Nest-building by crested tit Parus cristatus males: an analysis of costs and benefits

In a population of crested tits in Belgium, one out of three breeding males participated in nest-building. Since variation in the amount of nest-building among 11 building males was low, analysis of male nest-building allowed a logistic regression design. The probability of building increased with male condition and for late nests. The effect of male condition decreased with date, and date was the only factor predicting nest-building for repeat broods. The effect of male condition on nest-building suggests that building entails important costs for males. Based on correlative data, we argue that building by males shortens the interval between the start of nest-building and the onset of egg-laying by about 5 days. Since clutch size, incubation and nestling time did not differ between early and late broods, male nest-building apparently affects fledging date. Since early fledgers (early dispersers) are more likely to settle in future winter flocks, building behaviour by crested tit males should be favoured by natural selection. So far, male nest-building in hole-breeding birds might have been overlooked due to the widespread use of artificial nest-boxes in behavioural studies.     

Immigration pattern and success in red squirrels

Summary We studied the characteristics of immigrants and the effects of immigration on reproductive activity and spacing behaviour in red squirrels living in high-quality woodlands. Male immigration peaked in spring, female immigration in autumn. There was no sex bias in dispersal distance of local recruits or in the proportion of male/female immigrants, but more subadults than adults immigrated on the study plots. Hence, hypotheses explaining sex-biased dispersal were irrelevant in explaining immigration patterns in our study populations. Immigrant females were not in breeding condition, nor had they produced a litter prior to immigration. Hence breeding dispersal did not occur. Red squirrels are promiscuous, and females defend intrasexual territories while males have overlapping home ranges with a dominance hierarchy (Wauters et al. 1990; Wauters and Dhondt 1992). Site fidelity is very important to reproductive success and most parents still have a high residual reproductive value after having produced a litter. Under such circumstances, the resident fitness hypothesis (RFH; Anderson 1989) predicts that parents can benefit by forcing emigration of offspring if the latter are likely to find nearby vacancies. The settlement pattern of successful immigrants, which had a higher probability of becoming established when they had high body mass and when they were settling in plots with reduced intrasexual competition, agreed with the RFH and with the proximate dispersal mechanism suggested by Gliwicz (1992), that dispersal tendency in both sexes depends on the degree of intrasexual competition under local conditions. The fact that close inbreeding was never observed could indicate that random immigration of both sexes, within the social environment of a partly territorial, relatively long-lived species, has evolved not only to reduce competition for resources between parents and offspring but also as an inbreeding avoidance mechanism. Correspondence to: L. Wauters     

Male quality,reproduction, and survival in the great tit (Parus major)

Summary Three possible measures of male quality (social dominance, song, and size), reproduction, and survival were studied in a single population of great tits. Winter dominance position on a feeder was related to strophe length (number of phrases per strophe), inversely related to positive drift (decrease of the singing rate of the phrases in a strophe), but not related to song repertoire size. Neither winter dominance position nor song were related to size (wing length, tarso-metatarsus length, weight).Singing capacity was not correlated with individual reproductive success in a single breeding season, using a rather limited data set. However, better singers (males which sing longer strophes, show less positive drift, and have larger song repertoires) survived better and had a higher individual lifetime reproductive success (on the basis of a male's recruited offspring of all breeding seasons). Our results show that there exist measurable differences whereby birds that are dominant in winter sing better, survive longer, and produce more surviving offspring during their life time. We suggest that differences in male quality are the common cause (direct and indirect) of all these effects.     

Mate guarding and copulation behaviour in monogamous and polygynous blue tits: do males follow a best-of-a-bad-job strategy?

This study investigates the importance of mate guarding for males and females in the facultatively polygynous blue tit Parus caeruleus. We present observational data in combination with a paternity analysis using DNA fingerprinting to show that (1) male blue tits guard their mate, since they stay closer to their mate, initiate fewer flights and follow their mate more often during the female's presumed fertile period; (2) polygynous males do not suffer more from lost paternity despite lower mate guarding; (3) in monogamous pairs there is either no relation or a positive relation (depending upon the variable measured) between measures of mate guarding intensity and the proportion of extra-pair young in the nest; and (4) monogamous males that are more often followed by their fertile female suffered less from lost paternity. We conclude that, despite mate guarding, paternity seems to be largely under female control and unattractive males guarding their mate are making the best of a bad situation. Experimental evidence is provided showing that when males were temporarily removed from their territory, their mate suffered from increased harassment from neighbouring males that intruded in the territory and tried to copulate with the female. Almost all of these copulation attempts were unsuccessful because females refused to copulate. We conclude that mate guarding may be beneficial for females because harassment by neigbouring males is prevented.     

Survival and lifetime reproductive success in dispersing and resident red squirrels

Dispersal in red squirrels (Sciurus vulgaris) is not sex-biased and strict philopatry is rare. The immigration pattern suggests that nearly all animals have to disperse away from the natal site and that dispersal in this species is the outcome of local (intrasexual) competition. If this interpretation is correct, we predict that dispersers and residents, of both sexes, should have equal survival rates and lifetime reproductive success. Body mass, longevity, reproductive success and dominance rank of 34 resident offspring (settling within 400 m of the natal range) and 70 immigrants (dispersers) were compared. Immigrants did not weigh less than residents as adults, nor did they have a higher mortality during the pre-setding period. Survival rate, lifetime reproductive success (females) and the proportion of males obtaining a high dominance rank were similar for residents and dispersers, and no sex effect was found on either of the parameters studied. These results are consistent with the hypothesis that local competition determines whether an individual disperses further away or settles close to its birthplace.     

Chemistry of preen gland secretions of passerines: different pathways to same goal? why?

Summary. Passeriformes is the largest order of birds and includes one third of the bird species of the world, living in very diverse habitats. We investigated the chemistry of preen gland secretions of some groups of passerines from temperate regions found in diverse microhabitats. Some of the common components were mixtures of homologous monoesters made up of long chain acids and alcohols. Individual species had characteristic distribution of esters and was unique to a given species, although there were some individual variations. We compared the composition of acids and alcohols that formed same molecular weight esters in different species and we found that the combination of acids and alcohols to arrive at same molecular compositions varied distinctly between species. To compare compositions of over all acids and alcohols that formed the esters, the representative samples of secretions from the individual species were transesterfied the produce methyl esters and alcohols. We found that there were distinct differences in number of acids and alcohols that produced the combination of homologous mixtures of esters. Also they differed both qualitatively and quantitatively. There were also seasonal differences in the secretion components. Thus though the intact mixtures of esters in individual species had some similarities, they were very complex mixtures and differed characteristically for individual species. Here we discuss possible causes for evolution of these variations. We suggest that the evolution in variation of preen gland secretion is probably due to selective pressures caused by ectosymbionts such as feather-mites and feather-chewing lice that live on feathers and probably feed on the secretions and surrounding environments     

Harvesting of microalgae biomass from the phycoremediation process of greywater

The wide application of microalgae in the field of wastewater treatment and bioenergy source has improved research studies in the past years. Microalgae represent a good source of biomass and bio-products which are used in different medical and industrial activities, among them the production of high-valued products and biofuels. The present review focused on greywater treatment through the application of phycoremediation technique with microalgae and presented recent advances in technologies used for harvesting the microalgae biomass. The advantages and disadvantages of each method are discussed. The microbiological aspects of production, harvesting and utilization of microalgae biomass are viewed.     

Assessment of Temporal and Spatial Variation of Nitrate Removal in Riparian Zones

The aim of this study was to monitor long-term temporal and spatial groundwater NO₃^- removal efficiencies in different riparian zones via a limited number of sampling wells. Groundwater NO₃^- concentrations were measured fortnightly or monthly over a period of two years using transects of ground water sampling wells. Depending on the level of the NO₃^- load (up to 120mgNL^-1 at the input side of the riparian zone a distance of 10 to 30m was needed to remove NO₃^- from the groundwater below 11.3mgNL^-1. Considering all seasons, the mixed vegetation and grass riparian site succeeded to remove groundwater NO₃^- efficiently (92—100% within a distance of 30m. The forested riparian zone removed 72—90% of the total NO₃^- input within a distance of 30m. Evidence emerged that NO₃^- could also be removed actively at depths up to 2m, due to the presence of organically enriched layers of alluvial deposits or roots. Our four dimensional approach (three dimensional space and time), in combination with a limited number of sampling wells, was shown to be a useful monitoring tool to assess the variability of NO₃^- removal in riparian zones.     

Contrasting natural experiments confirm competition between House Finches and House Sparrows

After House Finches were introduced from the western to the eastern United States and rapidly increased in numbers, House Sparrows declined, leading to suggestions that the decline was caused by interspecific competition. However, other potential causes were not excluded. The rapid decline in House Finches following the emergence of a new disease (mycoplasmal conjunctivitis) caused by a novel strain of Mycoplasma gallisepticum (MG) in 1994 has provided a natural experiment and an opportunity to revisit the hypothesis that interspecific competition from House Finches drives population changes in House Sparrows. If true, the recent decline in House Finches should lead to an increase in House Sparrows. In this paper we test the hypothesis that House Sparrow and House Finch numbers in the northeastern United States vary inversely by examining data from three independent volunteer programs that monitor bird species' abundance and distribution (Christmas Bird Count, Project FeederWatch, and Breeding Bird Survey). In the first analysis we found that House Sparrow and House Finch numbers varied inversely during a time interval when House Finches were increasing and a time interval when House Finches were decreasing. In the second analysis, we found that the rates of geometric change in House Sparrow abundance (ln[HOSP(t+1)/HOSP(t)]) were negatively correlated with initial House Finch (HOFI(t)) and sparrow (HOSP(t)) abundances at individual sites, irrespective of the time period. Given that finch range expansion and subsequent declines in abundance are the result of two very different phenomena, it would be very unlikely for apparent competition or spurious correlations to cause the observed concomitant changes in House Sparrow abundance. We conclude that interspecific competition exists between these two species.