I'm not an experienced birdwatcher, so please forgive me if this is a stupid question!
I've been out twice in the last week, and both times I have seen several different species of birds together, but behaving as if they were a single flock. I've read about birds becoming more gregarious in winter, but I assumed this meant 'gregarious with their own species' not 'gregarious with other species'. But in both of the cases I observed, birds of different species seemed to be working together.
- On a field on the edge of the Peak District (near Redmires) I saw a large group of birds feeding on the ground. On closer view, they appeared to be around 100 fieldfares, a few redwings (perhaps 40?), and many starlings (100+). Occasionally, a group of all three would rise into the air, fly around in a circle, and land again. Meanwhile, some starlings separated themselves on telegraph wires, but then rejoined this strange 'mixed flock' later on. All three seemed to feed together very peacefully.
- On a patch of heathland near the edge of Sheffield, I saw a large group of goldfinches, yellowhammers, and redpolls on birch and alder trees, eating the seeds. When alarmed, they all flew off and relanded together., in much the same formation, on the next tree However, other birds nearby were not part of this mixed flock - the long-tailed tits, great tits, were very much feeding separately.
Is this caused by pressure of food resources - are the birds so desperate to get food that they are willing to work/eat together more than might be the case at other times of year?
As Alan says we can often get mixed flocks of particularly smaller birds gathering together in winter. The reason behind this is often thought to be either more eyes to look out for danger or more eyes seeking food and pass this information on. This must be a major point in winter time when food can be very scarce.
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