Ready or not, it’s the red tide red knots
This week has been a doozy for wildlife in the SW Florida area. One of our sister organizations in Sanibel, CROW (Center for the Rehabilitation of Wildlife), admitted over 90 red knots in less than 24 hours. These small shore birds appeared to have been affected by red tide and were in critical condition. Since there were so many, CROW reached out to neighboring facilities, including our own Peace River Wildilfe Center, and transferred some of the patients to be tube-fed and supported until the toxins could be flushed from their systems.
The red knot is in the sandpiper family. While its breeding plumage is a striking red, the winter plumage is an unremarkable gray and white, easily overlooked on the beach next to so many other shorebirds that differ only in minute details. It is known for its extraordinarily long migration from the breeding grounds in the arctic tundra to the wintering habitat in Tierra del Fuego, over 9,300 miles. The rufa subspecies, which is the one we see migrating through Florida, is listed as a federally threatened species due to the effects of climate change, costal development (their preferred habitat), and horseshoe crab overharvesting in the Delaware By area (an important food source during spring migration.)
Red tide is the common name given to an algal bloom, an unusually high concentration of aquatic microorganisms in the water, which can cause a reddish or brownish tint especially as seen from afar. In the Gulf of Mexico that organism is Karenia brevis and occurrence in late summer or early autumn is not uncommon. It is a natural phenomenon, but may be exacerbated by nutrient run-off from fertilizers. The presence of the organisms can cause a depletion of dissolved oxygen in the water. They also produce a toxin (brevetoxin) that paralyzes the central nervous system of fish so they cannot breathe. The asphyxiated fish are in turn eaten by other fish or birds and the toxin is passed on to the next victim. This toxin can also become airborne as waves crash on the beach breaking open the algae cells and releasing the toxin to become an ocular and respiratory irritant.
Bivalves like clams and oysters appear to be unaffected by the toxin, but they do accumulate it. Humans can become seriously ill by eating tainted crustaceans. Tiny coquina clams are a staple of the red knot’s diet as they pass through Florida beaches. From the symptoms exhibited, we assume these red knots stopped along the Sarasota coastline where red tide has been reported. The birds made it as far as Fort Myers when a storm forced them to land on the beach there. By that time the toxins had gotten the better of the birds and they were too weak to take off again.
The first group of 15 birds transferred to PRWC died within 24 hours of admission. The birds were basically paralyzed. While we were able to support them, giving them fluids and medications to try to flush the toxins, the paralysis of their respiratory tracts proved to be too advanced. The second group of 15, more alert on admission, is doing better. We have lost only two of those birds, and some of them are getting stronger already. A few are standing and a couple are starting to eat on their own. We have been gavaging them (feeding through a tube) with a special fish-based formula. As they are able to stay sternal and hold their heads up, we feed them chopped smelt. They are all getting antibiotics and antiprotozoal medications to try to alleviate the damage to the GI tract by the toxins.
The rehabbers and volunteers at PRWC have been struggling to keep up with all the demands of these critically ill patients. On top of that, the regular admissions do not stop. We have seen the usually high number of baby squirrels, the fortunately unusual gun-shot barred owl and everything in between. Ready or not, the red tide red knots are here and PRWC is up to the challenge, thanks to our supporters and donors who make it possible for us to treat orphaned and ill wildlife.
by–Robin Jenkins, DVM
