We investigated relationships between warbler abundance and survival rates measured on a Puerto Rican wintering site and rainfall patterns measured on the wintering site and in regions where these warblers breed, as estimated using stable-isotope analysis (dD) of feathers collected from wintering birds. We banded birds using constant-effort mist netting from January 1989–2003 in the Gunica Forest of southwestern Puerto Rico. Blackand- white Warblers (Mniotilta varia), American Redstarts (Setophaga ruticilla), and Ovenbirds (Seiurus aurocapilla) dominated the Neotropical migrant capture totals each winter, with resulting sample sizes large enough to estimate survival rates. Estimates of capture probability from survival modeling allowed us to estimate abundance from mist-netting capture totals for Black-and-white Warblers and Ovenbirds. Stable-hydrogen isotopes showed that the three focal species came mostly from the eastern United States. Black-andwhite Warbler abundance was related to rainfall total deviations from normal in Gua´nica Forest, and Ovenbird abundance was related to total annual rainfall in the United States. Survival models with rainfall covariates were weakly supported overall, but apparent survival of Black-and-white Warblers and American Redstarts was negatively related to rain during the first 6 months of the year at Gua´nica, and Ovenbird survival was related to rainfall during the spring in the southeastern U.S. Abundance and apparent survival exhibited similar, species-specific patterns of association with rainfall for Black-and-white Warblers and Ovenbirds. Winter rainfall was important to demographic parameters of Blackand- white Warblers, and breeding-season rain was important to Ovenbirds.

Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satellite-derived measure of habitat moisture, we identified a moisture gradient across home ranges of radiotracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the late-winter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable season-long declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that high-quality habitats may be limited and that there may be competition for them. The habitat-linked variation in performance we observed suggests that habitat limitation could impact individual and population-level processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of high-quality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted.

High abundance and production of juvenile Penaeus spp. in tropical estuaries has been attributed to high concentrations of mangrove-derived detritus in the nursery habitats. Examination of the diets of Penaeus notialis, P. subtilis, and P. brasiliensis in the mangrove-fringed Laguna Joyuda, Puerto Rico showed that even the smallest juveniles are predators consuming capitellid polychaetes (20-38% of diets) and amphipods (20-76%). Less than 25% of the diets was detritus. Ontogenetic variation in diets was greater than interspecific variation, and there was no evidence for dietary separation among the sympatric species. Seasonal shifts in foods reflected abundance patterns of macrobenthic prey species. Despite the consumption of prey organisms generally classified as detritivorous, stable carbon isotope ratios in the penaeids (-18.1 to -15.0%0), their food items (-18.8 to -17.7°/00), and primary producers indicated that shrimps and the majority of sediment dwellers in Laguna Joyuda obtain most of their carbon from benthic a1gae (-14.4°/00) and not from mangrove detritus (- 25.0 to - 22.9°/00).

Couplings between land use and marine food webs in tropical systems are poorly understood. We compared land–sea coupling in seven sites around Puerto Rico, differing in the degree of precipitation and urbanization, by measuring d13C and d15N in producers and consumers. d15N values were influenced by human activity: the food web from sites near urbanized centers was on average 1‰ heavier in d15N compared to undeveloped sites. This is most likely due to wastewater inputs from septic systems relatively near the shoreline. Changes in d13C were best explained by differences in the degree of marine influence. Where terrestrial inputs from a major river dominated, d13C values were lighter, whereas sites further from land and in locations exposed to oceanic currents had heavier d13C values, characteristic of a marine source of dissolved organic carbon. We found no significant effect of precipitation on connectivity in spite of a twofold difference in annual average rainfall between the north and south coast. The results suggest there is some connectivity between land and sea in Puerto Rico, despite high rates of evaporation relative to precipitation.