Why do some birds flock and others remain solitary?

Many birds form flocks year round like doves, starlings, waxwings, crows, jays, and goldfinches. Some species form flocks just during the winter like cardinals, bluebirds, chickadees, titmice, and nuthatches. Flock numbers can vary from a few birds to millions depending on the species. While other birds prefer to remain solitary like hummingbirds, woodpeckers, hawks, and wrens.

Advantages to flocking bird behavior:

Flock of American Goldfinches

1) Protection - When birds join forces to flock together they can spot predators quicker and then mob, distract or confuse attackers.   

2) Foraging efficiency – Sometimes scout birds are sent out in different directions and report back to the flock where the best food can be found. You can hear Blue Jays and American Crows call out in the mornings, signaling to fellow flock members where to find the best food.

3) Finding mates – After nesting season, young chickadees fly off to find a flock to winter with along with a mate for next spring.

4) Continuing Education – Young bluebirds form family groups in the fall. Parent birds continue to teach their young how to survive until they disperse in the spring to find their own mates.

5) Fly in formations – Certain birds’ aerodynamics conserves energy and allow flock members to see each other and communicate while in flight.

6) Roosting – When large flocks congregate at night, their shared body warmth can help them survive extremely cold temperatures.

Advantages to solitary bird behavior:

Solitary Northern Flicker

1) Protection – Single birds are quieter and attract less attention from predators.

2) Foraging efficiency – A solitary woodpecker or hawk can search for food without any competition from any flock members. Birds with low reserves forage alone, but birds with lots of food available flock.

3) Finding mates – Hummingbirds and wrens can find multiple mates while guarding a territory. Birds in flocks have an increased intensity in competing for mates.

4) No pecking order – Solitary birds depend on themselves to survive. If there is a food shortage, dominant birds in the flock feed first and subordinate birds may go hungry.

5) Stay Healthy – There is less risk of disease spreading between birds if they have little contact with each other.  

6) Roosting – Tiny areas can be used to roost at night. A flicker can find a small spot under the eves to spend a chilly night with some protection and little notice.

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