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Cooperative breeding (i.e. when alloparents care for the offspring of other group members) has been studied for nearly a century. Yet, inconsistent definitions of this breeding system still hamper comparative research. Here, we identify two major inconsistencies, discuss their consequences and propose a way forward. First, some researchers restrict the term 'cooperative breeding' to species with non‐breeding alloparents. We show that such restrictive definitions lack distinct quantitative criteria to define non‐breeding alloparents. This ambiguity, we argue, reflects the reproductive‐sharing continuum among cooperatively breeding species. We therefore suggest that cooperative breeding should not be restricted to the few species with extreme reproductive skew and should be defined independent of the reproductive status of alloparents. Second, definitions rarely specify the type, extent and prevalence of alloparental care required to classify species as cooperative breeders. We thus analysed published data to propose qualitative and quantitative criteria for alloparental care. We conclude by proposing the following operational definition: cooperative breeding is a reproductive system where >5% of broods/litters in at least one population receive species‐typical parental care and conspecifics provide proactive alloparental care that fulfils >5% of at least one type of the offspring's needs. This operational definition is designed to increase comparability across species and disciplines while allowing to study the intriguing phenomenon of cooperative breeding as a behaviour with multiple dimensions. [ABSTRACT FROM AUTHOR]

Extreme reproductive skew occurs when a dominant female/male almost monopolizes reproduction within a group of multiple sexually mature females/males, respectively. It is sometimes considered an additional, restrictive criterion to define cooperative breeding. However, datasets that use this restrictive definition to classify species as cooperative breeders systematically overestimate reproductive skew by including groups in which reproduction cannot be shared by definition (e.g. groups with a single female/male). Here, we review the extent of reproductive sharing in 41 mammal and 37 bird species previously classified as exhibiting alloparental care and extreme reproductive skew, while only considering multi-female or multi-male groups. We demonstrate that in groups where unequal reproduction sharing is possible, extreme reproductive skew occurs in a few species only (11/41 mammal species and 12/37 bird species). These results call for significant changes in datasets that classify species' caring and mating system. To facilitate these changes, we provide an updated dataset on reproductive sharing in 63 cooperatively breeding species. At the conceptual level, our findings suggest that reproductive skew should not be a defining criterion of cooperative breeding and support the definition of cooperative breeding as a care system in which alloparents provide systematic care to other group members' offspring. [ABSTRACT FROM AUTHOR]

Kin-biased behavior (that is responding differentially to kin and non-kin) is thought to be adaptive in many social interactions. One example of this kin bias is behaving less aggressively toward a relative than a non-relative, a behavior which yields inclusive fitness benefits. However, data are lacking about the ability of animals to weigh their preference for kinship and the density of conspecifics simultaneously and to respond accordingly. Fire salamanders (Salamandra infraimmaculata) larviposit in high densities in ponds. Thus, larvae of different females confront competition and predation by other larvae. We studied whether larvae prefer their kin over particular density or vice versa. We experimentally used a transparent glass aquarium with inner chambers to test the responses of a focal larva toward its siblings and non-siblings. Specifically, we quantified the time a focal larva spent near its siblings or non-siblings, presented in varying densities, and the aggression level it demonstrated. We found that focal larvae spent more time near non-siblings if non-sibling and sibling groups were of equal density. The focal larvae were also more aggressive toward non-siblings. The results may be explained by the cannibalistic nature of these larvae: high density may provide more opportunities for food, especially when non-siblings are present. Further explanations for these findings may include other advantages of staying in a larger group and/or the stronger olfactory and visual stimulation offered by groups compared to a single individual. These findings suggest that larvae make differential responses toward conspecifics depending simultaneously on the level of relatedness and the density of the group. Such responses have important implications for social—aggregation decisions and may especially affect the fitness of cannibalistic species. [ABSTRACT FROM AUTHOR]

Most papers on the physical condition of birds during spring migration focused on food availability preceding migratory take-off. Only a few studies examined the effect of climate conditions at the wintering grounds upon autumn arrival on bird physical condition later on. Here, we hypothesized that environmental conditions upon arrival at the wintering grounds, and not necessarily upon departure, have a crucial carry-over effect on bird spring migration. Using 29,000 observations of the lesser whitethroat, Sylvia curruca, and the eastern Bonelli’s warbler, Phylloscopus orientalis, we found temperatures upon arrival at the African wintering grounds to be the only climatic variable correlated with birds’ body state upon spring stopover in Israel, six months later. Two different mechanisms could explain these results. One possibility is that high temperatures create favorable conditions for insect activity, which allows rapid recovery from autumn migration and hence successful winter survival and maintenance. Another possible scenario is that harsh conditions, due to the heat and dry environment, cause high mortality, permitting survival of larger individuals which, then, enjoy reduced inter- and intra-specific competition. Whatever the mechanism is, our findings suggest that conditions upon autumn arrival, and not necessarily at the end of winter as traditionally thought, may have a major impact on migrating birds. [ABSTRACT FROM AUTHOR]

Although interspecific competition is suggested to be one of the major forces dictating community structure, interspecific interference competition for nest sites in birds has been reported mainly from observational studies. Here, we asked whether interference by the larger House Sparrow (Passer domesticus) could reduce breeding success and parental behavior in the smaller Great Tit (Parus major) following clutch completion, by experimentally allowing House Sparrows to access half of the Great Tit nest boxes. Significantly more tit pairs failed to raise young in nest boxes that House Sparrows were able to enter during their breeding period compared to those that were not able to do so, because House Sparrows usurped 77.8% of the Great Tit nests. Great Tits also increased the duration of nest defense in the presence of House Sparrows. As the outcome of interference competition may lead to breeding failure, birds should necessarily evolve ways to avoid nest competitors either by selecting nests that restrict access to their larger competitors and/or by initiating breeding earlier. Conservation efforts should be directed toward attaching a metal restrictor plate around the entrance of nest boxes to prevent woodpeckers from enlarging the entrance and larger species from entering nests. [ABSTRACT FROM AUTHOR]

The evolution of traits in hosts may be influenced by their parasites and vice versa and a coevolutionary arms race often develops between the two. As part of such an arms race, the common cuckoo mimics the eggs of its hosts to avoid egg rejection. Traits related to this arms race may also be influenced by climatic conditions, such as temperature, affecting, for example, food availability and, thus, female condition and egg size (therefore may reflect Bergmann's rule or the resource rule). The potential interaction between coevolution and climate has rarely been studied. We investigated whether egg and body size of cuckoos and reed warblers from Britain and Denmark had undergone change between 1868 and 1956, and whether such changes were correlated with climatic factors. Cuckoo egg size decreased during the studied period while warbler egg size remained stable. Hence, cuckoo and warbler eggs have become more similar in size over time. Cuckoo egg volume decreased with increasing annual precipitation, but annual precipitation decreased over time. Warbler egg volume increased with spring temperatures (which could not reflect Bergmann's rule, but may support the resource rule). Hence, it seems that the measured climatic indices did not affect cuckoo egg size but may in part affect warbler egg size. Therefore, the decrease in cuckoo egg size may be the result of the coevolutionary arms race. Body and egg sizes in the cuckoos were negatively correlated whereas warbler body and egg sizes were uncorrelated, suggesting that selection probably acted on egg size directly and not via selection on body size. Taken together, these findings may indicate that climate change, the coevolutionary arms race, or both, affected egg sizes. It is suggested that drawing conclusions regarding the arms race without taking into account other selective pressures (e.g., climate) may confound conclusions regarding parasite-host systems. [ABSTRACT FROM AUTHOR]

The trade-off between parents feeding themselves and their young is an important life history problem that can be considered in terms of optimal behavioral strategies. Recent studies on birds have tested how parents allocate the food between themselves and their young. Until now the effect of food consumption by parent birds on their food delivery to their young as well as other parental activities has rarely been studied. I have previously shown that parent Palestine sunbirds (Nectarinia osea) will consume nectar and liquidized arthropods from artificial feeders. However, they will only feed their young with whole arthropods. This provided a unique opportunity to experimentally manipulate the food eaten by parents independent of that fed to their offspring. Here, I hypothesized that parents invest in their current young according to the quality of food that they themselves consume. Breeding pairs with two or three nestlings were provided with feeders containing water (control), sucrose solution (0.75 mol) or liquidized mealworms mixed with sucrose solution (0.75 mol). As food quality in feeders increased (from water up to liquidized mealworms mixed with sucrose solution): 1) Parents (especially females) increased their food delivery of whole arthropod prey to their young. 2) Only males increased their nest guarding effort. Nestling food intake and growth rate increased with increasing food quality of parents and decreasing brood size. These results imply that increasing the nutrient content of foods consumed by parent sunbirds allow them to increase the rate at which other foods are delivered to their young and to increase the time spent on other parental care activities. [ABSTRACT FROM AUTHOR]

Plant secondary metabolites (PSMs), such as alkaloids, are often found in many parts of a plant, including flowers, providing protection to the plant from various types of herbivores or microbes. PSMs are also present in the floral nectar of many species, but typically at lower concentrations than in other parts of the plant. Nectar robbers often damage floral tissue to access the nectar. By doing so, these nectar robbers may initiate an increase of PSMs in the floral nectar. It is often assumed that it takes at least a few hours before the plant demonstrates an increase in PSMs. Here, we addressed the question of whether PSMs in the floral tissue are immediately being released into the floral nectar following nectar robbing. To address this research question, we investigated whether there was an immediate effect of nectar robbing by the Palestine Sunbird ( Nectarinia osea) on the concentration of nectar alkaloids, nicotine and anabasine, in Tree Tobacco ( Nicotiana glauca). We found that the concentration of anabasine, but not nicotine, significantly increased in floral nectar immediately following simulated nectar robbing. These findings suggest that nectar robbers could be ingesting greater amounts of PSMs than they would if they visit flowers legitimately. As a consequence, increased consumption of neurotoxic nectar alkaloids or other PSMs could have negative effects on the nectar robber. [ABSTRACT FROM AUTHOR]

Floral color is an important cue that converged in many ornithophilous flowers and can be used by nectarivorous birds to make foraging decisions. Wild ornithophilous flowers are frequently red, although they are more often yellow in Israel. The Palestine sunbird (Nectarinia osea) is the only nectarivorous bird in Israel and surrounding Mediterranean areas. Given the prevalence of yellow flowers in their habitats (along with sunbirds' expected sensitivity increase in this region of color vision), we predicted that Palestine sunbirds prefer yellow food sources over red. We examined sunbird foraging behavior when they were presented simultaneously with a yellow and red feeder, each containing the same quantity and quality of food. We investigated whether sunbirds had a side bias in the color preference experiment, but also in a separate experiment where both feeders were white. Sunbirds did not exhibit a significant color bias, while they did have a significant preference for a particular side of the cage. Location appears to be a more important cue than color to Palestine sunbirds, likely because location can offer information on the most rewarding plants and recently depleted flowers. However, color may still provide useful information that could influence foraging decisions in different contexts. [ABSTRACT FROM PUBLISHER]

Winter habitat use and the magnitude of migratory connectivity are important parameters when assessing drivers of the marked declines in avian migrants. Such information is unavailable for most species. We use a stable isotope approach to assess these factors for three declining African-Eurasian migrants whose winter ecology is poorly known: wood warbler Phylloscopus sibilatrix, house martin Delichon urbicum and common swift Apus apus. Spatially segregated breeding wood warbler populations (sampled across a 800 km transect), house martins and common swifts (sampled across a 3,500 km transect) exhibited statistically identical intra-specific carbon and nitrogen isotope ratios in winter grown feathers. Such patterns are compatible with a high degree of migratory connectivity, but could arise if species use isotopically similar resources at different locations. Wood warbler carbon isotope ratios are more depleted than typical for African-Eurasian migrants and are compatible with use of moist lowland forest. The very limited variance in these ratios indicates specialisation on isotopically restricted resources, which may drive the similarity in wood warbler populations' stable isotope ratios and increase susceptibility to environmental change within its wintering grounds. House martins were previously considered to primarily use moist montane forest during the winter, but this seems unlikely given the enriched nature of their carbon isotope ratios. House martins use a narrower isotopic range of resources than the common swift, indicative of increased specialisation or a relatively limited wintering range; both factors could increase house martins' vulnerability to environmental change. The marked variance in isotope ratios within each common swift population contributes to the lack of population specific signatures and indicates that the species is less vulnerable to environmental change in sub-Saharan Africa than our other focal species. Our findings demonstrate how stable isotope research can contribute to understanding avian migrants' winter ecology and conservation status. [ABSTRACT FROM AUTHOR]

Pollutants as endocrine disrupting chemicals (EDCs) are of worldwide concern, due to their detrimental effects on the physiology and behaviour of wildlife. One major source of EDCs is sewage treatment works which serve as foraging grounds for many bird species. However, the risks of consuming EDCs to wild birds at these sites have been largely overlooked. We have previously quantified contamination levels of invertebrates from within filter beds of sewage treatment works and the intake rates of these invertebrates by wild European starlings feeding at these sites. Our work to date has shown that environmentally-relevant EDC exposure results in reduced immunocompetence, increased song behaviour and neural development in adult starlings. In the present study, we hypothesized that nestling starlings exposed to similar EDC levels from contaminated prey, from parental feeding at sewage treatment works, would show altered growth and physiology. Our findings show that EDC exposure results in reduced growth and immunocompetence in nestling birds. However, there was no effect on corticosterone or haematocrit levels. As growth rates and immunocompetence are likely to be related to survival rates, we suggest that these exposure levels are likely to adversely affect recruitment into the adult population. Synthesis and applications. These results highlight the potential transfer of EDCs between semi-aquatic or aquatic organisms and terrestrial organisms up the food chain at sites of sewage treatment works, broadening the scope of potential routes of exposure. Our findings suggest that birds foraging in these sites are at risk of physiological manipulation from EDCs and reduced body condition as a result. We advocate further work to evaluate the potential for EDCs from sewage treatment works to bioaccumulate and modulate the condition of wild organisms feeding on contaminated prey. Our results suggest that changes in management practices of sewage treatment works are required. We support measures to reduce EDC levels in sewage treatment works and that these sites should be designed to exclude or deter wildlife from foraging on contaminated prey. The management implications of such policy - oriented steps will ensure the health of wildlife foraging at sewage treatment works. [ABSTRACT FROM AUTHOR]

Ecology Letters (2010) 13: 1129–1138 Prey species commonly use predator-released kairomones (PRKs) to detect risk of predation, yet the chemical identity of PRKs remains elusive. Chemical identification of PRKs will facilitate the study of predator–prey interactions and the risk of predation, and when the prey are pests, will potentially provide environmentally friendly means of pest control. In temporary pools of the Mediterranean and Middle East, larvae of the mosquito Culiseta longiareolata Macquart are highly vulnerable to the common predatory backswimmer, Notonecta maculata Fabricius. We demonstrate that N. maculata releases two hydrocarbons, n-heneicosane and n-tricosane, which repel ovipositing females of C. longiareolata. In behavioural tests with environmentally relevant chemical concentrations in outdoor mesocosm experiments, the repellent effects of the two compounds were additive at the tested concentrations. [ABSTRACT FROM AUTHOR]

Responding differentially to kin and non-kin is known to be adaptive in many species. One example is the inclusive fitness benefits of reducing aggression toward closer relatives. Little is known, however, about the ability of animals to assess differential degrees of genetic relatedness and to respond accordingly with differential levels of aggression. In the present study, we tested whether aggressiveness between body mass-matched pairs of fire salamander ( Salamandra infraimmaculata) larvae covaried with the genetic similarity between them. We quantified aggressiveness at three levels of genetic similarity by selecting pairs within and across pools from recently genotyped populations. We also assessed aggression between pairs of siblings. Aggression and associated injuries decreased as genetic similarity increased across the groups. These findings suggest that cannibalistic salamanders can assess their degree of genetic relatedness to conspecifics and vary their behavioral responses depending on the degree of similarity between them along a genetic relatedness continuum. [ABSTRACT FROM AUTHOR]

Environmental pollutants which alter endocrine function are now known to decrease vertebrate reproductive success. There is considerable evidence for endocrine disruption from aquatic ecosystems, but knowledge is lacking with regard to the interface between terrestrial and aquatic ecosystems. Here, we show for the first time that birds foraging on invertebrates contaminated with environmental pollutants, show marked changes in both brain and behaviour. We found that male European starlings (Sturnus vulgaris) exposed to environmentally relevant levels of synthetic and natural estrogen mimics developed longer and more complex songs compared to control males, a sexually selected trait important in attracting females for reproduction. Moreover, females preferred the song of males which had higher pollutant exposure, despite the fact that experimentally dosed males showed reduced immune function. We also show that the key brain area controlling male song complexity (HVC) is significantly enlarged in the contaminated birds. This is the first evidence that environmental pollutants not only affect, but paradoxically enhance a signal of male quality such as song. Our data suggest that female starlings would bias their choice towards exposed males, with possible consequences at the population level. As the starling is a migratory species, our results suggest that transglobal effects of pollutants on terrestrial vertebrate physiology and reproduction could occur in birds. [ABSTRACT FROM AUTHOR]

The timing of the chick-rearing phase is known to have a profound effect on the reproductive success of birds. However, little is known about the energetic costs faced by the parents during different periods of the breeding season. These costs may have vital consequences for both their survival and future reproduction. In most studies, daily energy expenditure (DEE) of breeding and non-breeding birds has been compared, without controlling for the effect of season. In the present study, we examined the energy demands of breeding compared to non-breeding Palestine sunbirds Nectarinia osea and whether there were sex-specific differences in DEE within and between different seasons. We predicted that DEE would be elevated when birds rear chicks, especially at cooler ambient temperatures. Time-energy budgets were constructed for pairs of sunbirds, rearing chicks, or not breeding, in spring and summer. There were significant seasonal differences in estimates of DEE in non-breeders that were 21% higher in spring than in summer. We attributed these to increases in non-flight metabolic rate rather than changes in time spent on different activities. Our estimates of DEE for the birds that were rearing chicks were higher than non-breeding adults. In females the increase in DEE when breeding, compared to when not breeding, was similar in both spring and summer, while males increased their DEE much less when breeding in spring. The differences in estimated DEE, however, were not significant between male and female birds in any season. Between seasons, female breeders had 17.1% higher DEE in spring than in summer, while male breeders showed no difference in DEE when rearing chicks in different seasons. Accordingly, our initial prediction was supported, as DEE in chick-rearing adults was higher than in non-breeding adults. In addition, although temperatures are lower in spring, breeding in the spring is only more costly than breeding in summer for females. Apparently, males are more flexible in reallocating their time and energy spent on different activities. [ABSTRACT FROM AUTHOR]

Sex-specific foraging behaviour might be influenced by digestive constraints. However, evidence for sex differences in digestive performance is limited. Various physiological traits are known to be body size dependent. Therefore, we hypothesized that body size differences between male and female birds may lead to differences in their digestive characteristics. We predicted that if food intake and digestive functions are only governed by body mass, then males that are heavier than females would have higher food intake, food assimilation efficiency and gut transit time, but not after controlling for the effect of body mass. We fed a diet of equicaloric solutions of sucrose and a 1:1 mixture of glucose and fructose (hexose mixture) solutions to Palestine sunbirds (Nectarinia osea). When fed sucrose solutions, males had longer transit times but similar absorption efficiencies as females. Transit times, corrected for differences in body mass and food intake, were still longer in males than in females when fed on sucrose solutions. The sex-specific differences in transit time disappeared when the birds were fed the hexose mixture. Our results suggest that males take longer to digest than females when fed on sucrose-rich nectars as opposed to hexose-rich nectars, and therefore can allow themselves a relatively lower digestive capacity. This may suggest sex-specific co-evolution of sunbirds within mixed plant communities, which have both sucrose- and hexose-rich nectar-producing plants. Furthermore, future studies on digestion in birds may pay attention to sex-specific differences. [ABSTRACT FROM AUTHOR]

Despite its importance in the evolution of central-place foraging strategies, few studies have distinguished between patch use by parent birds for their own consumption vs. patch use for the purpose of provisioning young in the nest. Adult Palestine sunbirds (Nectarinia osea) consume nectar and arthropods, but feed only arthropods to their nestlings. This partial separation of food types allowed us to experimentally test sex-specific trade-offs in parental foraging effort between two patches. A ‘variable’ patch on one side of a pair's territory contained only artificial nectar for parental self-feeding (in varying sucrose concentrations between 0·25 and 0·75 mol kg&sup-1; H2O). A ‘constant’ patch on the other side of the territory contained artificial nectar for parental self-feeding (sucrose concentration = 0·25 mol kg&sup-1; H2O), plus a dish of flightless houseflies for provisioning young. Experimental increases in sucrose concentration in the variable patch led the parents to: (a) consume greater amounts of sucrose solution from this patch; (b) collect more flies from the constant patch to feed their young; and (c) persistently use the 0·25 mol kg&sup-1; H2O feeder near the dish of flies. By titration (gradually changing the sucrose concentration in the variable patch), we demonstrate that at concentrations of 0·47 mol kg&sup-1; H2O for males and 0·55 mol kg&sup-1; H2O for females, the birds spent an equal amount of time foraging in both patches. Therefore, sucrose concentration in the variable patch (for self-feeding only), had to be higher for the females than for the males, in order to balance the additional value females placed upon the flies provided for chick-feeding in the constant patch. These results reflect previously described sex-specific parental roles in this species, with females provisioning young mainly in the nest and males patrolling more and guarding against nest predators. Furthermore, we demonstrate for the first time the fine details of alternative adaptive trade-offs in foraging effort by parent birds when using patches for self-feeding or for delivery of food to the young. [ABSTRACT FROM AUTHOR]