Advantages of gregarious vs solitary behaviour?

Question

I'm trying to explain why birds (specifically wildfowl) are gregarious during the winter and solitary during the summer. I think that in winter, birds are gregarious to reduce the risk of predation and to share foraging information. But gregariousness also brings with it competition, and because birds have offspring to feed in the summer, they trade-off increased predation/loss of information with reduced competition. Does this sound correct?

Answer 1

Interesting question! There is a lot of potential detail here, but, in general, waterfowl (eg ducks, geese) are solitary during the spring breeding season when they form male-female pairs to mate, lay eggs, brood and raise their young. They're solitary during this period to reduce interference during mating, competition for nesting habitat and to avoid drawing the attention of predators. As their offspring fledge, waterfowl often move north, forming increasingly large flocks as they gather in highly productive lakes and wetlands. They become more gregarious (socially active) both as a consequence of the fact that they're converging in the most productive areas and in order to take advantage of the benefits of group formation in avoiding predators and, in some instances, feeding. During this time, they moult and eat as much as possible to store fat reserves for their migration south in the fall. Most waterfowl fly south in flocks (ie maintaining that gregarious behavior), as more experienced birds lead the way during the migration, following known routes and stopping at key locations along the way. In other words, there's a significant benefit to younger, inexperienced birds in learning from the older birds. There are additional biomechanical advantages to flying in a flock too. During this migration, waterfowl forage and roost together--again, taking advantage of the improved ability to detect and respond to predators and forage effectively. Individuals from some species will also begin to court and pair; traveling in a group increases the number of potential partners.