One example of a record card is
This is only an example. Many types of cards are obtainable from pigeon supply stores. If you do an online search, you might use search terms such as "breeding record keeping."
This particular form is demonstrated in this video https://youtu.be/y4LocVdT55M
Computer programs also provide loft management applications, such as
Again, this is only an example. Several computer loft management programs are available through various dealers. If you do an online search, you might use search terms such as "breeding software for pigeons."