Habitat use by loggerhead sea turtles <Emphasis Type="Italic">Caretta caretta</Emphasis> off the coast of eastern Spain results in a high vulnerability to neritic fishing gear

Previous studies of loggerhead sea turtles have concluded that drifting longlines were the main threat for immature specimens in the western Mediterranean, because immature loggerhead sea turtles mainly inhabit oceanic waters. However, recent aerial surveys have revealed large numbers of immature loggerhead sea turtles over the continental shelf of eastern mainland Spain, where turtles are exposed to neritic fishing gears but not to drifting longlines. We satellite-tracked seven loggerhead sea turtles (minimum straight carapace length (SCLmin) range: 36.5–55.0 cm) to assess whether the turtles in this region are vagrants from the adjoining oceanic regions or whether these loggerheads mostly inhabit the continental shelf. Satellite-tracking revealed that six of the tagged turtles avoided the oceanic realm and made extended use of the continental shelf, whereas only one individual could be considered a true vagrant as it avoided the continental shelf and primarily used the oceanic habitat. These results are in sharp contrast with those previously reported for immature loggerhead sea turtles of similar size from the south-western Mediterranean and fit well a relaxed ontogenic model that was recently proposed for loggerhead sea turtles in the central Mediterranean. Furthermore, these results demonstrate the vulnerability of loggerhead sea turtles of eastern mainland Spain to neritic fishing gears, as three of the seven turtles died and one was bycaught incidentally while being tracked over the continental shelf.     

Dealing with double trouble: consequences of single and double herbivory in Brassica juncea

In their natural environment, plants are often attacked simultaneously by many insect species. The specificity of induced plant responses that is reported after single herbivore attacks may be compromised under double herbivory and this may influence later arriving herbivores. The present study focuses on the dynamics of induced plant responses induced by single and double herbivory, and their effects on successive herbivores. Morphological (leaf length, area and trichome density) and chemical changes (leaf alkenyl and indole glucosinolates) in Brassica juncea were evaluated 4, 10, 14 and 20 days after damage by the specialist Plutella xylostella alone, or together with the generalist Spodoptera litura. To assess the biological effect of the plant’s responses, the preference and performance of both herbivores on previously induced plants were measured. We found that alkenyl glucosinolates were induced 20 days after damage by P. xylostella alone, whereas their levels were elevated as early as 4 days after double herbivory. Trichome density was increased in both treatments, but was higher after double herbivory. Interestingly, there was an overall decrease in indole glucosinolates and an increase in leaf size due to damage by P. xylostella, which was not observed during double damage. S. litura preferred and performed better on undamaged plants, whereas P. xylostella preferred damaged plants and performed better on plants damaged 14 and 10 days after single and double herbivory, respectively. Our results suggest that temporal studies involving single versus multiple attacker situations are necessary to comprehend the role of induced plant responses in plant–herbivore interactions.     

Cuckoo growth performance in parasitized and unused hosts: not only host size matters

The quality and quantity of food delivered to young are among the major determinants of fitness. A parental provisioning capacity is known to increase with body size. Therefore, brood parasitism provides an opportunity to test the effects of varying provisioning abilities of different-sized hosts on parasitic chick growth and fledging success. Knowledge of growth patterns of common cuckoo, Cuculus canorus, chicks in nests of common hosts is very poor. Moreover, no study to date has focused on any currently unused hosts (i.e., suitable cuckoo host species in which parasitism is currently rare or absent). Here, I compare the growth performance of cuckoo chicks in nests of a common host (the reed warbler, Acrocephalus scirpaceus) and two unparasitized hosts (the song thrush, Turdus philomelos, and the blackbird, Turdus merula). Parasitic chicks were sole occupants of the observed nests, thus eliminating the confounding effect of competition with host chicks. Experiments revealed striking differences in parasitic chick growth in the two closely related Turdus hosts. Cuckoo chicks cross-fostered to song thrush nests grew much quicker and attained much higher mass at fledging than those in nests of their common reed warbler host. Alternatively, parasitic chicks in blackbird nests grew poorly and did not survive until fledging. I discuss these observations with respect to host selection by parasitic cuckoos.     

Ecological Correlates of Whooping Crane Use of Fire-Treated Upland Habitats

The only remaining wild population of the endangered Whooping Crane ( Grus americana ) winters in salt marsh habitats of the Texas (U.S.) coast. Whooping Cranes are known to respond and utilize nearby upland habitats after a tire treatment has been applied. We investigated several factors that may attract Whooping Cranes to recently burned sites at Aransas National Wildlife Refuge between 1982 and 1994 and whether cranes utilize upland habitats primarily in response to a recent fire treatment or whether they occur regularly on uplands regardless of burning. We evaluated the effect of different years, burn site location, date of burn, and acorn production on crane use of specific burn sites. Crane use was determined with ground surveys from 1982 through 1985 and from weekly aerial surveys between 1986 and 1994. Whooping Cranes used fire-treated upland habitats to a significantly greater extent than unburned sites. The response of cranes to recently burned sites was greatest immediately after fire treatment and declined with time. No significant difference was found in crane use of burned sites among different years. Similarly, time of burn and acorn production had no significant effect on crane use of fire-treated habitats. Crane use among specific burn units differed significantly. We suggest that Whooping Cranes may be using fire-treated upland habitats to feed on recently killed vertebrates and invertebrates plus recently exposed plant items. Because cranes primarily inhabit salt marsh habitats, the availability of alternate food sources may be of considerable importance, particularly during years when marsh foods are scarce. But because it appears that areas must be burned to facilitate use by Whooping Cranes, we suggest that the extent of prescribed burning be based on reduced availability of marsh food resources and not on acorn production estimates alone.     

JES Special issue in Mercury Biogeochemistry and Fate

正The global and regional redistribution of mercury within the environment is of primary importance to both natural ecosystems and human health.The ratification of the Minamata Convention on Mercury by 91 parties represents a key step in protecting ecosystems and future societies from increasing mercury accumulation.However,key to the continued quanti-     

The importance of exogenous contamination on heavy metal levels in bird feathers. A field experiment with free-living great tits, Parus major

Feathers have been used extensively as non-destructive biomonitors for heavy metal pollution. Birds excrete heavy metals into growing feathers during moult. After feather formation, the feathers become isolated from the rest of the body, suggesting that the feathers contain information of circulating heavy metal concentrations in the blood at the time of their development. However, heavy metal levels may change due to exogenous contamination, resulting in higher concentrations in feathers that are exposed most to exogenous conditions. We studied the effect of exogenous contamination in free-living adult great tits (Parus major) by measuring--within the same individual--the concentrations of twelve heavy metals (Ag, Al, As, Cd, Co, Cu, Fe, Hg, Mn, Pb, Tl and Zn) in three outermost tail feathers that were exposed to exogenous contamination for different periods of time. In particular, for each individual heavy metal levels in the removed left outermost tail feather were compared with levels in the regrown left and the right outermost tail feather, that were both removed 40 days after removal of the original left feather. This study revealed that, with the exception of mercury, the concentration of all heavy metals was significantly different among the three outermost tail feathers. Our results suggest that concentrations of most heavy metals build up with increasing age of the feather, indicating that exogenous contamination may be an important source of heavy metals in feathers. However, we found no significant differences in Hg concentrations and we found only small differences in Zn concentrations among tail feathers. Consequently, the concentrations of zinc and mercury in feathers are probably primarily due to endogenous deposition.     

Improving National-Scale Carbon Stock Inventories Using Knowledge on Land Use History

National-scale inventories of soil organic carbon (SOC) and forest floor carbon (FFC) stocks have a high uncertainty. Inventories are often based on the interpolation of sampled information, often using a number of covariables to help such interpolation. The rationale for the choice of these covariables is not always documented, despite the fact that many local-scale studies have identified the factors explaining spatial variability of SOC and FFC stocks. These studies indicate, among others the importance of long-term land use history. Despite this, information on the effects of land use history has never been used to explain variability of carbon stocks in national-scale inventories. We designed an alternative method to improve national-scale inventories of SOC and FCC for the Dutch sand area that takes stock of the findings of detailed case studies. Determinants for SOC and FFC stocks derived from landscape-scale case studies were used to map national-scale spatial variability and to calculate national totals. The resulting national-scale spatial distribution was compared with the SOC stock map from the current Dutch greenhouse gas inventory. Using land use history to explain SOC variability decreased the error of the SOC stock estimate in 60 % of the area. The error in FFC stocks decreased in half of the forest area after including soil fertility, tree species, and forest age as explanatory factors. Estimates with reduced uncertainty will make land use and land management a more attractive and acceptable mitigation option to reduce emissions of greenhouse gases for the LULUCF sector.     

Statewide Survey of Hormones and Antibiotics in Surface Waters of Delaware

Water‐quality surveys have confirmed the presence of hormones and antibiotics in surface waters of the United States, which may be of concern to aquatic life. We investigated the concentrations of hormones and antibiotics in surface waters of the state of Delaware to determine – how they compared against environmental thresholds, how they varied across the state, and if they were correlated with land use type. Fifty surface water locations were sampled during early spring and late summer. Water samples were initially screened with ELISA followed by analysis with LC/MS/MS. The measured ranges of hormone concentrations were: 0‐3.71 ng/l for estrone, 0‐4.65 ng/l for estrone‐3‐sulfate, and 0‐6.27 ng/l for 17β‐estradiol. The measured ranges of antibiotics were: 0‐3.30 ng/l for sulfamerazine, 0‐10.74 ng/l for sulfamethoxazole, and 0‐2.29 ng/l for tetracycline. The predicted no‐effect concentration (PNEC) for estrone was exceeded for three samples and the PNEC for 17β‐estradiol was exceeded for 11 samples. In general, concentrations and detection frequencies were lower in the summer than the spring. The highest concentrations of hormones and antibiotics were spatially distributed in agricultural and urban areas; however, the correlations between land use type and the concentrations were weak. This study was the first statewide survey of hormones and antibiotics for Delaware and provided important baseline data on these emerging contaminants.