Effects of Tropical Cyclones and Other Severe Weather Events on Reddish Egret (Egretta rufescens) Populations in Louisiana, U.S.A.

Abstract

Tropical cyclones (i.e. tropical depressions, tropical storms, and hurricanes) and other extreme weather events directly impacting Louisiana from 2016-21 were examined to determine their effects on adult Reddish Egrets equipped with satellite transmitters in SE (n ¼ 11) and SW (n ¼ 14) Louisiana. Fourteen tropical cyclones (six hurricanes, five tropical storms, one tropical depression, and two extratropical cyclones) impacted Louisiana during the study, and telemetry data were reviewed immediately on and around (61 day) the arrival of each storm to monitor any movements and individual survival. As many as nine of 25 (36%) transmittered Reddish Egrets presumably died from the direct impacts of five tropical cyclones; seven of nine mortalities were associated with three major hurricanes. Mortality was presumed based on stationary GPS fixes for multiple days or the termination of data transmission following a storm. All mortalities were presumed, as no carcasses were recovered. Previous telemetry studies reported Reddish Egrets often survived intense tropical cyclones and direct impacts were not appreciable at the population level. Yet, more than one-third of the transmittered birds in the sample population potentially died from storm-related impacts, and the population may have declined drastically, assuming some unmarked individuals also likely died. Because the Reddish Egret is restricted to coastal habitats, the species appears to be particularly vulnerable to tropical cyclone effects. If predictions of increased frequency and intensity of tropical cyclones by the end of this century are accurate, these storms pose a significant threat to Reddish Egret populations. With accelerated loss and degradation to suitable coastal habitats, protection and restoration of key foraging and nesting sites for sensitive species similar to the Reddish Egret are needed in Louisiana and other disturbance-prone areas along the Gulf Coast.