Abstract:

The degradation of critical nesting islands for colonial waterbirds has prompted a move to rehabilitate eroding islands in Texas. In the last decade, large investments of money (>$27 million) have been, and will continue to be, committed towards colony island projects along the Gulf Coast as recognition grows that existing islands are facing threats, which could leave entire areas without nesting habitat. To date, island creation and rehabilitation projects have been largely the product of opportunity, with location and design largely a function of engineering feasibility and available funding. The ”build it and they will come” approach has yielded some good outcomes for birds, but predicting the degree to which species will benefit from islands in particular locations and with certain physical features has been based on expert opinion with high uncertainty and no understanding of the contribution of a rehabilitated island to the regional population of birds. Therefore, a prioritization tool that reduces uncertainty in management decisions by developing a data-driven model incorporating bio-geophysical constraints, as well as economic considerations, is needed to prioritize islands that have the greatest potential to increase waterbird populations on the Texas coast, and by extension for the Gulf of Mexico region. The objective of the Colony Island Network Design and Implementation (CINDI) Project, is to develop a Geographic Information System (GIS)-based prioritization model from stakeholder input and long-term bird nesting data and calibrate the model with stakeholder knowledge and field data on foraging habitat and colony characteristics. The end result will be a tool to prioritize a network of colony islands and sites on the Texas coast that have the highest potential for enhancing waterbird nesting and provide the maximum conservation benefit for colonial waterbirds, accounting for bio-geophysical constraints, relative sea level rise, as well as economic feasibility and social factors. Pursuant to the above objectives, we will produce datasets of long-term bird nesting productivity data for five focal species (Great Egret [Ardea alba], Tricolored Heron [Egretta tricolor], Reddish Egret [Egretta rufescens], Caspian Tern [Hydroprogne caspia], and Black Skimmer [Rhynchops niger] using drone-derived imagery of transects collected weekly at up to 20 colony islands during the breeding seasons of 2024, 2025, and 2026. Imagery will be stitched together in Agisoft Metashape and the resulting orthomosaic will be scanned for nests, which will be identified to species and tracked weekly until fledging or failure occurs. Daily nest survival and overall nest survival for each focal species will then be calculated for each island. This dataset includes orthomosaic GeoTIFFs (.tif) of full colony island surveys that are performed at least once during the breeding season.