Complex sentence: Whilst he is working for the Duke of Hampshire, the Monkey and the Giraffe notice an armed burglar stealing the Duchess' jewellery, whereupon the Pelican traps the thief in the pouch of his enormous bill and later gives him to the police.
Split into simpler sentences: Whilst he is working for the Duke of Hampshire, however, he and the Giraffe happen to notice an armed burglar stealing the Duchess' jewellery. The Pelican traps him in the pouch of his enormous bill and he is handed over to the police.