How the most widespread African crow,the Pied Crow Corvus albus,depends on man

The frequently reported close association between the Pied Crow and man suggests a possible explanation for the crow's wide distribution throughout sub-Saharan Africa, but the mode and origin of this association have received little attention. In the present study, roadside counts of Pied Crows were made in Madagascar and Cameroon to search for preferred biotopes among natural reserves, artificial pastures, cultivations and towns, while roadside counts in Botswana and Kenya served to compare the Pied Crow and the Somali Crow Corvus edithae, a species probably more similar to common ancestors, in terms of their association with wild and domestic ungulates. The occurrence of the sympatric Cape Crow Corvus capensis, assumed to be a less human-dependent species, was also taken into consideration for the association with ungulates. Pied Crow biotope preference was similar in both Madagascar and Cameroon and the combined data showed a significant preference for artificial pasture over cultivation and artificial pasture over natural reserve, and the preference for artificial pasture over town was near to significance. The combined data of the Pied Crow in Botswana and the Somali Crow in Kenya showed a significant preference for domestic ungulates. However, this preference may have been weaker in Kenya, the Somali Crow being rather similar to the Cape Crow in this respect. The Pied and Somali Crows may have diverged somewhere around Ethiopia and the Pied Crow may have expanded its range by following the environmental changes made by ungulate-raising people, who created new savanna-like biotopes.     

The Crow Corvus corone hybrid zone in southern Denmark and northern Germany

In hybrid zones genetically differentiated populations meet and interbreed. As they result from ongoing divergence and potential speciation, such zones provide opportunities to study how different factors affect this process. One well-known avian hybrid zone is that between the Hooded Crow Corvus corone cornix and Carrion Crow C. c. corone , which extends throughout much of Europe. We compare the current position and width of the zone in southern Denmark and northern Germany with that described in detail by Meise in 1928. A GPS technique was used to determine the geographical position of more than 1000 Crows in established pairs in which all individuals were classified as either Carrion, Hooded or hybrid phenotype. The data show that the Carrion Crow has expanded northwards and that this is most pronounced at the eastern side of the study area. Here the hybrid zone has moved around 19 km. However, the width of the zone seems to have remained stable over time. Possible reasons for why the zone may have moved are discussed.     

Expression of the Axd (axial defects) mutation in the mouse is insensitive to retinoic acid at low dose

The Axd mutation in the mouse acts by an unknown mechanism to cause lumbosacral open neural tube defects and a variety of tail anomalies. Retinoic acid (RA) plays a number of different physiological and developmental roles and has been shown to affect neurulation in mice and other species. Indeed, reports have shown that this biologically active compound (or its metabolites) at low dose can alter the incidence of neural tube defects (NTD) in curly-tail (ct), splotch (Sp), and delayed splotch (Spd) mice, strains that are genetically predisposed to such abnormalities. The aim of the present study was to determine if RA administered under similar conditions would affect the penetrance or expression of the Axd mutation or survival of Axd homozygotes. Axd/+ and +/+ dams were exposed to RA intraperitoneally (5 mg/kg) on D9 postcoitus. No difference in incidence or extent of neural tube defects or other axial anomalies was detected among embryos of Axd/+ dams given RA compared with those administered vehicle only. This finding is consistent with the diversity of gene-controlled steps required for neurulation and the differing sensitivities of specific mutants to rescue by extrinsic agents.     

Co-breeding involving herons and a potential egg predator,the Indian House Crow (Corvus splendens), in Peninsular India

Association between species may strengthen the fitness of the species involved It is not rare that avian species associate on the breeding and feeding grounds. However, a species associated with a potential egg predator is less common. In this study, a synchronized breeding of Indian House Crow (Corvus splendens) and breeding Indian Pond Herons (Ardeola grayii) in urban conditions is reported. Both the crow abundance and the crow nest abundance increased with the number of heronry nests on sites. Crows were mostly observed when flying over or when resting nearby, but they also attempted egg predation from heronry nests. Crows also used the heronry sites for collecting nesting resources, such as twigs, scavenging dead chicks and for stealing the food brought to feed the heronry chicks. A dearth of suitable nesting places and provisions in an urban environment may be the reason why these birds share nesting trees. Vigilant breeding crows, despite their ability to depredate heron nests, may be more beneficial to herons as they are known to mob and distract heron predators, but a full cost-benefit analysis needs to be undertaken.     

Ontogeny of heart rate in embryonic and nestling crows (Corvus corone and Corvus macrorhynchos)

The developmental patterns of mean heart rate (MHR) and instantaneous heart rate (IHR) were investigated in embryos and chicks of altricial Corvuscorone and Corvus macrorhynchos. The MHR of embryos increased linearly with time from 250 beats · min⁻¹ at mid-incubation to 290 beats · min⁻¹ in hatchlings. MHR during the pipping period was maximal, but only marginally higher than in hatchlings. MHR was stable at about 290–300 beats · min⁻¹ during the 1st week after hatching. Spontaneous heart rate (HR) decelerations and accelerations were found in embryos and chicks, disturbing the baseline HR with increasing frequency during development. However, the IHR accelerations developed later and were less frequent than in precocial species. IHR and body temperature decreased during mild cold exposure (23–25 °C) and IHR accelerations were reduced in nestlings during the 1st week. We suggest that the development of parasympathetic control of HR in crows occurs at 60% of incubation, similar to precocial embryos, but sympathetic control may be delayed and suppressed in contrast to precocial embryos. Accepted: 3 March 1999     

Social dominance in captive jackdaws (Corvus monedula)

Social hierarchy was studied in two flocks (14 and 10 individuals, respectively) of captive jackdaws. Parent birds acquired high-ranking positions during the nesting period. Outside the breeding season the hierarchy seemed to be stable. Males generally dominated females. When the top-ranking male arrived at the feeding place it tended to supplant one of the feeding birds rather than choose an unoccupied site.     

Cooperative problem solving in rooks (Corvus frugilegus)

Recent work has shown that captive rooks, like chimpanzees and other primates, develop cooperative alliances with their conspecifics. Furthermore, the pressures hypothesized to have favoured social intelligence in primates also apply to corvids. We tested cooperative problem-solving in rooks to compare their performance and cognition with primates. Without training, eight rooks quickly solved a problem in which two individuals had to pull both ends of a string simultaneously in order to pull in a food platform. Similar to chimpanzees and capuchin monkeys, performance was better when within-dyad tolerance levels were higher. In contrast to chimpanzees, rooks did not delay acting on the apparatus while their partner gained access to the test room. Furthermore, given a choice between an apparatus that could be operated individually over one that required the action of two individuals, four out of six individuals showed no preference. These results may indicate that cooperation in chimpanzees is underpinned by more complex cognitive processes than that in rooks. Such a difference may arise from the fact that while both chimpanzees and rooks form cooperative alliances, chimpanzees, but not rooks, live in a variable social network made up of competitive and cooperative relationships.     

The length of adaptive walks is insensitive to starting fitness in Aspergillus nidulans

Adaptation involves the successive substitution of beneficial mutations by selection, a process known as an adaptive walk. Gradualist models of adaptation, which assume that all mutations are small relative to the distance to a fitness optimum, predict that adaptive walks should be longer when the founding genotype is less well adapted. More recent work modeling adaptation as a sequence of moves in phenotype or genotype space predicts, by contrast, much shorter adaptive walks irrespective of the fitness of the founding genotype. Here, we provide what is, to the best of our knowledge, the first direct test of these alternative models, measuring the length of adaptive walks in evolving lineages of fungus that differ initially in fitness. Contrary to the gradualist view, we show that the length of adaptive walks in the fungus Aspergillus nidulans is insensitive to starting fitness and involves just two mutations on average. This arises because poorly adapted populations tend to fix mutations of larger average effect than those of better-adapted populations. Our results suggest that the length of adaptive walks may be independent of the fitness of the founding genotype and, moreover, that poorly adapted populations can quickly adapt to novel environments.     

Determination of stability constants between complexing agents and At(I) and At(III) species present at ultra-trace concentrations

A competition method is proposed to determine the complexation constants between At(I) and At(III) species and complexing agents. The method, tested with an inorganic ligand, thiocyanate ion (SCN⁻), and an organic macromolecule, thiacalix[4]arenetetrasulfonate (LH₄) is based on solid/liquid separation or liquid/liquid extraction. For the solid/liquid separation, the cationic exchanger Dowex 50X8 was used. The interaction of At(I) and At(III) with the cationic exchanger is specific but could not be described by the expected cation exchange process. Most probably, At(I, III) interacts with a “strong” site (in weak amount) to form a surface complex at the surface of the resin organic skeleton. For the liquid/liquid separation, chloroform, toluene and hexane were used. All solvents extract astatine species with distribution coefficients varying between 0.7 and 120. The extraction process was shown to be independent of aqueous phase characteristics (pH, ionic strength) and was explained by the solvation of astatine species by the organic solvent. The effect of the addition of the thiacalix[4]arenetetrasulfonate on the solid/liquid or liquid/liquid distribution coefficients could be well described by the formation of a 1:1 complex with stability constants of log β₁ = 4.5 ± 0.4 and 3.3 ± 0.3 for At(I) and At(III), respectively. For the thiocyanate ion, the data measured in the presence of the organic solvents could be explained by the formation of both 1:1 and 1:2 At:SCN complexes. In the case of the solid/liquid separation, data analysis was hampered by the probable formation of a ternary complex between At(I, III), SCN⁻ and the functional groups of the resin. As for the calixarene, the interaction strength appeared slightly higher for At(I) (log β₂ = 5.9 ± 0.3 and log β₁ = 3.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively) than for At(III) (log β₂ = 5.3 ± 0.2 and log β₁ = 2.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively).     

Puromycin insensitive leucyl-specific aminopeptidase (PILSAP) is involved in the activation of endothelial integrins

We previously reported that mouse orthologue of puromycin insensitive leucyl-specific aminopeptidase (mPILSAP) played an important role in angiogenesis by regulating the proliferation and migration of endothelial cells (ECs) (Miyashita et al., 2002. Blood 99:3241-3249). Here, we examined the mechanism as to how mPILSAP regulates the migration of ECs. Cell adhesion through integrins plays a crucial role in cell migration, and ECs use at least type-1 collagen receptor integrin alpha2beta1, fibronectin receptor alpha5beta1, and vitronectin receptors alphavbeta3 and alphavbeta5. mPILSAP antisense oligodeoxynucleotide (AS-ODN) or leucinethiol (LT), a leucyl-aminopeptidase inhibitor, did not affect the attachment but did significantly inhibit the spreading of cells of the murine endothelial cell line MSS31 when they were plated on vitronectin-, fibronectin-, or type-1 collagen, although they did not affect the expression of integrin alpha2, alpha5, alphav, beta1, beta3, and beta5 subunits on the cell surface. AS-ODN and LT also inhibited the tyrosine phosphorylation of FAK when cells were plated on vitronectin, fibronectin, or type-1 collagen. This inhibition of cell spreading and of tyrosine phosphorylation of FAK could be negated by Mg(2+). These results suggest that mPILSAP is involved in the activation of endothelial integrins.     

The Breeding Distribution and Habitats of the Pied Flycatcher (Muscicapa Hypoleuca) in Britain

Examination of the plumage of Palaearctic warblers as migrants or wintering birds at Kampala, Uganda, provided useful material for a consideration of moult in relation to the timing of spring and autumn migration. Reasons are suggested for observed interspecific differences in the moult pattern, and for the variation reported from different wintering areas in the African continent.     

Effects of Group Size on Approach to Novel Objects in Ravens (Corvus corax)

Neophobia may constrain explorative behaviour, learning and innovation, while social context may facilitate approach to novel objects and acceptance of novel food. We examined the effects of neophobia on the exploration of novel objects in relation to social context in ravens (Corvus corax). Ravens are suitable subjects for studying effects of social context, as they are highly neophobic scavengers that recruit conspecifics to food. We tested two groups of six and 11 hand‐raised birds in three conditions: single‐bird, in dyadic combinations and sibling sub‐groups of three to six birds. Contrary to expectation, individuals of both groups were quicker to approach novel objects when tested alone than when tested with conspecifics. However, they spent more time close to and manipulating the novel objects in the social conditions (dyadic and group) than when being alone. We discuss the possibility that the higher latencies of dyads and groups to approach novel objects may reflect a ‘negotiation’ process in a ‘war of attrition’ between the individuals over risk‐taking.     

Foot-use laterality in the Japanese jungle crow (Corvus macrorhynchos)

Laterality of foot-use behaviour was examined in jungle crows (Corvus macrorhynchos). Consistency of laterality was also verified in comparison with two different behaviours. One was beak-scratching, and another was food-holding. Significant bias of foot-use laterality was found in 11 of 13 tested subjects for beak-scratching and in 10 of 12 tested subjects for food-holding. Bias of foot-use laterality was not common among footed subjects, suggesting no population-level bias. However, a significant number of footed subjects (10 of 12) who were tested in both behaviours showed consistent laterality irrespective of behavioural differences. These results suggest that jungle crows have strong individual-level laterality in foot-use behaviour.     

Preferential learning from non-affiliated individuals in jackdaws (Corvus monedula)

It has been suggested that affiliated social relations may facilitate information transfer between individuals. We here tested this rarely examined hypothesis with juvenile and adult jackdaws (Corvus monedula) in three stimulus enhancement tasks, both in a non-food context (experiment 1) and in a food context (experiments 2 and 3). We first show that siblings and pair partners maintain stronger bonded social relations than do non-siblings and non-pair partners. We therefore tested individuals in sibling and non-sibling dyads and, later in ontogeny, in pair and non-pair dyads. Jackdaws either did not learn from any other conspecific (experiment 1), or they learned from non-affiliated individuals (non-siblings, non-pair partners in experiments 2 and 3). This may be related to two main characteristics of jackdaws' affiliated relationships. First, affiliates share food at a high rate and may rely on their knowledgeable partners to secure food rather than learning from them. Second, affiliates spend most time in close spatial proximity to each other which increases the probability that they simultaneously experience occurrences in their environment. Hence, spatially more distant individuals, which are more likely to be non-affiliated, face different foraging situations and may therefore provide more relevant information which may lead to selective social learning.     

The bombesin receptor is coupled to a guanine nucleotide-binding protein which is insensitive to pertussis and cholera toxins

The neuropeptide bombesin acts on a variety of target cells to stimulate the processes of secretion and cell proliferation. In this study we determined whether bombesin receptors interact with known guanine nucleotide-binding proteins in four different cell types: GH4C1 pituitary cells, HIT pancreatic islet cells, Swiss 3T3 fibroblasts, and rat brain tissue. Maximal concentrations of nonhydrolyzable GTP analogs decreased agonist binding to bombesin receptors in membranes from all four sources. In GH4C1 and HIT cell membranes GTP analogs inhibited bombesin receptor binding with IC50 values of about 0.1 microM, whereas GDP analogs were approximately 10-fold less potent. In contrast, GMP and the nonhydrolyzable ATP analog adenylyl-imidodiphosphate had no effect at 100 microM. Equilibrium binding experiments in GH4C1 and HIT cell membranes indicated a single class of binding sites with a dissociation constant (Kd) for [125I-Tyr4]bombesin of 24.4 +/- 7.0 pM and a binding capacity of 176 +/- 15 fmol/mg protein. Guanine nucleotides decreased the apparent affinity of the receptors without significantly changing receptor number. Consistent with this observation, guanine nucleotides also increased the rate of ligand dissociation. Pretreatment of GH4C1 or HIT cells with either pertussis toxin (100 ng/ml) or cholera toxin (500 ng/ml) for 18 h did not affect agonist binding to membrane bombesin receptors, its regulation by guanine nucleotides, or bombesin stimulation of hormone release. Although pertussis toxin pretreatment has been reported to block bombesin stimulation of DNA synthesis in Swiss 3T3 cells, it did not alter the binding properties of bombesin receptors in Swiss 3T3 membranes or inhibit the rapid increase in intracellular [Ca2+] produced by bombesin in these cells. In summary, our results indicate that the bombesin receptor interacts with a guanine nucleotide-binding protein which exhibits a different toxin sensitivity from those which regulate adenylate cyclase as well as those which couple some receptors to phospholipases.