Winter bird use of the Chinese tallow tree in Louisiana

Chinese tallow (Triadica sebifera) is a non-native invasive tree that is of particular concern in the Southeastern United States. It has become naturalized in a variety of habitats and can be found in monospecific stands. The use of tallow woodlands by overwintering birds is poorly documented. I compared use of tallow woodlands to use of bottomland hardwood forests by birds in the Mermentau River Basin, Louisiana. Species richness and evenness were greater in the bottomland hardwood sites. Three species were more abundant in tallow woodlands, six species were more common in bottomland hardwoods, and six species exhibited no difference between habitats. Information-theory methodology was used to determine the relative importance of woodland type and certain landscape variables to species richness and bird abundance. Model-averaged parameter estimates and relative Akaike weights were calculated. In most cases, woodland type was a better predictor of species richness and abundance than percent forest cover, distance to nearest forest patch, or the number of forest patches within 1 km. Energy assimilation of tallow fruit by captive birds was measured to determine if apparent metabolizable energy differed between bird species and plant species. Assimilation of tallow fruit pulp differed significantly between birds. Yellow-rumped Warblers (Dendroica coronata) exhibited the highest assimilation of tallow, followed by American Robins (Turdus migratorius) and then Northern Cardinals (Cardinalis cardinalis). Yellow-rumped Warblers, which where more common in the tallow woodlands, were able to metabolize tallow fruit more effectively than wax myrtle (Morella cerifera) and poison ivy (Toxicodendron radicans) fruit. Metabolization of wax myrtle and poison ivy fruit did not differ significantly. Cardinals metabolized deciduous holly fruit (Ilex decidua) more efficiently than either hackberry (Celtis laevigata) or tallow. Overall, bottomland hardwoods supported more bird species and exhibited a higher measure of species evenness. Tallow may provide an alternate food source for some species and could potentially influence the local winter distribution of Yellow-rumped Warblers

Cationic Alkylaluminum-Complexed Zirconocene Hydrides: NMR-Spectroscopic Identification, Crystallographic Structure Determination, and Interconversion with Other Zirconocene Cations

The ansa-zirconocene complex rac-Me_2Si(1-indenyl)_2ZrCl_2 ((SBI)ZrCl_2) reacts with diisobutylaluminum hydride and trityl tetrakis(perfluorophenyl)borate in hydrocarbon solutions to give the cation [(SBI)Zr(μ-H)_3(Al^iBu_2)_2]^+, the identity of which is derived from NMR data and supported by a crystallographic structure determination. Analogous reactions proceed with many other zirconocene dichloride complexes. [(SBI)Zr(μ-H)_3(Al^iBu2)_2]^+ reacts reversibly with ClAl^iBu_2 to give the dichloro-bridged cation [(SBI)Zr(μ-Cl)_2Al^iBu_2]^+. Reaction with AlMe_3 first leads to mixed-alkyl species [(SBI)Zr(μ-H)_3(AlMe_x^iBu_(2−x))_2^]+ by exchange of alkyl groups between aluminum centers. At higher AlMe_3/Zr ratios, [(SBI)Zr(μ-Me)_2AlMe_2]^+, a constituent of methylalumoxane-activated catalyst systems, is formed in an equilibrium, in which the hydride cation [(SBI)Zr(μ-H)_3(AlR_2)_2]^+ strongly predominates at comparable HAl^iBu_2 and AlMe_3 concentrations, thus implicating the presence of this hydride cation in olefin polymerization catalyst systems

Culture, Utility or Social Systems?:Explaining the Cross-National Ties of Emigrants from Borsa, Romania

Emigrants from Borşa, Romania, display two quite distinct patterns of ties with their community of origin: migration to Italy is discernibly transnational, with a strong reliance on migrant networks; while migration to the UK is more individualistic, with emigrants shunning interaction with compatriots and retaining only weak ties to Borşa. We argue that prevalent theories of cross-national ties fail adequately to explain this divergence. Instead, we draw on systems theory to explain the discrepancy in terms of divergent conditions for societal inclusion. In Italy, incorporation into parallel, unofficial structures of work, welfare and accommodation encouraged a reliance on cultural criteria for maintaining social ties. In the UK, migrants were obliged to integrate into state-sponsored systems, encouraging the relinquishing of ethnic ties in favour of more strategic networking to facilitate societal inclusion