If bird nests are declining in a protected area, which investigation is most suitable?

Correct answer: Check breeding sites, trees, food and disturbance

Direct answer: Option A is correct. A fall in bird nests may indicate fewer suitable trees, loss of breeding sites, less food, predators, disease, pollution, or disturbance from people, vehicles, noise, tourism, or construction. A proper investigation should therefore examine breeding sites, tree cover, food availability, and disturbance, and compare present observations with earlier records. Option A is correct because it searches for several possible causes instead of guessing from one clue. Option B is wrong because bird colour usually does not explain why nests are declining. Option C is wrong because ticket numbers show visitors or sales, not the direct ecological cause, and they may not even measure all disturbance. Option D is wrong because removing more nests would worsen the problem and destroy breeding evidence. Conservation requires cause analysis followed by suitable action, such as protecting nesting trees and reducing disturbance. Memory cue: fewer nests means check habitat, food, and disturbance.