There are often local scale maps of parks, lakes and other features that can be used to draft a map and set it to scale. Once you finish an outline map mark in relative density of tricolors, areas used only by redwings and other features. These details will help you refine your estimate of numbers. Repeat visits later in the breeding season are encouraged to determine the fate of active colonies. Under no circumstances should you enter an active colony or otherwise disturb the birds while attempting to census them.
Some colonies provide a good look from a distant vantage point and can be observed at leisure.
If possible, coordinate your survey efforts with others in your area. If two or more parties cover the same site get together and arrive at an agreed upon estimate of numbers if possible. By late April, all tricolors usually are associated with colonies. If you find scattered small flocks in the vicinity of colonies report them as you have in the past. All-male flocks are males associated with breeding colony females that are incubating.