Walking alongside the Exeter Ship Canal, my attention was drawn to a large flock of finches flying into the tops of the trees nearby.
I stood quietly in the shadows below and listened to the constant contact call chatter of this restless gathering. Within half a minute the birds were up from the branches and into the grey sky, across to another row of trees a short distance away.
Scanning the group with my binoculars, I could see that this assembly consisted of chaffinches, goldfinches and siskins. A loose, temporary three-species alliance designed to help each individual make it through the day.
There is a certain nervous energy and excitability which runs through a mixed species winter flock. One can sense that drive to find food and given the ever-shortening days, that need to maximise all available opportunities.
Daylight hours are limited, environmental conditions potentially tough and challenging, each finch needing to find enough food to maintain energy levels. At the same time, the group must be aware of threats and dangers. Vigilance is essential and it is not surprising the flock may seem on edge, ready to take flight in an instant. To feed and not to be fed upon!
Feeling confident, several chaffinches flew down to the ground in search of scattered seeds. The goldfinches began to feed amongst the teasels, burdocks and thistle heads close to the towpath, whilst a siskin settled in an alder. Many of the finches preferred to forage high up in the canopy.
For all of these birds, nutritious, energy-rich seeds top the autumn/winter menu. Given the overlap which exists in the diets of different types of finch, one would expect there to be competition between rival species. Why, therefore, are mixed flocks formed at this time of the year? The benefits gained must justify the need for a level of mutual tolerance and compromise.
One good reason for joining a mixed flock is to achieve safety in numbers. With many pairs of eyes on the lookout, it is much more likely that a threat will be spotted. As an individual you can invest much more of your time in feeding whilst others are watching for predators.
The acoustic qualities of warning calls are very similar when comparing different finch species. Therefore, if just a single bird calls, there will be instant recognition and all will respond.
Another good reason for joining forces is to increase the chances of locating food. You do not want to waste energy searching, so the best strategy is for you and your relatives to team up with other individuals of your species and with flocks of similar species.
Some of Exeter's winter finches are likely to be migrant birds. They possess no local knowledge so it is vital for them to join up with the residents.
The arrival of a very energetic Labrador, tail a-wagging and nose into everything, sent the finches up into the trees. A moment or two later and the flock was on its way again. Birds of a feather (and of a similar feather) flocking together.
