Consider the following scenario .A drought hits the habitat of a semi-aquatic bird population. All ponds dry up, and fish populations decline. There are two groups of birds in the population that differ in leg length and diet. Long-legged birds eat fish, while short-legged birds eat insects. The drought has little effect on insect populations

What is the main selective pressure in this scenario?

Oleg length
Odrought
Ofish population
OInsect population