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At least 217 records · Page 12Linked to original sources
PubMed1996

Characteristics of naturally acquired Plasmodium relictum capistranoae infections in naive Hawaiian crows (Corvus hawaiiensis) in Hawaii.

Indigenous to Hawaii, the Hawaiian crow (Corvus hawaiiensis) is the world's most severely endangered species with only 3 reproductively active pairs remaining in the wild. Seven captive-reared, avian malaria-naive C. hawaiiensis were exposed in an outdoor aviary and hematologically and serologically monitored for 9 wk. Three birds showed Plasmodium relictum capistranoae parasitemia (6.35%, 2.15%, and 0.60%). All birds were seroconverted for malaria on week 7 as determined by enzyme-linked immunosorbent assay (ELISA). Malaria IgG levels of exposed parasitemic birds did not differ from those of exposed nonparasitemic C. hawaiiensis and were not significantly correlated with the level of parasitemia. Four of 9 hematological parameters, e.g., white blood cell count (WBC), relative and absolute lymphocytosis, and total solids (TS), showed significant increases related to ELISA-determined malarial infection. The sensitivity, specificity, and the positive predictive values of these 4 parameters for malarial infections in C. hawaiiensis were higher than 66%, with the WBC and TS sensitivity reaching 100%. The reference range of 9 hematological parameters was established based on uninfected, clinically healthy C. hawaiiensis. Seven birds were successfully treated and released, increasing the total wild C. hawaiiensis world population by approximately 50%.

Animals↗
PubMedDate not supplied

[Neuronal spike responses to visual stimuli in the hyperstriatal region of the brains of Corvus corone crows].

Studies of impulse activity in 452 neurons of the hyperstriatal part of the forebrain in crows revealed visual projectional zone within Wulst. With deepening of microelectrode, the receptive fields shifted upward and increased in the diameter from 3--4 to 30--50 and even 90 degrees; the relative amount of directionally sensitive neurons with the preferred movement of the stimuli backward and upward increased. In rostral regions, neurons with the receptive fields in temporal areas of the visual field are located, whereas nasal areas are projected to caudal parts of the Wulst. Selectivity of neuronal reactions to changes in illumination, the size and the rate of movement of the stimuli, as well as neuronal sensitivity to repeated stimulation were demonstrated.

Animals↗
PubMed2005

Wall thickness of gas- and marrow-filled avian long bones: measurements on humeri, femora and tibiotarsi in crows (Corvus corone cornix) and magpies (Pica pica).

We studied how the ratio K of the internal to external diameter of gas- and marrow-filled avian long bones follows the biomechanical optima derived for tubular bones with minimum mass designed to fulfil various mechanical requirements. We evaluated radiographs of numerous humeri, femora and tibiotarsi in Corvus corone cornix and Pica pica. The K-values of the gas-filled humerus (K=0.78+/-0.03) and the marrow-filled femur (K=0.79+/-0.02) in Corvus are practically the same, while K of the marrow-filled tibiotarsus (K=0.71+/-0.04) is significantly smaller. The same is true for the gas-filled humerus (K=0.78+/-0.02) and the marrow-filled femur (K=0.77+/-0.02) and tibiotarsus (K=0.67+/-0.05) in Pica. K in Corvus is slightly larger than K in Pica, but the differences are statistically not significant. The standard deviation DeltaK of the tibiotarsi (DeltaK=0.04-0.05) is approximately two times as large as that of the humeri (DeltaK=0.02-0.03) and femora (DeltaK=0.02) in both species. Accepting the assumption of earlier authors that the ratio Q of the marrow to bone density is 0.5, our data show that the marrow-filled tibiotarsi of Corvus and Pica are optimized for stiffness, while the marrow-filled femora are far from any optimum. The relative wall thickness W=1-K of the gas-filled avian humeri studied is much larger than the theoretical optimum W*=1-K*=0.07, and thus these bones are thicker-walled than the optimal gas-filled tubular bone with minimum mass.

Animals↗
PubMed2004

The mentality of crows: convergent evolution of intelligence in corvids and apes.

Discussions of the evolution of intelligence have focused on monkeys and apes because of their close evolutionary relationship to humans. Other large-brained social animals, such as corvids, also understand their physical and social worlds. Here we review recent studies of tool manufacture, mental time travel, and social cognition in corvids, and suggest that complex cognition depends on a "tool kit" consisting of causal reasoning, flexibility, imagination, and prospection. Because corvids and apes share these cognitive tools, we argue that complex cognitive abilities evolved multiple times in distantly related species with vastly different brain structures in order to solve similar socioecological problems.

Animals↗