You will enjoy having a field notebook. Even though it will take work to keep it updated with your latest birding adventures and birding data. There are two important things about having a field notebook. One is that you can look back at that notebook and read about what you saw that day and what you did that day that you barely remember. The second reason is that you can record important data in the field that you will need later. For example if you are doing BBA ( Breeding Bird Atlas) then you need to be able to write down the data you collect if you dont have the official sheet with you or you left it back in the car a few miles away. For those who don't know BBA is where you bird specific areas of the map, and find out how many pairs of each species of bird are nesting in that area. If you cannot be sure if they are nesting you can write down stuff like possible breeder. A field notebook should keep you organized, and if you keep it updated it should provide some info that you will want or need later.
John Mark Simmons