Estimate the population size of a bird species if in 100 sightings along a migration path, 25 were ringed, and it is known that 500 of the birds had been ringed before the sightings?
To estimate the population size of the bird species, we can use the Lincoln-Petersen Index, also known as the capture-recapture method. This method assumes that the population is closed, meaning there are negligible births, deaths, immigration, and emigration during the time of the study.
The formula for the Lincoln-Petersen Index is as follows:
Population Size = (Total tagged individuals in the first sampling * Total individuals in the second sampling) / Number of recaptured tagged individuals
Let's break down the information provided in the question to calculate the estimated population size.
1. The number of bird sightings along the migration path is 100.
2. Out of these 100 sightings, 25 birds were ringed (tagged).
3. It is known that 500 of the birds had been ringed before the sightings.
Using the formula, we can substitute the given values:
Population Size = (25 * 100) / (500 / 100)
First, let's calculate the number of recaptured tagged individuals:
Number of recaptured tagged individuals = Total tagged individuals in the first sampling = 25.
Now, substitute the values into the formula:
Population Size = (25 * 100) / (500 / 100)
= (2500) / (5)
= 500
According to the Lincoln-Petersen Index, the estimated population size of the bird species is 500.