Video documentation of predators and nest defense at Bachman’s Sparrow nests

Abstract

Bachman's Sparrow (Peucaea aestivalis) is a species of conservation concern throughout its range and an effective indicator of healthy pine savanna ecosystems in the southeastern United States. Their secretive nesting behavior means that many aspects of their nesting ecology, including specific knowledge of the nest predator community and nest defense behaviors are insufficiently described. This information is an important first step in determining the link between management practices and reproductive success. We monitored 86 Bachman's Sparrow nests, 65 with constant video surveillance, to describe the nest predator community, cause-specific nest mortality rate, and nest defense behavior. We identified 12 predator species from 37 predation events. Snakes were the dominant predator type, responsible for 51% of identified predation events, followed by mesomammals (19%), small mammals (16%), and others (14%). Nest defense behavior included ptiloerection and chasing but was rare (16% of predation events) and effective 67% of the time. Daily nest survival was 0.936 (CI: 0.894-0.967) and neither season, year, nor site explained a significant amount of variation in estimates of cause-specific daily nest mortality. Raccoons were not detected at Bachman's Sparrow nests despite being one of the most common nest predators in other avian nest surveillance studies. Future studies should explore the link between prescribed fire, nest predation, and snake abundance or activity in southeastern pine savanna. Documentation vidéo de prédateurs et de comportements de défense aux nids chez le Bruant des pinèdes RÉSUMÉ. Le Bruant des pinèdes (Peucaea aestivalis) est une espèce préoccupante dans l'ensemble de son aire et est un bon indicateur d'écosystèmes de pinèdes sains dans le sud-est des États-Unis. Leur comportement discret au nid explique que de nombreux aspects de leur écologie de nidification soient encore mal décrits. Cette connaissance est une première étape importante si l'on veut établir les liens entre les pratiques de gestion et le succès de reproduction. Nous avons surveillé 86 nids de Bruant des pinèdes, dont 65 sous vidéo continue, afin de décrire la communauté de prédateurs de nids, le taux de mortalité au nid spécifique aux causes et les comportements de défense au nid. Nous avons identifié 12 espèces de prédateurs à partir de 37 cas de prédation. Les serpents étaient les principaux prédateurs, responsables de 51 % des cas de prédation identifiés, suivis des mésomammifères (19 %), des petits mammifères (16 %) et d'autres prédateurs (14 %). Les comportements de défense au nid comprenaient la ptiloérection et la poursuite, mais ils survenaient rarement (16 % des cas de prédation) et étaient efficaces 67 % du temps. La survie quotidienne au nid était de 0,936 (CI: 0,894-0,967), et ni la saison, l'année ou le site n'ont expliqué l'importante variation des estimations de mortalité quotidienne au nid spécifique aux causes. Les ratons laveurs n'ont pas été détectés aux nids de bruants, bien qu'ils se soient avéré un des p...

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