Rookery Island Productivity for Priority Waterbird Species

Principal Investigator

Rookery islands are being eroded by ship traffic, storms, and rising seas, leading managers to begin putting 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 which is a key component of their conservation value. With roughly 200 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. Some rookeries initiate every year but repeatedly fail, whereas 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 scarce resources used for management of rookery islands on the most beneficial islands.

The project leverages information provided by a project led by the Harte Research Institute for Gulf of Mexico Studies (HRI) and initiated in 2022 to develop an island prioritization tool that incorporates traditional expert knowledge, the available food in the habitat around each colony, and the productivity of the four priority species above for a small set of islands. The productivity portion of the HRI project will be incorporated into this project at no cost to 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.

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. Sampling will occur at two large rookeries (e.g., Shamrock Island and Pita Island) and 18 rookeries that span the range of smaller island types. The results of the project will also support ongoing efforts by the Coastal Bend Bays and Estuaries Program (CBBEP) and partners to prioritize funding for island management and restoration efforts towards projects that will have the greatest impact on coastal bird populations.