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Young animals often solicit care from their parents using behaviors and morphologies collectively termed begging. Many nestling altricial birds add to their familiar postures and vocalizations by displaying colorful mouthparts, hypothesized to enhance their visual conspicuousness and/or be favored by choosy parents. We evaluated these two hypotheses with experimental manipulations of the flange tissue of house sparrow (Passer domesticus) nestlings. We allowed parents to interact with nestlings that appeared to have either carotenoid-rich or carotenoid-poor flanges, and then with nestlings that appeared similar in carotenoid-richness but differed in either brightness (total light reflected) or ultraviolet (UV) richness. These three features of flange color comprise much of the variation observed both within and among species. None of our three manipulations shaped parents' ability to transfer prey efficiently to nestlings, a proxy for how visually detectable nestlings were. Parents preferentially allocated prey to nestlings that appeared carotenoid-rich, but did not bias allocation when we manipulated brightness or UV reflectance. These patterns suggest that nestlings displaying carotenoid-rich flanges benefit from parental favoritism, but that variation in brightness and UV reflectance do not independently shape parental care, at least within the range a house sparrow parent might encounter in nature. Efforts to understand mouth color in the context of offspring-parent communication and visual signal evolution may benefit from considering the component parts of color, as they may function, be constrained, and evolve independently. [ABSTRACT FROM AUTHOR]

Global urbanization processes have highlighted the importance of understanding the effects of urban habitats on animal behavior. Behavioral changes are usually evaluated along an urbanization gradient, comparing urban and rural populations. However, this metric fails to consider heterogeneity between urban habitats that can differ significantly in their characteristics, such as their level of environmental variability. We suggest incorporating dimensions of environmental variability into the urbanization metric when evaluating behavioral changes. We tested the importance of both level of urbanization and level of urban change (i.e. the rate of anthropogenic changes measured as the change in the level of urbanization over time) on animals' behavioral flexibility by comparing reversal learning abilities in house sparrows from sites differing in the rate of urbanization and urban change levels. We show that at least for males, urban change better explains levels of behavioral flexibility than urbanization level. We further show that urban change corresponds to other behavioral traits such as scrounging behavior and foraging activity. Thus, considering environmental stability and predictability in the form of urban changes can help better understand the mechanisms allowing behavioral changes and adaptations to urban environments. Evaluating the dynamics of the urban built environment could provide a better metric with which to understand urbanization effects on wildlife behavior and an important next step in urban ecology. [ABSTRACT FROM AUTHOR]

Individuals can behave as either leaders or followers in many taxa of collectively moving animals. Leaders initiate movements and may incur predation risks, while followers are thought to be more risk-averse. As a group encounters different challenges and ecological situations, individuals in the group may change their social role. We investigated leader and follower roles using dyads of captive house sparrow (Passer domesticus) during both exploration of a novel environment and a simulation of predator attack. During the exploration of a novel environment, individuals behaved consistently either as leaders or followers. However, in the simulated attack tests, individuals in the dyads switched their roles, with "followers" leading the escape flights and "leaders" following them. Our study provides evidence of 1) consistent differences between individuals in behavior during social escape and 2) a relationship between social roles across different situations. We suggest that such relationship hinges on individual risk-taking tendencies, which manifest through different social roles across different ecological situations. We further speculate that risk-taking individuals might gain benefits by following risk-averse individuals during an escape flight. [ABSTRACT FROM AUTHOR]

Determining how an animal's social context alters its immune responses will help us understand how pathogens impact individual health and spread within groups. Several studies have shown that group-housed animals can suppress components of the acute phase immune response, specifically sickness behaviors like lethargy. However, we do not know whether individuals alter sickness behaviors or other components of the acute phase response, including thermoregulation, in response to the infection status of other group members. We used automated radio telemetry on captive house sparrows (Passer domesticus) to test whether sickness behaviors and thermoregulation differed during immune challenge under 2 social contexts: 1) all of the flock inoculated with lipopolysaccharide (LPS), a non-replicating component of gram-negative bacterial cell walls, or 2) half of the flock inoculated. We predicted that with half of the flock inoculated, LPS-treated birds would be under more pressure to maintain competitive behaviors, so would suppress components of the acute phase response. As we predicted, LPS-inoculated birds showed less pronounced heterothermia (fever) when housed with a mixture of inoculated and healthy flockmates. In contrast, LPS-inoculated birds exhibited similar degrees of lethargy regardless of the infection status of their flockmates. Our results show that the infection status of an individual's social group did exert an effect on the acute phase response but surprisingly did not impact the expression of lethargy, a canonical sickness behavior. Determining the mechanisms underlying these responses will require testing additional social contexts with different ratios of infected to uninfected birds. [ABSTRACT FROM AUTHOR]

Differences between individuals in correlated responses across contexts have both functional and mechanistic implications. Such syndromes may have either beneficial or harmful consequences when novel changes in the environment occur. We used wild-caught house sparrows, Passer domesticus, to test in functionally relevant circumstances, whether neophobia (initial fear of novelty), habituation, and the learning of novel cues (discriminant learning) were linked by a common underlying mechanism or reflected separate processes. We repeatedly measured individual latencies to approach and also to feed from a familiar feeding site in 3 contexts: a baseline control for mild disturbance, in the presence of a novel object and to a novel cue indicating hidden food. House sparrows on average exhibited neophobia, habituated to novel objects, and learned to associate new cues with a reward. We also found evidence for consistent individual differences in both latencies within most contexts but there was no evidence of individual differences in plasticity with repeated trials within either the novel object (habituation) or novel cue (learning) contexts. There was also little or no correlation between the 2 latencies within individuals within contexts. Individual differences in latencies to arrive at the food station exhibited strong correlations across contexts but latencies to feed were weaker. These results suggest a personality trait that exists regardless of novelty but no syndrome affecting reactions to different forms of novelty. House sparrows appear strongly plastic when responding to novel environments. Such plasticity is likely favored by the varied consequences of novelty across environments. [ABSTRACT FROM AUTHOR]

Over the last century, expanding urbanization has led to a strong increase in the levels of background noise. This noise pollution has been shown to negatively affect wildlife (e.g., reduced species diversity and density, reduced breeding success), especially birds. Most research addressing the effects of anthropogenic noise has focused on avian communication and, to date, very little is known regarding the impact of chronic noise exposure on nonvocal behavior such as antipredator behavior. Here, we exposed free-living house sparrows (Passer domesticus) breeding in nest-boxes to either a playback of traffic noise (disturbed birds) or the rural background noise of the study site (no playback: control birds) during their first breeding attempt. We tested whether one of the female's antipredator behaviors (i.e., flushing distance) was affected by exposure to chronic noise and investigated the impact of chronic noise on reproductive performances. Disturbed females flushed more rapidly than controls, suggesting that birds may compensate for reduced ability to detect predators with increased vigilance. However, we found no significant effect of exposure to chronic noise on reproductive performances. Our findings show, for the first time, that chronic noise exposure can affect the antipredator behavior of a breeding bird. [ABSTRACT FROM AUTHOR]

Finding and exploiting novel resources are essential for survival in unfamiliar habitats. Here, we show that individuals at a range edge are faster to try novel foods than those in longer established areas but did not differ in response to novel objects. Although novelty may be associated with risks (e.g., predators, parasites, toxins), the potential of gaining a high nutritional value resource might outweigh risks in areas where familiar resources are relatively unknown.The ability to adjust behavioral responses to environmental cues probably contributes to an individual’s ability to persist in unfamiliar habitats. One behavior, how an individual responds to novelty, influences the acquisition of resources (e.g., novel foods) and identification of stressors, but it may also increase exposure to risks. Here, using house sparrows (Passer domesticus) recently introduced to Kenya, we tested how range expansion influenced individuals’ responses to novel foods and objects. We predicted that range edge birds would be less averse to novelty than birds at the site of introduction and that this effect would be more pronounced for novel foods than novel non-nutritional items. We also expected range edge individuals to be more sensitive to changes in the environment and therefore more apt to adjust their behavior in response to different cues; in other words, individuals at the range edge would have a more flexible behavioral repertoire than individuals at the site of introduction. As predicted, individuals at the range edge ate novel foods faster than those from established areas; however, latency to touch novel objects did not vary across the range. Individuals throughout the range were variable in their response to novelty, but there was no indication that individual flexibility was greater at the range edge. Although many novel items might be useful to introduced organisms, novel foods are likely more valuable, and therefore individuals should be most apt to risk the potential costs associated with novelty for a high nutritional payoff. [ABSTRACT FROM PUBLISHER]

Innovations help animals adapt to new or altered environments. But what makes individuals innovative? Our study shows that good health is important. Problem solving success in novel food-extracting tasks was promoted by superior physiological condition in a context-specific manner in house sparrows. Birds with more antioxidants solved easy tasks faster, while birds with less stress hormones were faster in solving and learning a difficult task.Innovative behaviors such as exploiting novel food sources can grant significant fitness benefits for animals, yet little is known about the mechanisms driving such phenomena, and the role of physiology is virtually unexplored in wild species. Two hypotheses predict opposing effects of physiological state on innovation success. On one hand, poor physiological condition may promote innovations by forcing individuals with poor competitive abilities to invent alternative solutions. On the other hand, superior physiological condition may ensure greater cognitive capacity and thereby better problem-solving and learning performance. To test these hypotheses, we studied the behavior of wild-caught house sparrows (Passer domesticus) in 4 novel tasks of food acquisition, one of which was presented to the birds in repeated trials, and we investigated the relationships of individual performance with relevant physiological traits. We found that problem-solving performance across the 4 tasks was moderately consistent within individuals. Birds with lower integrated levels of corticosterone, the main avian stress hormone, solved the most difficult task faster and were more efficient learners in the repeated task than birds with higher corticosterone levels. Birds with higher concentration of total glutathione, a key antioxidant, solved 2 relatively easy tasks faster, whereas birds with fewer coccidian parasites tended to solve the difficult task more quickly. Our results, thus, indicate that aspects of physiological state influence problem-solving performance in a context-dependent manner, and these effects on problem-solving capacity, probably including cognitive abilities, are more likely to drive individual innovation success than necessity due to poor condition. [ABSTRACT FROM PUBLISHER]

First, they suggest that individuality in task-independent behavior may, through various feedbacks, lead to task specialization. Loftus et al. also distinguish between the behaviors that define a task (e.g., behaviors specifically associated with obtaining a group benefit) and task-independent behaviors. I bet applying the multilevel, multivariate framework will reveal more variation than usually assumed, but note that Loftus et al. do not explain the relative influence of early-life individuality and feedback affecting task specialization as opposed to other developmental pathways. However, in social insects, colonies are the reproductive individuals: colonies send out reproductives that mate and then form new colonies. [Extracted from the article]

Among avian species with biparental care, male alternative reproductive opportunities can occur in the form of either extrapair fertilizations or additional social mates. We manipulated testosterone (T) levels in male house sparrows to assess whether participation in parental care detracts from male success in securing alternative matings; we also compared the annual reproductive success of males that engaged in normal levels of care with the success of males that displayed increased mating effort at the expense of parental care. Our results showed that the incidence of polygyny among high-T/low-parenting males was elevated relative to control males, but that success in obtaining extrapair mates was independent of hormonal treatment. Thus, male parental care seems to carry an opportunity cost in terms of reduced acquisition of additional social mates. Despite this cost, between-treatment comparisons of the estimated number of fledglings sired annually suggest that, in this species, the value of male contributions to care is sufficiently high to favor the reductions in T that facilitate normal male parenting. [ABSTRACT FROM PUBLISHER]

Males frequently signal their resistance against parasites by elaborate ornaments. By mating with more ornamented males, females may choose less parasitized partners, and benefit by reducing the probability of contagion of parasites with direct transmission. Chewing lice (order Phthiraptera) are parasites of birds that considerably harm hosts, even decreasing survival. Previous studies showed that male house sparrows (Passer domesticus) can signal resistance against chewing lice by the size of the white wing bar, with more resistant birds having a larger bar. Here, in a mate-choice experiment, 16 female sparrows were presented to 16 dyads of males having similar initial wing bar sizes. In each dyad, the wing bar was experimentally reduced in a randomly selected male. Female house sparrows chose males with larger wing bars. Nevertheless, females also preferred males with less feather holes caused by chewing lice and larger males. By choosing males with larger wing bars, females choose males with larger uropygial glands, an organ involved in the resistance against chewing lice in this species. Therefore, white patches, which are widespread in birds, might be used by females in order to evaluate male resistance against chewing lice. [ABSTRACT FROM PUBLISHER]

Ho do parents resolve their conflict over parental care? The classical “sealed-bid” model of biparental care suggested that parents use a fixed best effort given the partners effort. Alternatively, parents may “negotiate” their actual effort until the efforts of both partners settle down to limiting values, but in this case, the resulting efforts will not be the best responses to one another. Consequently, under the best response scenario, the response of 1 parent to the removal of its mate can be predicted from the response to a reduction in its partners effort, whereas the “negotiation” model predicts that such an extrapolation will underestimate the effort of a parent caring alone. We tested this prediction in free-living house sparrows (Passer domesticus). We experimentally manipulated the males’ parental care as follows: males’ care in group 1) was reduced by using a capture–handling–release stress protocol, 2) stopped by removing the male, and 3) left as control. In response to these manipulations, control females kept their feeding rate constant, whereas male-stressed-released females showed a moderate increase of feeding rate. When this response was extrapolated to zero male effort, their effort was still significantly lower than the observed effort of male-removed females. These results suggest that females may use the negotiation rule to determine their actual parental effort. [ABSTRACT FROM AUTHOR]

One of the central questions in invasion biology involves why some introductions succeed and others fail. Although several correlates of invasion success have been identified, patterns alone cannot identify the mechanisms underlying the invasion process. Here, we test the hypothesis that one predictor of invasion success, behavioral flexibility, is different between invading and established populations of the same species of bird. We predicted that neophobia (fear of novelty), a surrogate of behavioral flexibility, would be weaker in an actively invading population (28 years resident; Colon, Republic of Panama) of house sparrows (Passer domesticus) compared to a population that had been resident for more than 150 years (Princeton, New Jersey, USA). To test this hypothesis, we compared latency to consume novel foods and phobia of novel objects between populations when both were kept under similar environmental conditions in captivity. As predicted, birds from the 150-year-old population took significantly longer to approach and consume novel foods than birds from the 28-year-old population. Responses to novel objects were not different between populations however; both populations fed more readily near some novel objects, which to our knowledge is the first such occurrence in a wild vertebrate species. Overall, a predilection for trying new foods and being attracted to novel objects may in part explain how this species has so successfully invaded new areas. [ABSTRACT FROM AUTHOR]

We examined the effect of patch size and competitor number on aggression among house sparrows, Passer domesticus, foraging at patches of seven different sizes in a doubling series (0.014, 0.029, 0.058, 0.116, 0.230, 0.462, and 0.922 m2). Contrary to our expectations, the birds did not defend an entire patch, even when it was small as 0.014 m2. The frequency of aggression among the birds decreased gradually with increasing patch size, in contrast to the step decline predicted by resource defense theory. Moreover, the birds fought more frequently and more intensely as competitor density increased. Both results are consistent with the predictions of a modified hawk-dove model for shared patches. Females were more aggressive and fed at a higher rate than did males. The proportion of females increased as patch size decreased, and aggression became more frequent and intense. Even when patches are shared, patch size has an important effect on the frequency and intensity of foraging competition and the size and composition of foraging groups. [ABSTRACT FROM AUTHOR]

Although the killing of unrelated young (usually designed as infanticide) has been typically considered a male behavior, recent research has shown that females may commit infanticide even more frequently than do males. In rodents and primates, female infanticide represents a strategy associated to competition for resources or infant exploitation, but little is known about the causes and reproductive consequences of the killing of conspecifics by females in other vertebrates. In the present article, I focus on infanticide committed by females that replace mates of territorial males in a population of the house sparrow. I show that (1) replacement females regularly committed infanticide, (2) experienced females committed infanticide more frequently than did novel females and tended to select polygynous males to take over their nests, and (3) laying date and reproductive success after a territory takeover did not differ between infanticidal and noninfanticidal females. These results seem to indicate that infanticide has not evolved in females because of the short-term reproductive benefits it accrues to the perpetrator. I suggest that the killing of unrelated young by females relates to dominance status among potential female breeders and that this behavior benefits the perpetrators in terms of mate selection. [ABSTRACT FROM AUTHOR]

Extrapair paternity (EPP) is common among birds, but the reasons why it varies within and among species are less clear. In particular, few studies have experimentally examined how food availability influences paternity and sexual behavior. We manipulated food supply in a nest-box population of house sparrows, Passer domesticus, a colonial passerine with extensive biparental care. During three successive breeding attempts, we changed food availability at nest sites and examined behavior and genetic parentage. DNA fingerprinting revealed that the level of EPP within broods was five times lower in pairs nesting at sites continuously supplied with extra food. With extra food, mates spent longer time together at the nest, but this was mainly due to a change in female behavior; females but not males increased total nest attendance. Moreover, we found that individual males did not change within-pair copulation frequency across treatments, suggesting that our experiment did not influence male control over fertilizations through copulation behavior. Instead, our study shows that ecological factors can have a strong influence on the time budgets of males and females, which consequently affects the occurrence of EPP. [ABSTRACT FROM AUTHOR]

We tested the differential maternal allocation hypothesis in a population of house sparrows. We experimentally altered the attractiveness of males by treating them with implants filled with crystalline testosterone (T) or left empty (C). We subsequently monitored maternal investment as a function of male hormonal treatment and the size of the black patch of feathers on the throat (i.e., the badge), a sexually selected trait. The differential allocation hypothesis predicts that females should adjust their investment with respect to the benefits they receive by mating with an attractive male. Given that both circulating levels of T and badge size are condition-dependent traits, we expected that females mated with T males and/or with large-badged males should invest more into current reproduction. Contrary to this prediction, we found no evidence that suggested differential maternal allocation in this population of house sparrows. Female investment in yolk T, yolk mass, clutch size, chick brooding, and feeding was not affected by male hormonal treatment or by male badge size. As expected, T males invested less into chick brooding and feeding. More surprisingly, females did not compensate the reduced paternal contribution to chick feeding. As a consequence, the breeding success of T pairs was largely reduced compared with that of C pairs. The absence of differential allocation in a system in which it could have an adaptive role raises the question about the possible constraints or overriding factors operating on patterns of reproductive investment in this species. [ABSTRACT FROM AUTHOR]

The offspring of birds and mammals use a combination of movements and vocalizations, known as begging, to solicit food from their parents. A widespread interpretation of begging is that it constitutes an honest signal of offspring need. But we know that in the house sparrow (Passer domesticus) the intensity of begging calls reflects the past experience of offspring in addition to their need. Here we show that this result generalizes to other species. An experiment with hand-reared magpies (Pica pica) and great spotted cuckoos (Clamator glandarius) indicates that the begging strategies depend on the past experience of chicks and the composition of their brood. In asynchronous two-magpie broods, both chicks begged at the same intensity when the large chick obtained food more easily than its sibling, but the large chick begged at higher intensity when it was easier for the smaller chick to obtain food. Cuckoo chicks begged at higher intensity than magpies. [ABSTRACT FROM AUTHOR]

We explored the responses of monogamous house sparrow parents to deviations in their mates' contributions to nestling provisioning. Following 1-2 days of baseline measurement of parental food delivery rates, we applied small lead fishing weights to the tail feathers of either male or female parents. Weighting had much greater immediate impact on male parental care than on female care, but the handicapping had little long-term effect on either male or female provisioning behavior. When parental performance of handicapped males was most impaired, their mates did not show significant increases in parental care as compensation, nor did females mated to handicapped males reduce their provisioning as their mates recovered from weighting. Similarly, males mated to handicapped females did not respond to their partners' recovery with declines in their own efforts; paradoxically, these males showed a sustained elevation of provisioning throughout the post-treatment interval, despite no significant reduction in provisioning by weighted females. The apparent insensitivity of both males and females to changes in their mates' parental behavior, and the ineffectiveness of current partner behavior at predicting an individual's provisioning effort, fail to conform to assumptions of biparental care models that require facultative responses to partner deviations in effort. Instead, the remarkable consistency of each individual's behavior supports the notion of “sealed bids” and suggests that variation in nestling provisioning is largely attributable to factors that are independent of the mate's current behavior, such as differences in individual quality. [ABSTRACT FROM AUTHOR]

A correction to the article "Assessing the function of house sparrows' bib size using a flexible meta-analysis method," is presented.

Several studies have found that island populations of passerines exhibit lower levels of extrapair paternity (EPP) than mainland populations. An explanation proposing that lower levels of genetic diversity in isolated populations reduce the indirect genetic benefits of EPP to females has been supported by observational study but not tested experimentally. Here, we present the results of a manipulative study on an island population of house sparrows (Passer domesticus), which previously exhibited a significantly lower frequency of EPP than mainland populations. Fifty adults from a mainland population with significantly more genetic diversity than the island population (across 17 microsatellite loci) were introduced into the island population, and the incidence of EPP was subsequently monitored over 3 breeding seasons. In the year of the introduction, the incidence of EPP rose to approximately the level seen in mainland populations of house sparrows but dropped to an intermediate frequency in the following 2 years. Unexpectedly, parentage assignment showed that in the year of the introduction, all females producing extrapair offspring were native island birds, as were all the extrapair and cuckolded males. These results suggest that EPP in this experimental population was not driven by females trying to maximize the genetic diversity of their offspring. [ABSTRACT FROM AUTHOR]

The black throat patch or bib of male house sparrows, Passer domesticus, is often referred to as a “badge of status” or a “badge” because previous studies have shown bib size to be correlated with the social status of males. Yet, little is known about how strong and robust this relationship is and how the strength of this relationship compares with that of other associations. We conducted a meta-analysis for 6 well-studied correlates of bib size: fighting ability, parental ability (egg incubation and food provisioning), age, body condition, cuckoldry, and reproductive success. We introduce a flexible meta-analysis method in this study that is better suited in the biological sciences than the methods usually employed in popular meta-analysis software because our method accounts for a common form of nonindependence of the data. The relationship between fighting ability and bib size was found to be strong and robust, and the relationship between age and bib size was moderate and robust. Also, body condition was weakly but significantly correlated with badge size. The other parameters showed nonsignificant small effects and/or large confidence intervals. Therefore, we conclude that bib size signals dominance and to a lesser extent age and possibly reflects body condition in house sparrows. There was weak evidence that bib size is currently under sexual selection because there was little association between reproductive success and bib size. This is surprising as the bib size probably affects the outcome of male–male competition. Empirical data on sparrow bib size could not be reconciled with sexual selection theory, although there is ample evidence that it is a condition-dependent trait. [ABSTRACT FROM AUTHOR]