Some suet even has flavoring which is totally unnecessary. If you have House Sparrows eating suet, then you have a problem because they do not eat suet but will eat the large amounts of millet some suet has as filler. Suet should be placed away from the seed feeder so there are fewer disturbances for Woodpeckers and Bushtits. If Starlings and Jays discover the suet, there are feeders that will exclude them. These feeders require birds to hang upside down which Jays and Starlings do poorly.
Some newer ones have wire screen to keep out larger birds.
Where attracting birds and butterflies into your garden becomes an Art.