Luis Bautista - Academia.edu (original) (raw)
Papers by Luis Bautista
Animal Behaviour, 2006
Small birds show the greatest rates of body mass gain at dawn and before dusk. Some environmental... more Small birds show the greatest rates of body mass gain at dawn and before dusk. Some environmental and internal factors may change the intensity and duration of the first period of body mass gain relative to the second one, and thus may change the shape of daily fattening trajectories. A frequent problem for researchers is setting the periods of the day when each of the main environmental factors operates, because its effects usually decay or increase smoothly from dawn to dusk. We solved this problem by fitting the body mass to time of day with a model generated with a differential approach. This model shows the typical bimodal pattern of daily fattening routines in small birds and allows calculation of the inflexion point, that is, the time of day when the trajectory ends the decelerated period of body mass gain and starts the accelerated increase in body weight. A delay or advance in the inflexion point can be related to environmental stress that may otherwise pass unnoticed. We calculated a mean delay of 10% in the inflexion point in a sample of studies with limited food availability, and a mean advance of 6% in a sample of studies with increased predation risk. The change in the shape of daily trajectories of body mass between stressful and nonstressful conditions was inversely correlated with body mass at dawn.
Animal Behaviour, 2006
Theoretical models predict that small birds should adjust daily patterns of body mass gain in res... more Theoretical models predict that small birds should adjust daily patterns of body mass gain in response to environmental and internal factors. In a companion paper, we described a model on daily fattening that allows the analysis of precise changes in the shape of hourly patterns of body mass. In this study, we tested one of the main predictions of the model: the inflexion point of the body mass trajectory should be delayed in response to a decrease in food availability, increasing body mass as soon as possible when food is scarce. This effect might be stronger in subordinate than in dominant birds. We tested both predictions with four pairs of coal tits, Periparus ater, kept in cages where food was delivered at high and low rates. Daytime increase in body mass was 1 g in both treatments. As predicted by the model, the tits increased body mass as soon as possible when food was delivered at a low rate, and the inflexion point of the body mass trajectory was 16.7% delayed compared to the high food delivery rate. However, dominance rank had no significant effect on the shape of daily body mass increase. To our knowledge, this is the first precise estimate of the change in the shape of body mass trajectories. Our findings have important implications for the analysis of daily patterns of body mass and for the design of studies of body mass in small birds.
Behavioral Ecology, 2002
In a dominance-structured flock, social status may determine priority of access to food. Birds of... more In a dominance-structured flock, social status may determine priority of access to food. Birds of low social status may perceive present and future access to food as less predictable, and so have a higher risk of starvation, than birds of high social rank. Theoretical models predict that subordinate birds should carry larger fat reserves and incur higher mass-dependent costs than dominants. However, empirical tests of the assumptions of these models are still scarce and controversial. We investigated the effect of dominance rank on daily mass gain under conditions of fluctuating food availability in a laboratory experiment using four flocks of four coal tits (Parus ater) each. The same amount of food was delivered in two treatments, but in one treatment the food was offered at a constant rate between days (fixed treatment), while in the other treatment the daily food supply varied in an unpredictable sequence between days (variable treatment). All birds showed greater variance in body mass in the variable treatment than in the fixed treatment. Body mass within birds showed the same variability at dawn than at dusk in the fixed treatment, but less variability at dawn than at dusk in the variable treatment. This may be a mechanism to reduce the immediate risk of starvation at the beginning of the day, when fat reserves are at their lowest and the aggression between flock members when feeding highest. Subordinate birds were excluded from the feeders by dominants more often in the early morning than in the rest of the day, and they showed more variability in daily mass gain and body mass at dawn than dominant birds. These results support the hypothesis that subordinate birds have a reduced probability of surviving when food availability changes unexpectedly compared to dominants.
Animal Behaviour, 1998
Optimal foraging theory predicts that an individual should resort to intraspecific kleptoparasiti... more Optimal foraging theory predicts that an individual should resort to intraspecific kleptoparasitism when this foraging strategy helps to maximize its intake rate. Thus aggressor and victim should be foraging at lower and higher rates, respectively, than the flock average (intake rate maximization). Independent of the maximization principle, moreover, an aggressor should attack when its intake rate falls below a threshold critical for survival, and select a victim foraging at an intake rate high enough to ensure survival (starvation risk minimization). We tested both hypotheses using 324 aggressive displacements from feeding sites observed in flocks of common cranes, Grus grus, foraging on cereal fields. Aggressors attacked cranes feeding at higher rates than average birds. The immediate consequences of a successful attack were an increase in intake rate for the aggressor and a decrease for the victim. The intake rate of the aggressor prior to the attack was lower than both the mean intake rate of the flock and the minimum intake rate necessary to cover basic metabolic needs. After displacing its victim, the intake rate of the aggressor was higher than before the attack and also higher than the average intake rate of the flock. The intake rate of the aggressor after the attack was not higher than the mean intake rate of the flock, however, when the time spent on the attack was included. We conclude that cranes used a kleptoparasitic strategy to recover from temporary reductions in feeding rate. This was particularly the case below the threshold of intake necessary for survival.
Ibis, 2010
Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural ... more Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural steppes to arable farmland, where the species initially benefited from favourable feeding conditions. More recently, the species has suffered severe declines due partly to agricultural intensification. Nest losses and juvenile mortality are amongst the factors most seriously affecting survival probabilities of many populations of this endangered species, suggesting that management of nesting habitats would bring conservation benefits. We studied nest-site selection in a Great Bustard population of central Spain by radiotracking 42 females for periods of between 1 and 4 years. Females selected nest-sites in fallows or cereal fields, in areas of low patch-type diversity, far from human infrastructure, and with good horizontal visibility. These results suggest that females look for shelter, but also need to have good visibility while incubating, and they support the hypothesis that nest selection is a trade-off between concealment and visibility. We interpret both preferences as adaptations to reduce predation pressure, one of the main causes of nest failure in this species. Nests were placed on slopes significantly orientated to the southeast, which suggests that females also seek sites protected from the cold north-westerly winds that are prevalent in the study area. To reduce nest destruction, harvesting should be delayed as long as possible and habitat conservation measures should not be restricted to lek sites but also include nesting areas, which are frequently located far from leks.
Journal of Avian Biology, 2004
We describe winter territoriality in common cranes, Grus grus, a long-lived migrant species with ... more We describe winter territoriality in common cranes, Grus grus, a long-lived migrant species with long-lasting pair bonds and parental care extending throughout the winter. Cranes are territorial in the breeding season, and usually gregarious during migration and wintering. Only 2% of the families present in our study area were territorial, all other families foraged in flocks with immatures and adult pairs. Territorial pairs defended the same winter territory year after year, but only when they had offspring. They were gregarious otherwise. The average breeding success measured throughout several years was higher in territorial pairs. Winter territories were small (0.7 km2 on average), but included a higher diversity of habitats than the areas visited by gregarious birds (11.7 km2 on average). Adults of territorial families showed longer vigilance times, and lower food intake rates than did adults in flocks, which were compensated with a longer time spent foraging per day. The accumulated daily food intake did not differ between adults in flocks and in families. We suggest that winter territoriality is a facultative strategy, conditioned by parental experience and habitat availability.
Journal of Animal Ecology, 2002
Interference is a key component of food competition, but is difficult to measure in natural anima... more Interference is a key component of food competition, but is difficult to measure in natural animal populations. Using data from a long-term study, we show that interference between common cranes Grus grus L., feeding on patches of cereal seeds, reduces intake rates at high competitor densities, and that the strength of interference is unrelated to food abundance.
Behavioral Ecology and Sociobiology, 1997
We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when ... more We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when they changed their main daily foraging area between consecutive days during two winter seasons. Individuals went to a new foraging zone when on the previous day their morning food intake had fallen below their mean morning food intake measured over the whole winter. Food intake on the day before a change in foraging area was positively correlated with dominance rank. Dominant cranes changed to new zones with higher numbers of birds and food density, while subordinate cranes went to new zones with lower numbers of birds. As a result, all birds increased their food intake over that of the previous day. Dominant cranes remained more faithful to their most preferred foraging zone, where they spent 69% of the mornings, while subordinate birds were more mobile, switching among zones frequently. Dominant birds left the roost later than subordinate birds on the days they changed to a new zone, which could be used to track the main departing flows. The results suggest that the dynamics that led to a truncated phenotype-limited distribution were determined by social dominance and food abundance, with dominant cranes shifting to a new zone to maintain their high intake levels and subordinates changing more frequently whenever their daily intake did not reach the minimum metabolic requirements.
Animal Behaviour, 1995
The marginal value theorem states that foragers should leave patches when the instantaneous captu... more The marginal value theorem states that foragers should leave patches when the instantaneous capture rate has fallen to the average capture rate for the habitat. This predicts that patch residence time should increase with increasing patch quality and decrease with increasing habitat quality. These and other predictions from prescient, Bayesian and fixed-time models were tested using observations on 14 radio-tagged free-living common cranes, Grus grus, foraging in cereal farmland. Cranes behaved as Bayesian foragers. Their intake rates on leaving patches changed with patch and habitat quality. The behaviour of cranes was consistent with marginal value theorem predictions only in patches where energy return was lower than required to meet daily food requirements. In contrast, birds left richer patches earlier than expected and at higher intake rates than poor patches. In addition, cranes stayed longer in larger flocks. These results suggest that cranes changed their foraging rules according to their expected energy balance.
Water Air and Soil Pollution, 2011
The aim of this work was to determine the optimum values for the biodegradation process of six ab... more The aim of this work was to determine the optimum values for the biodegradation process of six abiotic factors considered very influential in this process. The optimisation of a polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and anthracene) biodegradation process was carried out with a degrading bacterial consortium C2PL05. The optimised factors were the molar ratio of carbon/nitrogen/phosphorus (C/N/P), the nitrogen source, the iron source, the iron concentration, the pH and the carbon source. Each factor was optimised applying three different treatments during 168 h, analysing cell density by spectrophotometric absorbance at 600 nm and PAH depletion by HPLC. To determine the optimum values of the factors, an analysis of variance was performed using the cell density increments and biotic degradation constants, calculated for each treatment. The most effective values of each factor were: a C/N/P molar ratio of 100:21:16, NaNO3 as nitrogen source, Fe2(SO4)3 as iron source using a concentration of 0.1 mmol l−1, a pH of 7.0 and a mixture of glucose and PAHs as carbon source. Therefore, high concentrations of nutrients and soluble forms of nitrogen and iron at neutral pH favour the biodegradation. Also, the addition of glucose to PAHs as carbon source increased the number of total microorganism and enhanced PAH biodegradation due to the augmentation of PAH degrader microorganisms. It is also important to underline that the statistical treatment of data and the combined study of the increments of the cell density and the biotic biodegradation constant have facilitated the accurate interpretation of the optimisation results. For an optimum bioremediation process, it is very important to perform these previous bioassays to decrease the process development time and, therefore, the costs.
Para resolver problemas recomendamos seguir las siguientes sugerencias.
Animal Behaviour, 2006
Small birds show the greatest rates of body mass gain at dawn and before dusk. Some environmental... more Small birds show the greatest rates of body mass gain at dawn and before dusk. Some environmental and internal factors may change the intensity and duration of the first period of body mass gain relative to the second one, and thus may change the shape of daily fattening trajectories. A frequent problem for researchers is setting the periods of the day when each of the main environmental factors operates, because its effects usually decay or increase smoothly from dawn to dusk. We solved this problem by fitting the body mass to time of day with a model generated with a differential approach. This model shows the typical bimodal pattern of daily fattening routines in small birds and allows calculation of the inflexion point, that is, the time of day when the trajectory ends the decelerated period of body mass gain and starts the accelerated increase in body weight. A delay or advance in the inflexion point can be related to environmental stress that may otherwise pass unnoticed. We calculated a mean delay of 10% in the inflexion point in a sample of studies with limited food availability, and a mean advance of 6% in a sample of studies with increased predation risk. The change in the shape of daily trajectories of body mass between stressful and nonstressful conditions was inversely correlated with body mass at dawn.
Animal Behaviour, 2006
Theoretical models predict that small birds should adjust daily patterns of body mass gain in res... more Theoretical models predict that small birds should adjust daily patterns of body mass gain in response to environmental and internal factors. In a companion paper, we described a model on daily fattening that allows the analysis of precise changes in the shape of hourly patterns of body mass. In this study, we tested one of the main predictions of the model: the inflexion point of the body mass trajectory should be delayed in response to a decrease in food availability, increasing body mass as soon as possible when food is scarce. This effect might be stronger in subordinate than in dominant birds. We tested both predictions with four pairs of coal tits, Periparus ater, kept in cages where food was delivered at high and low rates. Daytime increase in body mass was 1 g in both treatments. As predicted by the model, the tits increased body mass as soon as possible when food was delivered at a low rate, and the inflexion point of the body mass trajectory was 16.7% delayed compared to the high food delivery rate. However, dominance rank had no significant effect on the shape of daily body mass increase. To our knowledge, this is the first precise estimate of the change in the shape of body mass trajectories. Our findings have important implications for the analysis of daily patterns of body mass and for the design of studies of body mass in small birds.
Behavioral Ecology, 2002
In a dominance-structured flock, social status may determine priority of access to food. Birds of... more In a dominance-structured flock, social status may determine priority of access to food. Birds of low social status may perceive present and future access to food as less predictable, and so have a higher risk of starvation, than birds of high social rank. Theoretical models predict that subordinate birds should carry larger fat reserves and incur higher mass-dependent costs than dominants. However, empirical tests of the assumptions of these models are still scarce and controversial. We investigated the effect of dominance rank on daily mass gain under conditions of fluctuating food availability in a laboratory experiment using four flocks of four coal tits (Parus ater) each. The same amount of food was delivered in two treatments, but in one treatment the food was offered at a constant rate between days (fixed treatment), while in the other treatment the daily food supply varied in an unpredictable sequence between days (variable treatment). All birds showed greater variance in body mass in the variable treatment than in the fixed treatment. Body mass within birds showed the same variability at dawn than at dusk in the fixed treatment, but less variability at dawn than at dusk in the variable treatment. This may be a mechanism to reduce the immediate risk of starvation at the beginning of the day, when fat reserves are at their lowest and the aggression between flock members when feeding highest. Subordinate birds were excluded from the feeders by dominants more often in the early morning than in the rest of the day, and they showed more variability in daily mass gain and body mass at dawn than dominant birds. These results support the hypothesis that subordinate birds have a reduced probability of surviving when food availability changes unexpectedly compared to dominants.
Animal Behaviour, 1998
Optimal foraging theory predicts that an individual should resort to intraspecific kleptoparasiti... more Optimal foraging theory predicts that an individual should resort to intraspecific kleptoparasitism when this foraging strategy helps to maximize its intake rate. Thus aggressor and victim should be foraging at lower and higher rates, respectively, than the flock average (intake rate maximization). Independent of the maximization principle, moreover, an aggressor should attack when its intake rate falls below a threshold critical for survival, and select a victim foraging at an intake rate high enough to ensure survival (starvation risk minimization). We tested both hypotheses using 324 aggressive displacements from feeding sites observed in flocks of common cranes, Grus grus, foraging on cereal fields. Aggressors attacked cranes feeding at higher rates than average birds. The immediate consequences of a successful attack were an increase in intake rate for the aggressor and a decrease for the victim. The intake rate of the aggressor prior to the attack was lower than both the mean intake rate of the flock and the minimum intake rate necessary to cover basic metabolic needs. After displacing its victim, the intake rate of the aggressor was higher than before the attack and also higher than the average intake rate of the flock. The intake rate of the aggressor after the attack was not higher than the mean intake rate of the flock, however, when the time spent on the attack was included. We conclude that cranes used a kleptoparasitic strategy to recover from temporary reductions in feeding rate. This was particularly the case below the threshold of intake necessary for survival.
Ibis, 2010
Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural ... more Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural steppes to arable farmland, where the species initially benefited from favourable feeding conditions. More recently, the species has suffered severe declines due partly to agricultural intensification. Nest losses and juvenile mortality are amongst the factors most seriously affecting survival probabilities of many populations of this endangered species, suggesting that management of nesting habitats would bring conservation benefits. We studied nest-site selection in a Great Bustard population of central Spain by radiotracking 42 females for periods of between 1 and 4 years. Females selected nest-sites in fallows or cereal fields, in areas of low patch-type diversity, far from human infrastructure, and with good horizontal visibility. These results suggest that females look for shelter, but also need to have good visibility while incubating, and they support the hypothesis that nest selection is a trade-off between concealment and visibility. We interpret both preferences as adaptations to reduce predation pressure, one of the main causes of nest failure in this species. Nests were placed on slopes significantly orientated to the southeast, which suggests that females also seek sites protected from the cold north-westerly winds that are prevalent in the study area. To reduce nest destruction, harvesting should be delayed as long as possible and habitat conservation measures should not be restricted to lek sites but also include nesting areas, which are frequently located far from leks.
Journal of Avian Biology, 2004
We describe winter territoriality in common cranes, Grus grus, a long-lived migrant species with ... more We describe winter territoriality in common cranes, Grus grus, a long-lived migrant species with long-lasting pair bonds and parental care extending throughout the winter. Cranes are territorial in the breeding season, and usually gregarious during migration and wintering. Only 2% of the families present in our study area were territorial, all other families foraged in flocks with immatures and adult pairs. Territorial pairs defended the same winter territory year after year, but only when they had offspring. They were gregarious otherwise. The average breeding success measured throughout several years was higher in territorial pairs. Winter territories were small (0.7 km2 on average), but included a higher diversity of habitats than the areas visited by gregarious birds (11.7 km2 on average). Adults of territorial families showed longer vigilance times, and lower food intake rates than did adults in flocks, which were compensated with a longer time spent foraging per day. The accumulated daily food intake did not differ between adults in flocks and in families. We suggest that winter territoriality is a facultative strategy, conditioned by parental experience and habitat availability.
Journal of Animal Ecology, 2002
Interference is a key component of food competition, but is difficult to measure in natural anima... more Interference is a key component of food competition, but is difficult to measure in natural animal populations. Using data from a long-term study, we show that interference between common cranes Grus grus L., feeding on patches of cereal seeds, reduces intake rates at high competitor densities, and that the strength of interference is unrelated to food abundance.
Behavioral Ecology and Sociobiology, 1997
We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when ... more We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when they changed their main daily foraging area between consecutive days during two winter seasons. Individuals went to a new foraging zone when on the previous day their morning food intake had fallen below their mean morning food intake measured over the whole winter. Food intake on the day before a change in foraging area was positively correlated with dominance rank. Dominant cranes changed to new zones with higher numbers of birds and food density, while subordinate cranes went to new zones with lower numbers of birds. As a result, all birds increased their food intake over that of the previous day. Dominant cranes remained more faithful to their most preferred foraging zone, where they spent 69% of the mornings, while subordinate birds were more mobile, switching among zones frequently. Dominant birds left the roost later than subordinate birds on the days they changed to a new zone, which could be used to track the main departing flows. The results suggest that the dynamics that led to a truncated phenotype-limited distribution were determined by social dominance and food abundance, with dominant cranes shifting to a new zone to maintain their high intake levels and subordinates changing more frequently whenever their daily intake did not reach the minimum metabolic requirements.
Animal Behaviour, 1995
The marginal value theorem states that foragers should leave patches when the instantaneous captu... more The marginal value theorem states that foragers should leave patches when the instantaneous capture rate has fallen to the average capture rate for the habitat. This predicts that patch residence time should increase with increasing patch quality and decrease with increasing habitat quality. These and other predictions from prescient, Bayesian and fixed-time models were tested using observations on 14 radio-tagged free-living common cranes, Grus grus, foraging in cereal farmland. Cranes behaved as Bayesian foragers. Their intake rates on leaving patches changed with patch and habitat quality. The behaviour of cranes was consistent with marginal value theorem predictions only in patches where energy return was lower than required to meet daily food requirements. In contrast, birds left richer patches earlier than expected and at higher intake rates than poor patches. In addition, cranes stayed longer in larger flocks. These results suggest that cranes changed their foraging rules according to their expected energy balance.
Water Air and Soil Pollution, 2011
The aim of this work was to determine the optimum values for the biodegradation process of six ab... more The aim of this work was to determine the optimum values for the biodegradation process of six abiotic factors considered very influential in this process. The optimisation of a polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and anthracene) biodegradation process was carried out with a degrading bacterial consortium C2PL05. The optimised factors were the molar ratio of carbon/nitrogen/phosphorus (C/N/P), the nitrogen source, the iron source, the iron concentration, the pH and the carbon source. Each factor was optimised applying three different treatments during 168 h, analysing cell density by spectrophotometric absorbance at 600 nm and PAH depletion by HPLC. To determine the optimum values of the factors, an analysis of variance was performed using the cell density increments and biotic degradation constants, calculated for each treatment. The most effective values of each factor were: a C/N/P molar ratio of 100:21:16, NaNO3 as nitrogen source, Fe2(SO4)3 as iron source using a concentration of 0.1 mmol l−1, a pH of 7.0 and a mixture of glucose and PAHs as carbon source. Therefore, high concentrations of nutrients and soluble forms of nitrogen and iron at neutral pH favour the biodegradation. Also, the addition of glucose to PAHs as carbon source increased the number of total microorganism and enhanced PAH biodegradation due to the augmentation of PAH degrader microorganisms. It is also important to underline that the statistical treatment of data and the combined study of the increments of the cell density and the biotic biodegradation constant have facilitated the accurate interpretation of the optimisation results. For an optimum bioremediation process, it is very important to perform these previous bioassays to decrease the process development time and, therefore, the costs.
Para resolver problemas recomendamos seguir las siguientes sugerencias.