I had read on a trip report it could be crowded, because many school trips went there, but Monday was usually quiet. I found out why: The Guandu Nature Center was closed on Mondays. I could have gone back, but I decided to walk around the premises, an area that is outside the reserve and has some bird-watching fascilities (!) The first hours I didn't see much out of the usual. (Prinia's Cisticola's and Chinese Bulbuls) except for an enormous amount of Black-crowned Night Herons. They seemed to be everywhere!
Cattle Egret, Magpies and Myna's were also noted, but they didn't come out much during the rain. By the end of the afternoon it cleared a bit and I started seeing the Ibis flying over toward their nesting ground in the mangroves.