The energy cost of loaded flight is substantially lower than expected due to alterations in flight kinematics.
The effect of experimentally increased wing loading on the energy cost of flight was examined in cockatiels Nyphicus hollandicus. Five individuals were flown for periods of approximately 2 min, while carrying additional payload mass amounting to between 5 and 20% of unloaded body mass. The energy cost of flight was measured using the 13C-labelled bicarbonate technique, which was also calibrated in a separate experiment on resting birds, by comparing the elimination rate of 13C in breath with a simultaneous measurement of oxygen consumption by indirect calorimetry. It was not possible to perform a similar calibration during flight when energy costs were higher, so we extrapolated the relationship from the resting calibration to predict flight cost. Flight cost in the pre-manipulated individuals averaged 16.7+/-1.8 W. Flight cost in the pre-manipulated birds was significantly related to the interaction between downstroke duration and flight speed. There was no significant increase in flight cost with increases in payload mass. The birds responded to payload masses between 5 and 15% of their unloaded body mass by decreasing flight speed relative to unloaded birds, while maintaining wing beat frequency (Fb). At a payload mass equivalent to 20% of body mass, however, the birds flew at higher speeds than unloaded controls, and had a significantly higher Fb, generated by a reduction in both the upstroke and downstroke durations. Wing amplitude was unaffected by the increase in loading. Using the measured flight parameters, the effect of loading was not significantly different than predicted using aerodynamic models. (+info)
Morphoregulation of avian beaks: comparative mapping of growth zone activities and morphological evolution.
Avian beak diversity is a classic example of morphological evolution. Recently, we showed that localized cell proliferation mediated by bone morphogenetic protein 4 (BMP4) can explain the different shapes of chicken and duck beaks (Wu et al.  Science 305:1465). Here, we compare further growth activities among chicken (conical and slightly curved), duck (straight and long), and cockatiel (highly curved) developing beak primordia. We found differential growth activities among different facial prominences and within one prominence. The duck has a wider frontal nasal mass (FNM), and more sustained fibroblast growth factor 8 activity. The cockatiel has a thicker FNM that grows more vertically and a relatively reduced mandibular prominence. In each prominence the number, size, and position of localized growth zones can vary: it is positioned more rostrally in the duck and more posteriorly in the cockatiel FNM, correlating with beak curvature. BMP4 is enriched in these localized growth zones. When BMP activity is experimentally altered in all prominences, beak size was enlarged or reduced proportionally. When only specific prominences were altered, the prototypic conical shaped chicken beaks were converted into an array of beak shapes mimicking those in nature. These results suggest that the size of beaks can be modulated by the overall activity of the BMP pathway, which mediates the growth. The shape of the beaks can be fine-tuned by localized BMP activity, which mediates the range, level, and duration of locally enhanced growth. Implications of topobiology vs. molecular blueprint concepts in the Evo-Devo of avian beak forms are discussed. (+info)
A survey of avian polyomavirus (APV) infection in imported and domestic bred psittacine birds in Japan.
Although birds infected with avian polyomavirus (APV) subclinically could be a source of infection, no epidemiological studies of APV in psittacine birds have been reported in Japan. In the present study, we investigated subclinical morbidity rate of APV in imported and domestically bred psittacine birds by polymerase chain reaction (PCR). Of 402 live birds from which blood or feather samples were taken between April, 2003 and March, 2004, 11 (2.7%) were found to be APV positive. The DNA sequences of the APV t/T antigen region were determined for five APV-positive randomly selected samples and were found to be conserved. (+info)
Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). I. Kinematic and neuromuscular control of turning.
Maneuvering flight has long been recognized as an important component of the natural behavior of many bird species, but has been the subject of little experimental work. Here we examine the kinematics and neuromuscular control of turning flight in the rose-breasted cockatoo Eolophus roseicapillus (N=6), testing predictions of maneuvering flight and control based on aerodynamic theory and prior kinematic and neuromuscular studies. Six cockatoos were trained to navigate between two perches placed in an L-shaped flight corridor, making a 90 degrees turn midway through each flight. Flights were recorded with three synchronized high-speed video cameras placed outside the corridor, allowing a three-dimensional reconstruction of wing and body kinematics through the turn. We simultaneously collected electromyography recordings from bilateral implants in the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis muscles. The cockatoos maneuvered using flapping, banked turns with an average turn radius of 0.92 m. The mean rate of change in heading during a complete wingbeat varied through the turn and was significantly correlated to roll angle at mid-downstroke. Changes in roll angle were found to include both within-wingbeat and among-wingbeat components that bear no direct relationship to one another. Within-wingbeat changes in roll were dominated by the inertial effects while among-wingbeat changes in roll were likely the result of both inertial and aerodynamic effects. (+info)
Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). II. Inertial and aerodynamic reorientation.
The reconfigurable, flapping wings of birds allow for both inertial and aerodynamic modes of reorientation. We found evidence that both these modes play important roles in the low speed turning flight of the rose-breasted cockatoo Eolophus roseicapillus. Using three-dimensional kinematics recorded from six cockatoos making a 90 degrees turn in a flight corridor, we developed predictions of inertial and aerodynamic reorientation from estimates of wing moments of inertia and flapping arcs, and a blade-element aerodynamic model. The blade-element model successfully predicted weight support (predicted was 88+/-17% of observed, N=6) and centripetal force (predicted was 79+/-29% of observed, N=6) for the maneuvering cockatoos and provided a reasonable estimate of mechanical power. The estimated torque from the model was a significant predictor of roll acceleration (r(2)=0.55, P<0.00001), but greatly overestimated roll magnitude when applied with no roll damping. Non-dimensional roll damping coefficients of approximately -1.5, 2-6 times greater than those typical of airplane flight dynamics (approximately -0.45), were required to bring our estimates of reorientation due to aerodynamic torque back into conjunction with the measured changes in orientation. Our estimates of inertial reorientation were statistically significant predictors of the measured reorientation within wingbeats (r(2) from 0.2 to 0.37, P<0.0005). Components of both our inertial reorientation and aerodynamic torque estimates correlated, significantly, with asymmetries in the activation profile of four flight muscles: the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis (r(2) from 0.27 to 0.45, P<0.005). Thus, avian flight maneuvers rely on production of asymmetries throughout the flight apparatus rather than in a specific set of control or turning muscles. (+info)
Identification of a natural multi-recombinant of Newcastle disease virus.
Newcastle disease (ND), caused by ND virus (NDV), is one of the most serious illnesses of birds, particularly chickens, and has been one of the major causes of economic losses in the poultry industry. Live vaccines are widely used to prevent chicken from NDV all over the world. Given the implications that recombination has for RNA virus evolution, it is clearly important to determine the extent to which recombination plays a role in NDV evolution. In this study, we performed the phylogenetic and recombination analysis on complete NDV genomes. A natural multi-recombinant cockatoo/Indonesia/14698/90 (AY562985) was identified. Its two minor parental-like strains might be from the NDV vaccine lineage and anhinga/U.S.(Fl)/44083/93 lineage, respectively. Our study suggests that recombination plays a role in NDV evolution. Especially, the study also suggests that live vaccines have capacity to play roles in shaping NDV evolution by homologous recombination with circulating virus. (+info)
Ganglioneuroma of the brachial plexus in two cockatiels (Nymphicus hollandicus).