Rostam E. Mirzadi1, David A. Essian1, Liam G. Wolff1, Dale E. Gawlik1

Harte Research Institute, Texas A&M University-Corpus Christi, 6300 Ocean Dr, Corpus Christi, Texas, USA. 

Effective management of coastal waterbird populations requires integrating scientific research aimed at addressing uncertainties with on-the-ground management decisions. Along the Texas coast, islands provide breeding habitat for >26 species of colonially nesting waterbirds, including 4 species of special management concern; however, factors affecting nest survival and productivity are largely unknown. During the 2022–2025 breeding seasons, we collaborated with land managers to monitor 3,348 nests of five colonial waterbird species at 26 breeding colonies using a quadcopter drone to determine which factors affect nest survival and productivity. Using logistic exposure models, we found that Tricolored Heron (Egretta tricolor) had the greatest overall survival (mean, 95% CI, n) (85.4%, 83.0–87.4%, 547 nests), followed by Caspian Tern (Hydroprogne caspia, 82.8%, 79.8–85.4%, 477 nests), Great Egret (Ardea alba, 81.4%, 78.6–83.9%, 587 nests), Reddish Egret (Egretta rufescens, 74.5%, 70.4–78.1%, 358 nests), and Black Skimmer (Rynchops niger, 56.4%, 54.2–58.5%, 1,380 nests). Parameters affecting nest survival varied among species, but nest age, timing, and colony density affected most species. Older nests had higher survival for Great Egret, Reddish Egret, Black Skimmer, and Caspian Tern. Early nest initiation was associated with higher survival for Great Egret, Tricolored Heron, and Caspian Tern. High colony density increased survival for Reddish Egret and Caspian Tern. These results provide a baseline understanding of breeding biology and, through collaboration with managers, support targeted conservation actions and prioritization of colony islands for rehabilitation.