Donna M. Oddy

Habitat-specific breeder survival of Florida Scrub-Jays: inferences from multistate models.

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 Floridas 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.

DO HABITAT POTENTIAL, POPULATION DENSITY, AND FIRES INFLUENCE SCRUB‐JAY SOURCE–SINK DYNAMICS?

The concept of source and sinks can guide conservation, but empirical studies are needed to demonstrate that this concept applies to the real world. We investigated whether the source–sink concept could help to clarify the influence of habitat potential (scrub ridge characteristics), population density, and fires (shrub heights) on Florida Scrub-Jay (Aphelocoma coerulescens) demography and dispersal. We mapped territories and measured survival, recruitment, emigration, immigration, and shrub heights annually for 12 years. We classified territories as oak if they overlapped well-drained ridges, oak–palmetto if they overlapped poorly drained ridges >0.4 ha, and palmetto–oak if they only overlapped poorly drained ridges <0.4 ha. Territory size differed little among these categories but was negatively correlated with the annual number of breeding pairs, which ranged from 12 to 27. Scrub ridge characteristics influenced the locations of sinks and potential sources, whereas population density and fires caused t...

FLORIDA SCRUB-JAY DEMOGRAPHY IN DIFFERENT LANDSCAPES

AISTICT.--Florida Scrub-Jay (Aphelocoma coerulescens) demography and cooperative breed- ing were measured from 1988 to 1993 at two sites (HC and T4) on John F. Kennedy Space Center along Floridas Atlantic coast. The results from HC and T4 sites were compared with published results from the Archbold Biological Station in central Florida. The T4 population increased because of reproductive success and immigration, resulting in a nearly equal non- breeder sex ratio. Nearly all young Florida Scrub-Jays delayed breeding for at least two years after hatching at T4, similar to Archbold. The HC population decreased because of poor nesting success, and the nonbreeder sex ratio was biased towards males. During the first nesting season after hatching, nearly one of every five HC females bred. Pairs with non- breeders (potential helpers) usually had greater reproductive success than pairs without nonbreeders at HC and Archbold, but not T4. Pairs with nonbreeders usually had greater survival than pairs without nonbreeders at Archbold, but not at HC or T4. Female breeder mortality was slightly higher than male breeder mortality at T4 and HC, but not at Archbold. Evidence suggested that predation contributed to differences in demographic patterns be- tween study areas. Received 3 fuly 1995, accepted 21 September 1995. MOST STUDIES on the Florida Scrub-Jay (Aphel- ocoma coerulescens) are from oak-dominated scrub at Archbold Biological Station (Archbold), where optimal habitat is excessively drained, contains many open sandy areas, and has few trees (Woolfenden and Fitzpatrick 1984, 1991). One of the largest contiguous populations of the fed- erally threatened Florida Scrub-Jay occurs on John F. Kennedy Space Center (KSC; Cox 1987). Most KSC habitat is composed of patches of scrub oaks in a matrix of poorly drained flat- woods vegetation and marshes (Breininger et al. 1991, 1995). Because of alterations of the nat- ural fire regime, most KSC habitat has taller vegetation and fewer openings than optimal Archbold scrub (Breininger 1981; Breininger and Schmalzer 1990; Schmalzer and Hinkle 1992a, b). Florida Scrub-Jays inhabit all-purpose terri- tories defended year-round by a permanently monogamous breeding pair (Woolfenden and Fitzpatrick 1984, Breininger et al. 1995). Except where subject to habitat loss and fragmentation, most Florida Scrub-Jays disperse short distances (one to three territory widths) and occupy a territory for life after becoming breeders. Young Florida Scrub-Jays usually remain as nonbreed- ers (potential helpers) with the breeders for at

REPEATED CAPTURE OF BEACH MICE (PEROMYSCUS POLIONOTUS PHASMA AND P. P. NIVEIVENTRIS) REDUCES BODY MASS

Abstract Body mass is commonly used as an indicator of habitat quality and body condition in small-mammal populations. We examined the effects of consecutive days of livetrapping on body mass of 2 federally listed subspecies of beach mice on the eastern coast of Florida: the Anastasia Island beach mouse (Peromyscus polionotus phasma) and the southeastern beach mouse (P. p. niveiventris). Mean mass loss (approximately 0.5 g/recaptured day) was additive and occurred for Anastasia Island beach mice over 2 consecutive days and for southeastern beach mice over 3 consecutive days. Researchers should exercise caution when their trapping protocols call for consecutive nights of trapping.

Preventing Tracking-Tube False Detections in Occupancy Modeling of Southeastern Beach Mouse

Abstract Quantifying habitat occupancy of the southeastern beach mouse Peromyscus polionotus niveiventris is important for managing this threatened species throughout its limited range. Tracking tubes were used to detect the southeastern beach mouse in coastal areas on the federal lands of the Kennedy Space Center, Cape Canaveral Air Force Station, and Canaveral National Seashore. Because this method relied on observations of footprints, detections of beach mice were confounded by the co-occurrence of cotton mice Peromyscus gossypinus, which have wider but slightly overlapping footprint widths. Mice of both species were captured and footprinted using tracking tubes to collect a database of footprints of known identity. These data were used to develop a Bayesian hierarchical model of the cutoff width at which a print could be assigned as a beach mouse with a known probability of error. Specifically, within the model, observed footprint widths were used to estimate a mean and variance of footprint width for...

DETERMINANTS OF NEST SURVIVAL IN A MANAGED FLORIDA SCRUB-JAY POPULATION

Abstract. Bird populations occupying managed transitional habitats often have low nest success because optimal habitat conditions are not maintained. In such cases, quantifying determinants of nest survival provides information for habitat maintenance or restoration. Our goal was to determine the current factors affecting nest survival in a managed but declining population of the Florida Scrub-Jay (Aphelocoma coerulescens) in Merritt Island National Wildlife Refuge. We used an information-theoretic approach and nest-survival models in program MARK to test a priori hypotheses for survival of Florida Scrub-Jay nests. Failure of Florida Scrub-Jay nests was common; only 35% of 614 were successful in producing at least one fledgling. Ninety-four percent of 399 nest failures were due to predation. Nest survival was highest in oak-dominated territories, varied by population center, and decreased with proximity to forest edges, as the season progressed, and with increasing accumulated rainfall prior to the nesting season. Shrub height, a primary focus of current efforts at habitat-quality assessment and management, was not well supported as a determinant of survival of Florida Scrub-Jay nests at Merritt Island. We suggest hypotheses to explain the lack of support for an effect of shrub height, and we conclude that mitigation of low nest survival at Merritt Island may require additional actions.