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

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 a 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.