third last Possuk of the Parsha, the word Zecher is read twice, first with a Segol (Zecher), and then again with a Tzeirei (Zeicher).
There is a custom to eat buckwheat. In association with this, the Rebbe recounts that the Maharal of Prague instructed the teachers to gather the young children and their parents in the shul courtyard on Shabbos Shira and relate to them the story of the splitting of the sea, including how the birds sang and chirped while the Jews sang the Shirah, and how the little children fed the birds fruits they had plucked from trees that had miraculously grown in the sea. The Maharal then instructed that the children be given buckwheat to throw to the birds in commemoration of the above.
The Maharal would then bless the children, and also their parents – that they merit to educate and raise them to Torah, marriage and good deeds. [In practice, it is forbidden on Shabbos to feed birds that do not directly rely on humans for sustenance. Since it is no longer common for the typical household to care for birds, the Rebbe clarified that one should not actually feed the birds on Shabbos. Nevertheless, all the above should still be shared with the children, using the opportunity to implant within them the attribute of mercy towards all creations, as demonstrated in this story.]
