MIDDLE TWP. — The World of Birds aviary will be permanently closing its doors this spring at the Cape May County Zoo, according to zoo officials. They explained as one of the oldest attractions on the premise, years of tropical conditions has taken its toll on the building, and necessary maintenance and repairs have become unsustainable. Some birds will remain at the zoo, while others will be relocated across the country. The building, which opened in May of 1998, will be removed. The zoo hopes to bring new and upgraded avian habitats to its visitors.