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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. • We investigated breeders and helpers' feeding responses to offspring begging. • Breeding males, but not females, fed faster after experiencing more begging calls. • Feeding by helpers of different sex and relatedness did not vary with begging. • Second-order related helpers experienced more begging calls than other provisioners. [ABSTRACT FROM AUTHOR]

Many hosts of obligate brood parasitic birds invest more in parasitic nestlings than they do in their own young. The shiny cowbird, Molothrus bonariensis , a generalist parasite, is fed at a higher proportion than its host nestmates when it is reared in nests of a smaller-bodied host, the house wren, Troglodytes aedon. We test two hypotheses that could account for this differential allocation of food by host parents. The signal exaggeration hypothesis states that cowbird chicks have visual and/or acoustic begging signals that elicit preferential feeding. The size-advantage hypothesis states that hosts preferentially feed large chicks and/or that larger chicks outcompete host chicks in a scramble competition for food. To gain insight into the relative importance of size versus species-specific signals on food allocation by house wrens, we performed audio and video recordings in nests with experimental broods of (1) a 2-day-old cowbird chick and a 2-day-old wren chick (different species, different size), (2) a 2-day-old cowbird chick and an 8-day-old wren chick (different species, same size) and (3) a 2-day-old house wren and an 8-day-old house wren (same species, different size). When cowbirds shared the nest with a same-size wren chick, both chicks received food in equal proportion. In contrast, larger chicks (both cowbirds and wrens) paired with small wren nestmates always received a higher food share. Cowbird begging behaviour and call traits differed from house wrens, but these differences did not always coincide with increased food. We conclude that, at least when cowbird nestlings are young (2 days old), their relatively large size accounts for the larger share of food they receive from house wren hosts, rather than some quality of their begging signal. • The house wren is a small host of the brood-parasitic shiny cowbird. • Wren hosts fed cowbird nestlings more than they fed their own young. • Cowbird size, rather than begging, explains the higher investment by wrens. [ABSTRACT FROM AUTHOR]

In species with biparental care, begging offspring may preferentially associate with or beg more towards one of their parents. Such preferences may reflect that the benefits of begging vary with the parent's sex given that females and males often differ in the amount of care they provide and/or in their responsiveness to begging levels. Alternatively, they may reflect the outcome of sexual conflict over care as females may deposit compounds into eggs tha talter offspring begging behaviour such that it increases male contributions towards care. For example, females might use male presence during egg laying as a cue for whether they might receive male assistance in care. Here, we studied offspring begging behaviour towards male and female parents in the burying beetle Nicrophorus vespilloides by manipulating male presence or absence during egg laying and providing larvae with a simultaneous choice between an unfamiliar female and male adult beetle. We then recorded begging behaviour of (1) naïve newly hatched larvae that had no prior experience of a parent and (2) larvae after 24 h of care by foster parents. Larvae showed a clear preference for associating with and begging towards females both when naïve and after 24 h of care. We found no evidence for prenatal maternal effects on larval begging behaviour. Our study reveals that offspring are predisposed to preferentially beg towards females independently of prior experiences with parents and highlights the importance of considering responses of begging offspring to parental attributes, such as the parent's sex, for our understanding of family conflicts. [ABSTRACT FROM AUTHOR]

Egg size reflects the amount of energy that female parents have invested in their offspring prior to hatching, and is thus often used as a proxy for prehatching investment. According to life history theory, prehatching investment, in turn, trades off with posthatching investment, as the amount of resources allocated at the prehatching stage diminishes the resources available at the posthatching stage. As small eggs have smaller energy reserves than large eggs, the offspring originating from small eggs may have higher hunger levels, and thus beg more, offering the parents information about the need for more posthatching care. However, little is known about the relationship between egg size and begging behaviour, and the fitness correlates of the two. In this study, we directly investigated the association between these two traits in the burying beetle Nicrophorus vespilloides . Concurrently, we examined the effects of egg size on two components of offspring fitness: offspring growth and survival. We found no association between egg size and offspring begging behaviour. Egg size did, however, show a mostly positive, albeit indirect, association with offspring fitness traits (development time, size and survival). Therefore, an increase in egg size does have an impact on offspring fitness, but this impact is not mediated through offspring begging. To our knowledge, this is the first time the relationship between egg size and begging behaviour has been investigated directly. [ABSTRACT FROM AUTHOR]

The evolution of sibling competition is promoted when the brood's demand for resources (brood size) exceeds the parents' supply of resources (resource availability). However, little is known about the joint effects of brood size and resource availability and whether these effects are independent of each other. We conducted a study on the burying beetle Nicrophorus vespilloides , in which we manipulated both brood size and resource availability. We manipulated brood size by providing parents with 5, 10 or 20 larvae and resource availability by providing parents with a 5, 10 or 20 g mouse carcass. We found that resource availability had positive effects on parental care, larval body mass and larval survival, while brood size had a negative effect on larval body mass and larval survival. There were positive effects of the interaction between brood size and resource availability on larval begging and larval body mass, suggesting that the slopes describing the effect of brood size on larval begging and larval body mass became less negative as carcass size increased. When we repeated the analysis using larval density (i.e. brood size/resource availability) as a proxy for the shortage of resources, there were negative effects on parental care, larval body mass and larval survival. Our results have important implications by showing that there were main effects of both brood size and resource availability, and that their effects were not always independent of each other. Thus, treating brood size and resource availability as independent factors is preferential to using offspring density. [ABSTRACT FROM AUTHOR]

In species with parental care, offspring often solicit food through elaborate begging displays. Begging is thought to be a reflection of offspring need, but short-term fluctuations in begging do not necessarily provide reliable information. Parents thus have to adjust their provisioning behaviour to the changing demands of their offspring, while minimizing the costs of responding to unreliable information. We conducted two experiments with blue tits, Cyanistes caeruleus , in which we tested how parents respond to short-term and long-term changes in begging intensity. In the first experiment we investigated how parents respond to increased begging during a single nest visit. In the second experiment we investigated how parents respond to increased begging during every nest visit for 1 h. Parents did not return faster to the nest during the short-term manipulation. Contrary to our expectations, however, parents also did not return faster to the nest in response to long-term manipulation. Instead, parents spent more time in the nestbox during both the short-term and the long-term manipulation. Our results highlight that the general pattern of a positive parental response to increased begging may not be a universal one. Comparisons across species and populations may help reveal the factors underlying variation in parental responsiveness to begging. [ABSTRACT FROM AUTHOR]

Whether begging behaviour mediates food provisioning has been extensively studied in birds. However, begging behaviour occurs without direct offspring competition in some species and thus may be driven exclusively by intrabrood dynamics. We studied begging behaviour of individually housed offspring of the biparental mimic poison frog Ranitomeya imitator . We tested whether (1) begging is an honest signal of need or hunger, (2) begging is costly and (3) parents allocate food according to offspring need. Under manipulation of long-term diet, food-limited tadpoles increased begging effort over the course of development. Tadpoles that were induced to beg suffered a cost of taking longer to reach developmental stages and showed a marginal cost on growth rate. Finally, parents were more likely to feed the tadpole that was exposed to a nonsupplemented diet over its food-supplemented sibling. In R. imitator , begging behaviour appears to signal offspring need honestly and thus may predict differential food provisioning among offspring. [ABSTRACT FROM AUTHOR]

The differential allocation hypothesis (DAH) predicts that an individual should vary its reproductive investment according to the attractiveness of its mate. A recently revised version of the DAH makes explicit that investment can be positive, i.e. higher for the offspring of attractive males which should be of higher quality, or negative, i.e. higher for offspring of unattractive males, for example compensating for inheriting poor paternal genes. Moreover, investment can be made by the father and the mother. Here, we tested whether experimental manipulation of male attractiveness affected parental investment at different reproductive stages and thus influenced fitness-related traits in offspring. In two aviaries, all male zebra finches, Taeniopygia guttata , were given red leg rings to increase attractiveness and in two aviaries all males received green leg rings to decrease attractiveness. This controlled for assortative mating between treatments. Ring colour was merely an experimental manipulation of male attractiveness, not paternal quality, so we might expect additional investment to elevate offspring quality. Eggs were cross-fostered between and within treatments to allow differentiation of effects of investment in eggs and nestlings. Clutch and brood sizes were standardized. Both positive and negative investment were observed: Eggs from red-ringed fathers had higher yolk to albumen ratios than eggs from green-ringed fathers. Nestlings from eggs laid and incubated by parents in the red-ringed group had higher hatching masses than those in the green-ringed group. Both parents in the green-ringed group fed nestlings more frequently than red-ringed parents. Offspring performance was influenced by the treatment of both foster and biological parents, but combined effects of these different investment patterns on fitness-related traits were ambiguous. Male attractiveness appeared to affect patterns of reproductive investment but not consistently across all forms of reproductive investment suggesting that the costs and benefits of differential allocation vary among individuals and across contexts. [ABSTRACT FROM AUTHOR]

Offspring signalling models predict that the begging displays of obligate brood parasites are more intense than nonparasitic species because parasitic young are never reared by their genetic parents and often compete against unrelated host young during development. The brown-headed cowbird, Molothrus ater, has been described as having exaggerated begging relative to nonparasitic species, but an effective test of this idea is lacking because previous studies have not controlled for evolutionary history while simultaneously standardizing rearing conditions. We quantified the begging intensity of cowbirds and the closely related, nonparasitic red-winged blackbird, Agelaius phoeniceus, when both species experienced identical rearing conditions in two distinct nest environments: reared alone by a small cowbird host, or reared with two host young by a moderate-sized cowbird host. Against theoretical predictions, we found that in both nest environments four components of the cowbird begging display were similar to (or less intense than) blackbird begging displays (i.e. latency to beg, begging score, call rate and call amplitude) when nestlings were tested across a gradient of short-term need. Our results provide the first experimental evidence that a closely related, yet nonparasitic, species shares an exaggerated begging display with a brood-parasitic species when reared under conditions typically experienced by parasitic offspring. We discuss three nonexclusive explanations for our findings: (1) relatedness among cowbird nestmates reduced cowbird begging intensity (kin selection hypothesis), (2) reduced body condition of blackbirds elevated their begging intensity (body condition hypothesis) and (3) intense competition in blackbird nest environments led to increased blackbird begging intensity (competitive environment hypothesis). [ABSTRACT FROM AUTHOR]

Anthropogenic noise can have serious implications for animals, especially when they communicate acoustically. Yet, the impacts of noise may depend not only on noise characteristics but also on an individual's coping style or personality. We tested whether noise is more disturbing if it masks communication signals, and whether characteristics of both the noise and the individual affect its impact. Using a unique population of personality-typed great tits, Parus major, we tested whether the kind of noise and parental personality affect parental nestbox visits and nestling begging. Nestboxes were exposed to automated noise playbacks, differing in spectral composition (noise masking begging calls, nonmasking noise or no noise). Parental nestbox visits were recorded using RFID transponders. Video and audio recordings were used to quantify nestling begging. Nestlings mainly begged in silence and in the presence of parents. Parents reduced nestbox visits during noise treatments regardless of the kind of noise and initially reacted more strongly to nonmasking noise. Moreover, slower explorers took longer to enter the nestbox during noise than faster explorers. Total visit rates during noise depended on parental sex and personality. In females, bolder individuals, but in males shyer individuals, reduced total visits during noise. These results extend previous findings in showing experimentally that the disturbance effects of noise do not depend on whether or not the noise directly interferes with information exchange by masking signals. Moreover, personality- and sex-specific responses to noise indicate that anthropogenic disturbance can differentially affect individuals within populations, which will influence mitigation strategies. [ABSTRACT FROM AUTHOR]

Parent birds respond to a variety of cues from their offspring when provisioning them with food. Bright flange colours and large body size are two traits of offspring that many parents seem to favour, but little is known about how such traits interact. By experimentally altering the difference in mass between nestmates while concurrently blackening the flanges of either the large or small nestlings in the brood, we tested whether large body size could compensate for dull coloration. In three species of cavity nesters (northern flicker, Colaptes auratus, great tit, Parus major, and pied flycatcher, Ficedula hypoleuca), doubly disadvantaged offspring that were both small and dull performed the worst, whereas large and bright offspring received the most provisioning, consistent with the idea of additive effects. We used regression to show that, for flickers, dull (blackened) nestlings performed as well as bright nestlings when they were 20% larger than their bright nestmates. For passerines, dull nestlings had to be 30–40% larger than bright nestlings to receive equivalent amounts of food from parents. Within-brood differences in mass before manipulation were often greater than this size difference threshold, suggesting that hatching asynchrony has a stronger influence on food allocation than do colour differences among siblings. [Copyright &y& Elsevier]

Begging behaviour in birds is frequently studied in nestlings, but the function of adult female begging behaviour remains unknown. We examined begging behaviours of adult female yellow warblers, Setophaga petechia, during incubation at the northern limit of their breeding range. Female yellow warblers beg only when their mate arrives at the nest, and vocalization duration, intensity of wing fluttering and position of the female''s body on the nest varies between begging events. We measured changes in these characteristics for 696 begging events from nine incubating females and examined how begging intensity changed with temperature and time since a female''s last feeding. Begging intensity increased as the duration between feedings increased especially during colder temperatures. Next, we investigated how male feeding rates changed in response to variation in female begging intensity. Males fed females more quickly in response to intense begging during warm temperatures but not during cold temperatures. Finally, we investigated whether male feeding rates influenced the frequency or duration of the female''s bouts away from the nest (i.e. ‘off-bouts’) during which the female had the opportunity to forage. Females that were fed more frequently reduced the average duration, but not the frequency, of their off-bouts. These results suggest that variation in the intensity of female begging behaviour signals energetic need, and that begging during incubation may be an important adaptation allowing female yellow warblers to maximize incubation time when breeding in sub-Arctic environments. [Copyright &y& Elsevier]

It is generally assumed that begging signals provide parents with reliable information on the state of their young, allowing them to decide accordingly how much to invest in their nestlings. Avian brood-parasitic nestlings exhibit begging displays that are highly exaggerated. In most species, they also increase their begging level in relation to their level of hunger, as predicted by models of honest signalling. However, it has been suggested that great spotted cuckoo, Clamator glandarius, nestlings are an exception to this general rule because they spit out food when satiated and continue begging at a high intensity. We tested this assertion by using both natural observations of food delivery by foster parents and a laboratory experiment in which we hand-fed both cuckoo and host magpie, Pica pica, and carrion crow, Corvus corone, nestlings while controlling for the degree of food deprivation. First, we found that cuckoo nestlings did not throw out food because they are satiated. Second, as in host magpie nestlings, during a period of food deprivation the cuckoo nestlings begged at a significantly higher frequency and intensity than when fed ad libitum (a period of food abundance) and begging signals increased with an increased level of hunger in both species. These results indicate that in this cuckoo species the frequency and intensity of begging are in accordance with food requirements, and, thus, that begging is not dishonest in the sense of being unreliable. [Copyright &y& Elsevier]

The evolution of begging display may be influenced by gene–environment interaction, through the mechanisms that adjust begging behaviour to environmental conditions of offspring, including intensity of sibling competition within broods. We decomposed the complex begging display of yellow-legged gull, Larus michahellis, chicks into two different functional components: begging for food (pecks) and drawing the attention of parents (chatter calls). We examined these begging components in 2-day-old chicks that hatched and grew up in foster nests, by performing a begging test for each chick alone without the hindrance of its foster siblings. Male chicks and those with poorer body condition begged for food at higher rates than females and those with better body condition, respectively. Chicks from larger broods begged for food more frequently, but chicks from male-biased broods begged less frequently. If begging is costly, chicks may adjust their begging efforts to the intensity of sibling competition. Frequency of chatter calls varied with sex, chick order within broods and body condition: females, the third chicks and those with poorer condition produced chatter calls more frequently. Genetic origin had a significant effect on frequency of chatter calls but not on begging for food, while foster nest effect was null in both traits. Therefore, chatter calls (but not pecks) can be subject to evolution under directional selection. Different begging components may have evolved through different evolutionary pathways. [Copyright &y& Elsevier]

Recently, there has been much interest in the role of endogenous and maternal hormones as regulators of offspring begging and mediators of parent–offspring conflict. Here, we review recent work in this field, and identify inconsistencies in the literature. We find good evidence that hormones play a role as regulators of begging: 13 studies report a positive effect on begging and six a negative effect. There is also good evidence that hormones influence offspring fitness, but the direction of reported effects is inconsistent: eight studies report a positive effect on offspring fitness and 10 a negative effect. We explore potential pathways linking hormonal effects on begging and growth. We find that our current understanding of these pathways is incomplete, and suggest a simple model linking hormonal effects on begging and growth. We next discuss the role of hormones as mediators of parent–offspring conflict. We find little evidence that maternal hormones provide a mechanism for parental favouritism. We use graphical models to explore the hypothesis that maternal hormones act as honest signals, and find that costs of hormone production can ensure the honesty of maternal hormones but only under very restricted conditions. We discuss evidence from recent cross-fostering experiments suggesting that maternal hormones act in the context of overlapping interests between parents and offspring. Finally, we highlight the need for more studies on nonavian taxa to establish whether hormonal regulation of begging is specific to birds or general across taxa where offspring beg for food from their parents. [Copyright &y& Elsevier]

The manipulating androgens hypothesis (MAH) proposes that female birds increase the level of testosterone (T) in their eggs to promote greater offspring begging, and thereby elicit increased provisioning by their mates. We examined the effect of a positive in ovo manipulation of T on provisioning by house wren, Troglodytes aedon, parents, and concomitantly examined the begging response of nestlings. We also examined the mass of nestlings throughout their growth to assess the effect of T on their development, and three measures of nest performance: hatching success, nestling survival and the proportion of nestlings that fledged. Nestlings hatching from T-injected eggs begged more than nestlings hatching from control (oil-injected) eggs early in the nestling period, but not later in the nestling period. However, treatment had no effect on the levels of parental provisioning or nestling mass gain, nor any effect on hatching success or nestling survival. There was a significant increase in parental provisioning rate, but a decline in the size of prey taken to the nest over the course of the breeding season, which was likely the result of declining environmental quality. Our results support neither the MAH, nor the expectation that nestlings should grow at different rates in relation to in ovo titres of T. [Copyright &y& Elsevier]

Parents allocate food resources to their offspring in proportion to the intensity of begging behaviour. Begging encompasses several activities including vocalizations that should honestly signal need and jostling for the position in the nest where parents predictably deliver food items. Although siblings are known to adjust begging level to each other, the underlying mechanism remains unknown. We examined this issue in experimental two-chick broods of the barn owl, Tyto alba, a species in which siblings communicate vocally with each other in the prolonged absence of parents. The function of sib–sib vocal communication, so-called sibling negotiation, is to resolve conflicts over which individual will have priority of access to the next delivered indivisible food item. We found that when a nestling produced longer negotiation calls and stood closer to the nestbox entrance in the absence of parents, its sibling vocally negotiated at a lower rate. Additionally, when an individual produced more negotiation calls in the absence of parents, its sibling begged less intensely at the parent’s return, with begging being the key factor that determined which nestling obtained a food item. We conclude that position in the nest and the duration of negotiation calls produced in the absence of parents influence the rate of producing negotiation calls, which in turn influences the rate at which siblings beg for food from their parents. Adjusting begging behaviour could therefore depend on complex sib–sib interactions taking place in the prolonged absence of parents. [ABSTRACT FROM AUTHOR]

Vocal communication between parents and offspring, including feeding solicitations by parents and begging calls of young, can increase the risk of predation by attracting predators. Parents can use a ‘switch-off’ signal (alarm call) to suppress progeny vocalizations or movement, making chicks less detectable to predators. Alternatively, a ‘switch-on’ signal (feeding or solicitation call) may be used to initiate a begging display in young by parents. The presence and species specificity of either or both of these signals have rarely been tested, as acoustically similar cues may have evolved amongst avian species. We examined the behavioural and acoustic responses of individual grey warbler, Gerygone igata, nestlings to both feeding and alarm calls at 12 and 16 days of age (nestling period: 17 days) in a sound-isolation chamber. Overall, nestlings consistently reduced the amplitude of begging calls in response to alarm calls, regardless of the developmental stage. Nestlings responded by gaping only to conspecific, and not heterospecific, begging solicitation calls or other acoustic stimuli. After alarm calls, nestlings did not cease begging, but altered the structure of the begging call. Differences in several begging call acoustic structures were also detected between age groups. These patterns are consistent with a trade-off in chicks'' signal-specific responses to parental calls, which optimizes the probability of being fed during parental nest visits whilst also reducing predator detection. [Copyright &y& Elsevier]

Avian brood parasites typically depress the fitness of their hosts by reducing the number of host offspring produced, yet little is known about how parasitic nestlings influence the behaviour of host parents and host offspring. In this study, we used three hosts of the brown-headed cowbird, Molothrus ater, that varied in size (i.e. smaller, similar to and larger than cowbirds of a given age) to determine whether parasitic nestlings altered patterns of food provisioning by host parents and begging by host young under field conditions. Adult provisioning did not change in the presence of a cowbird but instead was influenced by feeding treatment and host size. In parasitized broods where nestlings differed in size (i.e. the small and large hosts), the larger nestling received the majority of food brought to the nest, regardless of whether it was the cowbird or host nestling. In contrast, similar-sized host nestlings received a similar amount of food in parasitized and unparasitized host broods. Relative to unparasitized broods, the presence of a cowbird led to increased begging intensity by the small host, had no clear effect on begging behaviour of the intermediate-sized host, and reduced begging intensity of the large host. Taken together, these results suggest the presence of a cowbird did not lead to changes in provisioning behaviour in parents, and the extent to which cowbirds influenced host begging behaviour depended on the size of the host. [Copyright &y& Elsevier]

The bright colours of nestlings'' mouths are conspicuous when they beg. Three main hypotheses suggest that nestling mouth colour (1) increases detectability in dim ambient light, (2) signals health or quality, or (3) provides a means of offspring recognition. To distinguish these hypotheses, we manipulated both the flange colour (visual and UV spectrum) and the ambient light in the nest of three cavity-nesting species: a woodpecker and two passerines. Parents avoided nestlings with black-painted flanges to a greater extent in dim than in bright ambient light conditions, and the effect was most pronounced in the woodpecker, which had the deepest and darkest nest cavity of the three species studied. There was no difference in mass gain of nestlings with flanges painted white or yellow or with UV-block cream relative to controls, suggesting that neither UV reflectance nor carotenoid colour was a cue of nestling quality. These results support the detectability hypothesis and not the health-signalling or recognition function for bright flanges. Black-painted flycatcher nestlings were more disadvantaged in short trials (<3h) than in longer trials (>3h), and we developed a model to explain how nonvisual components of begging, such as vocalizations or movements, may become more important than visual cues as nestlings become hungrier and beg more intensively over time. Our results suggest that bright flanges in cavity-nesting birds evolved primarily so that parents can locate offspring in dim light, but competition among nestlings may lead to exaggerated brightness. Furthermore, other components of begging such as movements or vocalizations may temporarily override a disadvantage of dull mouth colour. [Copyright &y& Elsevier]

Interactions among parents, offspring and the environment are a critical aspect of parental care. Begging by offspring usually results in increased parental provisioning. Yet, parents also vary their behaviours to reduce offspring predation. Both begging sounds and provisioning activity can increase risk of nest predation. We predicted in a high nest-predation environment, parents would satiate young and reduce begging by increasing food load but maintaining the same provisioning rates. We also assessed whether increased begging was beneficial to offspring and whether parents changed the allocation of food to particular nestlings. We increased whole-brood begging via playbacks at nests of a tropical passerine bird, the western slaty antshrike, Thamnophilus atrinucha. We observed that parents increased provisioning rates and reduced food load in response to elevated begging. Selection may therefore favour feeding hungry nestlings even when predation risk is elevated, or begging sounds may place offspring at a higher risk than increased activity. Parents reduced the time between arrival to the nest and feeding of nestlings, potentially to reduce begging sounds. Exaggerated begging did not appear to be beneficial to offspring since parents did not deliver more food. Parents switched to preferentially feed the closest offspring during the begging treatment. This suggests that, under elevated begging, parents either allowed sibling competition to influence feeding decisions, or fed the closer nestling to reduce the time between arrival to the nest and feeding. Studying species in different environments provides insight into how ecological factors such as nest predation influence parental behaviour. [Copyright &y& Elsevier]

When the potential contributions that offspring can make to parental fitness vary, parents benefit by diverting resources towards the offspring offering the highest return on investment. In birds, nestling begging has been hypothesized to allow parental assessment of the relative contribution that each offspring can make to parental fitness. Although begging is often interpreted as a signal of need, studies of nestling morphology, specifically carotenoid-based mouth colours, suggest that these traits signal not the need, but the quality of the nestlings. Here, I manipulated flange colour in a free-living population of house sparrows with experimental paints that did not feature a UV reflectance peak, but otherwise approximated carotenoid-based colours within the range of natural variation. I presented parents with one nestling that appeared to have the carotenoid-rich rictal flanges associated with high condition and one that appeared to have the carotenoid-poor flange colour associated with poor condition. Parents delivered more food items to the nestling that appeared to have carotenoid-rich flanges, a pattern driven by a strong female bias and a similar, but nonsignificant, trend in males. This study shows that parents attend to these visual signals rather than correlated features of nestling physiology associated with carotenoids. Broadly, this result suggests that at least some components of begging are used by parents to bias resource allocation towards their most promising, rather than most needy, offspring. [Copyright &y& Elsevier]

Food begging is common in nutritionally dependent young of many animals, but structurally homologous calls recur in adult signal repertoires of many species. We propose eight functional hypotheses for begging in adults; these stem from observations in birds but apply broadly to other taxa in which begging occurs. Adult cooperatively breeding white-throated magpie-jays, Calocitta formosa, use loud begging vocalizations, particularly near the nest site during reproduction. We analysed the social context and behavioural phenology of loud calling and allofeeding in this species and compared these with predictions from each functional hypothesis. We found that reproductive females were the primary producers of beg calls, and their begging peaked during the fertile period when reproductive conflict among males and females was highest. Loud begging rates correlated positively with provisioning rates, but females called more in the pre-incubation fertile period than they did after they had initiated incubation. Based on the context, phenology and active space of the signal, we conclude that female loud begging vocalizations function to signal nutritional need to group members, but also have been evolutionarily co-opted to advertise fertility to potential extrapair partners. The location of calling is probably a consequence of nest guarding by breeding females to prevent intraspecific brood parasitism. [Copyright &y& Elsevier]

In biparental species, the response of parents when their mates are disadvantaged is highly variable. Moreover, experimental studies on parental effort have mainly focused on short-lived birds whose breeding constraints largely differ from those of long-lived species such as seabirds. We investigated the short- and long-term consequences of handicapping one parent within Adélie penguin, Pygoscelis adeliae, pairs. We also examined whether handicapped mates and offspring could convey cues informing the other parent of the need to increase breeding effort and whether this parent adjusted its behaviour accordingly. While handicapped penguins foraged for longer and lost more mass than controls, partners, fasting for longer at the nest, did not change their behaviour or lose more mass suggesting that they compensated at least for themselves. Information exchange was increased between mates after the return of handicapped females from foraging. However, partner males did not respond to this. Handicapped-pair chicks, which were smaller than control chicks, did not increase their solicitation rate for food. In the subsequent breeding season, compared to controls, 40% of previously handicapped females laid fewer eggs, the resight rate of previously handicapped males was lower and pair instability was higher. No additional cues seemed to be detected by Adélie penguins when their mates were handicapped and, for handicapped-pair offspring, the cost associated wih a higher solicitation rate was probably too high for these small chicks to support. Consequently, we found no compensatory behaviour from partners in this long-lived species: handicapped individuals and offspring both supported the whole additional cost in both the short term and the long term. [Copyright &y& Elsevier]

Begging by young provokes adults to provide food for them. However, eventually begging by young and provisioning by adults cease and young become nutritionally independent. Why do young cease begging and so forgo food brought to them by adults? Three explanations have been proposed: (1) adults may not respond to begging anymore and cease feeding begging young; (2) young may voluntarily switch from begging to independent foraging as they gain more rewards from this; (3) young may become unable to produce stimulating begging calls. We tested these three explanations using meerkat, Suricata suricatta, pups. Playback of begging calls at groups where begging had naturally ceased provoked adults to resume provisioning, suggesting that adults had not stopped responding to begging. Experimental provision of food to pups mimicking either natural pup feeding or foraging success produced no differences in subsequent changes in begging or foraging behaviour, suggesting that pups were not assessing the most rewarding means of obtaining food and switching from begging to foraging accordingly. The begging calls of pups (aged 40–60 days) were acoustically different to those produced when they were juveniles (aged 100–120 days), and adults discriminated between rate-controlled playbacks of the two age classes of calls, delivering less food to calls of a juvenile than to the same individual''s calls recorded when a pup. Adult meerkats paid attention to the acoustic structure of begging calls, and ceased provisioning when the call structure changed. We suggest that older pups are unable to produce stimulating begging calls. [Copyright &y& Elsevier]

Young herring gull, Larus argentatus, chicks peck at the red patch on the lower mandible of their parent''s yellow beak. In a famous study on the ‘instinctive behaviour’ of herring gull chicks, Tinbergen examined whether the presence, colour and position of the patch affected the pecking of the chicks. While this experiment is often cited as demonstrating a preference for a red patch, the original data showed that chicks pecked more at a black-patched model (Tinbergen 1948, De Levende Natuur, 51, 49–56). Tinbergen later ascribed this unexpected outcome to a methodological error in his experiment: the red-patched model was presented more frequently than all the others, which made him adjust his data later on. We repeated Tinbergen''s experiment (experiment 1), using replicas of the original models. We also did the experiment as Tinbergen described it later on (but which he never carried out), presenting all models equally often (experiment 2). Our results confirm that red is not the most preferred colour when it is presented more often than other colours. In experiment 2 the relative ranking of all models was the same as in experiment 1, with the exception of the red-patched one, which was now preferred most, as expected by Tinbergen. Our findings also confirm that the more frequent exposure to the red model in experiment 1 resulted in a disproportionate decline in interest for this model. So, although he never did the actual experiment, Tinbergen''s intuition and corrected data show a reasonable match to the results of our experiment. [Copyright &y& Elsevier]

Game theory states that iterative interactions between individuals are necessary to adjust behaviour optimally to one another. Although our understanding of the role of begging signals in the resolution of parent–offspring conflict over parental investment rests on game theory implying repeated interactions between family members, empiricists usually consider interactions at the exact moment when parents allocate food among the brood. Therefore, the mechanisms by which siblings adjust signalling level to one another remain unclear. We tackled this issue in the barn owl, Tyto alba. In the absence of parents, hungry nestlings signal vocally to siblings their intention to contest vigorously the next, indivisible, food item. Such behaviour deters siblings from competing and begging when parents return to the nest. In experimental two-chick broods, nestlings producing the longest calls in the absence of parents, a signal of hunger level, were more successful at monopolizing the food item at the first parental feeding visit of the night. Moreover, nestlings increased (versus decreased) call duration when their sibling produced longer (versus shorter) calls, and an individual was more likely to call again if its sibling began to vocalize before or just after it had ended its previous call. These results are in agreement with the hypothesis that siblings challenge each other vocally to reinforce the honesty of sib–sib communication and to resolve conflicts over which individual will have priority of access to the next delivered food item. Siblings challenge each other vocally to confirm that the level of signalling accurately reflects motivation. [Copyright &y& Elsevier]

The evolution of asynchronous hatching is a central yet controversial issue in evolutionary ecology and animal behaviour. Although asynchronous hatching has a widespread taxonomic distribution, past research has focused almost exclusively on altricial birds. We tested the peak load reduction hypothesis for the evolution of asynchronous hatching in the burying beetle Nicrophorus vespilloides, an insect in which parents provide their offspring with food after hatching. This hypothesis posits that caring parents benefit from asynchronous hatching because it reduces the parent''s maximum workload during the peak in the offspring''s demand for food. To test this hypothesis, we established three types of broods, synchronous, asynchronous and highly asynchronous, with a hatching span of 0, 24 and 48h, respectively, and monitored effects on brood demand and female parental care. As expected, there were sharp peaks in both brood demand and female food provisioning, and the peak in brood demand decreased as a function of increasing levels of asynchronous hatching. However, in contrast to what we expected, the peak in female food provisioning was similar regardless of the level of asynchronous hatching, and offspring survival was substantially lower in highly asynchronous broods than in synchronous or asynchronous broods. We conclude that our results provide no overall support for the peak load reduction hypothesis. Further experiments are needed to establish the adaptive benefits of asynchronous hatching in this species. [Copyright &y& Elsevier]

In many bird species with biparental care for young in the nest, hungry chicks beg repeatedly and parents adjust their feeding rate to the call rate of young. Repetitive calling also occurs in fledglings and in some mammals where offspring follow provisioners. It is not yet clear whether, in mobile systems with dispersed young where adults cannot compare the vocal behaviour of all young simultaneously, the calls represent a signal of need. We investigated repetitive begging by cooperatively reared meerkat, Suricata suricatta, pups that foraged with the group. Pups produced two types of begging calls: repeat calls over long periods and high-pitched calls mainly confined to feeding events. Food-deprived pups stayed closer to feeders, and begged for longer and more intensely by calling at a higher rate. Hungry pups increased both the rate of repeat calls, which were given continually, and the number of high-pitched bouts, but adults increased their food allocation only in relation to the rate of repeat calls. Our study indicates that hunger may lead to several changes in vocal behaviour, only some of which may be used by adults to assess need. [Copyright &y& Elsevier]

Despite the fact that in many bird species offspring are provisioned by two parents, few studies to date have examined the implications of biparental care for offspring solicitation behaviour. Male and female parents can differ in their potential value to individual offspring if they follow different allocation rules and/or have different provisioning rates. If such differences occur, offspring should use different rules when soliciting to the male and female parent. This study looked at how the begging behaviour of nestling blue tits, Cyanistes caeruleus, is influenced by their hunger, size and by the sex of the provisioning adult. Nestling hunger was manipulated across size ranks, using periods of hand feeding or food deprivation. While nestling hunger influenced all aspects of nestling begging behaviour, nestling size and the sex of the provisioning adult only affected the position of nestlings in the nest cup. When hungry, nestlings moved closer to the male parent and the largest nestlings in a brood primarily obtained the closest positions. This may be the result of offspring responding to a difference between the sexes in parental food allocation rules. [Copyright &y& Elsevier]

Recent studies on birds show that two steroid hormones, testosterone and corticosterone, stimulate nestling begging and growth. Here, we seek to investigate whether juvenile hormone, a major regulatory insect hormone, has similar effects on larval begging and growth in insects. To this end, we experimentally elevated larval juvenile hormone levels by topical application of methoprene, a potent and stable synthetic juvenile hormone analogue, and monitored effects on larval begging and growth in the burying beetle Nicrophorus vespilloides. In this species, larvae feed partly by begging for predigested carrion from parents and partly by self-feeding. We showed that elevated juvenile hormone levels stimulate larval begging, suggesting that juvenile hormone in insects could have a similar function to that of testosterone and corticosterone in birds. We also showed that elevated juvenile hormone levels have a negative effect on larval growth and that this negative effect occurs regardless of whether larvae forage by begging or by self-feeding. This finding shows that the effects of juvenile hormone on larval growth are independent of the effects on begging, suggesting that the mechanisms by which juvenile hormone affects offspring growth in insects differ from those by which testosterone and corticosterone affect growth in birds. [Copyright &y& Elsevier]

When provisioning offspring many bird parents give specific calls, which typically stimulate begging. Previous studies have investigated the benefits of food calling during the nestling phase, however, there is a current paucity of data on the use of food calls after young have fledged. This study describes the use of ‘purr’ calls, given by adult pied babblers, Turdoides bicolor, when feeding both nestlings and fledglings. Offspring associated these calls with food delivery: nestlings begged in response to experimental playbacks of purr calls; whereas fledglings, which were no longer confined to the nest, approached calling adults. As well as with feeds, adults also gave purr calls in nonfeeding contexts. Playbacks of purr calls given in feeding and nonfeeding contexts elicited the same responses, suggesting that offspring expected food when they responded to both ‘feed’ and ‘no-feed’ purr calls. Adults seemed to use the association between purr calls and food delivery by giving no-feed purr calls to promote fledgling movement, for example when leading young away from predators. Fledglings directly benefited when they approached adults who gave no-feed purr calls, despite not receiving any food. This study raises the possibility that food calling during the fledgling phase is a widespread, but understudied form of parent–offspring communication in birds and may be a more important aspect of avian parental care than is currently realized. [Copyright &y& Elsevier]

Nestling birds could minimize the risk of being overheard by predators by becoming silent after parental alarm calls, begging only when parents arrive with food, and independently assessing cues that a predator is nearby. Begging only to parents is challenging because young that respond quickly can be more likely to be fed, so there is a benefit of using subtle cues of parental arrival, potentially leading to erroneous begging. Parents might reduce the risk of error by giving food calls signalling that they have arrived with food, but there have been few studies contrasting begging to food calls compared with other parental vocalizations. Furthermore, it is unknown whether nestlings can use acoustic cues to independently detect predators. White-browed scrubwren, Sericornis frontalis, nestlings become silent after parental alarm calls, but it is unknown whether they respond specifically to parental food calls or directly to predator sounds. We conducted a field playback experiment, and found that young begged more vigorously to food calls than other parental vocalizations tested, and nearly as strongly to playback as during real feeding visits by parents. However, nestlings also mistakenly begged to playback of superb fairy-wren, Malurus cyaneus, song, possibly because of acoustic similarities to food calls. Finally, nestlings responded with silence to playback of the sound of their major predator (pied currawong, Strepera graculina) walking on leaf litter. Scrubwren nestlings can therefore be ‘switched on’ and ‘switched off’ by parental vocalizations, are prone to error, and may independently assess risk. [Copyright &y& Elsevier]

Nestling begging behaviour may be an honest signal of need used by parents to adjust optimally both feeding rate and within-brood food allocation. Although several studies showed that mothers and fathers can be differentially responsive to nestling begging behaviour with one parent showing a stronger tendency to feed the offspring that beg the most, little information is yet available on whether offspring beg for food at different intensities from the mother than father. In the present study, we investigated in nestling barn owls whether the intensity of vocal begging behaviour in the presence of the mother and in the presence of the father is different. A difference is expected because reproductive tasks are divided between the sexes with fathers bringing more food items to the nest than mothers. The results show that although mothers transfer their prey item to one of the offspring more rapidly than fathers once in their nestbox, nestlings begged more intensely in the presence of their mother than in the presence of their father. To our knowledge, this is the first empirical evidence that offspring vocalize to different levels in the presence of their mother than in the presence of their father. [Copyright &y& Elsevier]

Offspring of many animal species signal their nutritional needs to the parents by conspicuous vocal, visual or tactile begging displays. Studies on asynchronously hatching altricial birds show that junior (i.e. late-hatched) offspring beg more than senior (i.e. early-hatched) offspring for a given level of food deprivation, but that juniors and seniors otherwise respond similarly to changes in their hunger levels. Asynchronous hatching and begging are not unique to altricial birds but occur in some nonavian species, such as the burying beetle Nicrophorus vespilloides. We investigated the effects of asynchronous hatching on offspring begging behaviour in N. vespilloides. Food-deprived larvae spent more time begging than fed larvae and junior larvae spent more time begging than senior larvae. However, we found no evidence that seniors and juniors responded differentially to food deprivation. We conclude that asynchronous hatching has a remarkably similar effect on offspring begging in altricial birds and burying beetles. Furthermore, we suggest that the effects of asynchronous hatching on the evolution of offspring begging tactics are independent of whether the offspring obtain all their food by begging from the parents, as is the case in altricial birds, or whether the offspring obtain some food by begging from the parents and some by self-feeding independently of the parents, as is the case in burying beetles. [Copyright &y& Elsevier]