This little manuscript sold for $0.35 when it was published in 1950 and provided a thorough summary of information learned from the hot technology of the day: bird banding. The North American Bird Banding Program was formed in response to the Migratory Bird Treaty Act of 1918, which sought to protect birds and regulate the commercial trade of bird feathers.
250,000 or more birds were banded by trained personnel each year but the program relied on information collected from the community. Anyone who found a banded bird was encouraged to mail details to a central office which added it as another data point in their models. Handling thousands of paper scraps must have been challenging in those pre-computer years, but collectively they illuminated the ranges and migration patterns of many species and established the concept of migration flyways. It's also a great example of how we make science stronger when we band together as a community and support government research.
The image on the left shows the "Summer and winter homes of the black and white warbler" as created using banding data available for publication. Compare that with the distribution map shared by All About Birds in the center, and Audubon's Migration Explorer (based on eBird data). It is easy to spot differences between the old and new maps, but there are some pretty obvious differences between the two more modern maps.
The manuscript also had some isochronal migration lines which showed the speed at which various species returned to their North American breeding grounds in the spring.
Compare the relatively early migration of the Canada Goose (left) to the later Gray-cheeked Thrush (right) in these two maps.
These data-fueled maps are a good baseline for any changes that scientists (including community scientists) may be seeing as a result of a warming climate.