Survival of juvenile Florida Scrub-Jays is positively correlated with month and negatively correlated with male breeder death

ABSTRACT Juvenile survival in birds is difficult to estimate, but this vital rate can be an important consideration for management decisions. We estimated juvenile survival of cooperatively breeding Florida Scrub-Jays (Aphelocoma coerulescens) in a landscape degraded by fire suppression and fragmentation using data from marked (n = 325) and unmarked juveniles (n = 1,306) with an integrated hierarchical Bayesian model. To assess the combined analyses, we also analyzed these datasets separately, with a Cormack–Jolly–Seber model (marked) and young model (unmarked). Our data consisted of monthly censuses of territorial family groups from Florida Scrub-Jay populations in East Central Florida collected over a 22-year period. Juvenile survival was estimated from July when young Florida Scrub-Jays begin developing independence to March when they become first-year individuals and grouped according to the habitat quality class of their natal territory that were based on shrub height (with intermediate shrub heights being optimal and short and tall shrub heights being suboptimal) and the presence of sandy openings (the preferred open having many sandy openings; closed not having enough). Parameter estimates in the combined analysis were intermediate to the separate analyses. Notable differences among the separate analyses were that suboptimal habitat survival was lower in the unmarked analysis, the unmarked analysis showed a linear effect of time not seen in the marked analysis, and there was an effect of male breeder death in the marked but not unmarked analysis. The combined data analysis provided more inference than did either dataset analyzed separately including juveniles in optimal-closed territories unexpectedly had higher survival than those in optimal-open, survival increased through time, and male breeder death had a negative effect on survival. This study suggests that optimal-closed habitat may play an important role in juvenile Florida Scrub-Jay survival perhaps by providing better cover from predators and warrants further investigation for management implications. How to Cite Carter, G. M. , E. D. Stolen, D. R. Breininger, S. A. Legare, D. K. Hunt, C. D. Schumann, and W. V. Payne (2023). Survival of juvenile Florida Scrub-Jays is positively correlated with month and negatively correlated with male breeder death. Ornithological Applications 125:duad033. LAY SUMMARY Habitat management is an important tool for species conservation in degraded habitat, especially when habitat quality is transitional (i.e. varies with disturbance and succession) and where high-quality habitat is an exporter of individuals to low-quality habitat (i.e. source sink dynamics). Considering how management actions affect all life stages is important. Survival of juvenile birds can be difficult to estimate because of dispersal or migration but may be needed for proper species management. Nonmigratory species offer a unique opportunity to include juvenile survival estimates into management plans. We estimated survival based on resighting marked and unmarked juvenile Florida Scrub-Jays (Aphelocoma coerulescens) using an integrated hierarchical Bayesian model. By also analyzing each dataset separately, we show the strength of using a combined model to make inference. We investigated survival in 3 habitat classes related to shrub height and the amount of open sandy patches that vary according to fire and subsequent shrub regrowth. Juvenile survival was highest in territories with medium height shrubs and few sandy openings. This result is unexpected and may have management implications. Survival increased across the post-fledgling period possibly indicating that juvenile Scrub-Jays learn predator avoidance. Survival was negatively affected by male breeder death, demonstrating the importance of family stability and possibly the number of siblings because larger groups of naïve juveniles attract predators. RESUMEN La supervivencia de los juveniles en las aves es difícil de estimar, pero esta tasa vital puede ser una consideración importante para las decisiones de manejo. Estimamos la supervivencia de los juveniles de Aphelocoma coerulescens, una especie que cría de modo cooperativo, en un paisaje degradado por la supresión de incendios y la fragmentación, utilizando datos de juveniles marcados (n = 325) y no marcados (n = 1,306), empleando un modelo bayesiano jerárquico integrado. Para evaluar los análisis combinados, también analizamos estos conjuntos de datos por separado, con un modelo de Cormack-Jolly-Seber (marcados) y un modelo de jóvenes sin marcar (no marcados). Nuestros datos consistieron en censos mensuales de grupos familiares territoriales de poblaciones de A. coerulescens del centro-este de Florida, recolectados durante un período de 22 años. La supervivencia de los juveniles se estimó desde julio, cuando los juveniles de A. coerulescens comienzan a desarrollar independencia, hasta marzo, cuando se convierten en individuos de primer año, y se agruparon según la clase de calidad del hábitat de su territorio natal, que se basó en la altura de los arbustos (con alturas intermedias de arbustos siendo óptimas y alturas bajas y altas de arbustos siendo sub-óptimas) y la presencia de espacios abiertos arenosos (el espacio abierto preferido tiene muchos espacios arenosos; el cerrado no tiene suficientes). Las estimaciones de los parámetros en el análisis combinado fueron intermedias en comparación con los análisis por separado. Las principales diferencias entre los análisis separados fueron que la supervivencia en hábitats sub-óptimos fue menor en el análisis sin marcar, el análisis sin marcar mostró un efecto lineal del tiempo que no se observó en el análisis marcado, y hubo un efecto de la muerte de los machos reproductores en el análisis marcado, pero no en el análisis sin marcar. El análisis combinado de los datos proporcionó más inferencias que cualquier conjunto de datos analizado por separado, incluyendo que los juveniles en territorios óptimos cerrados tuvieron inesperadamente una mayor supervivencia que aquellos en territorios óptimos abiertos, la supervivencia aumentó con el tiempo y la muerte de los machos reproductores tuvo un efecto negativo en la supervivencia. Este estudio sugiere que el hábitat óptimo cerrado puede desempeñar un papel importante en la supervivencia de los juveniles de A. coerulescens, quizás al proporcionar una mejor protección contra los depredadores, y justifica una investigación adicional para las implicaciones de manejo.