Winter Bird Photography in the Forest and Flocking Dynamics: Part 2

Well it happened again…life got a little in the way of posting blog posts. 

I have spent a few days out in the cold windswept grasslands, photographing northern harriers and the other birds that call that amazing landscape home.  I will be sharing some of my stories from there with you shortly on upcoming YouTube videos and posts elsewhere in the coming days and weeks. 

Now it is time to get back and wrap up what we were talking about in flock dynamics for songbirds in the winter. 

In last week’s post we discussed the flocking dynamics of forest birds in the winter and how it related to their improved ability to find food.  As the amount of food decreased and becomes harder to find, these birds flock together, finding strength in numbers to aid every individual in the flock to find more food than they would have otherwise alone. 

This strength in numbers has a second, and also, very important role, threat detection. 

It is obvious that the more individuals in a group, the higher the likelihood that one of the individuals in the group will detect a threat when spotted.  This is found in all kinds of animals, from herds of deer and elk, to geese all roosting together in an open field during the winter.  They are all benefiting from having more eyes looking around in every direction, to be on the lookout for danger.  Because there are more eyes looking around, each individual is then able to spend less time being alert, and more time searching for food.  This allows these birds to devote more energy to foraging and making sure they can survive the winter, than being vigilant. 

A Merlin, Falco columbarius, perches on op of a tree keeping a watchful eye on the thickets below. This small falcon’s main prey are small birds, which it is able to pursue and capture in mid air.

For small birds in the forest, this threat can come in many forms.  A variety of birds of prey live hidden in the shadows of the forest.  Coyotes, foxes, and bobcats are also real dangers for these small birds.  These small flocks work together to not only identify these threats quickly, but they also work together to scare off the threat as best as they can.  These flocks of birds will do something that is called “mobbing” which is essentially flying down and attacking these threats.  Many times, these birds do not actually make contact with the predator, but they fly close to the threat in an attempt to pester and aggravate the threat enough to make them want to leave the area. 

If you have aver seen crows flying low and pestering a hawk perched in a tree, this is the same concept but with smaller birds.  Even tiny hummingbirds can sometimes take part in the mobbing!

These mobbing attacks can cause a ruckus in the forest, and they are great to listen for as they may hint that something is lurking in the forest that may be worth checking out. 

A Red-tailed Hawk, Buteo jamaicensis, flys out from its perch to attack a squirrel. While red-tailed hawks do not typically go after birds for their main source of food, they are often on the receiving end of mobbing attacks by song birds.

Another benefit worth mention here regarding flocks and predators is in something called the dilution effect.  This is the idea that the more prey is in one area, the chance of any one individual in that group becoming the prey is reduced the larger the group is.  This means that if you are alone in the forest and a predator is nearby, you are the only source of food and are the only target for the predator.  Now if you are in a group of 20 other individuals, in simplest terms, your chance of becoming prey is now only 5%.  It is clear to see that being a part of a flock has a dramatic influence on any one individual’s chance of avoiding predation.    

Now this does not take into consideration if there are any individuals sick or injured in the flock, or very young or older, as these things tend to decrease fitness of that specific individual and their chance of becoming prey may still be higher even if they are in a large flock.

The size of the flock also helps individuals avoid predation in a second factor and that is the ability for large flocks to potentially disorient and confuse the predator making their hunting unsuccessful.  If a lot of individuals all flee at the same time, a predator may not be able to follow and track their target, and thus the small bird may be able to get away.

That is all for flock dynamics and the benefits of being part of a flock in the winter months.  These flocks work together to survive the winter as best as they can, particularly when food becomes scarce. 

Talk soon,

Todd 

A Barred Owl, Strix varia, perched in a forest at dusk. Perhaps one of the easiest ways to find owls in the forest is by listening for songbird alert calls and listening for mobbing activity. The owls typically do not pay much attention to these mobs and the small birds typically leave the owl alone after a few minutes so you only have a short time frame to use these calls to alert you to their location.