Thought I would post another inquiry about bird behavior. For the past two summers (in August), I've witnessed a very large group of double crested cormorants on Biscayne Bay near Chicken Key. I estimate the number of birds to be range from about 100 to 150. They were swimming in open water, close together and do not appear to be doing anything obvious like fishing or preening. One or two on the periphery seemed to do some diving but not catching fish. While the birds were hanging out in the water, laughing gulls came around and began to dive in and around the group of cormorants. The birds were fishing but why they chose to do it near the cormorants is a mystery to me. The first time I witnessed this, the cormorants became agitated by the gulls and one by one began to fly off to another spot on the bay.
There is a rookery near by and year round the area is crazy with cormorants. All summer I watch the fledglings grow and begin to swim and fly and wondered if these groups I see are the young cormorants (although they have the emerald eyes of an adult).
Any ideas as to what these birds are doing?
Thank you!
Connie
Last edited by Connie Mier; 07-19-2009 at 04:16 PM.
Reason: correction
Hi Connie- Waterbirds often feed in mixed-species groups. I see cormorants and gulls feeding together at one of my field sites quite often. In these cases it is clear that they use each other's presence to indicate the possibility of food. I think what you might be observing is gulls reacting to the sight of a flock of cormorants by "prospecting" for food in amongst them. The cormorants may be there for some reason other than food (although it is probably ultimately food-related) but the gulls don't know this so they use a simple rule of thumb- " if you see cormorants or other gulls bunched up in a flock, it may indicate food nearby so go see if there is".