Development of individual call recognition in young ring-billed gulls (Larus delawarensis): An effect of feeding

Individual recognition has been documented in young gulls, but less is known of the relevant developmental mechanisms. Since parents normally emit mew calls during feeding of the young, I tested the hypothesis that feeding with individually distinctive mew calls constitutes one such mechanism. experimentally trained birds provided support for the hypothesis. Initially high approach and vocalization levels were maintained to the reinforced call, while responses to the other call declined, as did responses to both calls in untrained controls. Comparison with other species suggests that this developmental pattern is adapted to the natal social environment. In gulls, food is a potentially important mechanism influencing call ‘meaning’ (Smith 1977) between parents and offspring and between mates during courtship feeding.     

Parental preference for red mouth of chicks in a songbird

Parental preferences during feeding and care-giving may select for ornamental traits in young, such as bright coloration. For chicks of coots, there is experimental evidence for this idea. We examined the hypothesis that bright yellow, orange and red mouths of chicks of songbirds have been favoured by feeding preferences in parents. In a field experiment, the orange–yellow mouths of great tit nestlings were dyed brightly red, and the feeding response of parents recorded. In nest boxes with extra daylight through a window, experimental chicks were on average given twice as much food (biomass) as control chicks (sham dyed). In normal nest boxes, the tendency was similar, but not significant. Thus, at least in good light, great tit parents prefer to feed young with red mouths, a preference for colourfulness that helps explain the evolution of bright gapes in chicks of songbirds (passerine birds).     

Costs of parental care on hunting behaviour of Helobdella papillornata (Euhirudinea: Glossiphoniidae)

Helobdella papillornata, an Australian freshwater leech, feeds primarily on snails and has a high level of parental care involving brooding eggs and young, with direct feeding of young. Parental costs and offspring benefits from these behaviours are poorly understood. A potential cost of parental care may be a change in the time taken to hunt prey. To test this hypothesis, the hunting behaviour of adults without progeny, parents with eggs, and parents with young were compared. We found that parents brooding eggs had a significantly (P = 0.029) longer lag time to begin hunting than parents brooding young, and spent significantly (P = 0.018) less time actively hunting than non-brooding adults. These costs, which may represent lost potential for the parent’s future reproductive success, should be outweighed by the fitness benefits of improved growth and survival of offspring, if parental care is favoured by selection. The hunting costs of care in Helobdella and other benthic, dorsoventrally flattened leeches in the family Glossiphoniidae may be smaller than the costs of brood tending that would be imposed on other freshwater leeches, and this difference may help explain the restriction of care to a single clade of the Euhirudinea.     

An Experimental study of reduced parental effort and future reproductive success in the puffin, Fratercula arctica

1. The puffin, a long-lived seabird, was studied on the Isle of May, East Scotland between 1990 and 1992. During two of these years, parental effort was experimentally decreased by supplementary feeding of young. This aimed to identify inter-year reproductive costs, and show whether they took the form of reduced adult survival, reduced fledging success and/or a reduction in the 'quality' of offspring in the following year.
2. The feeding treatment significantly reduced the daily number of feeds delivered by experimental parents by 67% in 1990 and 87% in 1991.
3. The proportions of experimental and control parents returning to the colony in the year following manipulation did not differ significantly, although in 1991, 2·5 times as many controls (young unfed) as experimental birds (young fed) failed to return.
4. The fledging success of experimental pairs in the year following manipulation (68%) was significantly higher than that of controls (24%).
5. Experimental pairs raised young with significantly higher body condition (Residual Peak Mass) than that of controls in the year following manipulation (1992).
6. Experimental parents did not differ from controls in their body condition (Lipid Reserve Mass) or rate of reserve depletion, either in the year of manipulation or in the following breeding season; hence there was no evidence for a role of the measured component of body condition in the cost mechanism.
7. The study demonstrated inter-year reproductive costs for puffins and supported the hypothesis that long-lived species reduce the 'quality' of their offspring or abandon a breeding attempt rather than compromise their survival and future opportunities to reproduce.     

Nestling detectability affects parental feeding preferences in a cavity-nesting bird

In many avian species, nestlings have evolved striking plumage, behaviours and mouth colours to obtain a greater share of parental investment. Studies revealing parental feeding preferences for nestlings with red gapes have proposed that red mouth colour in songbirds can act as a signal of nestling need or condition. Alternative hypotheses suggest that bright nestling mouths in cavity-nesting birds evolved to increase nestling detectability by the parents. We tested whether nestling mouth colour affects parental feeding preferences in great tits, Parus major L. In broods of six young, we experimentally painted mouth gapes and flanges either red or yellow and tested the effect of mouth colour on nestlings' mass gain under two lighting conditions. In nests with high luminosity, there was no significant effect of mouth colour on mass gain. In nests with low luminosity, nestlings with red gapes and flanges gained less mass than nestlings with red gapes and yellow flanges or both yellow gapes and flanges. Our results suggest that, in nests with low luminosity, red mouths decreased nestling detectability to the feeding parents and support the hypothesis that poor luminosity in nesting cavities can select for pale mouths. Overall, our results do not support the hypothesis that red mouth colour signals nestling need or condition to parent great tits.     

Description of the basic features of parent‐offspring stomodeal trophallaxis in the subsocial wood‐feeding cockroach Salganea esakii (Dictyoptera,Blaberidae, Panesthiinae)

In subsocial xylophagous cockroaches it is thought that parental feeding is important for the survival and growth of the altricial offspring, but the details of parental feeding in these groups are poorly known. We observed stomodeal (oral) trophallaxis between parents and the 2nd or 3rd instars of the wood‐feeding cockroach Salganea esakii Roth, and here report basic features of trophallaxis in young families. Both the female and male parents fed young nymphs with stomodeal food, and there was no difference in the frequency of the behavior between parental sexes. Up to three nymphs could be fed simultaneously during a single trophallactic event. Adults occasionally rejected contact with nymphs by blocking them with their forelegs. Nymphs utilized trophallactic food from parents more frequently than feeding independently on wood pieces or fecal pellets. Trophallaxis between sibling nymphs was never observed. These results suggest that the 2nd and 3rd instar nymphs rely on the stomodeal substances provided by their parents, and that provisioning is an essential component of subsocial behavior in biparental wood‐feeding cockroaches.     

Common loon parents defend chicks according to both value and vulnerability

In many territorial breeders, conspecifics that intrude during the chick‐rearing period pose a threat to survival of young. Defense of young from intruders is costly to parents, so it is likely that intense selective pressure has shaped chick defense so as to maximize parental fitness. We simulated territorial intrusion by exposing adult common loons Gavia immer and their chicks to a decoy and used mixed models to investigate responses. We tested two hypotheses: 1) the value hypothesis, which holds that parents should defend large broods of offspring more strongly because of the greater potential fitness benefits they offer, and 2) the vulnerability hypothesis, which predicts vigorous defense of young offspring, whose small size and limited mobility render them vulnerable to sudden attacks from intruders that approach under water. Under natural conditions, parents spent over 80% of their time within 20 m of chicks younger than two weeks (‘young chicks’) but 66% or less of their time close to chicks four weeks or older (‘old chicks’). Parents of young chicks associated less with the decoy but yodelled and penguin danced more during decoy trials than did parents of old chicks, supporting the conclusion that the parents protected young chicks not by engaging intruders directly but by remaining close to chicks and using vocalization and display to keep intruders at a distance. While these findings lent clear support to the vulnerability hypothesis, the value hypothesis too was supported, as males with two‐chick broods were almost three times more likely to yodel than males with singleton chicks. Age of parents was not associated with any aspect of chick defense, but the paucity of known‐aged parents in the oldest age classes makes future investigation of age effects warranted.     

Hatching Asynchrony Decreases the Magnitude of Parental Care in Domesticated Zebra Finches: Empirical Support for the Peak Load Reduction Hypothesis

Parent–offspring conflict over the supply of parental care results in offspring attempting to exert control using begging behaviours and parents attempting to exert control by manipulating brood sizes and hatching patterns. The peak load reduction hypothesis proposes that parents can exert control via hatching asynchrony, as the level of competition amongst siblings is determined by their age differences and not by their growth rates. Theoretically, this benefits the parents by reducing both the peak load of the offspring's demand and their overall demand for food and benefits the offspring by reducing the amplification of their competition. However, the peak load reduction hypothesis has only received mixed support. Here, we describe an experiment where we manipulated the hatching patterns of domesticated zebra finch Taeniopygia guttata broods and quantified patterns of nestling begging and parental feeding effort. There was no difference in the begging intensity of nestlings raised in asynchronous or experimentally synchronous broods, yet parental feeding effort was lower when provisioning asynchronous broods and particularly so when levels of nestling begging were low. Further, both parents acted in unison, as there was no evidence of parentally biased favouritism in relation to hatching pattern. Therefore, our study provided empirical support for the prediction that hatching asynchrony reduces the feeding effort of parents, thereby providing empirical support for the peak load reduction hypothesis.     

Comparison of optimal foraging versus life‐history decisions during nestling care in Lincoln's Sparrows Melospiza lincolnii through stable isotope analysis

In short‐lived species, parents are expected to favour their offspring and may therefore have to sacrifice the best part of their diet to feed their young (‘conflict hypothesis’). In addition, they need to maximize energy delivered per unit of time to the young (‘delivery hypothesis’). We examined the influence of these two factors on food allocation in Lincoln's Sparrows Melospiza lincolnii by measuring plasma δ¹⁵N and δ¹³C values in both parents and offspring. Adults’ isotopic values were unchanged when feeding chicks, but their δ¹⁵N values were higher than those of their chicks. Using the isotopic signature of Lincoln's Sparrows and that of prey available in their habitat, we reconstructed the diet of parents and chicks using mixing models for stable isotope analyses. The main difference between the diet of chicks and that of adults was that the proportion of spiders was lower in chicks than in adults, while the proportion of grasshoppers was higher. Spiders appear more valuable than grasshoppers, as they are more easily digested and richer in lipids, proteins and essential amino acids. However, grasshoppers are larger than spiders and are therefore likely to be better suited to maximize energy delivery to chicks. As parents keep their diet constant when breeding and as the contribution of large prey is higher in the diet of chicks than in that of their parents, our results suggest that the influence of optimal foraging strategy is predominant over the influence of parent–offspring conflict on food allocation in Lincoln's Sparrows, thereby supporting our delivery hypothesis. However, this relative influence may differ when resource availability constrainsing parent–offspring conflict varies.     

Brood division and transition to independence in Blackbirds Turdus merula

Blackbirds Turdus merula rearing young in the Botanic Garden, Oxford, were observed over three summers (1979–81). Between 0 and 10 days after fledging the young were divided between the parents so that each fed only certain fledglings and refused to feed others. This division was temporally stable. In broods where another nesting attempt followed, the male usually took responsibility for all the young, but in final broods they were divided fairly evenly. The probability of a fledgling surviving to independence declined as the number of young a parent fed increased; thus division should be favoured. However, if the female fed some young the inter-nest interval increased and the potential number of young that could be raised in that season was curtailed. This trade-off is examined by means of a model. After fledging the young improved in their ability to capture prey successfully and increased the size of the prey taken. At 15–24 days after fledging, self-feeding became more profitable than parental feeding and the young became fully independent. The timing of this transition is influenced by the parents, and it is suggested that by dividing the brood, parental feeding can be more carefully regulated so that finer control over the timing of independence is achieved.     

Lethality and abnormal condition of the pelage of the latvian mouse (dominant-naked)

Summary and Conclusions The above-described examination of dominant-naked mice shows that with homozygotes (NN) lethality occurs in various degrees, dependent on the combinations of parents and grandparents. The difference in lethality is manifested not only in the percentages but also in the difference in age when the young die. These two manifestations run parallel.The lethality for the greater part becomes manifest postnatally, but is already determined prenatally, also by the nature of the mother, who herself is again more or less favourably influenced by the nature of her parents.The postnatal influence of the mother, viz. feeding and care, is of little or no value for the lethality, but apparently there is a clearly detrimental influence of the milk of homozygous naked females on the pelage of normal and heterozygous young.On the ground of the observed facts the hypothesis is suggested that we have to deal here with a case of allelomorphism the gene B causing the production of a substance necessary for the normal hair growth and viability and the allelomorphB ₁ (=N) that of a quantitatively or qualitatively abnormal substance with consequent hairlessness and lethality.     

Parental Sex Differences in Food Allocation to Junior Brood Members as Mediated by Prey Size

Individual offspring within a brood may receive different amounts of provisioning from the male and female parents. Some hypotheses suggest that this bias is the result of an active and adaptive choice by parents. An alternative hypothesis is that feeding biases arise as a result of a constraint of fitting large prey items into small gapes. In an experiment with pied flycatchers, Ficedula hypoleuca , we tested for sex-biased allocation to junior nestlings in asynchronous broods and whether this could be explained by active parental choice or by passive allocation according to prey size and gape size. In both control broods and broods with experimentally increased degree of asynchrony, prey types did not differ between parents but females brought smaller prey than males at younger but not older nestling stages. At younger but not older nestling stages, the majority of feeds to junior nestlings were from females, and the smaller nestlings consumed smaller prey than older siblings. However, there was no evidence of active preference of small nestlings by females as parents did not differ in the tendency to bypass a begging senior nestling in order to feed a junior nestling. Provisioning rates by females were lower than those by males when nestlings were young and we suggest that foraging time constraints caused by the need to brood offspring result in females bringing smaller prey than males. In turn, the larger prey brought by males was more often transferred to larger offspring after the smaller ones failed to swallow it. In such cases, 'preferential' feeding of small nestlings by females may simply be a passive side effect of foraging constraints and gape-size limitations.     

Communal feeding of nestlings in the Mexican jay (Aphelocoma ultramarina): Interflock comparisons

Observations were made on the individuals that fed the nestlings at six nests in four colourbanded flocks of the Mexican jay in Arizona. Communal feeding of the nestlings was found in one flock for the second successive year. Data collected over the entire nestling period show that helpers accounted for 46 to 68 per cent of the feedings at the five nests most intensively studied. At some nests certain individuals brought food to the nestlings more frequently than did the parents.     

Does begging call convergence increase feeding rates to nestling tree swallows Tachycineta bicolor?

Some studies suggest that offspring might coordinate their begging displays to send a more effective brood signal, which in turn, could increase parental feeding rates. In tree swallows Tachycineta bicolor , when nestlings call together, their calls are more similar in structure than when they call alone. Here, we tested the hypothesis that call convergence enhances the overall brood signal, thus increasing parental provisioning rates. We played back similar and dissimilar calls (as measured by cross-correlation) to parents during a one-h playback period, and filmed the response of parents and nestlings. Contrary to our hypothesis, parental feeding rates did not differ in relation to call similarity. Based on these results, call similarity does not appear to function as a coordinated brood signal in tree swallows.     

Parental Self-Feeding Effects on Parental Care Levels and Time Allocation in Palestine Sunbirds

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

Food division in the Arabian babbler nest: adult choice or nestling competition?

Many studies have found that food division among nestmates isnegatively correlated with hatrhing order. The hypothesis thatfeedings are distributed according to the provisioners' selectionis compared here with the hypothesis that feedings are dividedas a consequence of nestling competition. Food distributionamong Arabian babbler nestmates was negatively correlated withhatching order and was so skewed that many last-hatched nestlingsdied as a consequence of starvation. No feeding preference wasfound between any adult and any given nestling. No differencewas found in feeding distribution among parents, partial parents,and nonparents. When an older foreign nestling was introducedinto the nest, adults fed the newcomer more intensively thantheir own offspring, implying that feeding division among nestmateswas not determined by die feeders but by the nestlings' relativeability to obtain food. In two-nestling nests, the older nestlingobtained 62% of the feedings, on average. However, followingselective feedings of the second-hatched nestling by the investigator,which equalized the two siblings' feeding amounts by the endof their second day, no difference was found between their feedingrates. The relative advantage of the older nestlings was eliminatedby introducing a barrier into the nest. Under these conditions,feedings were distributed equally among the nestmates. Sinceneither hatching order, previous priority order, nor individualidentification were used by the provisioning adults, the proximatefactor determining food division among the neslings appearsto be the result of nestling competition     

Breast feeding and lower respiratory tract illness in the first year of life. Group Health Medical Associates.

OBJECTIVE--To assess the relation between breast feeding and subsequent experience of lower respiratory tract illness. DESIGN--Prospective (from well child visits) and retrospective (from maternal recall) study of breast feeding and prospective assessment by paediatricians of lower respiratory tract illness in infants during first year of life. SETTING--Health maintenance organisation. PARTICIPANTS--Over 1000 infants who were healthy at birth and whose parents used the paediatricians of a local health maintenance organisation. MAIN OUTCOME MEASURES--Duration of breast feeding and type of lower respiratory tract illness (wheezing and non-wheezing) at different age intervals during the first year of life. RESULTS--Breast feeding was associated with a decreased incidence of wheezing illnesses only in the first four months of life. Interactions existed between breast feeding and sharing a room, being Mexican American, and being a boy. Multivariate techniques showed that after controlling for a variety of factors children who received minimal breast milk had a greater risk of early wheezing illnesses; the risk was further increased by simultaneous exposure to sharing a room. CONCLUSION--Breast feeding seems to protect against wheezing respiratory tract illnesses in the first four months of life, particularly when other risk factors are present.     

Better nutritional condition changes the distribution of juvenile dispersal distances: an experiment with Spanish imperial eagles

We investigated the distribution of juvenile dispersal distances of a territorial long‐lived species with deferred maturity, the Spanish imperial eagle Aquila adalberti. Here we used a reintroduction program as an experimental approach to test predictions of different hypotheses about the distribution of juvenile dispersal distances: competition and wandering behavior. We determined maximal juvenile dispersal distances of 59 young eagles; 1) 30 wild non‐manipulated individuals, and 2) 29 tranlocated young under an ad libitum feeding program, released with adults breeding in the area. The competitive displacement hypothesis predicts a leptokurtic distribution of distances in wild non‐manipulated young as well as in released young. Under the ‘wandering’ hypothesis, however, a leptokurtic distribution is expected in wild young but a normal distribution would be expected in young released (with adults in the release area), owing to a general improvement in the nutritional status of released young that have been fed ad libitum, as is usual in reintroduction programs. Additionally, a negative relationship between hatching date and dispersal distances is expected in wild young but no relationship in released young under ad libitum feeding. Mean maximum dispersal distances for all the juvenile eagles was 142.8 km. No differences between sexes were found, nor between populations or between wild and reintroduced young. Wild young distances were not normally distributed, being closer to a Poisson distribution. In contrast, released young with adults (under ad libitum feeding) showed a normal distribution. Wild birds showed a significant negative relationship between dispersal distance and hatching date, with young that hatched late in the season dispersing shorter distances. However, released young under ad libitum feeding showed no significant relationship between hatching date and dispersal distance. These results support the ‘wandering’ hypothesis as the main driver of the distribution of dispersal distances.     

SOCIAL BEHAVIOUR OF BREEDING WESTERN SANDPIPERS CALIDRIS MAURI

The behavioural interactions among breeding Western Sandpipers ( Calidris mauri ) are described, and interpreted in terms of their adaptive characteristics.
Upon arrival in early spring, males disperse onto territories through mutual antagonism. Territorial advertisement and maintenance is accomplished through display flights low over the ground, which are accompanied by soft buzzy vocalisations. These characteristics of display are related to the fact that this species occurs in dense, localised breeding populations, where longdistance communication is unnecessary.
Because densities are high and feeding often occurs in communal areas off territory, violations of territorial boundaries are frequent. The result is an extremely high intensity of interactions among individuals. Chasing and physical combat between males is frequent and generally un-stereotyped. Birds nesting on territories away from the feeding sites often fly high above the other territories, and in doing so avoid being chased.
Western Sandpipers form monogamous pair-bonds which are maintained until the young are ready to fly. The initial association of the pair is facilitated by a strong tendency to return to the previous site and by the advertisement of the males in which a specific vocalisation is given. Once the female is present on a male's territory, she is courted persistently by him and gradually begins to participate in his scraping displays. Pair-bonds are re-enforced by the close association of the pair during the pre-nesting period and through a simultaneous preening display.
An hypothesis is developed that the participation of both sexes in incubation serves primarily as a means of pair-bond maintenance, acting to keep both parents present until after the young hatch. At this time, their presence is needed to provide protection for the precocial young against predators.     

Chick parasitism by blowflies affects feeding rates in a Mediterranean population of blue tits

Offspring fitness depends on interactions between parental care and environmental constraints. It has been suggested that in altricial birds parents are able to compensate for the detrimental effects of ectoparasites by improving food provisioning. We tested this prediction in a population of blue tits highly parasitized by blowfly larvae. The frequency of parental feeding visits was significantly higher in parasitized broods than in broods experimentally deparasitized. Despite a strong increase in parental care, chicks of parasitized broods were lighter, smaller, and more anaemic than chicks in deparasitized broods. Parents invest more in feeding parasitized young but cannot fully compensate for the negative effects of parasites, hence young are in poor condition at fledging.