Question

Experiments have shown that when bird males characterized by longe tails when manipulated and added longer tails, they do much better than males with "normal" tail feathers (getting most of copulations and nests). Briefly explain why given this measurable advantage, we do not see in nature birds with these long tail feathers? It would seem that Sexual Selection would favor those individuals with longer than normal long feathers right, but we do not see them in nature? Why? (Short Essay)

Answer 1

The conservation of a character in nature depends upon the adaptive fitness of the trait to the given environmental conditions. i.e. adaptive fitness of a trait ultimately determines the frequency of a trait (Allele) in a given population.

Each trait can have adaptive as well as deleterious effects on the fitness of an organism. If the advantageous effects of the trait are greater than adverse effects, the trait would be conserved and maintained in the population.

In the given case, longer tails provide a selective advantage for mate choice. However, longer tails may provide several other disadvantages to the bird.
1. It may make the bird easier to be spotted by a predator
2. It may make the bird fly slower
3. It may make the bird easy to be captured by the predator
4. It may make the bird difficult to catch its prey.

This phenomenon was elegantly explained by the Handicap theory (Proposed by an Israeli scientist Amotz Zahavi)