Final answer:
Using the mark and recapture method, and by calculating (80 * 60) / 15 = 320, we estimate that there are approximately 320 birds in the sanctuary.
Step-by-step explanation:
Nasser is using a method called mark and recapture which is commonly used in ecology to estimate animal populations. The formula he can use to estimate the total number of birds is (first catch * second catch) / number of marked birds in second catch. In this case, the first catch is 80 birds, the second catch is 60 birds and the number of marked birds in the second catch is 15.
The calculation would thus look like this: (80 * 60) / 15 = 320. So, based on these catches, Nasser would estimate that there are approximately 320 birds in the sanctuary.
Learn more about mark and recapture