Shabbos Shira is always one of the best examples of how minhagim change over the years.

This shabbos there is the custom of feeding the birds with bread crumbs. The reason for this is two-fold, connected to the manna and connected to the shira.

One reason is because when Hashem first gave the manna, and on Friday the Jews were told to collect double portions as the manna would not fall on shabbos itself. When some decided to make trouble and put manna back out on Friday night so when everyone would wake up shabbos morning and see the manna outside they would think Moshe was wrong and it did fall on shabbos, the birds came to save the day. The birds came and ate the manna and the plot was foiled.

As thanks to them, this shabbos, on the portion of the giving of the manna, we put out bread for the birds.

The second connection is the birds speak in song. Song is considered the realm of birds. Ever hear the phrase "She sings like a bird"? So on this shabbos, when we use the tool of the birds, we sing the praise of Hashem for splitting the sea and saving us, we thank the birds for allowing us their tool, and we put out bread for them.

I remember growing up that we would put out the bread crumbs for the birds on shabbos. That was the minhag for SHabbos Shira. Only much later did I learn that many say that one should preferably put the bread out on Friday, as it is prohibited to feed wild birds on shabbos. One can only feed on shabbos pets that are in your own possession. I was told that you must put the bread out for the birds on Friday before Shabbos Shira.

I recently found in the Aruch HaShulchan (324:3) that he says "There are those who speak otu against the minhag on Shabbos SHira of throwing wheat kernels to the birds, because of the problem that you are not responsible for feeding them. But, to me it seems that minhag yisrael torah - we are not troubling oruselves for them, but rather it is for ourselves, as we are returning the favor, so to speak, and the intention of it is to remember the joy of Shiras Ha'Yam, and there are those who write that because this is our intention, it is therefore allowed [to feed the birds on this Shabbos].

However, the custom still stands and some people say this is the exception. So some put the bread out on Friday, and some put the bread out on Shabbos. If you wish to put out bread as per the custom and are unsure of what to do (Friday or Shabbos), ask your local Rabbi for advice as to the best way of dealing with this custom.