This spring and summer, while the pandemic raged across our state, it seemed the Florida coast was clear of the red tide and blue-green algae that beleaguered nesting efforts in 2019. Despite the necessary reduction in volunteer-assisted monitoring efforts, our team began the 2020 nesting season with optimism, especially as stay-at-home orders promised fewer people on area beaches to disturb sensitive nesting colonies. Tropical Storm Cristobol, which hit in June, threw a curve ball, but the resilient birds adjusted and renested.
But, everything changed quickly for the Black Skimmers at one southwest Florida colony. Biologist Adam DiNuovo has been monitoring birds using the stretch of beach on Marco Island from Tigertail Beach to the tip of Sand Dollar for five years.
This past June, he started encountering skimmer chicks that were limping around the colony with swollen ankles and became concerned. He helped transport several sick birds to rehabilitation facilities but they did not survive. He also sent bird remains to Florida Fish and Wildlife Conservation Commission for analysis. More than onethird of the chicks at this colony was lost to an invisible enemy that later was identified as sepsis.
According to DiNuovo, “several banded birds were among the casualties and these were big, healthy chicks when banded ten days prior to being found dead. The season high count of chicks was hovering around 220 before this outbreak intensified.”
In total, about 100 young skimmers were lost to this disease in 2020, with few clues to its origin.
Sepsis, also called septicemia, is a bacterial infection in the blood that causes irreparable damage to internal organs. It is known to infect the young, the old, and people (or animals) with weakened immune systems. In 2020, this disease was only observed affecting Black Skimmer chicks at the Marco Island colony. More research is needed to better understand the cause of this infection.
The sepsis summer of 2020 caps off a series of mortality events in the region. In summer of 2018, while conducting his banding research on Black Skimmers, DiNuovo noticed that many of the chicks he captured were underweight and fledged with poor body condition. Later, necropsies on their remains found coccidiosis and moderate levels of brevetoxin (from red tide).
That fall, DiNuovo began observing sick and dying Common Terns and Sandwich Terns loafing on this same stretch of beach. Analysis of their remains confirmed the presence of brevetoxicosis (directly caused by red tide) and Bisgaard Taxon 40-induced sepsis. A manuscript published in the Journal of Comparative Pathology, authored by professional pathologists and co-authored by DiNuovo, describes this multi-species mortality event and the bacteria isolated from bird remains on Marco Island.
According to Audubon Florida Director of Bird Conservation Marianne Korosy, Ph.D., DiNuovo and Audubon volunteers have been instrumental in documenting mortality, transporting sick birds, and working with FWC pathologists and others to identify the pathogens responsible for these illnesses. This work will continue in 2021 and going forward until we identify and treat the causes — which may be from multiple sources.