Technical Report

Middle Rio Grande Yellow-billed Cuckoo Study Results – 2024 Isleta Pueblo to Elephant Butte Reservoir, New Mexico, Upper Colorado Basin Region; Technical Report No. ENV-2025-002

URL: https://webapps.usgs.gov/mrgescp/documents/2024-Middle-Rio-Grande-Yellow-billed-Cuckoo-Study-Results.pdf

Date: 2025/04/01

Author(s): Reibsome E., Bullard M., Moore S.D.

Publication: Prepared by Bureau of Reclamation, Technical Service Center, Denver, Colorado.

Abstract:

During the summer of 2024, Bureau of Reclamation personnel conducted presence/absence surveys for the federally threatened Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis; YBCU) within the Middle Rio Grande (MRG) riparian corridor between the Isleta Pueblo and Elephant Butte Reservoir, New Mexico. In accordance with established protocols, surveys were conducted during the YBCU breeding season (June 15 to August 15) to determine the distribution and abundance of YBCUs throughout this stretch of the MRG.

During the 2024 breeding season, 511 YBCU detections were recorded within the MRG study area. From these detections, 125 territories were delineated; 69 were possible breeding pairs, and 56 were probable breeding pairs, as defined in Halterman et al. (2016). As in previous years, the San Marcial Reach contained the largest breeding population of YBCUs within the MRG study area, with 351 detections and an estimated 88 breeding territories. Forty-six of these territories were in the exposed pool of Elephant Butte Reservoir. The Bosque del Apache Reach produced the second highest number of territories — 16 from 64 detections. The Escondida Reach included 9 territories from 38 detections, the Tiffany Reach included 5 territories from 19 detections, the San Acacia Reach included 4 territories from 18 detections, and the Sevilleta Reach included 3 territories from 20 detections. The Belen Reach had a reduced number of surveys and produced zero territories and one detection.