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The mountain blue bird build nests to attract females and exhibit aggression towards other males during breeding season. Which of the following is likely to give the birds maximal evolutionary fitness?

a) stronger aggressive behaviour only during egg laying

b) stronger aggressive behaviour during nest building rather than during hatching of eggs

c) stronger aggression when egg is first laid than during nest building

d) greater aggression during hatching eggs than during nest building

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Can you provide some of your thoughts on what the answer should be (and why?)? I personally think it is too less information to decide upon, but taking a thought-out guess, I think it can be (b). –  Satwik Pasani Oct 3 '13 at 5:40
    
@SatwikPasani Yes the answer is b. What did you think ? I am really confused with the question. –  biogirl Oct 3 '13 at 17:29
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For the trait to be beneficial it needs to happen before mating. If the male scares off other males but the bird has already mated with another bird it wont be beneficial. So the answer is B, because its the only answer that happens before mating –  von Mises Oct 4 '13 at 15:14

1 Answer 1

up vote 3 down vote accepted

a) stronger aggressive behaviour only during egg laying

c) stronger aggression when egg is first laid than during nest building

d) greater aggression during hatching eggs than during nest building

These all occur after the stage which determines fitness. Egg laying (a and c) and Egg hatching (d) occur after the male has won the right to mate.

b) stronger aggressive behaviour during nest building rather than during hatching of eggs

Assuming the behavior increases mating success and fitness, the answer is B because this is the only strategy that attracts more females and gets rid of rival males before it is too late (i.e. before the female mates). This is also assuming that the female can/will only mate once.

In chronological order the answers run "B,C/A,D" (C & A are really one and the same in my eyes). Mating occurs between B and C.

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