Post-fledging survival, movements, and habitat associations of Gray Vireos in New Mexico

Abstract

Annual population growth in songbirds can be particularly sensitive to post-fledging survival, but research and management are frequently biased toward the nesting stage. Post-fledging information is particularly scarce for species breeding in desert bird communities, many of which have collapsed in recent decades. During 2017-2019 at Sevilleta National Wildlife Refuge, New Mexico, USA, we used radio telemetry to monitor survival, movements, and habitat associations of 90 fledgling Gray Vireos (Vireo vicinior), a desert-dwelling species of conservation concern. We used logistic exposure models to investigate the relationship between fledgling survival and habitat features at two spatial scales. Overall, we estimated that 51 ± 8% of fledglings survived the monitoring period. All mortalities occurred during the first 12 days post-fledging and were attributed to predation and environmental exposure. In daily survival models focused on predation mortalities, age was the strongest predictor of survival. Daily survival rate was not related to any habitat variables we measured. Percent tree cover used by birds during the first 12 days post-fledging was similar to that of nesting sites and greater than that of random locations. Similarly, fledglings occupied individual trees and shrubs with lateral vegetation cover similar to that of nest locations. Minimum daily distance traveled, distance from nests, and variance associated with these measures, all increased with age. Except for the use of a larger area, habitats used by Gray Vireos during the post-fledging period were similar to those used for nesting in our study population, indicating that maintenance of large patches of moderately dense juniper is desirable for this species. More study is needed from populations in less pristine and more heterogeneous landscapes. More broadly, given the importance of first-year survival in demographic models and the declines of dryland birds, information is needed on the postfledging period of many desert songbirds. Survie après l'envol, déplacements et associations avec l'habitat de Viréos gris au Nouveau-MexiqueRESUME_. La croissance annuelle des populations de passereaux peut être particulièrement sensible à la survie après l'envol, mais la recherche et la gestion sont souvent orientées vers le stade de la nidification. Les données suivant l'envol sont particulièrement rares pour les espèces nichant au sein de communautés d'oiseaux de désert, dont beaucoup se sont effondrées au cours des dernières décennies. En 2017-2019, au Sevilleta National Wildlife Refuge au Nouveau-Mexique (États-Unis), nous avons utilisé la radiotélémétrie pour suivre la survie, les déplacements et les associations avec l'habitat de 90 Viréos gris (Vireo vicinior) prêts à l'envol, une espèce désertique dont la conservation est préoccupante. Nous avons utilisé des modèles logistiques d'exposition pour étudier la relation entre la survie des oisillons et les caractéristiques de l'habitat à deux échelles spatiales. Dans l'ensemble, nous avons calculé que 51 ±...

Post-fledging survival, movement patterns, and habitat associations of Bendire's Thrashers ( Toxostoma bendirei ) in the Chihuahuan Desert

“…While some studies have also found that survival was not associated with specific vegetation characteristics (Hovick et al 2011, Fischer et al 2022, research in more complex habitats has shown that vegetation characteristics influence fledgling survival (King et al 2006, Moore et al 2010, Jenkins et al 2016. Research on another desert passerine, the Gray Vireo (Vireo vicinior), also found similar habitat associations for nesting and rearing fledglings, and no association between fledgling survival and measured habitat characteristics (Fischer et al 2022).…”

“…The median duration of passerine parental care has been reported to be 16 days for 126 north-temperate species (Russell 2000), and 77 species exhibit parental care for less than 20 days (Russell 2000). Bendire's Thrashers may benefit from prolonged parental care after fledging, which could lead to increased body mass, and reduced fledgling movements, and thus, higher recruitment (Tarwater and Brawn 2010, Vitz and Rodewald 2011, López-Idiáquez et al 2018, Fischer et al 2022.…”

“…Predation is the main cause of post-fledging mortality (Suedkamp Wells et al 2007, Davis and Fisher 2009, Vitz and Rodewald 2011, Raybuck et al 2020. Survival estimates vary with fledgling age; they tend to be lowest immediately after fledging and increase as fledglings become increasingly mobile (Jenkins et al 2016, Naef-Daenzer and Grüebler 2016, Raybuck et al 2020, Fischer et al 2022. Generally, fledglings gradually move away from the nest site and occupy locations with dense cover that provide concealment and food resources (Vega Rivera et al 2000, Yackel-Adams et al 2001.…”