James A. Gessaman

TRANSMITTER LOADS AFFECT THE FLIGHT SPEED AND METABOLISM OF HOMING PIGEONS

Eight homing pigeons (Columba livia) were flown distances of 90 and 320 km with and without transmitters (weighing either 2.5% or 5.0% of the pigeons body mass, M,) mounted on a back harness. Flight times in April through June for the 90-km distance were 60 min without a transmitter or harness, 69 min with a harness alone and about 76 min with a harness and transmitter (weighing either 2.5% or 5.0% of M,). Flight times for the 320-km distance were 4 hr 16 min for the controls and 5 hr 35 min for the two fastest pigeons wearing a harness and transmitter weighing 2.5% of M,. The results show that on 90-km flights harnesses alone slow birds by 15% and harnesses and transmitters (5 5%M,) slow birds 25 to 28%; on 320-km flights harnesses and transmitters slow birds >31%. Moreover, on the 320-km flights, CO, production of the pigeons (measured with the doubly- labeled water method) was 41 to 52% higher per hour when encumbered with a transmitter and harness. Thus, encumbered pigeons produced 85 to 100% more total CO, covering the 320-km distance. Therefore, high performance homing pigeons work substantially harder and longer during a long distance flight when wearing harnesses and transmitters.

Bioenergetics of the Snowy Owl (Nyctea Scandiaca)

Oxygen consumption and CO2 production were measured on four female snowy owls at several different ambient temperatures and two air speeds. Food consumption and existence metabolism were measured o...

An evaluation of heart rate as an indirect measure of daily energy metabolism of the American kestrel

Abstract 1. 1. The average daily heart rate (HR) of eight kestrels was used with O2 consumption ( V O 2 )-HR relationships measured on each individual to estimate their daily energy metabolism. Hea rate provided a good index of daily metabolism (i.e. less than 10% error) in some individuals. The unpredictable shifts that occur in the resting VO2-HR relationship over periods of days, weeks or months is a major shortcoming of the heart rate method. 2. 2. Heart rate, when sampled for l min every 10 min throughout a 24-hr period provides a very good measure of the true average daily HR of some kestrels. 3. 3. Suggestions for potential users of the heart rate method are given.

The combined effects of air temperature, wind and radiation on the resting metabolism of avian raptors

1. 1.VO3 values were measured on American kestreis, red-tailed hawks and golden eagles perched in a wind tunnel and multiple regression equations were developed to predict resting metabolism of each species as a function of body mass, ambient temperature, wind speed, and radiant flux density. 2. 2.Increases in metabolism due to wind ranged from non-linear in kestrels to linear in eagles. 3. 3.Wind speeds below 4.47 m.s−1 produced relatively greater increases in metabolism than wind speeds above 4.47 m.s.−1. 4. 4.Radiation produced linear decreases in metabolism in all birds at all wind speeds, and it extended the thermoneutral zone to lower ambient temperatures.

An evaluation of heart rate as a measure of dailymetabolism in pigeons (Columba livia)

Abstract 1. 1. A positive, linear relationship of heart rate (HR) to metabolic rate, as measured by O 2 consumption ( V o 2 ), was demonstrated in 7 pigeons. 2. 2. Heart rate-O 2 consumption regressions measured within a 1- or 2-week period on 7 pigeons did not differ significantly. However, the slopes of the regressions increased significantly in all birds over the next 6 weeks. 3. 3. v o 2 - T a data extrapolated to a body temperature of 40.7°C at zero metabolism and thermal conductance was − 0.23 cal/hr g °C. 4. 4. The individual regression equations were used in conjunction with average 24-hr heart rate to predict the existence metabolism (EM) of these same pigeons measured in each of three food consumption trials. Predicted EM values averaged 41.7 ± 7.1% higher than measured values. The data suggest that the HR- V o 2 relationship of a solitary bird changes in the presence of social interactions.

Energy cost of incubation in the American kestrel

Abstract 1. 1. Metabolic rates are presented for (1) two females and one male kestrel incubating eggs in the field. (2) the same individuals in the laboratory immediately following the incubation period, (3) non-breeding kestrels and (4) kestrel eggs for 10 days during their development. 2. 2. The results from one male and one female support the idea that incubation can be accomplished at the level of adult resting metabolism. 3. 3. Metabolism of the other female during incubation was greater than adult resting metabolism at air temperature below 15°C. Egg metabolism rises exponentially during mid-incubation period and reaches a plateau in the last 5–6 days at 21.2 mg CO 2 /egg per hr. 4. 4. In the last 5 days of the incubation period a clutch of five eggs contributes 19–25% of the total heat required for incubation.

Influence of air temperature, wind and irradiance on metabolism of white-tailed jackrabbits

Abstract 1. 1.High wind speed and low air temperature interact and increase the metabolic rate of white-tailed jackrabbits ( Lepus townsendii ); this effect is greater in summer than in winter. 2. 2.Most variance in metabolism is explained (approx. 90%) when a term for the temperature—wind interaction is included in regresson models. Metabolism is best described with linear terms for wind in summer, and non-linear terms for wind in winter regression equations. 3. 3.Core temperature increases with wind; heat production apparently overcompensates for convective heat loss. 4. 4.Metabolic rate was reduced with 540 and 1080 W/m 2 irradiance (0.3–2.8 μ) at air temperatures below the lower critical temperature in winter. There was no reduction in summer with 400 W/m 2 , perhaps due to decreased penetrance of radiation into brown pelage. 5. 5.Mean ground-level wind speeds in sagebrush habitat are low throughout the year and should usually have minimal influence on metabolic rate. High winds and low air temperatures during severe winter storms may radically elevate metabolic heat produced for thermoregulation.

The thermal conductance of winter and summer pelage of Lepus californicus

Abstract 1. 1.The thermal conductance of the winter and summer pelage of L. californicus at negligible wind speed was 1.966 and 2.929 W/m 2 .°C, respectively. 2. 2.The rate of increase in thermal conductance at wind velocities in excess of 2.8 m/s was greater for the summer ( b = 0.4087) than winter pelage ( b = 0.1195).

Evaluation of the cyclopropane absorption method of measuring avian body fat

-The mean absolute percent error of predicting the fat mass of 40 Rock Doves (Columba livia) by the cyclopropane absorption method was 11%. A sensitivity analysis of some of the 15 variables used in computing fat mass by the cyclopropane absorption method showed that: (1) cloacal temperature was a good measure of body-fat temperature, (2) the lipid solubility coefficient of cyclopropane reported for rats was appropriate for pigeons, (3) minimum error occurred with an animal density of 1.08, (4) error was relatively insensitive to a range of reasonable estimates of body water, and (5) the most accurate method of measuring chamber volume was unclear. We list advantages and disadvantages of this user-unfriendly method and provide recommendations for future users. This method does not require a calibration based on fat extracted from dead birds; the accuracy and precision of a system assembled to measure the fat mass of live birds can be evaluated with olive oil standards. The accuracy of estimating fat mass of a living bird seems to be dictated, in large part, by the analytical equipment and procedures used rather than by the bird. Received 14 April 1997, accepted 21 July 1997. THE LACK OF AN ACCURATE nondestructive or noninvasive technique for determining whole body-fat storage is one of the greatest hindrances to studies of avian ecological energetics. Fat, which has an energy content of about 2.5 times that of protein or carbohydrate per unit dry mass and about 8 times per unit wet mass, is the main energy store in birds (Pond 1981, Blem 1990). Mass of body fat (FM) is one quantitative measure of a birds preparedness for successfully completing an energy-demanding activity such as migration or egg laying and surviving such energy-demanding periods as: (1) prolonged starvation (Cherel et al. 1987), (2) summit (peak) rates of energy metabolism during a severe winter period, or (3) an unseasonably cold storm during a nonwinter period (see Gessaman and Worthen 1982, Elk-

Prediction of raptor resting metabolism: Comparison of measured values with statistical and biophysical estimates

Abstract 1. 1.| V O 2 values were measured on American kestrels, red-tailed hawks and golden eagles perched in a wind tunnel. Resting metabolism of each species is described by a regression equation as a function of body mass ambient temperature, wind speed and radiant flux density. 2. 2.|Resting metabolism is also described by a heat transfer model as a function of feather thermal conductance. 3. 3.|Resting metabolism computed from multiple regression and heat transfer models were similar, but the latter estimates paralleled actual values better than regression estimates. 4. 4.|Biophysical modelling may provide a more accurate estimate of metabolic heat production than contemporary statistical approaches such as multiple regression and least-squares analysis.