Being a bird biologist is not so different from being a detective. You set up cameras to catch your subject in action. You dig through their trash in search of evidence. And as Audubon Florida Rooftop Biologist Kara Cook will tell you, uncovering a clue is a thrilling moment that often leads to more questions than answers. 

It was late July when Cook climbed atop one of the gravel rooftops where she manages an American Oystercatcher nesting site, preparing to close out the nesting season by removing cameras and chick shelters. Under one of the shelters, she made a discovery: dozens of shells clustered on the gravel rooftop. 

“I was really surprised by the amount and variety of shells,” Cook says. “And I’ve never seen large piles like that.” 

Typically, American Oystercatchers eat—you guessed it—oysters, along with mussels, clams, and other mollusks. Under the chick shelter, Cook and her colleagues identified at least four different types of shells: oyster, mussel, pinnidae or pen shell, and banded tulip shell. The pile of shells provides clues that Audubon coastal biologists can use to better understand the different challenges rooftop-nesting oystercatchers face compared to their more traditional counterparts that nest on the beach. 

Whether they nest on a beach or a rooftop, oystercatchers forage along the shore, waiting for the tide to deliver their prey and breaking or prying shells open to gobble up the meaty insides or bring it back to their chicks. Chicks that hatch in beach nests get to observe the whole process from the moment they hatch, and may even begin foraging on their own before their parents stop feeding them. 

Chicks hatched in rooftop nests don’t get to watch their parents forage until they can fly on their own, at around five weeks old. They must wait on the rooftops, ideally under the chick shelters that rooftop biologists like Cook install to protect them from predators and sun exposure, while their parents make the journey to the beach. These rooftop-nesting parents also expend more energy to bring food to their chicks than the beach-nesters, and they have limited capacity for what they can carry back to the rooftop. 

This is a known challenge for rooftop nesters, but what researchers don’t yet know is how long rooftop-hatched chicks stay with their parents after fledging, compared to how long beach-hatched chicks stay with their parents. Audubon’s coastal team works with Florida Fish and Wildlife Conservation Commission staff to band birds when the opportunity arises, so resighting those banded birds in the future could provide some answers, but it will take many sightings to draw any conclusions. On August 8, Anchor Steward Shannon Curran resighted a banded rooftop nester with two of its fledges on St. Pete Beach—a sure sign that this family is doing well and staying together for at least a few weeks after they leave the rooftop. 

Cook and her colleagues on Audubon Florida’s coastal team hope to learn more about how long rooftop oystercatcher chicks stay with their parents after they fledge, and how they eventually learn to forage without those early lessons. For now, it’s another mystery to be solved. 

Banded Birds: See Something, Say Something!

Bird banding is like scientists putting a note in a bottle and tossing it back into the sea of migration. The note only gives us information if someone observes and reports it when the bottle arrives on a far-off shore. Thanks to resighting reports from around the state, we are learning more about the movements, populations, and breeding success of our banded species.

If you see a banded bird:

• Note date, time, and location—with GPS if possible
• Note the species
• Note which leg or legs have bands
• Note the color and order of bands—upper or lower. If the band or flag has an alphanumeric code, try to note the code.
• Take a picture! Digital cameras work great through scopes or binoculars and sometimes enable eagle-eyed biologists to record numbers off of the band.

Report a band at reportband.gov