Flocking

February 27, 2023

When I recorded the birds for the Great Backyard Bird Count (GBBC) I mentioned how one day I had seen a large flock of Northern Grackle’s (Quiscalus quiscula).  I rarely see this flocking behavior around our house, except in winter or early spring.  Melissa and I saw 1,000’s of Redwing Blackbirds (Agelaius phoeniceus) flocking together when we visited the wildlife preserve in the fall.  Later in the week Melissa called me to come see as the birds were flocking again, except this time it was in our front yard.  I quietly stepped onto the front porch to get a photo and they all took off together.  They did not go far and landed across the street in the neighbor’s yard.  Apparently, I was not too much of a threat.

When I looked online, I found Birds are social creatures that use flocking for protection and to make it easier to find food.  When a large group of birds take off at the same time, they form a group that is easily seen by predators.  The tighter the group the more birds can fit into a given area and a tight group makes it harder for a predator to pick out an individual bird.  When they move as a flock it allows the birds to escape when a predator attacks as the birds take off in the same direction at the same time, making it even more difficult to focus on a single bird.  This makes it more likely the flock itself will escape even if a few individuals are lost.  Birds also flock together for warmth.  When the birds are tightly packed together, they can share body heat and stay warm even in cold weather.  The last reason for bird’s flocking behavior is to help birds find mates.  Males actively looking for females often practice flocking with other males.  This makes it easier for the males and makes it more likely the females will find a compatible mate.

Flocking behavior in birds can create large numbers of birds flying together called a swarm.  The largest recorded bird swarm was in November of 2011, when between 200 and 300 million birds of 20 different species swarmed over Lake Texoma on the Texas-Oklahoma border.  The event lasted several days and was likely caused by a combination of bad weather and natural migration patterns.  While this swarm was extraordinarily large, most bird swarms are more modest and are not unusual.  The smallest recorded swarm consisted of just two birds.  This event was documented in a paper published in the Wilson Journal of Ornithology in May of 2009 and described how two Dickcissels (Spiza americana) were seen flying together near Lincoln, Nebraska.  This is the only known instance of this species engaging as an “aerial flock”.  The author theorized this was a courtship display as male birds often fly in close formation with a female, even touching beaks or clasping claws.  For whatever the reason, this remains the smallest recorded bird swarm with just two individuals.

THOUGHTS:  The natural flocking behavior that results in bird swarms typically last around three to four days.  These flocks may reform, and with different birds, at later times.  Several days after the flock first arrived behind our house, I heard Zena barking franticly as she does when she encounters something new in her space.  This went on for several minutes until I went outside to investigate.  There was a single Grackle standing on our wood pile.  Zena did not attack, and the bird did not move.  I eased it off the pile and out of Zena’s sight.  Two days later I noticed it had succumbed to the cold.  It could not make it without the flock.  While humans are not prone to flocking, we are social animals.  This was proven again during the isolation of the pandemic as people joined in Europe to form nightly choirs singing from their windows.  Our species is made stronger when we come together in all our diversity.  Act for all.  Change is coming and it starts with you.