Which of the following is not an example of reproductive isolation?
a. differences in courtship song between two populations of meadowlarks b. difference in the timing of breeding seasons of male frogs
c. differences in food preferences between two populations of birds
d. failure of sperm and egg production in hybrids between two populations of insects

C.differences in food preferences between two populations of birds.

Explanation:

Reproductive isolation is a type of isolating mechanism which may further lead to speciation.

In this type of isolating mechanisms, the two types of organisms are isolated as they are unable to either mate or even if they mate, they fail to produce a viable progeny.

Reproductive isolation can occur due to :

1. Different mating strategies, time or place.

2. Inability to fertilize.

3.Production of a sterile or viable progeny.

Therefore, from the given option differences in food preferences is not a type of reproductive isolation as it does not follow any of the three listed mechanisms.

i think the answer would be a. after sentence 14! i hope i at least a little