Long-term effects of flipper bands on penguins.

Changes in seabird populations, and particularly of penguins, offer a unique opportunity for investigating the impact of fisheries and climatic variations on marine resources. Such investigations often require large-scale banding to identify individual birds, but the significance of the data relies on the assumption that no bias is introduced in this type of long-term monitoring. After 5 years of using an automated system of identification of king penguins implanted with electronic tags (100 adult king penguins were implanted with a transponder tag, 50 of which were also flipper banded), we can report that banding results in later arrival at the colony for courtship in some years, lower breeding probability and lower chick production. We also found that the survival rate of unbanded, electronically tagged king penguin chicks after 2-3 years is approximately twice as large as that reported in the literature for banded chicks.

Respiratory mechanics of Pekin ducks under four conditions: pressure breathing, anesthesia, paralysis or breathing CO2-enriched gas.

Impedance magnitude (Z) of the lower respiratory system was studied in Pekin ducks, using forced oscillations of a small volume at the airways opening in the range 1.6-16 Hz. The experiments were performed on 5 awake ducks enclosed in a body plethysmograph and spontaneously breathing ambient air at a transrespiratory pressure (Prs, the pressure difference between the lung and the body surface) which was varied in steps from -10 cm H2O (compression) to +10 cm H2O (distension). In 3 anesthetized birds, the effects of CO2 breathing and muscular paralysis were also studied. Analysis of end-expiratory Z data yielded estimates of respiratory resistance (R), inertance (I) and compliance (C). During positive or negative pressure breathing in conscious ducks, minute volume (V) and end-tidal CO2 (PETCO2) remained unchanged from normal (Prs = zero) while tidal volume (VT) and ventilatory period (Ttot) decreased. The respiratory system in late expiration can be modelled well with a simple series R-I-C mechanical model at Prs values of zero, +10 and -10 cm H2O. The value of Z increased at all frequencies studied during compression of the respiratory system (Prs = -10 cm H2O) and did not change much from normal (Prs = zero) during distension (Prs = +10 cm H2O). Both resistance and inertance increased during compression. During distension contradictory changes in resistance and inertance suggest that complex changes in flow profile and/or in flow pathways occurred with positive pressure breathing. Anesthesia or paralysis did not noticeably change the oscillatory resistance or inertance, but increased oscillatory compliance. CO2-breathing did not affect the respiratory impedance in late expiration, but reduced its flow dependence along the ventilatory cycle.

Impedance of the lower respiratory system in ducks measured by forced oscillations during normal breathing.

The lower respiratory system of 10 conscious Pekin ducks breathing normally was subjected to superimposed oscillations of 1.3 to 16 Hz by a small volume piston pump. Induced sinusoidal flow (VO) and pressure (PO) signals were measured in late expiration, when the gas flow ventilated by the animal was minimum. The modulus of the respiratory impedance was calculated as the ratio PO/VO. The values obtained at the various oscillatory frequencies were compared to those predicted on the basis of a series mechanical network model consisting of resistive, inertial and compliant elements (RIC) using a least squares non linear regression method. The experimental data fitted well the frequency response of a simple RIC mathematical model. After correcting for the effects of the endotracheal tube, the mean values +/- SE of the optimized parameters were: resistance 4.8 +/- 0.4 cm H2O . L-1 . sec; inertance: 0.05 +/- 0.01 cm H2O . L-1 . sec2; compliance: 7.7 +/- 0.5 ml . cm H2O-1; natural frequency: 8.0 +/- 0.4 Hz. It is concluded that: (1) the lower respiratory system in ducks can be closely modeled by a RIC mechanical series network model; (2) the forced oscillation method can be used to investigate avian mechanics of breathing, with the birds awake and breathing spontaneously.