Birds love a good, round letter to build their home in, as seen here with a nest made in the sign at the CVS Pharmacy at 3100 Geer Rd.
Birds are sometimes attracted to nest in the letters of store signs because they are high enough for them to look out for predators; in modern society the letters often look like a good spot to settle to birds.
There are options to prevent birds from gathering, such as spikes or visual deterrents (like owl decoys), but not all businesses utilize these options due to various reasons. There are also various “bird gels” that are sticky enough to discourage the animals from landing but that claim to be nontoxic for the birds and for humans. While the gel is supposed to remain un-seen though, it can accelerate the collection of grime and dust that leads to dirty signs.
But it looks as if none of those measures were used here, leaving a cozy home for the birds.