You want your counters to be free and versatile, and unlike An Offer You Cant Refuse, Swan Song, Force of Negation, Flusterstorm, Dispel, and Spell Pierce, this can counter creatures
Red is quite rare for rat strategies, but Freya is a solid include if Totentanz, Swarm Piper (more on him later) is your Commander as long as youre also focusing on equipment
It is not that Bird is so high on this list that is surprising, more so that there are four other cards between it an Noble Hierarch which is a very similar card and situationally better than the Birds
The chances of finding an Enchanted card is around 1 in 100 packs
The more colored cards youre using in your sideboard, the more likely you are to want seventeen lands since it usually means four of them are Glimmervoid