Rookery Island Productivity for Priority Waterbird Species

Rookery islands are being eroded by ship traffic, storms, and rising seas, leading managers to put significant resources toward rookery island rehabilitation.  Their efforts are guided by the Texas Colonial Waterbird Survey, an annual statewide effort to document the location and size of colonial waterbird rookeries.  However, there is no corresponding information on how many fledglings rookeries produce – a key component of their conservation value.  With roughly 300 rookery islands on the Texas coast, agencies will not have enough funds to intensively manage all rookery islands.  Nor do all islands have the same potential to increase waterbird nesting populations.  While some rookeries repeatedly fail, others seem to consistently produce fledglings, although the numbers have rarely been measured.  Information to help prioritize islands that have the greatest potential to sustain waterbird populations based on actual reproductive performance of birds is urgently needed to guide the selection of islands for restoration and to focus funds for management of rookery islands on the most beneficial islands.

The project leverages information from a pilot study led by the Harte Research Institute for Gulf of Mexico Studies with support from the Knobloch Family Foundation that used drones to measure the nesting success of five priority species (Great Egret, Reddish Egret, Tricolored Heron, Caspian Tern, and Black Skimmer) on rookery islands in the upper Laguna Madre of Texas and Corpus Christi Bay.  This project expands the pilot study area northward to Galveston Bay.

The expected outcome of this assessment is an improved understanding of the degree to which different rookery island types produce fledglings and therefore have the greatest potential to increase colonial waterbird populations.  The results of the project will also support ongoing efforts by the Coastal Bend Bays and Estuaries Program and partners to improve rookery island management and restoration efforts.  Information from this study will be incorporated into the “Colony Island Network Design and Implementation” project to help develop an island prioritization tool to rehabilitate colony islands on the Texas Coast.  Inclusion of this project will boost both the sample of islands where productivity is measured and the power of the analysis to test for differences in reproductive performance among island types.