Question

Clutch size vs. age at first reproduction

Two hawk populations (same species, different environment) start with one individuals each. In one population, reproductive adults must attain two years of age, and their average clutch size is 1.5. In the other population, adults can reproduce the first year, but their average clutch size is only 1. Both species are iteroparous. Assume that all adults of reproductive age reproduce every year, and survive.

How many hawks will be in each population after one year?

Two years? Three years?

Four years?

Five years?

Make a diagram to represent individuals of the two populations.

What conclusion can you make about the relative

importance of age of first reproduction vs. clutch size?

Answer 1

After 2 years: Population one will also reproduce and will give two eggs and hence the population will become three sea hawks after two years.

In population 2: the two sea hawk will reproduce to produce two more eggs one from each and the population size will become 4

After 3 years: In population one only the first hawk will reproduce as the second one did not achieved reproduction age yet. So the polulation size will be three (2+1)

Population 2 : 4 hawks reproduce to give four more hawks and the size will be 8 hawks

After 4 years: Population 1: Sea hawk 1 and 2 will reproduce but not the third obtained after 3 years.

So the size will be (2+1+2+1) = 6

Population two: all will treproduce and the size will be 16.

After five years: three of last generation will not reproduce, but three others will reproduce

6+2+2+1 = 11

Population 2: 16 will produce 32 hawks.

Conclusion: It can be seen that the population two have smaller clutch size but lesser reproduction age has a larger population after 5 years on the other hand the population 1 is having a larger clutch size but higher reproduction age has very less population size at the end of five years(less than 50%).

It means there is no direct correlation of reproduction age to the clutch size, it is beneficial only if a avian species has less reproduction age with high clutch size to increase the population.