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Most papers on the physical condition of birds during spring migration focused on food availability preceding migratory take-off. Only a few studies examined the effect of climate conditions at the wintering grounds upon autumn arrival on bird physical condition later on. Here, we hypothesized that environmental conditions upon arrival at the wintering grounds, and not necessarily upon departure, have a crucial carry-over effect on bird spring migration. Using 29,000 observations of the lesser whitethroat, Sylvia curruca, and the eastern Bonelli’s warbler, Phylloscopus orientalis, we found temperatures upon arrival at the African wintering grounds to be the only climatic variable correlated with birds’ body state upon spring stopover in Israel, six months later. Two different mechanisms could explain these results. One possibility is that high temperatures create favorable conditions for insect activity, which allows rapid recovery from autumn migration and hence successful winter survival and maintenance. Another possible scenario is that harsh conditions, due to the heat and dry environment, cause high mortality, permitting survival of larger individuals which, then, enjoy reduced inter- and intra-specific competition. Whatever the mechanism is, our findings suggest that conditions upon autumn arrival, and not necessarily at the end of winter as traditionally thought, may have a major impact on migrating birds. [ABSTRACT FROM AUTHOR]

Responding differentially to kin and non-kin is known to be adaptive in many species. One example is the inclusive fitness benefits of reducing aggression toward closer relatives. Little is known, however, about the ability of animals to assess differential degrees of genetic relatedness and to respond accordingly with differential levels of aggression. In the present study, we tested whether aggressiveness between body mass-matched pairs of fire salamander ( Salamandra infraimmaculata) larvae covaried with the genetic similarity between them. We quantified aggressiveness at three levels of genetic similarity by selecting pairs within and across pools from recently genotyped populations. We also assessed aggression between pairs of siblings. Aggression and associated injuries decreased as genetic similarity increased across the groups. These findings suggest that cannibalistic salamanders can assess their degree of genetic relatedness to conspecifics and vary their behavioral responses depending on the degree of similarity between them along a genetic relatedness continuum. [ABSTRACT FROM AUTHOR]

Despite its importance in the evolution of central-place foraging strategies, few studies have distinguished between patch use by parent birds for their own consumption vs. patch use for the purpose of provisioning young in the nest. Adult Palestine sunbirds (Nectarinia osea) consume nectar and arthropods, but feed only arthropods to their nestlings. This partial separation of food types allowed us to experimentally test sex-specific trade-offs in parental foraging effort between two patches. A ‘variable’ patch on one side of a pair's territory contained only artificial nectar for parental self-feeding (in varying sucrose concentrations between 0·25 and 0·75 mol kg&sup-1; H2O). A ‘constant’ patch on the other side of the territory contained artificial nectar for parental self-feeding (sucrose concentration = 0·25 mol kg&sup-1; H2O), plus a dish of flightless houseflies for provisioning young. Experimental increases in sucrose concentration in the variable patch led the parents to: (a) consume greater amounts of sucrose solution from this patch; (b) collect more flies from the constant patch to feed their young; and (c) persistently use the 0·25 mol kg&sup-1; H2O feeder near the dish of flies. By titration (gradually changing the sucrose concentration in the variable patch), we demonstrate that at concentrations of 0·47 mol kg&sup-1; H2O for males and 0·55 mol kg&sup-1; H2O for females, the birds spent an equal amount of time foraging in both patches. Therefore, sucrose concentration in the variable patch (for self-feeding only), had to be higher for the females than for the males, in order to balance the additional value females placed upon the flies provided for chick-feeding in the constant patch. These results reflect previously described sex-specific parental roles in this species, with females provisioning young mainly in the nest and males patrolling more and guarding against nest predators. Furthermore, we demonstrate for the first time the fine details of alternative adaptive trade-offs in foraging effort by parent birds when using patches for self-feeding or for delivery of food to the young. [ABSTRACT FROM AUTHOR]

Attempts to study parental care responses of monogamous male orange-tufted sunbirds, Nectarina osea, to experimental tail-weight manipulations of their partners under various brood size conditions. Methods; Results; Discussion.

Studies the effect of male removal on female parental care in the orange-tufted sunbirds, Nectarinia osea. Critical nature of male nest guarding; Deterrence of infanticidal floater males by male orange-tufted sunbirds; Performance of usual levels of nest guarding and sanitation by female sunbirds; Sex specific roles in parental care among sunbirds.

Presents information on a study which tested the hypothesis that adult Orange-tufted Sunbirds would feed on flower nectar but would not feed it to their chicks. Methods and results; Discussion; Conclusion.