I have received a few reports recently of “invasions” of blackbirds at feeders. I think most of these reports refer to common grackles, the large, slim, iridescently plumaged blackbirds.
Like most blackbirds in our area, these tend to form large flocks in winter. They tend to leave residential areas to spend the colder months foraging in rural places.
Typically they will form huge, mixed roosts at night along with other blackbird species. If you live along any of these flocks’ travel routes, you have noticed the long, streaming lines of birds going and coming in the early mornings or evenings.
By this time each year, the flocks have broken up and the grackles have moved into suitable nesting sites, often in or close to residential areas.
The nesting colonies are quite obvious, as is the birds’ presence at feeders. They are quite ravenous, enjoying sunflower seeds and especially suet dough. A group of hungry grackles can make short work of a suet cake. This is frustrating for backyard birds and birders alike.
I experienced this myself last year when a large colony was established in a pine grove near my home. There was an initial impact, and then it seemed to slow as the birds got preoccupied with raising young. Once the young fledged, the feeder dominance resumed, only by then there were adults and young birds.
Unfortunately any actions a feeder host can take to discourage these birds will result in some desirable species being discouraged too. It seems a temporary suspension of feeding is sometimes the best approach if supporting the diets of local grackles gets too expensive.
I was really unlucky last year when European starlings also moved in about the same time the grackles appeared. These non-natives can really tear up a suet cake in a hurry too. They are the chunky, short-tailed, dark-plumaged birds you may see. They are not blackbirds but are members of the myna family. I hope you do not have to deal with this issue this year. If you do, let me know if you find effective means to handle it.