Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Etats Unis → 2021 → Nest Survival and Post-fledgling Survival, Movement, and Habitat Use of Bendire’s Thrashers (Toxostoma bendirei) in the Chihuahuan Desert

New Mexico State University (2021)

Nest Survival and Post-fledgling Survival, Movement, and Habitat Use of Bendire’s Thrashers (Toxostoma bendirei) in the Chihuahuan Desert

Salas, Allison J

Titre : Nest Survival and Post-fledgling Survival, Movement, and Habitat Use of Bendire’s Thrashers (Toxostoma bendirei) in the Chihuahuan Desert

Auteur : Salas, Allison J

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) 2021

Résumé
Passerine species within the continental United States and Canada are declining at rapid rates. One species exhibiting steep population declines is the Bendire’s Thrasher (Toxostoma bendirei), an arid land passerine endemic to the Southwest. To properly conserve for species in decline, investigation into the demographics of local populations is required, especially measures of reproduction. In this study, I modeled Bendire’s Thrasher nest survival in relation to temporal variables, and vegetation variables at the nest site and within the breeding territory and monitored post-fledgling survival, movement and habitat use. For nest survival, I monitored Bendire’s Thrasher nests (n = 75) across Hidalgo and Grant counties in New Mexico and Cochise county in Arizona during the 2018 and 2019 breeding seasons. Nest initiation differed by a month between the two years of study, where average initiation date was later in 2018 compared to 2019. The daily nest survival estimate was 0.969 ± 0.005 (95% CI = 0.956-0.978), resulting in cumulative nest survival estimate of 0.414 ± 0.040 (95% CI = 0.339-0.450) for a single 28-day nesting attempt. Predation pressure was strong and multiple predators were documented consuming eggs and nestlings. Nest survival was primarily influenced by temporal variation, including year, time, and nest age, but not strongly influenced by vegetation characteristics within the nest site and territory. Findings from this study highlight an important breeding hotspot within the bootheel of New Mexico, plasticity in nest initiation dates, and annual and seasonal differences in nest survival. This study will serve as a baseline estimate for nest survival of Bendire’s Thrashers and may be used for comparison of estimates in other habitats and in future years. I also examined juvenile Bendire’s Thrasher survival during the post-fledgling period, movement patterns from the nest site and habitat use. I attached transmitters to 25 nestlings and tracked 19 fledglings using radio-telemetry. I modeled fledgling survival in relation to year, time, and body condition. I also modeled habitat use in relation to vegetation characteristics at both used and paired-available sites. Fledgling weekly survival was estimated as 0.800 ± 0.05 (95% CIs 0.694-0.876), resulting in a cumulative survival rate of 0.38 ± 0.10 (95% CIs 0.197-0.570) (38% chance of survival) for 4.3 weeks (30 days) post-fledging, based on the average age of dispersing fledglings. Predation pressure was strong on fledglings as they were not capable of flight for the first few days after leaving the nest site and were vulnerable to predators. Distances moved from the nest site increased with fledgling age, and in general, fledglings remained with family units (siblings and adults) on the breeding territory until the family unit dispersed. Fledgling habitat use was positively influenced by overall shrub cover and tall shrubs, and negatively influenced by overall shrub density, which resulted in less bare ground for foraging. The overlap in habitat use from the nesting and post-fledging stages highlights the need to conserve breeding hotspots.

Présentation

Aperçu du document (ProQuest)

Page publiée le 5 décembre 2021