Tweets,

The observation of mergansers congealing at various sites around the PNW
raises an interesting question: What is the adaptive value of staging?

Presumably those individuals who stage gain a survival or reproductive
advantage over solitary individuals. There may also be a cost to
individuals who join these groups (pathogen transmition, food competition,
etc). Some possible functions of staging may include:

Safety in numbers from predators during migration.
Aggregrating around schooling prey.
Social facilitation for migratory timing or hormone regulation.
Keeping track of other competing males.

Any other possible functions?

Fred