While being led by Michael through the jungle, Michael, Jack, Kate, Sawyer and Hurley had a seemingly giant, green bird swoop down over their heads. Hurley asked if the bird screeched his name and Sawyer replies "It sure did... right before it crapped gold." ("Live Together, Die Alone, Part 1")
Gulls appeared during an apparent migration. Claire wanted to catch one after noting that they were tagged. Desmond, believing that an attempt by Charlie to catch a gull would result in his death, convinced Charlie not to help and then thwarted Claire's attempts to catch one with Jin and Sun. Soon after, Desmond retrieved a gull by himself for Claire. She and Charlie then attached a message to the captured gull and set it free, hoping for the message to be found by the outside world. ("Par Avion")
Assuming that the flock consisted of the same species as Claire and Desmond's captured specimen (an adult bird), they are Silver Gulls (Larus novaehollandiae), resident gulls of Australia, New Zealand, and New Caledonia. They do not migrate outside of their year-round range and do not venture far out to sea. This fact could mean one of three things; the Lost staff simply don't understand the Silver Gull's habits (unlikely, seeing as they specifically chose an Australian gull while filming in Hawaii); the gulls were NOT banded by ornithologists (bird scientists), but by Dharma (speculative) or someone else keeping a population on the island (like the Polar Bear); or the Losties are much closer to Australia/New Zealand/New Caledonia than they think.
The message attached to the seagull reads:
"To whom it may concern: We are survivors of Oceanic Flight 815. We have survived on this island for 80 days. We were six hours into the flight when the pilot said we were off course and turned back toward Fiji. We hit turbulence and crashed. We've been waiting here all this time--waiting for rescue that has not come. We do not know where we are. We only know you have not found us. We've done our best to live on this island. Some of us have come to accept we may never leave it. Not all of us have survived since the crash. But there is new life, too, and with it, there is hope. We are alive. Please don't give up on us."
Charlie said that Claire wrote this message.
After Brian wouldn't pay attention to Walt's report on birds, a bird ran into the window. Brian seems to think Walt had something to do with it. Walt had been reading a page about the "Bronze Cuckoo". ("Special")