Source–sink theory provides an approach to identify habitat arrangements needed to sustain populations in spatially and temporally varying landscapes. Our objective was to investigate whether source–sink ideas could be applied to quantify how habitat arrangements influenced Florida Scrub‐Jay (Aphelocoma coerulescens) population dynamics, in order to enhance habitat restoration. From 1988 to 2001, we measured reproductive success, survival, immigration, emigration, pair bond fidelity, and the duration of delayed breeding by young. The arrangement of shrub height in each territory was used to classify habitat quality each year, according to the following categories: short (<120 cm tall), optimal (short plus 120–170 cm tall), tall mix (short or optimal and >170 cm), and tall (>170 cm). Annual demographic performance rates were calculated in each territory by summing the recruitment of potential breeders (the number of yearlings produced) and then subtracting the number of breeders that died. The mean demographic performance per breeding pair was −0.57, 0.33, −0.26, and −0.35, respectively, for short, optimal, tall mix, and tall territories. Optimal territories functioned as sources because recruitment exceeded mortality; hence, the optimal territories were net exporters to marginal habitat. Potential breeders were exported to sink territories by active dispersal and by “territory quality transitions,” whereby territories produced an excess of potential breeders while in optimal condition and then became marginal because of shifting territory boundaries and habitat conditions. Short, tall mix, and tall territories functioned as sinks because they were net importers, mortality exceeded recruitment, and because there were no density‐dependent reductions in their demographic performance. The population declined because there were too few optimal territories to offset declines in sinks, which usually had too much tall scrub even though most of the landscape had been burned recently. Successful habitat restoration requires greater emphases on improving habitat quality at the territory scale because this is the fundamental landscape unit related to demography. Source–sink ideas, complemented by territory quality transitions, provide a quantitative approach to directly relate habitat and demographic objectives. Corresponding Editor: D. J. Levey.

Quantifying habitat-specific survival and changes in habitat quality within disturbance-prone habitats is critical for understanding population dynamics and variation in fitness, and for managing degraded ecosystems. We used 18 years of color-banding data and multistate capture-recapture models to test whether habitat quality within territories influences survival and detection probability of breeding Florida Scrub-Jays (Aphelocoma coerulescens) and to estimate bird transition probabilities from one territory quality state to another. Our study sites were along central Florida's Atlantic coast and included two of the four largest metapopulations within the species range. We developed Markov models for habitat transitions and compared these to bird transition probabilities. Florida Scrub-Jay detection probabilities ranged from 0.88 in the tall territory state to 0.99 in the optimal state; detection probabilities were intermediate in the short state. Transition probabilities were similar for birds and habitat in grid cells mapped independently of birds. Thus, bird transitions resulted primarily from habitat transitions between states over time and not from bird movement. Survival ranged from 0.71 in the short state to 0.82 in the optimal state, with tall states being intermediate. We conclude that average Florida Scrub-Jay survival will remain at levels that lead to continued population declines because most current habitat quality is only marginally suitable across most of the species range. Improvements in habitat are likely to be slow and difficult because tall states are resistant to change and the optimal state represents an intermediate transitional stage. The multistate modeling approach to quantifying survival and habitat transition probabilities is useful for quantifying habitat transition probabilities and comparing them to bird transition probabilities to test for habitat selection in dynamic environments.

Many ecosystems are influenced by disturbances that create specific successional states and habitat structures that species need to persist. Estimating transition probabilities between habitat states and modeling the factors that influence such transitions have many applications for investigating and managing disturbance-prone ecosystems. We identify the correspondence between multistate capture-recapture models and Markov models of habitat dynamics. We exploit this correspondence by fitting and comparing competing models of different ecological covariates affecting habitat transition probabilities in Florida scrub and flatwoods, a habitat important to many unique plants and animals. We subdivided a large scrub and flatwoods ecosystem along central Florida's Atlantic coast into 10-ha grid cells, which approximated average territory size of the threatened Florida Scrub-Jay (Aphelocoma coerulescens), a management indicator species. We used 1.0-m resolution aerial imagery for 1994, 1999, and 2004 to classify grid cells into four habitat quality states that were directly related to Florida Scrub-Jay source-sink dynamics and management decision making. Results showed that static site features related to fire propagation (vegetation type, edges) and temporally varying disturbances (fires, mechanical cutting) best explained transition probabilities. Results indicated that much of the scrub and flatwoods ecosystem was resistant to moving from a degraded state to a desired state without mechanical cutting, an expensive restoration tool. We used habitat models parameterized with the estimated transition probabilities to investigate the consequences of alternative management scenarios on future habitat dynamics. We recommend this multistate modeling approach as being broadly applicable for studying ecosystem, land cover, or habitat dynamics. The approach provides maximum-likelihood estimates of transition parameters, including precision measures, and can be used to assess evidence among competing ecological models that describe system dynamics.

Population declines among birds are often linked to habitat change and associated increases in nest predation rates. In species of conservation concern identifying nest predators is an important first step in developing management strategies to mitigate low nesting success caused by depredation. Because predator composition varies geographically and with landscape factors habitat restoration may need to be tailored to reduce locally important predators. We used miniature video cameras to identify nest predators in a population of Florida Scrub-Jays (Aphelocoma coerulescens) significant to conservation. At 22 nests we observed 25 predation events; 22 (88%) of these events were nocturnal. Yellow rat snakes (Elaphe obsoleta) had the highest daily predation rate and accounted for 76% of egg and nestling losses. Florida Scrub-Jays are vulnerable to nocturnal nest predation because their vigilance behavior is ineffective against nocturnal predators, breeders cannot defend against nocturnal predators, and brooding females are at risk of being killed by nocturnal predators. If current habitat restoration efforts do not reduce numbers of yellow rat snakes and improve scrub-jay nesting success, management actions to reduce populations of nocturnal snakes may need to be considered. SINOPSIS. Depredación nocturna de nidos: un obstáculo potencial para la recuperación de las poblaciones de Aphelocoma coerulescensLa reducción en números poblacionales de aves muchas veces ha sido ligada a cambios en el hábitat y aumentos en las tasas de depredación. En especies en donde hay preocupación por su conservación, el identificar los depredadores de nidos es un paso importante en el desarrollo de estrategias de manejo para mitigar el bajoéxito de anidamiento causado por los depredadores. Dado el caso de que la composición de depredadores varía geográficamente y con factores asociados al paisaje, la restauración del hábitat tiene que ser ajustada a modo de reducir depredadores locales que causen gran impacto negativo. Utilizamos cámaras de video en miniatura para identificar los depredadores de nidos en una poblacion de Aphelocoma coerulescens. Observamos 25 episodios de depredación (22 de ellos nocturnos) en 22 nidos estudiados. La culebra Elaphe obsoleta tuvo la tasa más alta de depredación y fue la responsable del 76% de la pérdida de huevos y pichones. Las aves estudiadas resultaron ser muy vulnerables a depredación nocturna, dado el caso de que su vigilancia es inefectiva contra los depredadores nocturnos. Inclusive las hembras que calientan los pichones entran en riesgo de ser depredadas. Si la restauración de hábitat no reduce el número de culebras y mejora eléxito de anidamiento del ave estudiada, se deben considerar acciones de manejo dirigidas a reducir la población de estas culebras.

A growing number of species require conservation or management efforts. Success of these activities requires knowledge of the species' occurrence pattern. Species-habitat models developed from GIS data sources are commonly used to predict species occurrence but commonly used data sources are often developed for purposes other than predicting species occurrence and are of inappropriate scale and the techniques used to extract predictor variables are often time consuming and cannot be repeated easily and thus cannot efficiently reflect changing conditions. We used digital orthophotographs and a grid cell classification https://ntrs.nasa.gov/search.jsp?R=20110024058 2018-05-13T02:08:21+00:00Z scheme to develop an efficient technique to extract predictor variables. We combined our classification scheme with a priori hypothesis development using expert knowledge and a previously published habitat suitability index and used an objective model selection procedure to choose candidate models. We were able to classify a large area (57,000 ha) in a fraction of the time that would be required to map vegetation and were able to test models at varying scales using a windowing process. Interpretation of the selected models confirmed existing knowledge of factors important to Florida scrub-jay habitat occupancy. The potential uses and advantages of using a grid cell classification scheme in conjunction with expert knowledge or an HSI and an objective model selection procedure are discussed.