The Rock of Gibraltar is dominated by a dense cover of maquis and garrigue, including many important fruit-bearing shrubs that support large passerine populations on passage and during the winter.
Gibraltar is a well-known migratory bottleneck site for birds of prey, with an estimated 250,000 raptors crossing the Strait in a season. If the winds are right then most of these pass over Gibraltar, and numbers may in fact be higher. It is also a stop-over site for passerines and near-passerines, with a rapid turnover of birds on passage during both northward and southward migration.
BirdLife International (2018) Important Bird Areas factsheet: Rock of Gibraltar. Downloaded from http://www.birdlife.org on 16/12/2018.