Life-history evolution and cooperative breeding in the sociable weaver

Includes bibliographical references.When compared to northern temperate counterparts, birds in the tropics and Southern Hemisphere regions, are characterised by low fecundity, long developmental periods and high Survival. This pattern has been attributed to hypotheses relating to food limitation, nest predation, and reduced seasonality leading to high adult survival. Still, to date few studies have investigated this issue. In particular, detailed studies from southern regions are scarce and as a result our understanding of this question remains weak. Another characteristic of 'southern' birds is a higher frequency of cooperatively-breeding species. It has previously been shown that cooperative breeding is most frequent amongst species with high survival and low fecundity. An explanation for this could be that long occupancy of territories by long-lived breeders leads to reduced opportunities of independent breeding by young birds. However, the biology of some species is such, that they do not experience shortage of breeding territories or other constraints, while still showing delayed dispersal and cooperative breeding. This study investigates what factors drive life-history evolution in a cooperatively breeding southern African passerine, the sociable weaver Philetairus socius. This species departs from the traditional cooperative breeding model in being a non-territorial colonial nester that inhabits an unpredictable semi-arid environment. Sociable weavers face no obvious constraints on independent reproduction, yet cooperative breeding is common. Therefore, I also aimed at determining what factors prompt delayed reproduction in this species, since this life history trait is the first step leading to cooperative breeding

Multistate Estimates of Survival and Movement in Relation to Colony Size in the Sociable Weaver

We estimated survival and movement probabilities in relation to breeding-colony size in the sociable weaver (Philetairus socius) by using multistate statistical methods, in which survival and movement to time t + 1 is conditional on an individual’s colony size at time t. The sociable weaver is a colonial, cooperatively breeding species that builds a massive communal nest, with colony size ranging from fewer than 20 to more than 500 individuals in some areas. We conducted an 8-year capture/mark/re-capture study of sociable weavers near Kimberley, South Africa. By comparing the fit of different multistate models to our data, we found evidence that annual survival probability of adults was lower in small colonies (less than 30 individuals) and medium-sized colonies (30–60 individuals) than in large colonies (more than 60 individuals). First-year survival of birds banded as juveniles also increased with natal colony size. Statistically, however, these effects were weak, and models without an effect of colony size were equally well supported by our data. Movement probabilities illustrated that individuals seldom moved between colonies of different size classes, and showed a preference to use colonies of size classes similar to what they had occupied the preceding year, even when changing colony sites between years. The potential survival differences among birds in different colonies, if real, translated into differences of 39–45% in average lifespan. First-year survival is probably enhanced through antipredator advantages of being in larger groups during the fledgling period. Adult survival in larger groups may be increased by thermal advantages of a large nest during cold winter weather. The fidelity of weavers to a particular colony-size class between years may reflect phenotypic specialization for certain group sizes

Antagonistic effect of helpers on breeding male and female survival in a cooperatively breeding bird.

1. Cooperatively breeding species are typically long lived and hence, according to theory, are expected to maximize their lifetime reproductive success through maximizing survival. Under these circumstances, the presence of helpers could be used to lighten the effort of current reproduction for parents to achieve higher survival. 2. In addition, individuals of different sexes and ages may follow different strategies, but whether male and female breeders and individuals of different ages benefit differently from the presence of helpers has often been overlooked. Moreover, only one study that investigated the relationship between parental survival and the presence of helpers used capture-mark-recapture analyses (CMR). These methods are important since they allow us to account for the non-detection of individuals that are alive in the population but not detected, and thus, the effects on survival and recapture probability to be disentangled. 3. Here, we used multi-event CMR methods to investigate whether the number of helpers was associated with an increase in survival probability for male and female breeders of different ages in the sociable weaver Philetairus socius. In this species, both sexes reduce their feeding rate in the presence of helpers. We therefore predicted that the presence of helpers should increase the breeders' survival in both sexes, especially early in life when individuals potentially have more future breeding opportunities. In addition, sociable weaver females reduce their investment in eggs in the presence of helpers, so we predicted a stronger effect of helpers on female than male survival. 4. As expected we found that females had a higher survival probability when breeding with more helpers. Unexpectedly, however, male survival probability decreased with increasing number of helpers. This antagonistic effect diminished as the breeders grew older. 5. These results illustrate the complexity of fitness costs and benefits underlying cooperative behaviours and how these may vary with the individuals' sex and age. They also highlight the need for further studies on the sex-specific effects of helpers on survival.Our research has received funding from the DST-NRF Centre of Excellence at the Percy FitzPatrick Institute of African Ornithology (South Africa), FEDER (Operational Programme for Competitiveness Factors – COMPETE) and Portuguese Foundation for Science and Technology (FCT; PTDC/BIA-BEC/103818/2008), Project “Biodiversity, Ecology and Global Change” co-financed by North Portugal Regional Operational Programme 2007/2013 (ON.2), under the NSRF, ERDF. to RC, the region Languedoc Roussillon to CD, the Natural Environment Research Council (UK) to BJH, St John's College, Cambridge and the University of Cape Town to CNS , and the European programme Marie Curie-IRSES (FP7-PEOPLE-2012-IRSES; ‘Cooperation’ 318994). This research was conducted within the International Associate Laboratory LIA “Biodiversity and Evolution”.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/1365-2656.12377 Data are available from Dryad digital repository http://dx.doi.org/10.5061/dryad.mk44

Tactical planning of urban water services at utility level

The scope of this TRUST series of best practice manuals is the integrated planning of urban water services, focusing on Infrastructure Asset Management (IAM). IAM aims at ensuring that infrastructures are managed in such a way that sustainability of the service is ensured by maximizing service performance at the minimum cost and with acceptable risk levels, in the long term. This manual is addressed to the utilities of urban water services whose main activity is based on network infrastructures. Urban water services include water supply, wastewater and storm water management. This manual provides guidance on the tactical planning process that utilities need to carry out in order to ensure sustainable water services in the medium-term, assuring an alignment with the strategic plan.Alegre, H.; Brito, R.; Covas, D. (2015). Tactical planning of urban water services at utility level. http://hdl.handle.net/10251/5414

Fine-scale genetic structure reflects sex-specific dispersal strategies in a population of sociable weavers (Philetairus socius).

Dispersal is a critical driver of gene flow, with important consequences for population genetic structure, social interactions and other biological processes. Limited dispersal may result in kin-structured populations in which kin selection may operate, but it may also increase the risk of kin competition and inbreeding. Here, we use a combination of long-term field data and molecular genetics to examine dispersal patterns and their consequences for the population genetics of a highly social bird, the sociable weaver (Philetairus socius), which exhibits cooperation at various levels of sociality from nuclear family groups to its unique communal nests. Using 20 years of data, involving capture of 6508 birds and 3151 recaptures at 48 colonies, we found that both sexes exhibit philopatry and that any dispersal occurs over relatively short distances. Dispersal is female-biased, with females dispersing earlier, further, and to less closely related destination colonies than males. Genotyping data from 30 colonies showed that this pattern of dispersal is reflected by fine-scale genetic structure for both sexes, revealed by isolation by distance in terms of genetic relatedness and significant genetic variance among colonies. Both relationships were stronger among males than females. Crucially, significant relatedness extended beyond the level of the colony for both sexes. Such fine-scale population genetic structure may have played an important role in the evolution of cooperative behaviour in this species, but it may also result in a significant inbreeding risk, against which female-biased dispersal alone is unlikely to be an effective strategy.The authors' research received funding from the Natural Environment Research Council (NERC, UK; NE/G018588/1 and NE/K015257/1) to BJH, the DST-NRF Centre of Excellence at the Percy FitzPatrick Institute of African Ornithology and the Portuguese Science and Technology Foundation (FCT PTDC/BIA-BEC/103818/2008) to RC, the CNRS and region Languedoc Roussillon to CD, St John’s College, Cambridge, and the University of Cape Town to CNS, and the European MC-IRSES (FP7-PEOPLE-2012-IRSES; ‘Cooperation’ 318994) to RC, CD, REvD and BJH.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/mec.1330

Begging and feeding responses vary with relatedness and sex of provisioners in a cooperative breeder

Begging behaviour can provide information on offspring hunger levels and be used by parents to adjust food provisioning efforts. In cooperative breeders, helpers also provide care by feeding the young. However, how helpers of different sex and relatedness to the offspring respond to begging behaviour has rarely been studied in cooperatively breeding species, which limits our understanding of the indirect and/or direct benefits that helpers may obtain by responding to offspring demand. Here, we used a cooperatively breeding bird, the sociable weaver, Philetairus socius, to investigate how nest intervisit intervals of breeders and different types of helpers, distinguished by sex and relatedness, varied with acoustic begging. Moreover, we tested whether these different classes of provisioners experienced distinct levels of begging. Our results show that only breeding males, but not breeding females or helpers of any sex and relatedness to the nestlings, returned faster to the nest to feed after experiencing more begging calls. When contrasted directly, we confirmed a statistically supported difference in responses to begging between male and female breeders. Surprisingly, second-order relatives experienced more begging calls than the other classes of more related helpers and breeders. These results show that we might find differences in how provisioners respond to begging levels when classifying group members according to their potential fitness gains. In sociable weavers, the benefits and costs of adjusting feeding efforts to begging seem to differ with sex and life history stage. Experimental and more detailed investigations on begging-feeding interactions are necessary to understand the origin and prevalence of these differences across cooperatively breeding systems. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/)

Nonparametric Estimation of Natural Selection on a Quantitative Trait using Mark-Recapture Data

Assessing natural selection on a phenotypic trait in wild populations is of primary importance for evolutionary ecologists. To cope with the imperfect detection of individuals inherent to monitoring in the wild, we develop a nonparametric method for evaluating the form of natural selection on a quantitative trait using mark-recapture data. Our approach uses penalized splines to achieve flexibility in exploring the form of natural selection by avoiding the need to specify an a priori parametric function. If needed, it can help in suggesting a new parametric model. We employ Markov chain Monte Carlo sampling in a Bayesian framework to estimate model parameters. We illustrate our approach using data for a wild population of sociable weavers (Philetairus socius) to investigate survival in relation to body mass. In agreement with previous parametric analyses, we found that lighter individuals showed a reduction in survival. However, the survival function was not symmetric, indicating that body mass might not be under stabilizing selection as suggested previously

Egg components and offspring survival vary with group size and laying order in a cooperative breeder

Prenatal resource allocation to offspring can be influenced by maternal environment and offspring value, and affect offspring survival. An important pathway for flexible maternal allocation is via egg components such as nutrients and hormones. In cooperative breeders, females with helpers may increase resource allocation to eggs-'differential allocation'-or reduce it-'load-lightening'. Yet, helper effects on egg composition have been poorly studied. Moreover, it is unknown how helpers' presence modulates laying order effects on egg content and survival. Here, we investigated how maternal allocation varied with group size and laying order in the cooperatively breeding sociable weaver (Philetairus socius). We estimated interactive effects of helpers and laying order on allocation to egg mass, yolk nutrients-yolk mass, proteins, lipids, carotenoids, vitamin A and vitamin E-and hormones-testosterone, androstenedione, and corticosterone. Results concurred with the 'differential allocation' predictions. Females with more helpers produced later-laid eggs with heavier yolks and more lipids, and laid eggs overall richer in lipids. Proteins, antioxidants, and hormones were not found to vary with helper number. We then analyzed how helper number modulated laying order effects on survival. Females with more helpers did not specifically produce later-laid eggs with higher survival, but eggs laid by females with more helpers were overall more likely to fledge. These findings show that some egg components (yolk mass, lipids) can positively vary according to females' breeding group size, which may improve offspring fitness

Maternal effects in relation to helper presence in the cooperatively breeding sociable weaver

In egg laying species, breeding females may adjust the allocation of nutrients or other substances into eggs in order to maximise offspring or maternal fitness. Cooperatively breeding species offer a particularly interesting context in which to study maternal allocation because helpers create predictably improved conditions during offspring development. Some recent studies on cooperative species showed that females assisted by helpers produced smaller eggs, as the additional food brought by the helpers appeared to compensate for this reduction in egg size. However, it remains unclear how common this effect might be. Also currently unknown is whether females change egg composition when assisted by helpers. This effect is predicted by current maternal allocation theory, but has not been previously investigated. We studied egg mass and contents in sociable weavers ( Philetairus socius ). We found that egg mass decreased with group size, while fledgling mass did not vary, suggesting that helpers may compensate for the reduced investment in eggs. We found no differences in eggs’ carotenoid contents, but females assisted by helpers produced eggs with lower hormonal content, specifically testosterone, androstenedione (A4) and corticosterone levels. Taken together, these results suggest that the environment created by helpers can influence maternal allocation and potentially offspring phenotypes

Rehabilitation of water mains and storage tanks: technologies and decision support tools

The scope of the current TRUST manual is the identification and organisation of best-practice and rehabilitation techniques of sewers and manholes at the operational level. This manual presents a service-oriented portfolio of rehabilitation techniques, based upon a thorough assessment of the existing and emerging offers in sewer systems. It provides an overview and guidance to professionals on available rehabilitation techniques for sewer systems, focusing on sewers and manholes given their importance for the overall infrastructure. However, some of these techniques can be applied to other components such as drains and laterals. It presents as well operational practices to support ehabilitation and repair strategies.Covas, D.; Almeida, MDC.; Carriço, N.; Azrague, K.; Bruaset, S.; Ugarell, R. (2015). Rehabilitation of water mains and storage tanks: technologies and decision support tools. http://hdl.handle.net/10251/5410