Possible Clues:

• Bird collection
• Monkey house : monkeys :: ___ : birds
• Ornithological enclosure
• Where birds may be accessed at first, using public transport?
• Where to look at some fliers
• Article going through boundaries of rookery – a place for birds
• A change involving one home for birds
• Where birds of a feather flock together
• Group in circulation taking train where air travel the norm
• Area by railway where air travel the norm?