Black Cormorants

By chance at 2:30 this afternoon I was bringing in the washing when I was amazed to count 1,497 Black Cormorants over a 40 – 45 minute period flying over the back of my property. The birds were in flocks as large as 60 down to smaller flocks of 2 and 3. With the BC were 6 Little Pied Cormorants and 7 Pelicans. All birds appeared to be flying south from Ningi / Bribie Island / Toorbul area heading south towards Brisbane. Would love to know where all these Cormorants might have been feeding north of me. Jude