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Papers by Berry Pinshow

Journal of Experimental Biology, 2002

SUMMARYMost aquatic vertebrates are ammonotelic, whereas terrestrial vertebrates are typically ur... more SUMMARYMost aquatic vertebrates are ammonotelic, whereas terrestrial vertebrates are typically uricotelic or ureotelic. However, the principal form of nitrogenous waste product in the urine of an animal may vary, depending on environmental conditions. Anna's hummingbird (Calypte anna) was found to switch from uricotely at high ambient temperature (Ta)to ammonotely at lower Ta, when energy demands and consequent nectar intake rates were high. In extension of this, we hypothesised that nectarivorous birds would switch from uricotely to ammonotely when water intake rates were high or when protein or salt intake rates were low. We examined the influence of water, electrolyte and protein intake and of Ta on the excretion of ammonia, urea and urate (uric acid and its salts) in nectarivorous Palestine sunbirds(Nectarinia osea). The proportion of ammonia in ureteral urine and excreted fluid was not influenced by total water or salt intake or by Ta. Protein intake did not influence nitro...

Proceedings of the Royal Society B: Biological Sciences, 2016

The water vapour permeability barrier of mammals and birds resides in the stratum corneum (SC), t... more The water vapour permeability barrier of mammals and birds resides in the stratum corneum (SC), the outermost layer of the epidermis. The molar ratio and molecular arrangement of lipid classes in the SC determine the integrity of this barrier. Increased chain length and polarity of ceramides, the most abundant lipid class in mammalian SC, contribute to tighter packing and thus to reduced cutaneous evaporative water loss (CEWL). However, tighter lipid packing also causes low SC hydration, making it brittle, whereas high hydration softens the skin at the cost of increasing CEWL. Cerebrosides are not present in the mammalian SC; their pathological accumulation occurs in Gaucher's disease, which leads to a dramatic increase in CEWL. However, cerebrosides occur normally in the SC of birds. We tested the hypothesis that cerebrosides are also present in the SC of bats, because they are probably necessary to confer pliability to the skin, a quality needed for flight. We examined the SC ...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2016

Life in deserts is challenging for bats because of their relatively high energy and water require... more Life in deserts is challenging for bats because of their relatively high energy and water requirements; nevertheless bats thrive in desert environments. We postulated that bats from desert environments have lower metabolic rates (MR) and total evaporative water loss (TEWL) than their mesic counterparts. To test this idea, we measured MR and TEWL of four species of bats, which inhabit the Negev desert in Israel, one species mainly restricted to hyper-arid deserts (Otonycteris hemprichii), two species from semi-desert areas (Eptesicus bottae and Plecotus christii), and one widespread species (Pipistrellus kuhlii). We also measured separately, in the same individuals, the two components of TEWL, respiratory water loss (RWL) and cutaneous evaporative water loss (CEWL), using a mask. In all the species, MR and TEWL were significantly reduced during torpor, the latter being a consequence of reductions in both RWL and CEWL. Then, we evaluated whether MR and TEWL in bats differ according to their geographic distributions, and whether those rates change with T a and the use of torpor. We did not find significant differences in MR among species, but we found that TEWL was lowest in the species restricted to desert habitats, intermediate in the semi-desert dwelling species, and highest in the widespread species, perhaps a consequence of adaptation to life in deserts. Our results were supported by a subsequent analysis of data collected from the literature on rates of TEWL for 35 bat species from desert and mesic habitats.

Mammalian Biology, 2015

Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food a... more Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food and low concentration of electrolytes therein. We examined the effects of salt content (NaCl) and sugar type (sucrose vs. glucose) on the intake rate of dilute sugar solutions by the Egyptian fruit bat (Rousettus aegyptiacus). Increased salt content did not bring about an increase in energy intake by bats fed dilute sucrose diets and the bats did not compensate by hyperphagia to achieve the energy intake of bats fed concentrated sucrose solution without salt. Moreover, increasing salt content had a negative effect on the total energy intake of Egyptian fruit bats fed equicaloric sucrose solutions. There were no differences in hematocrit in bats fed the diets of different sucrose concentration, but plasma osmolality was higher in those bats fed more concentrated sugar solutions, and urine osmolality was higher in those fed on highsalt diets. Food and energy intake did not differ between bats that were fed dilute glucose and sucrose solutions. Our findings indicate that Egyptian fruit bats do not modulate food intake when salt content of dilute sugar solutions is increased, and that increasing salt content might constrain their food intake rate. Sugar type did not affect food intake by Egyptian fruit bats, indicating that sucrose hydrolysis alone does not limit the intake of dilute sugar nectar.

The Journal of experimental biology, 2010

Clinicians commonly measure the (13)CO(2) in exhaled breath samples following administration of a... more Clinicians commonly measure the (13)CO(2) in exhaled breath samples following administration of a metabolic tracer (breath testing) to diagnose certain infections and metabolic disorders. We believe that breath testing can become a powerful tool to investigate novel questions about the influence of ecological and physiological factors on the oxidative fates of exogenous nutrients. Here we examined several predictions regarding the oxidative kinetics of specific carbohydrates, amino acids and fatty acids in a dietary generalist, the house sparrow (Passer domesticus). After administering postprandial birds with 20 mg of one of seven (13)C-labeled tracers, we measured rates of (13)CO(2) production every 15 min over 2 h. We found that sparrows oxidized exogenous amino acids far more rapidly than carbohydrates or fatty acids, and that different tracers belonging to the same class of physiological fuels had unique oxidative kinetics. Glycine had a mean maximum rate of oxidation (2021 nmol...

Physiological and Biochemical Zoology, 1999

Condensation of water vapor in the exhaled air stream as it passes over previously cooled membran... more Condensation of water vapor in the exhaled air stream as it passes over previously cooled membranes of the nasopharynx is thought to be a mechanism that reduces respiratory water loss in mammals and birds. Such a mechanism could be important in the overall water economy of these vertebrates, especially those species occupying desert habitats. However, this hypothesis was originally based on measurements of the temperature of exhaled air (T ex), which provides an estimate of water recovered from exhaled air as a proportion of water added on inhalation but does not yield a quantitative measure of the reduction in total evaporative water loss (TEWL). In this study, we experimentally occluded the nares of crested larks (Galerida cristata), a cosmopolitan species, and desert larks (Ammomanes deserti), a species restricted to arid habitats, to test the hypothesis that countercurrent heat exchange in the nasal passages reduces TEWL. T ex of crested larks increased linearly with air temperature, (T a):. Following T ϭ 8.93 ϩ 0.793 # T ex a Schmidt-Nielsen and based on measurements of T ex , we predicted that crested larks would recover 69%, 49%, 23%, and

Journal of Experimental Biology, 2008

SUMMARYFood resources are complementary for a forager if their contribution to fitness is higher ... more SUMMARYFood resources are complementary for a forager if their contribution to fitness is higher when consumed together than when consumed independently,e.g. ingesting one may reduce the toxic effects of another. The concentration of potentially toxic ethanol, [EtOH], in fleshy fruit increases during ripening and affects food choices by Egyptian fruit bats, becoming deterrent at high concentrations (⩾1%). However, ethanol toxicity is apparently reduced when ingested along with some sugars; more with fructose than with sucrose or glucose. We predicted (1) that ingested ethanol is eliminated faster by bats eating fructose than by bats eating sucrose or glucose, (2)that the marginal value of fructose-containing food (food+fructose) increases with increasing [EtOH] more than the marginal value of sucrose- or glucose-containing food (food+sucrose, food+glucose), and (3) that by increasing [EtOH] the marginal value of food+sucose is incremented more than that of food+glucose. Ethanol in b...

Journal of Experimental Biology, 2004

SUMMARYAlthough most birds are accustomed to making short flights, particularly during foraging, ... more SUMMARYAlthough most birds are accustomed to making short flights, particularly during foraging, the flight patterns during these short periods of activity differ between species. Nectarivorous birds, in particular, often spend time hovering, while non-nectarivorous birds do not. The cost of short flights is likely therefore to differ between nectarivorous and non-nectarivorous birds because of the different energetic contributions of different flight types to the behaviour. The 13C-labelled bicarbonate technique was used to measure the energy cost of short flights in the nectarivorous Palestine sunbird Nectarinia osea (mean mass 6.17±0.16 g, N=8)and the non-nectarivorous starling Sturnus vulgaris (mean mass 70.11±1.11 g, N=9). The technique was initially calibrated in five individuals for each species at temperatures ranging from 1 to 35°C,by comparing the isotope elimination rate to the metabolic rate measured simultaneously by indirect calorimetry. The cost for short intermittent...

Journal of Experimental Biology, 2012

SUMMARY We examined feeding performance of the flea Xenopsylla ramesis on three different hosts: ... more SUMMARY We examined feeding performance of the flea Xenopsylla ramesis on three different hosts: its natural, granivorous, rodent host, Sundevall’s jird (Meriones crassus); the frugivorous Egyptian fruit bat (Rousettus aegyptiacus); and an insectivorous bat, Kuhl’s pipistrelle (Pipistrellus kuhlii). Because these fleas are not known to occur on bats, we hypothesized that the fleas’ feeding performance (i.e. feeding and digestion rates) would be higher when feeding on their natural host than on either of the bats that they do not naturally parasitize. We found that mass-specific blood-meal size of both male and female fleas was significantly lower when feeding on Kuhl’s pipistrelles than on the other two species, but was not different in female fleas feeding on fruit bats or on jirds at all stages of digestion. However, more male fleas achieved higher levels of engorgement if they fed on Sundevall’s jirds than if they fed on Egyptian fruit bats. The fleas digested blood of fruit bats...

Journal of Experimental Biology, 2012

SUMMARY During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated ... more SUMMARY During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated organs in small birds decreases in size by as much as 40%, compared with the preflight condition because of the catabolism of protein. At stopover sites, birds need 2–3 days to rebuild their GIT so that they can restore body mass and fat reserves to continue migration. The source of protein used to rebuild the GIT may be exogenous (from food ingested) or endogenous (reallocated from other organs) or both. Because the relative contribution of these sources to rebuild the GIT of migratory birds is not yet known, we mimicked in-flight fasting and then re-feeding in two groups of blackcaps (Sylvia atricapilla), a Palearctic migratory passerine. The birds were fed a diet containing either 3% or 20% protein to simulate different refueling scenarios. During re-feeding, birds received known doses of 15N-l-leucine before we measured the isotope concentrations in GIT and associated digestive organ...

Journal of Experimental Biology, 2013

SUMMARYBats hibernate to cope with low ambient temperatures (Ta) and low food availability during... more SUMMARYBats hibernate to cope with low ambient temperatures (Ta) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (Tb) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat’s winter energy expenditure. This has been associated with variation in Tb, Ta or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with Ta and Tb. Ta and Tb were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and Tb or Ta. Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same Ta but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water lo...

Journal of Experimental Biology, 2010

SUMMARYPrevious studies reported that fed bats and birds mostly use recently acquired exogenous n... more SUMMARYPrevious studies reported that fed bats and birds mostly use recently acquired exogenous nutrients as fuel for flight, rather than endogenous fuels, such as lipids or glycogen. However, this pattern of fuel use may be a simple size-related phenomenon because, to date, only small birds and bats have been studied with respect to the origin of metabolized fuel, and because small animals carry relatively small energy reserves, considering their high mass-specific metabolic rate. We hypothesized that ∼150 g Egyptian fruit bats (Rousettus aegyptiacus Pteropodidae), which are more than an order of magnitude heavier than previously studied bats, also catabolize dietary sugars directly and exclusively to fuel both rest and flight metabolism. We based our expectation on the observation that these animals rapidly transport ingested dietary sugars, which are absorbed via passive paracellular pathways in the intestine, to organs of high energy demand. We used the stable carbon isotope rat...

Proceedings of the Royal Society of London. Series B: Biological Sciences, 2002

Parent Palestine sunbirds (Nectarinia osea) feed on ower nectar that is not fed to their nestling... more Parent Palestine sunbirds (Nectarinia osea) feed on ower nectar that is not fed to their nestlings. This phenomenon provided a unique opportunity to manipulate self-feeding rates of parent birds independently of the rate at which they feed arthropod prey to their offspring. Based on provisioning models, we predicted that parents would invest more in their young as the energy content of their own food increased. From our earlier work, we also predicted that the levels of sex-speci c activities of males and females would differ as the energy content of their food increased. Sunbird pairs with two or three nestlings were provided with feeders containing a low-, medium-or high-concentration sucrose solution. As the sugar concentration increased, the females delivered arthropods at a greater rate to their nestlings, removed proportionally more faecal sacs and spent longer at the nest, while the males increased their mobbing effort. Nestling food intake and body mass, but not tarsus length or bill size, were larger in small broods than in large broods, and increased with increasing feeder sugar concentration. These results imply that increasing the energy content of food consumed by parent sunbirds allows them to increase the rate at which other foods are delivered to their young and to increase other parental care activities as well. The results also add credence to the idea that behavioural decisions re ect life-history trade-offs between parental self-feeding and investment in current young.

PLoS ONE, 2010

Background: Many avian species soar and glide over land. Evidence from large birds (m b .0.9 kg) ... more Background: Many avian species soar and glide over land. Evidence from large birds (m b .0.9 kg) suggests that soaringgliding is considerably cheaper in terms of energy than flapping flight, and costs about two to three times the basal metabolic rate (BMR). Yet, soaring-gliding is considered unfavorable for small birds because migration speed in small birds during soaring-gliding is believed to be lower than that of flapping flight. Nevertheless, several small bird species routinely soar and glide. Methodology/Principal Findings: To estimate the energetic cost of soaring-gliding flight in small birds, we measured heart beat frequencies of free-ranging migrating European bee-eaters (Merops apiaster, m b ,55 g) using radio telemetry, and established the relationship between heart beat frequency and metabolic rate (by indirect calorimetry) in the laboratory. Heart beat frequency during sustained soaring-gliding was 2.2 to 2.5 times lower than during flapping flight, but similar to, and not significantly different from, that measured in resting birds. We estimated that soaring-gliding metabolic rate of European bee-eaters is about twice their basal metabolic rate (BMR), which is similar to the value estimated in the blackbrowed albatross Thalassarche (previously Diomedea) melanophrys, m b ,4 kg). We found that soaring-gliding migration speed is not significantly different from flapping migration speed. Conclusions/Significance: We found no evidence that soaring-gliding speed is slower than flapping flight in bee-eaters, contradicting earlier estimates that implied a migration speed penalty for using soaring-gliding rather than flapping flight. Moreover, we suggest that small birds soar and glide during migration, breeding, dispersal, and other stages in their annual cycle because it may entail a low energy cost of transport. We propose that the energy cost of soaring-gliding may be proportional to BMR regardless of bird size, as theoretically deduced by earlier studies.

PLoS ONE, 2013

Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, med... more Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by nonspecific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (e) and absorption rate of three paracellular probes (arabinose, L-rhamnose, cellobiose) and of 3-O-methyl D-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl D-glucose was high (e = 0.7360.04) and similar to other vertebrates; e of the paracellular probes was relatively low (arabinose e = 0.3160.03, Lrhamnose e = 0.1960.02, and cellobiose e = 0.1460.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl D-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).

Physiological and Biochemical Zoology, 2006

The diets of frugivorous and nectarivorous vertebrates contain much water and generally have high... more The diets of frugivorous and nectarivorous vertebrates contain much water and generally have high energy but low protein contents. Therefore, we tested the prediction that to save energy under conditions of high energy demands and high water intake, frugivorous Egyptian fruit bats (Rousettus aegyptiacus) will increase both the absolute quantity and the proportion of ammonia in their urine. We also examined whether such changes occur when protein intake is low and water intake is high. We did three feeding trials. In trials 1 and 2, bats were fed one of four liquid diets containing constant soy protein concentrations but varying in sucrose concentration and were kept at ambient temperatures (T a) of 30ЊC and 12ЊC, respectively. In trial 3, bats were kept at and fed one of four liquid diets T p 12ЊC a

Oecologia, 2004

We examined gender-dependent competitive interactions between two nocturnal desert gerbil species... more We examined gender-dependent competitive interactions between two nocturnal desert gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, by a field manipulation experiment. The study was done in two 1ha enclosed plots and included allopatric (only G. a. allenbyi) and sympatric (both species together) treatments. Seed trays and thermal imaging cameras were used to observe the gerbils' foraging activities and aggressive interactions. We found that the negative effect of the competitively dominant species, G. pyramidum, on time spent in seed trays, and ability to control these artificial food patches, was stronger on male than on female G. a. allenbyi. Consequently, the aggression of male G. a. allenbyi towards female G. a. allenbyi was markedly reduced, indicating that the dominant species mediated competition between the genders of the subordinate species. Furthermore, this interference-mediated indirect effect was associated with a decrease in the body mass of male G. a. allenbyi and an increase in the survival of female G. a. allenbyi. We suggest that both the reduction in intra-specific aggression and the positive effect on female survival can potentially stabilize competitive interactions and promote coexistence in this small mammal community.

Integrative and Comparative Biology, 2011

Synopsis During migration, birds undergo alternating periods of fasting and re-feeding that are a... more Synopsis During migration, birds undergo alternating periods of fasting and re-feeding that are associated with dynamic changes in body mass (m b) and in organ size, including that of the digestive tract. After arrival at a migratory stopover site, following a long flight, a bird must restore the tissues of its digestive tract before it can refuel. In the present study we examined how the availability of dietary protein influences refueling of migrating blackcaps (Sylvia atricapilla) during a migratory stopover. We tested the following predictions in blackcaps deprived of food and water for 1-2 days to induce stopover behavior: (1) birds provided with a low-protein diet will gain m b , lean mass and fat mass, and increase in pectoral muscle size slower than do birds fed a high-protein diet; (2) since stopover time is shorter in spring, birds will gain m b and build up fat tissue and lean tissue faster than in autumn; and (3) if low dietary protein limits a bird's ability to gain m b and fat reserves, then birds that do not obtain enough protein will initiate migratory restlessness (Zugunruhe) earlier than will birds with adequate dietary protein. These predictions were tested by providing captured migrating blackcaps with semisynthetic isocaloric diets differing only in their protein content. Each day, we measured m b , and food intake; also lean mass and fat mass were measured using dual energy X-ray absorptiometry. In addition, we monitored nocturnal activity with a video recording system. In both spring and autumn, birds fed diets containing either 3 or 20% protein increased in m b , lean mass and fat mass at similar rates during the experiment. However, the group receiving 3% protein ate more than did the group receiving 20% protein. In support of our predictions, m b , lean mass, fat mass, and intake of food all were higher in spring than in autumn. We also found that in spring all birds had higher levels of migratory restlessness, but birds fed 3% protein were less active at night than were birds fed 20% protein, possibly an adaptation conserving energy and protein. We conclude that protein requirements of migrating blackcaps during stopover are lower than expected, and that birds can compensate for low dietary protein by behavioral responses, i.e. hyperphagia and decreased migratory restlessness, that ensure rapid refueling.

Integrative and Comparative Biology, 2011

Since mammalian frugivores generally choose to eat ripe fruit in which ethanol concentration ([Et... more Since mammalian frugivores generally choose to eat ripe fruit in which ethanol concentration ([EtOH]) increases as the fruit ripens, we asked whether ethanol acts as an appetitive stimulant in the Egyptian fruit bat, Rousettus aegyptiacus, and also studied the effects of ethanol on their skin temperature (T s). We hypothesized that the responses of fruit bats to dietary ethanol are concentration dependent and tested the predictions that the bats' response is positive, i.e., they eat more when [EtOH] in the food is in the range found in naturally ripe fruit, while it negatively affects them at higher concentrations. We also tested the prediction that in winter, even when availability of fruit is low and thermoregulatory costs are high, ingestion of ethanol by fruit bats is low because assimilated ethanol reduces shivering thermogenesis and peripheral vasodilation; these, alone or together, are detrimental to the maintenance of body temperature (T b). In summer, captive bats offered food containing 0.1% ethanol significantly increased consumption over food with no ethanol; they did not change consumption when food contained 0.01, 0.3, or 0.5% ethanol; but significantly decreased consumption at higher levels of ethanol [EtOH], i.e., 1 and 2%. In winter, captive bats ate significantly less when their food contained 0.1% ethanol than when it contained 0, 0.3, or 0.5%. During summer, freshly caught bats ate significantly more ethanol-containing food than freshly caught bats in winter. Skin temperature (T s) in Egyptian fruit bats decreased significantly at an ambient temperature (T a) of 128C (winter conditions) after gavage with liquid food containing 1% ethanol. The effect was clearly temperature-dependent, since ethanol did not have the same effect on bats gavaged with food containing 1% or no ethanol at a T a of 258C (summer conditions). In conclusion, ethanol may act as an appetitive stimulant for Egyptian fruit bats at low concentrations, but only in summer. Bats are deterred by food containing [EtOH] corresponding to that in overripe, unpalatable fruit (1 and 2%). Furthermore, during winter, Egyptian fruit bats are deterred by ethanol-rich fruit, possibly due to the potential thermoregulatory consequences of ethanol consumption.

Integrative and Comparative Biology, 2011

Synopsis Migrating blackcaps (Sylvia atricapilla) were used to test the predictions that (1) the ... more Synopsis Migrating blackcaps (Sylvia atricapilla) were used to test the predictions that (1) the rebuilding of the digestive tract, as reflected by mass-specific consumption of food on the first 2-3 days of a stopover, is faster in birds with access to drinking water than in birds without, and (2) that adipose tissue and pectoral muscles grow faster and to a greater extent in birds with unlimited access to water. We simulated migratory stopover in two experiments. In Experiment I, each of 31 birds was randomly assigned to one of three experimental groups for 6 days. Along with mealworms ($64% water) ad libitum, Group 1 received drinking water ad libitum; Group 2 had 0.5 h/day access to water; and Group 3 had no access to water. In Experiment II, 30 birds were offered a mixed diet for insectivorous birds ($33% water) ad libitum for 6 days, while randomly assigned to two groups: (1) Water ad libitum-control; and (2) 30 min access to water twice a day. We measured lean mass and fat mass using dual energy X-ray absorptiometry, as well as body mass (m b), pectoral muscle index (PMI), and daily intake of food and water. Mean daily water intake was significantly different among the groups in both experiments. However, the availability of drinking water positively affected the rates of gain of lean and fat mass only in birds fed with the mixed, relatively dry diet. Furthermore, mass-specific daily food intake was affected by the availability of drinking water only in the mixed diet experiment, in which birds with unlimited access to drinking water reached an asymptote, 1 day earlier than birds in the water-restricted group. We suggest that in birds consuming diets with low water content, the lack of sufficient drinking water may result in slower rebuilding of the digestive tract, or may influence biochemical processes in the gut that result in slower growth of tissue. Although blackcaps obtained sufficient water from preformed and metabolic water to renew lost tissues when eating mealworms, given access to water, the birds drank prodigiously. Our results also suggest that if drinking water is unavailable to migrating blackcaps, their choices are restricted to water-rich foods, which may constrain their rate of feeding and thus the rate at which they deposit fat. Consequently, drinking water may have an important influence on birds' migratory strategies with respect to habitat selection, use of energy, and the saving of time.

Journal of Experimental Biology, 2002

SUMMARYMost aquatic vertebrates are ammonotelic, whereas terrestrial vertebrates are typically ur... more SUMMARYMost aquatic vertebrates are ammonotelic, whereas terrestrial vertebrates are typically uricotelic or ureotelic. However, the principal form of nitrogenous waste product in the urine of an animal may vary, depending on environmental conditions. Anna's hummingbird (Calypte anna) was found to switch from uricotely at high ambient temperature (Ta)to ammonotely at lower Ta, when energy demands and consequent nectar intake rates were high. In extension of this, we hypothesised that nectarivorous birds would switch from uricotely to ammonotely when water intake rates were high or when protein or salt intake rates were low. We examined the influence of water, electrolyte and protein intake and of Ta on the excretion of ammonia, urea and urate (uric acid and its salts) in nectarivorous Palestine sunbirds(Nectarinia osea). The proportion of ammonia in ureteral urine and excreted fluid was not influenced by total water or salt intake or by Ta. Protein intake did not influence nitro...

Proceedings of the Royal Society B: Biological Sciences, 2016

The water vapour permeability barrier of mammals and birds resides in the stratum corneum (SC), t... more The water vapour permeability barrier of mammals and birds resides in the stratum corneum (SC), the outermost layer of the epidermis. The molar ratio and molecular arrangement of lipid classes in the SC determine the integrity of this barrier. Increased chain length and polarity of ceramides, the most abundant lipid class in mammalian SC, contribute to tighter packing and thus to reduced cutaneous evaporative water loss (CEWL). However, tighter lipid packing also causes low SC hydration, making it brittle, whereas high hydration softens the skin at the cost of increasing CEWL. Cerebrosides are not present in the mammalian SC; their pathological accumulation occurs in Gaucher's disease, which leads to a dramatic increase in CEWL. However, cerebrosides occur normally in the SC of birds. We tested the hypothesis that cerebrosides are also present in the SC of bats, because they are probably necessary to confer pliability to the skin, a quality needed for flight. We examined the SC ...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2016

Life in deserts is challenging for bats because of their relatively high energy and water require... more Life in deserts is challenging for bats because of their relatively high energy and water requirements; nevertheless bats thrive in desert environments. We postulated that bats from desert environments have lower metabolic rates (MR) and total evaporative water loss (TEWL) than their mesic counterparts. To test this idea, we measured MR and TEWL of four species of bats, which inhabit the Negev desert in Israel, one species mainly restricted to hyper-arid deserts (Otonycteris hemprichii), two species from semi-desert areas (Eptesicus bottae and Plecotus christii), and one widespread species (Pipistrellus kuhlii). We also measured separately, in the same individuals, the two components of TEWL, respiratory water loss (RWL) and cutaneous evaporative water loss (CEWL), using a mask. In all the species, MR and TEWL were significantly reduced during torpor, the latter being a consequence of reductions in both RWL and CEWL. Then, we evaluated whether MR and TEWL in bats differ according to their geographic distributions, and whether those rates change with T a and the use of torpor. We did not find significant differences in MR among species, but we found that TEWL was lowest in the species restricted to desert habitats, intermediate in the semi-desert dwelling species, and highest in the widespread species, perhaps a consequence of adaptation to life in deserts. Our results were supported by a subsequent analysis of data collected from the literature on rates of TEWL for 35 bat species from desert and mesic habitats.

Mammalian Biology, 2015

Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food a... more Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food and low concentration of electrolytes therein. We examined the effects of salt content (NaCl) and sugar type (sucrose vs. glucose) on the intake rate of dilute sugar solutions by the Egyptian fruit bat (Rousettus aegyptiacus). Increased salt content did not bring about an increase in energy intake by bats fed dilute sucrose diets and the bats did not compensate by hyperphagia to achieve the energy intake of bats fed concentrated sucrose solution without salt. Moreover, increasing salt content had a negative effect on the total energy intake of Egyptian fruit bats fed equicaloric sucrose solutions. There were no differences in hematocrit in bats fed the diets of different sucrose concentration, but plasma osmolality was higher in those bats fed more concentrated sugar solutions, and urine osmolality was higher in those fed on highsalt diets. Food and energy intake did not differ between bats that were fed dilute glucose and sucrose solutions. Our findings indicate that Egyptian fruit bats do not modulate food intake when salt content of dilute sugar solutions is increased, and that increasing salt content might constrain their food intake rate. Sugar type did not affect food intake by Egyptian fruit bats, indicating that sucrose hydrolysis alone does not limit the intake of dilute sugar nectar.

The Journal of experimental biology, 2010

Clinicians commonly measure the (13)CO(2) in exhaled breath samples following administration of a... more Clinicians commonly measure the (13)CO(2) in exhaled breath samples following administration of a metabolic tracer (breath testing) to diagnose certain infections and metabolic disorders. We believe that breath testing can become a powerful tool to investigate novel questions about the influence of ecological and physiological factors on the oxidative fates of exogenous nutrients. Here we examined several predictions regarding the oxidative kinetics of specific carbohydrates, amino acids and fatty acids in a dietary generalist, the house sparrow (Passer domesticus). After administering postprandial birds with 20 mg of one of seven (13)C-labeled tracers, we measured rates of (13)CO(2) production every 15 min over 2 h. We found that sparrows oxidized exogenous amino acids far more rapidly than carbohydrates or fatty acids, and that different tracers belonging to the same class of physiological fuels had unique oxidative kinetics. Glycine had a mean maximum rate of oxidation (2021 nmol...

Physiological and Biochemical Zoology, 1999

Condensation of water vapor in the exhaled air stream as it passes over previously cooled membran... more Condensation of water vapor in the exhaled air stream as it passes over previously cooled membranes of the nasopharynx is thought to be a mechanism that reduces respiratory water loss in mammals and birds. Such a mechanism could be important in the overall water economy of these vertebrates, especially those species occupying desert habitats. However, this hypothesis was originally based on measurements of the temperature of exhaled air (T ex), which provides an estimate of water recovered from exhaled air as a proportion of water added on inhalation but does not yield a quantitative measure of the reduction in total evaporative water loss (TEWL). In this study, we experimentally occluded the nares of crested larks (Galerida cristata), a cosmopolitan species, and desert larks (Ammomanes deserti), a species restricted to arid habitats, to test the hypothesis that countercurrent heat exchange in the nasal passages reduces TEWL. T ex of crested larks increased linearly with air temperature, (T a):. Following T ϭ 8.93 ϩ 0.793 # T ex a Schmidt-Nielsen and based on measurements of T ex , we predicted that crested larks would recover 69%, 49%, 23%, and

Journal of Experimental Biology, 2008

SUMMARYFood resources are complementary for a forager if their contribution to fitness is higher ... more SUMMARYFood resources are complementary for a forager if their contribution to fitness is higher when consumed together than when consumed independently,e.g. ingesting one may reduce the toxic effects of another. The concentration of potentially toxic ethanol, [EtOH], in fleshy fruit increases during ripening and affects food choices by Egyptian fruit bats, becoming deterrent at high concentrations (⩾1%). However, ethanol toxicity is apparently reduced when ingested along with some sugars; more with fructose than with sucrose or glucose. We predicted (1) that ingested ethanol is eliminated faster by bats eating fructose than by bats eating sucrose or glucose, (2)that the marginal value of fructose-containing food (food+fructose) increases with increasing [EtOH] more than the marginal value of sucrose- or glucose-containing food (food+sucrose, food+glucose), and (3) that by increasing [EtOH] the marginal value of food+sucose is incremented more than that of food+glucose. Ethanol in b...

Journal of Experimental Biology, 2004

SUMMARYAlthough most birds are accustomed to making short flights, particularly during foraging, ... more SUMMARYAlthough most birds are accustomed to making short flights, particularly during foraging, the flight patterns during these short periods of activity differ between species. Nectarivorous birds, in particular, often spend time hovering, while non-nectarivorous birds do not. The cost of short flights is likely therefore to differ between nectarivorous and non-nectarivorous birds because of the different energetic contributions of different flight types to the behaviour. The 13C-labelled bicarbonate technique was used to measure the energy cost of short flights in the nectarivorous Palestine sunbird Nectarinia osea (mean mass 6.17±0.16 g, N=8)and the non-nectarivorous starling Sturnus vulgaris (mean mass 70.11±1.11 g, N=9). The technique was initially calibrated in five individuals for each species at temperatures ranging from 1 to 35°C,by comparing the isotope elimination rate to the metabolic rate measured simultaneously by indirect calorimetry. The cost for short intermittent...

Journal of Experimental Biology, 2012

SUMMARY We examined feeding performance of the flea Xenopsylla ramesis on three different hosts: ... more SUMMARY We examined feeding performance of the flea Xenopsylla ramesis on three different hosts: its natural, granivorous, rodent host, Sundevall’s jird (Meriones crassus); the frugivorous Egyptian fruit bat (Rousettus aegyptiacus); and an insectivorous bat, Kuhl’s pipistrelle (Pipistrellus kuhlii). Because these fleas are not known to occur on bats, we hypothesized that the fleas’ feeding performance (i.e. feeding and digestion rates) would be higher when feeding on their natural host than on either of the bats that they do not naturally parasitize. We found that mass-specific blood-meal size of both male and female fleas was significantly lower when feeding on Kuhl’s pipistrelles than on the other two species, but was not different in female fleas feeding on fruit bats or on jirds at all stages of digestion. However, more male fleas achieved higher levels of engorgement if they fed on Sundevall’s jirds than if they fed on Egyptian fruit bats. The fleas digested blood of fruit bats...

Journal of Experimental Biology, 2012

SUMMARY During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated ... more SUMMARY During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated organs in small birds decreases in size by as much as 40%, compared with the preflight condition because of the catabolism of protein. At stopover sites, birds need 2–3 days to rebuild their GIT so that they can restore body mass and fat reserves to continue migration. The source of protein used to rebuild the GIT may be exogenous (from food ingested) or endogenous (reallocated from other organs) or both. Because the relative contribution of these sources to rebuild the GIT of migratory birds is not yet known, we mimicked in-flight fasting and then re-feeding in two groups of blackcaps (Sylvia atricapilla), a Palearctic migratory passerine. The birds were fed a diet containing either 3% or 20% protein to simulate different refueling scenarios. During re-feeding, birds received known doses of 15N-l-leucine before we measured the isotope concentrations in GIT and associated digestive organ...

Journal of Experimental Biology, 2013

SUMMARYBats hibernate to cope with low ambient temperatures (Ta) and low food availability during... more SUMMARYBats hibernate to cope with low ambient temperatures (Ta) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (Tb) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat’s winter energy expenditure. This has been associated with variation in Tb, Ta or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with Ta and Tb. Ta and Tb were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and Tb or Ta. Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same Ta but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water lo...

Journal of Experimental Biology, 2010

SUMMARYPrevious studies reported that fed bats and birds mostly use recently acquired exogenous n... more SUMMARYPrevious studies reported that fed bats and birds mostly use recently acquired exogenous nutrients as fuel for flight, rather than endogenous fuels, such as lipids or glycogen. However, this pattern of fuel use may be a simple size-related phenomenon because, to date, only small birds and bats have been studied with respect to the origin of metabolized fuel, and because small animals carry relatively small energy reserves, considering their high mass-specific metabolic rate. We hypothesized that ∼150 g Egyptian fruit bats (Rousettus aegyptiacus Pteropodidae), which are more than an order of magnitude heavier than previously studied bats, also catabolize dietary sugars directly and exclusively to fuel both rest and flight metabolism. We based our expectation on the observation that these animals rapidly transport ingested dietary sugars, which are absorbed via passive paracellular pathways in the intestine, to organs of high energy demand. We used the stable carbon isotope rat...

Proceedings of the Royal Society of London. Series B: Biological Sciences, 2002

Parent Palestine sunbirds (Nectarinia osea) feed on ower nectar that is not fed to their nestling... more Parent Palestine sunbirds (Nectarinia osea) feed on ower nectar that is not fed to their nestlings. This phenomenon provided a unique opportunity to manipulate self-feeding rates of parent birds independently of the rate at which they feed arthropod prey to their offspring. Based on provisioning models, we predicted that parents would invest more in their young as the energy content of their own food increased. From our earlier work, we also predicted that the levels of sex-speci c activities of males and females would differ as the energy content of their food increased. Sunbird pairs with two or three nestlings were provided with feeders containing a low-, medium-or high-concentration sucrose solution. As the sugar concentration increased, the females delivered arthropods at a greater rate to their nestlings, removed proportionally more faecal sacs and spent longer at the nest, while the males increased their mobbing effort. Nestling food intake and body mass, but not tarsus length or bill size, were larger in small broods than in large broods, and increased with increasing feeder sugar concentration. These results imply that increasing the energy content of food consumed by parent sunbirds allows them to increase the rate at which other foods are delivered to their young and to increase other parental care activities as well. The results also add credence to the idea that behavioural decisions re ect life-history trade-offs between parental self-feeding and investment in current young.

PLoS ONE, 2010

Background: Many avian species soar and glide over land. Evidence from large birds (m b .0.9 kg) ... more Background: Many avian species soar and glide over land. Evidence from large birds (m b .0.9 kg) suggests that soaringgliding is considerably cheaper in terms of energy than flapping flight, and costs about two to three times the basal metabolic rate (BMR). Yet, soaring-gliding is considered unfavorable for small birds because migration speed in small birds during soaring-gliding is believed to be lower than that of flapping flight. Nevertheless, several small bird species routinely soar and glide. Methodology/Principal Findings: To estimate the energetic cost of soaring-gliding flight in small birds, we measured heart beat frequencies of free-ranging migrating European bee-eaters (Merops apiaster, m b ,55 g) using radio telemetry, and established the relationship between heart beat frequency and metabolic rate (by indirect calorimetry) in the laboratory. Heart beat frequency during sustained soaring-gliding was 2.2 to 2.5 times lower than during flapping flight, but similar to, and not significantly different from, that measured in resting birds. We estimated that soaring-gliding metabolic rate of European bee-eaters is about twice their basal metabolic rate (BMR), which is similar to the value estimated in the blackbrowed albatross Thalassarche (previously Diomedea) melanophrys, m b ,4 kg). We found that soaring-gliding migration speed is not significantly different from flapping migration speed. Conclusions/Significance: We found no evidence that soaring-gliding speed is slower than flapping flight in bee-eaters, contradicting earlier estimates that implied a migration speed penalty for using soaring-gliding rather than flapping flight. Moreover, we suggest that small birds soar and glide during migration, breeding, dispersal, and other stages in their annual cycle because it may entail a low energy cost of transport. We propose that the energy cost of soaring-gliding may be proportional to BMR regardless of bird size, as theoretically deduced by earlier studies.

PLoS ONE, 2013

Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, med... more Absorption of small water-soluble nutrients in vertebrate intestines occurs both by specific, mediated transport and by nonspecific, passive, paracellular transport. Although it is apparent that paracellular absorption represents a significant route for nutrient absorption in many birds and mammals, especially small, flying species, its importance in ectothermic vertebrates has not previously been explored. Therefore, we measured fractional absorption (e) and absorption rate of three paracellular probes (arabinose, L-rhamnose, cellobiose) and of 3-O-methyl D-glucose (absorbed by both mediated and paracellular pathways) by the large herbivorous lizard, Uromastyx aegyptia, to explore the relative importance of paracellular and mediated transport in an ectothermic, terrestrial vertebrate. Fractional absorption of 3-O-methyl D-glucose was high (e = 0.7360.04) and similar to other vertebrates; e of the paracellular probes was relatively low (arabinose e = 0.3160.03, Lrhamnose e = 0.1960.02, and cellobiose e = 0.1460.02), and decreased with molecular mass, a pattern consistent with other vertebrates. Paracellular absorption accounted for approximately 24% of total 3-O-methyl D-glucose uptake, indicating low reliance on this pathway for these herbivorous lizards, a pattern similar to that found in other terrestrial vertebrates, and different from small flying endotherms (both birds and bats).

Physiological and Biochemical Zoology, 2006

The diets of frugivorous and nectarivorous vertebrates contain much water and generally have high... more The diets of frugivorous and nectarivorous vertebrates contain much water and generally have high energy but low protein contents. Therefore, we tested the prediction that to save energy under conditions of high energy demands and high water intake, frugivorous Egyptian fruit bats (Rousettus aegyptiacus) will increase both the absolute quantity and the proportion of ammonia in their urine. We also examined whether such changes occur when protein intake is low and water intake is high. We did three feeding trials. In trials 1 and 2, bats were fed one of four liquid diets containing constant soy protein concentrations but varying in sucrose concentration and were kept at ambient temperatures (T a) of 30ЊC and 12ЊC, respectively. In trial 3, bats were kept at and fed one of four liquid diets T p 12ЊC a

Oecologia, 2004

We examined gender-dependent competitive interactions between two nocturnal desert gerbil species... more We examined gender-dependent competitive interactions between two nocturnal desert gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, by a field manipulation experiment. The study was done in two 1ha enclosed plots and included allopatric (only G. a. allenbyi) and sympatric (both species together) treatments. Seed trays and thermal imaging cameras were used to observe the gerbils' foraging activities and aggressive interactions. We found that the negative effect of the competitively dominant species, G. pyramidum, on time spent in seed trays, and ability to control these artificial food patches, was stronger on male than on female G. a. allenbyi. Consequently, the aggression of male G. a. allenbyi towards female G. a. allenbyi was markedly reduced, indicating that the dominant species mediated competition between the genders of the subordinate species. Furthermore, this interference-mediated indirect effect was associated with a decrease in the body mass of male G. a. allenbyi and an increase in the survival of female G. a. allenbyi. We suggest that both the reduction in intra-specific aggression and the positive effect on female survival can potentially stabilize competitive interactions and promote coexistence in this small mammal community.

Integrative and Comparative Biology, 2011

Synopsis During migration, birds undergo alternating periods of fasting and re-feeding that are a... more Synopsis During migration, birds undergo alternating periods of fasting and re-feeding that are associated with dynamic changes in body mass (m b) and in organ size, including that of the digestive tract. After arrival at a migratory stopover site, following a long flight, a bird must restore the tissues of its digestive tract before it can refuel. In the present study we examined how the availability of dietary protein influences refueling of migrating blackcaps (Sylvia atricapilla) during a migratory stopover. We tested the following predictions in blackcaps deprived of food and water for 1-2 days to induce stopover behavior: (1) birds provided with a low-protein diet will gain m b , lean mass and fat mass, and increase in pectoral muscle size slower than do birds fed a high-protein diet; (2) since stopover time is shorter in spring, birds will gain m b and build up fat tissue and lean tissue faster than in autumn; and (3) if low dietary protein limits a bird's ability to gain m b and fat reserves, then birds that do not obtain enough protein will initiate migratory restlessness (Zugunruhe) earlier than will birds with adequate dietary protein. These predictions were tested by providing captured migrating blackcaps with semisynthetic isocaloric diets differing only in their protein content. Each day, we measured m b , and food intake; also lean mass and fat mass were measured using dual energy X-ray absorptiometry. In addition, we monitored nocturnal activity with a video recording system. In both spring and autumn, birds fed diets containing either 3 or 20% protein increased in m b , lean mass and fat mass at similar rates during the experiment. However, the group receiving 3% protein ate more than did the group receiving 20% protein. In support of our predictions, m b , lean mass, fat mass, and intake of food all were higher in spring than in autumn. We also found that in spring all birds had higher levels of migratory restlessness, but birds fed 3% protein were less active at night than were birds fed 20% protein, possibly an adaptation conserving energy and protein. We conclude that protein requirements of migrating blackcaps during stopover are lower than expected, and that birds can compensate for low dietary protein by behavioral responses, i.e. hyperphagia and decreased migratory restlessness, that ensure rapid refueling.

Integrative and Comparative Biology, 2011

Since mammalian frugivores generally choose to eat ripe fruit in which ethanol concentration ([Et... more Since mammalian frugivores generally choose to eat ripe fruit in which ethanol concentration ([EtOH]) increases as the fruit ripens, we asked whether ethanol acts as an appetitive stimulant in the Egyptian fruit bat, Rousettus aegyptiacus, and also studied the effects of ethanol on their skin temperature (T s). We hypothesized that the responses of fruit bats to dietary ethanol are concentration dependent and tested the predictions that the bats' response is positive, i.e., they eat more when [EtOH] in the food is in the range found in naturally ripe fruit, while it negatively affects them at higher concentrations. We also tested the prediction that in winter, even when availability of fruit is low and thermoregulatory costs are high, ingestion of ethanol by fruit bats is low because assimilated ethanol reduces shivering thermogenesis and peripheral vasodilation; these, alone or together, are detrimental to the maintenance of body temperature (T b). In summer, captive bats offered food containing 0.1% ethanol significantly increased consumption over food with no ethanol; they did not change consumption when food contained 0.01, 0.3, or 0.5% ethanol; but significantly decreased consumption at higher levels of ethanol [EtOH], i.e., 1 and 2%. In winter, captive bats ate significantly less when their food contained 0.1% ethanol than when it contained 0, 0.3, or 0.5%. During summer, freshly caught bats ate significantly more ethanol-containing food than freshly caught bats in winter. Skin temperature (T s) in Egyptian fruit bats decreased significantly at an ambient temperature (T a) of 128C (winter conditions) after gavage with liquid food containing 1% ethanol. The effect was clearly temperature-dependent, since ethanol did not have the same effect on bats gavaged with food containing 1% or no ethanol at a T a of 258C (summer conditions). In conclusion, ethanol may act as an appetitive stimulant for Egyptian fruit bats at low concentrations, but only in summer. Bats are deterred by food containing [EtOH] corresponding to that in overripe, unpalatable fruit (1 and 2%). Furthermore, during winter, Egyptian fruit bats are deterred by ethanol-rich fruit, possibly due to the potential thermoregulatory consequences of ethanol consumption.

Integrative and Comparative Biology, 2011

Synopsis Migrating blackcaps (Sylvia atricapilla) were used to test the predictions that (1) the ... more Synopsis Migrating blackcaps (Sylvia atricapilla) were used to test the predictions that (1) the rebuilding of the digestive tract, as reflected by mass-specific consumption of food on the first 2-3 days of a stopover, is faster in birds with access to drinking water than in birds without, and (2) that adipose tissue and pectoral muscles grow faster and to a greater extent in birds with unlimited access to water. We simulated migratory stopover in two experiments. In Experiment I, each of 31 birds was randomly assigned to one of three experimental groups for 6 days. Along with mealworms ($64% water) ad libitum, Group 1 received drinking water ad libitum; Group 2 had 0.5 h/day access to water; and Group 3 had no access to water. In Experiment II, 30 birds were offered a mixed diet for insectivorous birds ($33% water) ad libitum for 6 days, while randomly assigned to two groups: (1) Water ad libitum-control; and (2) 30 min access to water twice a day. We measured lean mass and fat mass using dual energy X-ray absorptiometry, as well as body mass (m b), pectoral muscle index (PMI), and daily intake of food and water. Mean daily water intake was significantly different among the groups in both experiments. However, the availability of drinking water positively affected the rates of gain of lean and fat mass only in birds fed with the mixed, relatively dry diet. Furthermore, mass-specific daily food intake was affected by the availability of drinking water only in the mixed diet experiment, in which birds with unlimited access to drinking water reached an asymptote, 1 day earlier than birds in the water-restricted group. We suggest that in birds consuming diets with low water content, the lack of sufficient drinking water may result in slower rebuilding of the digestive tract, or may influence biochemical processes in the gut that result in slower growth of tissue. Although blackcaps obtained sufficient water from preformed and metabolic water to renew lost tissues when eating mealworms, given access to water, the birds drank prodigiously. Our results also suggest that if drinking water is unavailable to migrating blackcaps, their choices are restricted to water-rich foods, which may constrain their rate of feeding and thus the rate at which they deposit fat. Consequently, drinking water may have an important influence on birds' migratory strategies with respect to habitat selection, use of energy, and the saving of time.