Begging Behaviour Of Nestlings Research Articles

Novel sources of (co)variation in nestling begging behavior and hunger at different biological levels of analysis

Abstract Biological hypotheses predicting patterns of offspring begging typically concern the covariance with hunger and/or development at specific hierarchical levels. For example, hunger drives within-individual patterns of begging, but begging also drives food intake among individuals within broods, and begging and food intake can covary positively or negatively among genotypes or broods. Testing biological phenomena that occur at multiple levels, therefore, requires the partitioning of covariance between traits of interest to ensure that each level-specific relationship is appropriately assessed. We performed a partial cross-fostering study on a wild population of great tits (Parus major), then used multivariate mixed models to partition variation and covariation in nestling begging effort and two metrics of nestling hunger within versus among individual nestlings and broods. At the within-individual level, we found that nestlings begged more intensely when hungrier (positive correlation between begging and hunger). However, among individuals, nestlings that were fed more frequently also begged more intensely on average (negative correlation between begging and hunger). Variation in nestling mass did not give rise to the negative correlation between begging and hunger among nestlings, but we did find that lighter nestlings begged more intensely than their heavier biological siblings, suggesting that this effect may be driven by a genetic component linked to offspring size. Our study illustrates how patterns of covariance can differ across biological levels of analysis and addresses biological mechanisms that could produce these previously obscured patterns.

Effect of Variation in Nestling Hunger Levels on the Begging Behaviour of Nestlings and the Provisioning Behaviour of Adult American Kestrels

Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour ‘dishonest’ begging to obtain more food, the potential costs of ‘dishonest’ begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit.

Influence of corticosterone treatment on nestling begging in Florida scrub-jays (Aphelocoma coerulescens)

Altricial young are dependent on adults for protection and food, and they display nutritional need by begging to elicit feeding from parents. Begging at high levels can be energetically expensive and attract predators; thus, an individual must balance its nutritional needs with these potential costs. Further, because a parent is limited in the amount of food it can provide, begging can contribute to both parent-offspring conflict and sibling-sibling competition. Many extrinsic and intrinsic factors may contribute to begging behavior. One intrinsic factor of interest is corticosterone (CORT), a metabolic hormone hypothesized to play a role in regulating a nestling’s begging behavior. We investigated the hypothesis that increased exposure to CORT influences nestling begging behavior in an altricial species, the Florida scrub-jay (Aphelocoma coerulescens). We treated one nestling per treatment nest with a twice-daily dose of exogenous hormone via a CORT-injected waxworm, whereas a second individual received a vehicle-injected waxworm. We monitored individual nestling and adult behavior at all nests with the use of high-definition video cameras on several days during treatment. We found no difference in begging rate between CORT fed and vehicle fed nestlings within a treatment nest. Further, to determine whether CORT treatment had indirect effects on the entire brood, we monitored additional nests, in which nestlings were not manipulated. When treatment and controls were compared, overall begging rates of nestlings in treatment nests were greater than those in control nests. This result suggests that CORT treatment of an individual altered its behavior, as well as that of its siblings.

Begging blue tit nestlings discriminate between the odour of familiar and unfamiliar conspecifics

Summary Offspring often solicit, and compete for, limited parental care by elaborate begging behaviour. Kin selection theory predicts that competing offspring should modify the intensity of their begging depending on the degree of relatedness to their nest‐ or litter‐mates. Empirical evidence in birds, which are a key model in the study of parent‐offspring interactions, indeed indicates that a lower level of relatedness between offspring in the nest correlates with more intense begging (i.e. more ‘selfish’ behaviour). This implies that competing nestlings can recognize kin, but the mechanism underlying such discrimination is unclear. Birds have long been thought to mainly rely on visual and auditory cues in their social communication, but there is now growing evidence for the importance of olfactory cues too. To assess the potential importance of olfactory cues in modulating nestling begging behaviour, we experimentally tested in a free‐living bird, the blue tit Cyanistes caeruleus, if nestlings discriminate and adjust their begging behaviour depending on their familiarity with a conspecific nestling odour stimulus. We found that individuals responded with longer and more intense begging bouts to an unfamiliar compared with a familiar odour stimulus. Our findings provide first evidence for a role of olfaction in modulating offspring begging behaviour in a wild bird population. Although our experiment cannot differentiate between the effects of familiarity and relatedness, it raises the interesting possibility that blue tit nestlings may also discriminate between odours of close kin and less related individuals, and adjust their begging behaviour accordingly. This hypothesis requires further testing. A lay summary is available for this article.

Effects of variation in nestling hunger levels and begging on the provisioning behavior of male and female Eastern Phoebes (Sayornis phoebe)

ABSTRACT Nestling birds solicit food from their parents using conspicuous vocalizations and visual begging displays, and evidence suggests begging represents an honest signal of need that adults use to determine provisioning rates. Less is known about how adult males and females may differ in response to changes in nestling begging behavior as a result of variation in hunger levels or how nestling begging and adult provisioning may vary seasonally in multi-brooded species. To examine these parent-offspring interactions, we manipulated hunger levels of nestling Eastern Phoebes (Sayornis phoebe) during the 2011 breeding season in central Kentucky. Both first and second broods were divided into three treatments: whole brood fed (n = 12), whole brood deprived (n = 16), and some fed/some deprived (split; n = 14). Food-deprived nestlings begged with increased intensity, and fed broods begged with less intensity. Adult Eastern Phoebes adjusted their provisioning rates accordingly, provisioning food-deprive...

Factors affecting vocalization in Tengmalm's owl (Aegolius funereus) fledglings during post-fledging dependence period: scramble competition or honest signalling of need?

Begging behaviour of nestlings has been intensively studied for several decades as a key component of parent-offspring conflict. There are essentially two main theories to account for intensity of food solicitation among offspring: that intensity of begging is related to some form of scramble competition between nest mates or that it offers honest signalling of need to parents. The vast majority of studies which have addressed begging behaviour have been based on observations of, and experiments on, nestlings and have not considered begging behaviour, during the post-fledging period. Begging vocalizations in this post-fledging phase of dependence have rarely been studied, despite the importance of vocalizations as a communication method between offspring and parents, particularly for nocturnal species. We radiotracked 39 fledglings of the Tengmalm’s owl (Aegolius funereus) in two years with different availability of prey: 2010 (n = 29 fledglings) and 2011 (n = 10 fledglings) and made 1320 nightly localizations in which we recorded presence or absence of begging calls. Within years, the most important measures related to the probability of vocalization were body condition at fledging, time of night, number of surviving siblings, age and weather conditions. Begging intensity increased with age in both years; however, in the year with low prey availability fledglings vocalized significantly more often. The main factor causing these differences between years was probably the different availability of prey, affecting breeding success, post-fledging behaviour, and thus also both short- and long-term needs of offspring. We believe that our results suggest honest signalling of their fledgling’s need.

Hunger is not the Only Determinant of Nestling Begging behavior and Parental Feeding in the Black-Billed MagpiePica pica

Nestlings can employ a combination of tactics to obtain provisioning from the parents. In this observational study, we examined whether nestling begging behavior reflects hunger level and how parents respond to nestling beg- ging in the Black-billed Magpie Pica pica by putting small video-cameras in six Magpie nests. Our results revealed a strong effect of nestling begging behavior on parental feeding. Begging earlier than others and stretching the neck towards the parent was important in inducing parental provisioning regardless of age of the nestlings. Being closer to the nest entrance slightly increased the chance of being fed, but did not influence parental feeding priority. The num- ber of nestling begging events increased with the time interval since the last feeding, which indicates that begging fre- quency reflects the hunger level of the brood. However, in contrast to what can be predicted when begging behavior reflects hunger levels of nestlings, nestlings increased their begging level when parents provided more feedings in the previous visits and vocalized begging negatively affected the probability and the order of being fed by the parent. In addition, sensitivity in begging behavior and parental feeding decisions depended on nestlings' age, which suggests a possibility that parental feeding decisions change with growth stages of nestlings. Our results imply that begging behavior and food allocation in Magpies does not solely determined by the hunger level of nestlings.

Benefits associated with escalated begging behaviour of black-billed magpie nestlings overcompensate the associated energetic costs

Several experimental results support the existence of costs associated with exaggerated begging behaviour, which are assumed by some theoretical models of honest signalling in parent-offspring communication. However, to understand how honest begging behaviour is evolutionarily maintained in nature, the long-term cost-benefit output associated with exaggerated signals should also be estimated. As far as we know, the net cost-benefit balance of begging display has not previously been explored. Here, we used an appetite stimulant, cyproheptadine hydrochloride, to increase the feeling of hunger in some magpie nestlings. Supporting the use of cyproheptadine to manipulate hunger level and thereby begging behaviour, we found that experimental nestlings increased the frequency of begging and received more food than their control nestmates. Contrary to the expectation that physiological costs per se counteract the associated benefits of escalated begging signals, we found that near-fledging experimental magpies showed a better physical condition than control nestlings. These findings stress the interesting question of why magpie nestlings do not show to adults an escalated level of hunger if it implies an advantage. We discuss the responsibility of inclusive fitness costs and indirect genetic effects for the maintenance of honesty in parent-offspring communication.

Have brood parasitic cowbird nestlings caused the evolution of more intense begging by host nestlings?

Please cite this article in press as: Rivers, J.W host nestlings?, Animal Behaviour (2010), d Obligate avian brood parasites rely entirely on host species to raise their offspring, a unique behaviour that has made them an ideal group for a wide variety of ecological and evolutionary topics (Rothstein 1990; Davies 2000). Because brood parasites are raised by heterospecific parents and often share the nest with unrelated host nestlings (Rothstein 1990; Davies 2000), they are typically influenced only by the direct costs of begging (i.e. predation and growth costs; Dearborn 1999; Chappell & Bachman 2002; Haskell 2002; Johnstone & Godfray 2002) and have served as a model for studies of parental care, parenteoffspring conflict and nestling begging behaviour. Theory predicts that brood parasitic offspring should evolve more exaggerated begging displays than nonparasitic species for a given level of need (Harper 1986; Motro 1989; Holen et al. 2001), and a number of investigations have confirmed that parasitic nestlings show exaggerated begging vocalizations and postures relative to host species (Davies et al.

IBERIAN AZURE-WINGED MAGPIE CYANOPICA (CYANA) COOKI NESTLINGS BEGGING CALLS: CALL CHARACTERIZATION AND HUNGER SIGNALLING

ABSTRACT Nestling begging behaviour has long been seen as a signal by which nestlings solicit care from parents and most of the existing evidence provides some support for it being an honest signal. Begging is a multicomponent signal in which both sound and vision components are usually important. Although it is known that begging encodes information about nestling hunger the present knowledge about the specific behavioural features that convey the information is still scarce. The aim of this study was to describe begging calls of Iberian Azure-winged Magpie Cyanopica (cyana) cooki nestlings and examine how information on nestling hunger might be encoded in the begging calls. Nestlings were experimentally submitted to different periods of food deprivation and the call variation within individuals was studied. The young were individually tested and stimulated to beg by simulating parental visits. When subject to increasing food deprivation periods, nestlings increased the response level to simulated parental visits. The study also found that for the studied size differences, nestlings did not differ in their response level. Results confirmed that information on nestlings' hunger might be encoded in parameters of the calling behaviour. When the food deprivation periods increased, nestlings tended to start begging earlier, begged more often, extended their calling bout and increased the call duration, changing both at the level of the call and vocal begging bout. Overall the results support the view of begging as an honest signal, namely that begging should reflect nestling hunger and that only some call features might encode information about hunger.

Can hungry nestlings be trained to reduce their begging?

Nestling begging behavior is usually characterized by a behavioral response of increasing begging levels with an increase in nestling need or hunger. Recent evidence for the possible effect of learning on begging intensity raises the question of how learning can shape this response rule. In particular, it is not clear whether hungry nestlings can learn to reduce their begging when it is not successful or, rather, whether they must first acquire positive experiences with low begging levels in order to do so. To explore this question, we conducted 3 hand-feeding experiments with pairs of house sparrow (Passer domesticus) nestlings. In the first 2 experiments, the nestlings targeted to lower their begging were rewarded mainly or only for low begging postures. However, despite the high expected reward for low begging, these nestlings did not lower their begging. Controlled by their behavioral response function, hungry nestlings were “stuck” at high postures without being able to experience the potential success of low postures. In the third experiment, nestlings targeted to lower their begging levels were rewarded for any begging posture, ensuring that satiation would provide their initial “positive experience” with low begging postures. Begging postures were reduced by this treatment. In light of these results, we suggest that parents are unlikely to reduce offspring begging levels by simply ignoring them. However, they might be able to do so by attending to the begging as soon as possible, thereby allowing their offspring to explore low begging and learn that it is sufficiently effective.

Nestling begging intensity and parental effort in relation to prelaying carotenoid availability

Carotenoids are antioxidants playing major roles in physiological functions at various stages of an animal’s life. Female birds deposit large amounts of carotenoids into their eggs. Carotenoids are, however, a limiting resource, and females are expected to balance carotenoid deposition into the eggs with their utilization for themselves. Carotenoid availability is thus likely to determine both the levels of yolk carotenoids and maternal care during rearing. Carotenoids have been shown to benefit the embryo and the growing nestling, and it can be hypothesized that an increase in carotenoid availability during laying leads to higher nestling condition and competitive ability. We manipulated carotenoid availability to great tit pairs prior to and during egg laying and later partially cross-fostered chicks at hatching. During the rearing period, we measured how carotenoid availability affected nestlings begging behavior and male and female feeding effort. We also manipulated the ectoparasite load, predicting that carotenoid supplementation would help adults and nestling to cope with parasites. Nestlings hatched from eggs laid by carotenoid-supplemented females and raised in small broods begged more intensely. Nestlings in small deparasitized broods also begged more actively. The feeding effort of control females increased with brood size, whereas the feeding effort of carotenoidsupplemented females was high whatever the brood size. Male feeding effort was unaffected by our treatment. Our results support the hypothesis that maternally derived carotenoids increase nestling begging behavior and hence competitive ability. They further suggest that carotenoid availability determines the level of parental investment and can mediate trade-offs between life-history traits. Key words: begging, food provisioning, maternally derived carotenoids, parasites, parental care, reproductive investment. [Behav Ecol]

Biparental care and offspring begging strategies: hungry nestling blue tits move towards the father

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.

Nestling barn owls beg more intensely in the presence of their mother than in the presence of their father

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.

Nestling testosterone controls begging behaviour in the pied flycatcher, Ficedula hypoleuca

Begging signals and endogenous testosterone (T) levels of young birds have been shown to be positively correlated. If T is causally involved in controlling the level of begging effort, an endocrine control mechanism could explain the evolution of begging as a costly signal reflecting need. We tested experimentally whether elevated circulating T levels enhanced begging behaviour in nestling pied flycatchers, Ficedula hypoleuca. A pilot study confirmed that nestling T levels could be elevated within a natural physiological range using an oral dose of T. After T-dosing, nestling begging behaviour was measured as: i) the duration of begging displays and ii) the maximum height of begging stretches. Our results show that nestling T levels were elevated at 90 min post dosing and that at this time point both measures of begging behaviour were performed more intensely by T-dosed nestlings than controls. Nestling begging displays in response to dosing varied between individuals, which in part was explained either by the date in the breeding season or nestling mass. The results of this study confirm the causal nature of T in controlling nestling begging signals and suggest that it may be part of the mechanism that controls begging behaviour in nestling birds.

Food availability affects diurnal nest predation and adult antipredator behaviour in song sparrows, Melospiza melodia

Food and predators are thought to have independent effects on avian reproductive success. Several studies have now shown that extra food can reduce nest predation rates. Most hypotheses suggest that this is due to changes in adult and/or nestling behaviour. A critical test as to whether behaviour is key, is to examine when predation events occur for birds with and without extra food. If behaviour is important, extra food should lead to fewer nest predation events during the day, when birds are active, but have no effect at night. We conducted a food supplementation experiment on song sparrows and tested for food effects on timing of nest predation events, adult antipredator behaviour and nestling begging behaviour. Food supplementation significantly reduced the relative frequency of daytime nest predation especially during incubation. During incubation, fed females had shorter foraging bouts and longer bouts on the nest, and these behaviours were associated with a reduced probability of being preyed upon. During brooding, we found trends (P < 0.1) towards lower daytime predation and greater adult nest attendance for fed birds than for unfed birds, but nestling begging did not differ with food treatment. Our results show that food availability does influence nest predation through its effect on antipredator behaviour. We highlight the importance of examining adult behaviour and vulnerability to predation at both stages of the nesting period because behavioural changes with extra food were extreme at the egg stage and were more effective at reducing nest predation than were behavioural changes at the nestling stage.

Carotenoid-based nestling colouration and parental favouritism in the great tit

While elaborate carotenoid-based traits in adult birds may have evolved as honest signals of individual quality in the context of sexual selection or other social interactions, the function of carotenoid-based colours in juveniles is less well understood. We investigated the hypothesis that carotenoid-based nestling colouration has evolved in response to parental preference of intensely coloured offspring during food provisioning. In a field experiment, we manipulated nestling plumage colouration by a carotenoid-supplementation and analysed the parental food provisioning behaviour before feather appearance and at the end of the nestling stage. Carotenoids per se did not influence the nestling's begging behaviour or parental feeding decisions and we found no evidence that carotenoid-based colouration in nestling great tits has a signalling function in parent-offspring interactions. Parents did not discriminate between intensely coloured and control offspring in their food provisioning and in accordance with this finding intensely coloured nestlings were not heavier or larger at the end of the nestling stage. Alternative explanations for the evolution of carotenoid-based colours in nestling birds are discussed.

Selfish begging by screaming cowbirds, a mimetic brood parasite of the bay-winged cowbird

Screaming cowbirds, Molothrus rufoaxillaris, are specialist parasites that almost exclusively parasitize bay-winged cowbirds, Molothrus badius. Parasitic chicks are almost identical to the host young in their appearance and vocalizations until the chicks attain nutritional independence. This system provides an excellent opportunity to study the relationship between begging behaviour and hunger level for parasitic chicks and host young. Using video analysis of laboratory experiments, I compared the begging behaviour of screaming and bay-winged cowbird nestlings under controlled levels of food deprivation with and without a nestmate. The results of these analyses indicate that: (1) the begging behaviour of parasitic chicks and host young are influenced by their respective hunger levels; (2) the begging intensity of a cowbird chick is not influenced by the begging intensity of its nestmates; and (3) parasitic chicks beg more intensely than host young for the same degree of hunger. The greater selfishness of the parasitic chicks is what would be expected from theory, because, unlike host chicks, their greed will not be constrained by kinship with their nestmates or with the host parent's future broods. Alternative hypotheses explaining intense begging in terms of parasitic chicks being more hungry, or having to compensate for their alien appearance can be rejected, as the parasitic chicks and host young are similar in size and appearance.

Experimental evidence that nestling begging behaviour incurs a cost due to nest predation

The striking vocalizations, stretching, gaping and pushing that comprise the ‘begging’ behaviour of nestling birds have been of great interest to evolutionary biologists. Many models have been proposed to explain the evolution of this suite of traits. In this paper I describe the first experimental test of the assumption that forms the foundation of all these models: that begging behaviour bears a direct cost. Miniature two-way radios hidden inside artificial nests were used to measure changes in predation rates with changes in begging. This showed that begging was costly for birds that nest on the ground, but there was no cost for those that nest in trees. Further, the cost of begging for ground-nesters was an increasing function of begging rate. For ground nests, these data suggest that nest predation could act both as a check on the evolutionary exaggeration of begging traits, and as a mechanism to enforce the honesty of begging signals. The marked variation in the predation cost of begging in different nesting sites suggests that this cost may form a good framework for investigations of the interspecific diversity of begging calls.