Great spotted cuckoos respond earlier to the arrival of feeding foster parents and perform less erroneous begging when hungry than their magpie host nest‐mates

In many bird species, parents usually feed the first nestling that starts to beg before its nest‐mates. The pressure to avoid missed feeds could trigger nestlings to perform in erroneous begging in absence of parents, which has the same costs as begging in the presence of parents but without any reward. So, nestlings should try to minimize both erroneous begging and missed feeds simultaneously. The threshold to start begging is predicted to be lower for hungry nestlings and for nestlings that are unrelated to their nest‐mates, because they suffer lower inclusive fitness costs when depriving nest‐mates of food. In line with this idea, we found that brood parasitic great spotted cuckoo nestlings responded sooner than their magpie nest‐mates when an adult arrived to the nest. Under laboratory conditions, nestlings of both species rarely incurred in erroneous begging when food was abundant, but under conditions of restricted food, magpie nestlings increased erroneous begging while cuckoo nestlings did not. Highly conspicuous begging in cuckoos results in an increased predation risk, which could have resulted in stronger selection pressures on cuckoos to avoid erroneous begging, probably resulting in better developed perceptual abilities, allowing cuckoos to perform better than their host nest‐mates.     

Begging and the risk of predation in nestling birds

Theoretical models of the evolution of begging in nestling passerinesassume that begging is costly, either energetically or in termsof predation. However, few empirical measures of these costsexist. We examined whether nestling begging calls could attractpredators to nests by comparing predation rates at artificialnests with and without playbacks of tree swallow begging calls.Nests were baited with quail eggs and placed in pairs on theground or in modified nest-boxes. Nests with playbacks of beggingcalls were depredated before control nests significantly moreoften in both the ground and nest-box trials, suggesting thatpredators may use begging calls to locate nests. These resultssuggest that the risk of nest predation may be increased becauseof calling by nestlings and provide further support for theassumption that conspicuous begging is costly in terms of predation     

Interaction sequences between chimpanzees and human visitors at the Zoo

Data were collected on the behavior and physical characteristics of 259 human visitors and 24 chimpanzees at Chester Zoo. The successive responses of humans and chimpanzees to each other's behavior were recorded, the resulting long sequence being referred to as an interaction sequence. There was no particular set of characteristics that distinguished interactors from noninteractors in either humans or chimpanzees, although there was some evidence that chimpanzees were particularly likely to respond to men carrying objects. Chimpanzee responses were random with respect to the previous human behavior, but human responses were significantly associated with the preceding chimpanzee behavior. In particular, chimpanzee sounds were likely to be followed by human sounds, and begging was likely to be followed by the offer of food. Interaction sequences varied in length, but 9% of chimpanzee-initiated sequences went as far as a ninth interaction. Sequences resulted in the chimpanzees being given food in 25% of human-initiated, but only 8% of chimpanzee-initiated sequences. The results are consistent with the interpretation that humans and chimpanzees are motivated to interact with one another and that the chimpanzees do this primarily to obtain food. © 1995 Wiley-Liss, Inc.     

Nest mate size, but not short-term need, influences begging behavior of a generalist brood parasite

Hosts of generalist brood parasites often vary with regardsto their life-history traits, and these differences have thepotential to influence the competitive environment experiencedby brood-parasitic nestlings. Although begging by brood parasitesis more exaggerated than their hosts, it is unclear if generalistbrood parasites modulate their begging behavior relative tohost size. I examined the begging behavior of brown-headed cowbird(Molothrus ater) nestlings when competing against nest matesthat differ in size and under different levels of short-termneed. Cowbird nestlings begged on nearly all feeding visits,responded to adults as fast as (or faster than) their nest mates,and typically begged more intensively than their nest mates.Latency to beg, time spent begging, and maximum begging postureof cowbirds were similar during supplementation and deprivationtreatments, indicating begging intensity was not influencedby short-term need. Time spent begging by cowbirds varied amonghosts of 3 different sizes when short-term need was standardized,suggesting that nest mate size strongly influenced begging behavior.Cowbirds obtained more food when competing against an intermediate-sizedhost due to lower provisioning rates of small hosts or becauseof increased competitive ability of large host nestlings. Overall,cowbirds obtained the greatest volume of food per unit timespent begging when competing against intermediate hosts, butthis value approached that of the small host when adjusted formodal brood size. These results demonstrate that cowbirds adjusttheir begging relative to the size of the hosts against whichthey compete but not to levels of short-term need.     

An offspring signal of quality affects the timing of future parental reproduction

Solicitation signals by offspring are well known to influence parental behaviour, and it is commonly assumed that this behavioural effect translates into an effect on residual reproduction of parents. However, this equivalence assumption concerning behavioural and reproductive effects caused by offspring signals remains largely untested. Here, we tested the effect of a chemical offspring signal of quality on the relative timing and amount of future reproduction in the European earwig (Forficula auricularia). We manipulated the nutritional condition of earwig nymphs and exposed females to their extract, or to solvent as a control. There were no significant main effects of exposure treatment on 2nd clutch production, but exposure to extracts of well-fed nymphs induced predictable timing of the 2nd relative to the 1st clutch. This result demonstrates for the first time that an offspring signal per se, in the absence of any maternal behaviour, affects maternal reproductive timing, possibly through an effect on maternal reproductive physiology.     

Strategic adjustment of begging effort by banded mongoose pups

Variation in the intensity of conspicuous displays raises three basic questions: (i) the relationship between internal state and display intensity, (ii) the relationship between display intensity and receiver response, and (iii) the effect of variation in receiver responsiveness on signaller behaviour. Here, I investigate the interaction between pups and helpers in the communally breeding banded mongoose (Mungos mungo), where each pup forms an exclusive relationship with a single adult helper (termed its 'escort'). By experimentally manipulating pup need, I demonstrate that changes in begging rate correspond to changes in short-term need. The data then suggest that escorts in good condition may be more responsive to increased begging and that pups associating with them increase their begging more than do pups paired with escorts in poor condition. Escorts also appear more responsive to increased begging by female pups, and female pups increase their begging more than do male pups. These results suggest that banded mongoose pups may strategically adjust their investment in begging in relation to variation in the expected pay-off. I argue that such adjustment is likely to be a general phenomenon: wherever there is variation in responsiveness to signals, signallers will be selected to identify different categories of receiver and adjust their signals in order to maximize the pay-offs. Therefore, differences in signal intensity may be as much a product of context as an indication of variation in individual phenotypic or genotypic state.