Luis M. Bautista

Dynamics of ciliated protozoa communities in activated sludge process

Abstract The purpose of this research is to describe and examine the importance of ciliated protozoan communities in the activated-sludge process. During this study a total number of 21 species of ciliates was recorded and 19 physico-chemical variables measured in the wastewater. The presence of the most common species of ciliates was related to plant operational parameters using multivariate statistical procedures. Principal Component Analysis with Varimax rotation performed on the total biological and non-biological set of data showed that six component factors explained 73% of the variability of the process. The first factor has a significant biological importance; it groups together the species of ciliates and explains 25% of the variability of the sewage plant. This study helps to understand the ecology of these organisms and the operational and control methods of the activated-sludge process.

Patch use in cranes: a field test of optimal foraging predictions

Abstract 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.

Carrying capacity of staging areas and facultative migration extension in common cranes

This is a contribution to projects PB87-0389 and PB91-0081 of the Direccion General de Investigacion Cientifica y Tecnica.

Foraging site displacement in common crane flocks.

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. Copyright 1998 The Association for the Study of Animal Behaviour.

A 20-year study of wintering common crane fluctuations using time series analysis

The numbers of common cranes (Grus grus) staging and wintering at Laguna de Gallocanta (Gallocanta), northeastern Spain, have increased throughout the period 1970-90. Consequently, we modelled the use of this area by cranes using Box-Jenkins Time Series Analysis to evaluate the influence of local food availability, duck hunting, and habitat and food conditions at other more traditional crane wintering areas in southwestern Spain on Gallocanta crane numbers. Food availability was not correlated with crane numbers at Gallocanta except during mid-winter

Effects of habitat quality on ciliated protozoa communities in sewage treatment plants

Abstract Ciliated protozoa communities and physico‐chemical variables were measured in an activated‐sludge sewage‐treatment plant in order to know the influence of the environmental conditions on the ciliate populations during biological treatment. Data of biological and not biological variables were submitted to stepwise multiple regression analysis, revealing which environmental variables are important for the development of each ciliate species and for the whole ciliate population.

Dominance and the dynamics of phenotype-limited distribution in common cranes

Abstract 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.

Coal tits increase evening body mass in response to tawny owl calls

Abstract Current theory predicts small birds should have a reduced body mass when daytime predation risk is high. However, the influence that nighttime predators might have on changes in body mass or daytime foraging behaviour has not been addressed. We therefore studied the effect of changes in perceived nocturnal predation risk on the body mass of captive coal tits. In a soundproof room, eight coal tits were housed in individual cages and an experiment was performed in which the birds were subjected to two treatments. First, morning and evening body mass was monitored following nights that were quiet. Second, these parameters were measured following nights when the call of a tawny owl had been played once per hour. Evening body mass was 3% greater on days following owl-disturbed nights, but morning body masses did not differ between treatments. To ensure this result was a response to the owl calls per se, and not a general response to increased disturbance, a second experiment was necessary. Here the coal tits were exposed hourly to the calls of a nightjar, a non-predatory nocturnal bird, but no increases in body mass were observed compared to quiet nights. We suggest the coal tits increased body mass in response to owl calls to offset increased nighttime energy expenditure in attentive behaviour.

Breeding success of Azure-winged Magpies Cyanopica cyana in Central Spain

The breeding success of Azure-winged Magpies was studied in Central Spain during 1986. Nesting density was 1.01 nests/ha, but nests were clumped. Breeding season was short and synchronized. Clutches were initiated between 10 April and 25 May. Clutches were started in 69% and completed in 60% of 136 nests built. Mean clutch size was 6.2 eggs. Only 32% of nesting attempts were successful, with an average 5.1 young fledged. Success declined as the season advanced.

Males of a Strongly Polygynous Species Consume More Poisonous Food than Females

We present evidence of a possible case of self-medication in a lekking bird, the great bustard Otis tarda. Great bustards consumed blister beetles (Meloidae), in spite of the fact that they contain cantharidin, a highly toxic compound that is lethal in moderate doses. In addition to anthelminthic properties, cantharidin was effective against gastrointestinal bacteria that cause sexually-transmitted diseases. Although both sexes consumed blister beetles during the mating season, only males selected them among all available insects, and ingested more and larger beetles than females. The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness. This plausibly explains the intense cloaca display males perform to approaching females, and the meticulous inspection females conduct of the males cloaca, a behaviour only observed in this and another similar species of the bustard family. A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females. Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.