We love the Bronx zoo, and were just there on Memorial day. It's been updated fairly recently, although I think the sea-bird Aviary is still closed for renovations, (my 7-year old LOVES penguins.) If you buy the full ticket, (there's discounts through a lot of bank programs,) the gorilla trail and butterfly garden alone make the price worth it, and if you have kids, it includes the bug carousel.
Enjoy!