On the ever Shabbes before Tu B'Shvat, I always try to put some grains in the trees, for the birds to have after their return from the warm continents. This is done before the Shabbat Shira - the Shabbat of the song - stars, which happens this week. But there is more meaning to it than feeding the birds and here are some of them.
Shabbat Shira is taking place when the Parsha Beshalah is read, with tells the story of Kriat Yam Suf, when Hashem splitted the Red Sea for the Jewish people. A song was sung by the people of Israel, epitomizing the strength given by Hashem to the Jews against their enemies, a song where Gd was praised out of pure joy. Miriam, Moshe's sister, danced and played the tambourines, as an expression of gratitude towards the victory given by Hashem to the Jews against the powerful armies of the Pharaoh.
According to the Maharal of Prague, when the Red Sea split, fruits grew in the trees and children picked them to feed the birds, who sang and danced together with the Jews - Shirat HaYam. In the memory of their kiddush Hashem, it is customary to feed them the erev Shabbes before. This is a beautiful niggun inspired by the songs of birds on the hills around Jerusalem.
Following some traditions, birds are fed wheat, and Chabad followers eat kasha on this Shabbes, as a symbol of the manna fed to the Jews by Hashem.
Especially in the more liberal synagogues, it is customary to celebrate this Shabbat with music and dance, as a way to outline the importance of songs in the Jewish tradition, which comes in different colours and musical tones.