We investigated interindividual variation and intra‐individual phenotypic flexibility in basal metabolic rate (BMR), total evaporative water loss (TEWL), body temperature (Tb), the minimum dry heat transfer coefficient (h), and organ and muscle size of five species of larks geographically distributed along an aridity gradient. We exposed all species to constant environments of 15°C or 35°C, and examined to what extent interspecific differences in physiology can be attributed to acclimation. We tested the hypothesis that birds from deserts display larger intra‐individual phenotypic flexibility and smaller interindividual variation than species from mesic areas. Larks from arid areas had lower BMR, TEWL, and h, but did not have internal organ sizes different from birds from mesic habitats. BMR of 15°C‐acclimated birds was 18.0%, 29.1%, 12.2%, 25.3%, and 4.7% higher than of 35°C‐acclimated Hoopoe Larks, Dunn's Larks, Spike‐heeled Larks, Skylarks, and Woodlarks, respectively. TEWL of 15°C‐acclimated Hoopoe Larks exceeded values for 35°C‐acclimated individuals by 23% but did not differ between 15°C‐ and 35°C‐acclimated individuals in the other species. The dry heat transfer coefficient was increased in 15°C‐acclimated individuals of Skylarks and Dunn's Larks, but not in the other species. Body temperature was on average 0.4°C ± 0.15°C (mean ± 1 sem) lower in 15°C‐acclimated individuals of all species. Increased food intake in 15°C‐acclimated birds stimulated enlargement of intestine (26.9–38.6%), kidneys (9.8–24.4%), liver (16.5–27.2%), and stomach (22.0–31.6%). The pectoral muscle increased in 15°C‐acclimated Spike‐heeled Larks and Skylarks, remained unchanged in Hoopoe Larks, and decreased in 15°C‐acclimated Woodlarks and Dunn's Larks. We conclude that the degree of intra‐individual flexibility varied between physiological traits and among species, but that acclimation does not account for interspecific differences in BMR, TEWL, and h in larks. We found no general support for the hypothesis that species from desert environments display larger intra‐individual phenotypic flexibility than those from mesic areas. The coefficient of variation of larks acclimated to their natural environment was smaller in species from arid areas than in species from mesic areas for mass‐corrected BMR and surface‐specific h, but not for mass‐corrected TEWL. The high repeatabilities of BMR, TEWL, and h in several species indicated a within‐individual consistency on which natural selection could operate.

No abstract

Experimental studies evaluating the effects of food availability on the movement of free-ranging animals generally involve food supplementation rather than suppression. Both approaches can yield similar insights, but we were interested in the potential for using food suppression for the management and control of invasive predators, in particular, the brown treesnake (Boiga irregularis) on Guam. However, understanding a species' response to food resources is critical before employing such a strategy. We studied the movements of 24 radio-tagged B. irregularis initially caught within four 4-ha unfenced plots in rodent-abundant (control) and rodent-suppressed (treatment) grassland habitats over a 40-day period. Because monitoring duration differed among snakes, we also analyzed short-term (16-day) activity areas. Over the 16 days, snakes associated with rodent-suppressed plots had 86% larger activity areas (ha), 94% greater dispersal distances (m), and 43% greater movement rates (m/h) than snakes associated with control plots. Boiga irregularis moved extensively, but these movements were not always reflected in the size of the snake's total activity area. Movement rates did not differ between sexes, but snakes in above-average body condition moved greater distances per hour than those in below-average condition irrespective of treatment. Our study indicates that a relatively small prey suppression effort can cause almost immediate and significant changes in B. irregularis movement. On Guam, prey suppression might enhance control efforts by either increasing trap capture success or discouraging snakes from entering areas of conservation or management concern. However, the outcome of using prey suppression as a control tool in areas threatened with the accidental introduction of the brown treesnake is more difficult to predict and might have negative consequences such as elevated dispersal rates.

1. Three trials were designed to study the effects of axis of setting, turning frequency and axis and angle of rotation on the hatching success of ostrich eggs. The joint effects of axis of setting and angle of rotation were investigated in a fourth trial. 2. The hatchability of fertile ostrich eggs artificially incubated in electronic incubators (turned through 60 degrees hourly) was improved substantially in eggs set in horizontal positions for 2 or 3 weeks and vertically for the rest of the time. 3. The hatchability of fertile eggs set in the horizontal position without any turning was very low (27%). It was improved to approximately 60% by manual turning through 180 degrees around the short axis and through 60 degrees around the long axis at 08.00 and 16.00 h. A further improvement to approximately 80% was obtained in eggs automatically turned through 60 degrees around the long axis in the incubator. Additional turning through 180 degrees around the short axis twice daily at 08.00 and 16.00 h resulted in no further improvement. 4. The hatchability of fertile eggs set vertically in electronic incubators and rotated hourly through angles ranging from 60 degrees to 90 degrees around the short axis increased linearly over the range studied. The response amounted to 1.83% for an increase of 10 (R2=0.96). 5. The detrimental effect of rotation through the smaller angle of 60 degrees around the short axis could be compensated for by setting ostrich eggs in the horizontal position for 2 weeks before putting them in the vertical position.