Over the holiday, I spent time with family in New Jersey and was interested to hear about relatives’ observations of large flocks of blackbirds.

My mother was the first one to bring the subject up. She had glanced out her kitchen window one day to find her lawn covered with them; she was amazed at the racket they made. I guessed what she was seeing were common grackles, with perhaps a few red-winged blackbirds and cowbirds included in the flock. Winter aggregations of these birds in New Jersey have been known to number up to 500,000 birds, although the group in my mother’s yard probably contained only a few hundred.

I thought no more of it until I went to my aunt’s house for Christmas Eve dinner. A young cousin of mine again mentioned seeing a very large flock in her neighborhood. She, too, remarked on the noise they made. When I asked if they sounded like squeaky hinges, she said no, it wasn’t a vocal sound she had heard; rather, it was the impressive “whoosh” of hundreds of wings as the whole flock startled and took flight as one.

Then she said something that surprised me. She was afraid the birds would surround her and peck at her, as the fictional birds did in the infamous Hitchcock movie. She laughed about it and acknowledged that the movie influenced her thinking, but it reminded me of others I know who have the same irrational fear of birds. Again, the fear seemed to center on the image of birds seeking out humans just to peck at them (darn you, Alfred Hitchcock).

I tried to explain that the birds’ goal was to find something to eat, not seek out a human to peck. I think she did realize this, but that’s the nature of such fears: They make no sense and have no base in reality.

Another relative questioned what the birds would be finding on backyard lawns. Grackles are extremely opportunistic in their eating habits, eating a variety of insects such as larval beetles, caterpillars, and grasshoppers, as well as seeds and fruit. So I guessed they were finding insects made sluggish by the cold, or weed and grass seed. They particularly favor acorns and the seeds of sweet gum trees.

Grackles are so flexible in their eating habits, and so opportunistic, that they’ve become a major agricultural pest, causing millions of dollars in damage to sprouting corn and other crops. They’ve been known to kill and eat other birds’ eggs and nestlings, and even adult birds of other species. Although they aren’t the only bird species to do this (blue jays have been observed in this as well), their sheer numbers probably made this practice more noticeable.

Grackles are also flexible in their nesting habits; they may nest singly or in a colony of up to 200 pairs of their brethren. In addition, they have thrived in human-induced change in the environment. This adaptability has allowed them to expand their range from the East, and they’ve invaded the West within the last 50 years.

Now, some ornithologists speculate their declines in the East are the result of control measures taken to reduce their populations, and therefore the damage they do to agricultural crops. This seems unfair, until you consider that it might not be such an issue in the absence of our own wholesale effect on the planet.

It’s surprising what can come out of a few shared observations of the winter behavior of blackbird flocks.

BDN bird columnist Chris Corio can be reached at bdnsports@bangordailynews.net