On Friday, December 4th, 2020, Michelle Kerr Florida Fish and Wildlife Conservation Commission’s OPS Public Information Specialist, responded to the writer’s request for information on the cause of black skimmer chicks to die off at the nesting colony on Sand Dollar Island during the months of July and August. Below is her response.
There was an unusual mortality event of black skimmer chicks and fledglings at Big Marco Pass CWA this year. Sick skimmers displayed swollen joints and were unable to fly or walk. Any skimmers found alive but sick in the colony were taken to licensed and permitted wildlife rehabilitation facilities. Veterinary staff diagnosed bacterial arthritis in several of the admitted birds.
FWC sent suitable carcasses for necropsy to the Southeastern Cooperative Wildlife Disease Study (SCWDS) which provided a final diagnosis of bacterial dermatitis, tendinitis, and osteomyelitis, with multiple bacteria isolated (Enterococcus faecalis, Staphylococcus aureus, Serratia marcescens, Escherichia coli and Pseudomonas aeruginosa).
While these tests confirmed the cause of mortality in the young skimmers, the source of the pathogens is presently unknown. Adult black skimmers in the colony did not display the same evidence of illness as observed in the young birds during this event.
Multiple bacteria species (identified above) were isolated from the joints of two black skimmer fledglings. Due to the severity of their illness, the two birds were euthanized in late August at a wildlife rehabilitation center. The carcasses were shipped to a diagnostic lab in Georgia where the findings were determined. We do not know how the birds became infected with these bacteria.
At the November 18th BARC meeting, Adam DiNuovo the Lead Biologist for the Black Skimmer banding project at Sand Dollar Island mentioned three bacteria as possible causes of the death of the black skimmer chicks. Those were: Pseudomonas aeruginosa, Enterococcus faecalis, and Escherichia coli.
Per Ms. Kerr’s December 4th report, the following additional bacteria were also found—for a total of 5.
Staphylococcus aureus: is a bacterium that is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is a common cause of skin infections including abscesses, respiratory infections and food poisoning.
Serratia marcescens: is commonly involved in hospital-acquired infections particularly catheter-associated bacteremia, urinary tract infections and wound infections.
At the November 18th BACR meeting, member Andrew Tyler asked DiNuovo the following question regarding Staphylococcus infection, “Do birds peck each other a lot or do they incur bites or cuts?” Bacterial infection (staph) could have entered their system that way.
Per DiNuovo, one theory was that birds get cuts from sand spurs and as the chicks wandered to the water at 12 days old, bacteria could have entered their bodies. Member Tyler added that “there had to be a heck of bacterial concentration in the water to infect the birds.”
DiNuovo also stated that this is not something that is spread from bird to bird; it is either in the water that the birds are standing in or it is coming back in the food they are eating.
This Incident Raises Many Questions
Will we ever know the true origin of the bacteria that caused the infection and death of the chicks? What will FWC do with this information? Will the regulatory agencies (FWC for wildlife & Florida Department of Environmental Protection for water quality) have to wait for another episode to do something about it? You can only fix the problem if you know where it is coming from.
Collier County’s Healthy Beaches Program test the waters from Tigertail Lagoon every two weeks. The water is tested for the presence of Enterococcus faecalis and Escherichia coli bacteria. The other bacterial classes found in the birds are not tested as part of any routine screening.
More Upbeat Message on the Colony
Since 2017, BACR has supported the Black Skimmer banding project. Marco Island has one of the largest colonies of nesting black skimmers in the Eastern United States. According to DiNuovo, he is now seeing the birds he banded in 2017 (first year of banding) returning to Marco as adults and raising chicks of their own.
He also shared news that banded birds from Marco have been sighted at Carlos Point in Ft. Myers Beach and also in Pinellas County and the reverse is also happening. This is important to DiNuovo to see these birds in different locations interchanging genes and strengthening the overall fitness of the birds.
DiNuovo is upbeat about the Black Skimmer project in Marco as it has received a lot of community awareness and involvement since 2015.