Intraspecific nest parasitism in the grey starling (Sturnus cineraceus)

We studied intraspecific nest parasitism in the grey starling (Sturnus cineraceus) in 1992 and 1993. We used three criteria to detect nest parasitism: (i) the appearance of more than one egg per day while the host was laying; (ii) the appearance of extra eggs after the host completed its clutch; and (iii) the appearance of eggs which were of a different shape, size and color to other eggs in the clutch. There were 290 nests (157 nests in 1992; 133 nests in 1993) in which the clutch was completed early (clutches initiated before May 10). Twenty-nine (1992) and 32 (1993) nests contained at least one parasitic egg. Parasitic eggs hatched if they were laid during the laying period and early in the incubation period of their host, and a few of them fledged. Fledging success of parasitic eggs was not different from that of eggs in non-parasitized nests if parasitic eggs were laid during the host's laying period. However, fledging success of all parasitic eggs was fewer than that of eggs in non-parasitized nests. By comparison, fledging success of parasitized nests was not a great as that of non-parasitized nests.     

Parasitism strategy of the grey starling, Sturnus cineraceus: Selection based on host characters and nest location

The strategy used by the intraspecific brood parasite, the grey starling, Sturnus cineraceus (Temminck) and the degree to which this strategy reflected the sources of mortality for parasite eggs were examined. Approximately 74% of all parasite eggs failed to produce young that survived to fledglings. Most of this mortality was due to two factors: (i) laying in a nest that had been deserted by a host during its nesting cycle (19%); and (ii) mismatched timing of laying in the hosts nesting cycle (38%). It is important for parasites to select a suitable host in order to avoid this mortality and increase their reproductive success. However, grey starlings did not select hosts on the basis of nest location, host characteristics, or laying date. Lack of attention to these factors implies a failure on the part of the grey starlings to recognize cues that could direct them to select host nests that would provide the best environment for their eggs. Although some egg loss and egg replacement occurred before clutch initiation by hosts, no evidence was found that parasitic birds removed host eggs after clutch initiation by hosts. These results suggest that parasites did not adopt a successful strategy for enhancing the survival rate of their own eggs.     

Food availability and brood number do not influence intraspecific aggression in Argentine ants

Summary. Nestmate recognition cues can derive from both environmental and genetic factors, but can also be modulated in response to context-specific cues. Synchronous changes in nestmate recognition systems occur seasonally in some species of ants, however the mechanisms underlying these seasonal changes are often unknown. We studied two mechanisms, relative brood number and food availability, to determine if they generate temporal variation in intraspecific aggression in an introduced population of the Argentine ant, Linepithema humile. Using data from previous studies we found that seasonal increases in aggression levels correlate with seasonal increases in brood-to-worker ratios in the field. However, when we manipulated brood-to-worker ratios in paired experimental colonies, we found no direct evidence that relative brood numbers influenced aggression levels. To determine if food availability influenced aggression we conducted a second experiment in which we randomly assigned pairs of experimental colonies to starved or fed treatments and then measured aggression levels weekly for five weeks. We observed no difference in the level of aggression between these two treatment groups indicating that food availability also has no affect on aggression levels between hostile conspecific colonies.Received 24 August 2004; revised 15 September 2004; accepted 23 September 2004.     

Metabolic rate and evaporative water loss in the silky starling(Sturnus sericeus)

To better understand the physiological characteristics of the silky starling(Sturnus sericeus), its body temperature(Tb), basal metabolic rate(BMR), evaporative water loss(EWL) and thermal conductance(C) elicited by different ambient temperatures(Ta)(5-30 °C) were determined in the present study. Our results showed that they have a high Tb(41.6±0.1 °C), a wide thermal neutral zone(TNZ)(20-27.5 °C) and a relatively low BMR within the TNZ(3.37±0.17 mL O2/g·h). The EWL was nearly stable below the TNZ(0.91±0.07 mg H2O/g·h) but increased remarkably within and above the TNZ. The C was constant below the TNZ, with a minimum value of 0.14±0.01 mL O2/g·h·°C. These findings indicate that the BMR, Tb and EWL of the silky starling were all affected by Ta, especially when Ta was below 20 °C and the EWL plays an important role in thermal regulation.     

Experimental support for the role of nest predation in the evolution of brood parasitism

In 1965, Hamilton and Orians (HO) hypothesized that the starting point for the evolution of obligate interspecific brood parasitism in birds was the facultative laying of physiologically committed eggs in neighbouring active nests of con‐ and heterospecifics, following predation of a bird’s own nest during the laying stage. We tested this prediction of the HO hypothesis by using captive pairs of zebra finches (Taeniopygia guttata), a species with evidence for intraspecific parasitism both in the wild and in captivity. As predicted, in response to experimental nest removal, subjects laid eggs parasitically in simulated active conspecific nests above chance levels. Across subsequent trials, we detected both repeatability and directional change in laying patterns, with some subjects switching from parasitism to depositing eggs in the empty nest. Taken together, these results support the assumptions and predictions of the HO hypothesis, and indicate that the zebra finch is a potential model species for future behavioural and genetic studies in captive brood parasite research.     

Parent-absent begging: evidence for sibling honesty and cooperation in the spotless starling (Sturnus unicolor)

Begging in avian nestlings is a highly conspicuous behaviorwith important implications for the study of parent–offspringconflict. In some species, nestlings also call for long boutsin the absence of parents, and it has been proposed that thisbehavior is used by nestlings as a means of negotiating accessto food. We studied this phenomenon in the spotless starling(Sturnus unicolor). We found that parent-absent calls were acousticallydistinct from parent-present calls. Observations showed thatthe probability of parent-absent begging increased with nestlingage and brood size, whereas it decreased with increasing bodycondition. This result was confirmed by an experiment that showedthat nestlings produced higher parent-absent begging rates whenfood deprived than when satiated. Finally, we carried out aplayback experiment to test the reaction of nestlings to parent-absentbegging by fellow nestlings. Principle components analyses yielded2 independent components of begging: 1) a general begging componentand 2) a second factor that measures the relative contributionof communicative begging over competitive begging. Nestlingsexposed to playback decreased their general begging levels andsimultaneously increased the relative contribution of communicativeover competitive begging. This behavior may favor needy nestlingsto obtain impending feedings while keeping high levels of foodsolicitation from parents and is consistent with a cooperativestrategy among nestlings. Future research should consider theactual response of parents to these signals.     

Dominance, competition, and energetic reserves in the European starling, Sturnus vulgaris

We investigated the relationships between social dominance,competition for food, and strategies of body mass and fat regulationin the European starling (Sturnus vulgaris). In birds housedin groups of three, subdominant birds stored more fat than dominants.A removal experiment established a causal link between socialdominance and fat reserves; in groups that had the dominantindividual removed, the remaining birds reduced body mass andfat, relative to control groups that had the subordinate removed.In a second experiment, we investigated the influences of degreeof competition for food and dominance on body mass and fat reserves.Birds under high competition increased fat reserves and tendedto have higher body mass than birds under low competition. Theincrease in fat reserves was higher in the subdominants thanin the dominants. These results are consistent with hypothesesconcerning dominance-dependent access to food; subdominant birds,or birds under increased competition, may store more fat asan insurance against periods when food cannot be obtained. However,relations between dominance, body mass, and fat reserves mayalso arise through other proximate factors relating to dominance-dependentcosts and benefits of fat storage, such as predation risk andenergetic expenditure.     

Reproductive investment and parasite susceptibility in the Great Tit

1. Reproduction and parasite defence are assumed to be costly activities for hosts, and therefore trade-offs might exist between reproduction and parasite defence.
2. Brood sizes were manipulated in a population of Great Tits ( Parus major L.) to assess trade-offs between reproduction and parasite defence. Blood samples were taken from males and females during the late nestling phase, and parasite prevalence was compared among parents raising enlarged, reduced and control broods.
3. A higher prevalence of protozoan blood parasites dominated by Haemoproteus majoris was found among parents with enlarged broods, as compared with parents with control and reduced broods, respectively. Brood size manipulation did not affect parasite prevalence between the sexes or between age classes differently.
4. Mean parasite intensity (number of parasites per microscope field) among adult birds only infected with H. majoris was higher for parents with experimentally enlarged broods than controls and reduced broods, respectively.
5. These results support the hypothesis of a trade-off between parasite defence and reproduction.     

Energy expenditure, nestling age, and brood size: an experimental study of parental behavior in the great tit Parus major

A brood manipulation experiment on great tits Parus major was performedto study the effects of nestling age and brood size on parentalcare and offspring survival. Daily energy expenditure (DEE)of females feeding nestlings of 6 and 12 days of age was measuredusing the doubly-labeled water technique. Females adjusted theirbrooding behavior to the age of the young. The data are consistentwith the idea that brooding behavior was determined primarilyby the thermoregulatory requirements of the brood. Female DEEdid not differ with nestling age; when differences in body masswere controlled for, it was lower during the brooding periodthan later. In enlarged broods, both parents showed significantlyhigher rates of food provisioning to the brood. Female DEE wasaffected by brood size manipulation, and it did not level offwith brood size. There was no significant effect of nestlingage on the relation between DEE and manipulation. Birds wereable to raise a larger brood than the natural brood size, althoughlarger broods suffered from increased nestling mortality ratesduring the peak demand period of the nestlings. Offspring conditionat fledging was negatively affected by brood size manipulation,but recruitment rate per brood was positively related to broodsize, suggesting that the optimal brood size exceeds the naturalbrood size in this population.     

How brood influences caste aggregation patterns in the dimorphic ant species Pheidole pallidula

Spatial distribution of ant workers and, notably their aggregation/segregation behaviour, is a key-element of the colony social organization contributing to the efficiency of task performance and division of labour. In polymorphic species, specialized worker castes notably differ in their intrinsic aggregation behaviour. In this context, knowing the preponderant role of minors in brood care, we investigate how a stimulus such as brood can influence the spatial patterns of Pheidole pallidula worker castes. In a homogeneous area without brood, it was shown that minors display only a low level of aggregation while majors form large clusters in the central area. Here we find out that these aggregation patterns of both minors and majors can be deeply influenced by the presence of brood. For minors, it nucleates or enhances the formation of a large stable cluster. Such high sensitivity of minors to brood stimuli fits well with their role as main brood tenders in the colony. For majors, interattraction between individuals still remains the prevailing aggregation factor while brood strongly influences the localisation of their cluster. We discuss how the balance between interattraction and sensitivity to environmental stimuli determines the mobility of each worker castes and, consequently, the availability of minors and majors to participate in everyday colony tasks. Moreover, we will evoke the functional value of majors’ cluster location close to the brood, namely with respect to social regulation of the colony caste ratio. Received 30 May 2005; revised 11 January 2006; accepted 13 January 2006.     

A comparative analysis of the evolution of variation in appearance of eggs of European passerines in relation to brood parasitism

Host of brood parasites increase the ability of rejecting cuckooeggs by production of (1) a clutch with little variation amongeggs and (2) a clutch that differs the most from the modal phenotypeof the population. These hypotheses have been tested by Øienet at. (1995), although they did not control for common phylogeneticancestry. We analyze the evolution of egg color and markingpatterns in European passerines, which are potential hosts ofdie European cuckoo (Cuculus canorus), using Felsenstein's (1985)independent comparative method to control for the effect ofcommon phylogenetic descent We found a significant positiverelationship between interclutch variation in appearance ofhost eggs and parasitism rate, but this relationship disappearedwhen hole-nesting species were excluded from the analysis; andwe found a highly significant multiple regression between rejectionrate and intra- and interclutch variation in egg appearance,even when hole nesters were excluded from the analysis. Thepartial correlation coefficients were negative for intraclutchvariation and positive with interclutch variation in agreementwidi the hypotheses. Therefore, the use of the independent comparativemethod strengthens the hypothesis that the evolution of eggpatterns in hosts is associated with different stages of coevolutionwith the brood parasite.     

Growth, nutrition, and nitrogen fixation in grey alder at varied rate of nitrogen addition

Seedlings of grey alder (Alnus incana Moench), nodulated or unnodulated, were investigated at varied relative addition rate of nitrogen. Nitrogen fixation alone, without addition of mineral nitrogen, resulted in an almost optimum nitrogen status but only about half the maximum relative growth rate, probably mainly because of energy costs of nodulation and fixation. The growth deficit due to nodulation was much more than can be explained by the theoretical energy requirement for the amount of nitrogen fixed. Thus, the nitrogen fixation process was not very efficiently used. The nitrogen fixation rate was strongly stimulated by increasing nitrogen addition rate up to high levels. The fixation rate decreased rapidly close to optimum (maximum relative growth rate) and was negligible at maximum growth. A feed-back of mineral nitrogen on photosynthesis increased fixation rate with time, and the relative importance of fixation over mineral nitrogen nutrition increased. However, nitrogen fixation, also at maximum rate, supplied only a small proportion of the nitrogen amount required for maximum growth. The optimum nutrient solutions contained comparatively high nitrogen concentrations to secure free access to nitrogen. The nodules were damaged by this treatment, and it is concluded that the nitrogen additions must be adjusted to the current consumption of the plants to avoid an increased external nitrogen concentration. Strong linear regressions were found between relative growth rate, nitrogen status expressed as percentage content of fresh weight, and relative growth rate in unnodulated seedlings. There was a greater variability in nodulated seedlings than in unnodulated ones, because of the nitrogen fixation. The reactions of unnodulated grey alder were largely the same as previously reported for birch seedlings, but the maximum growth capacity was lower in grey alder. During an initial period of change in the internal nitrogen status, deficiency symptoms appeared, especially in unnodulated seedlings. As in birch, the leaves turned green again at stable nitrogen status, independent of level. The results are in sharp contrast to data from the literature where the external nitrogen concentration was used as the driving variable for the internal nitrogen status. The measured fixation rates for grey alder are much higher than those previously reported. Still, the maximum fixation rate observed is small compared to the total nitrogen uptake rate required for maximum growth, in contrast to reported relationships. These comparisons indicate that increased external nitrogen concentration obscures the real relations between mineral and fixed nitrogen, on one hand because of rapid inhibition of nitrogen fixation and, on the other hand, because of failure to obtain stable optimum nutrition and maximum growth by means of this treatment variable.     

Brood defense and brood size in the great tit (Parus major): a test of a model of unshared parental investment

To understand the interaction of the many contextual variablesthat affect parental behavior a number of static optimalitymodels have been developed. Among these the one by Lazarus andInglis (1986) is the only one to specifically predict the magnitudeof unshared parental investment (PI), i.e., of parental carethat carries a cost to the parent and that benefits all currentoffspring equally because it cannot be divided among them. Weinvestigated specifically how parent great tits (Parus major)gear their brood defense, a form of unshared PI, to the sizeof the brood at stake and to the risk incurred as a functionof the type of predator. The predators used were dummies ofthe great spotted woodpecker (Picoides major) and of the tawnyowl (Strix aluco). Normally, adults can approach the woodpeckerwith impunity; it had inflicted heavy losses to nestlings ofthe study populations of great tits near Wolfsburg, Lower Saxony.Parent great tits whose brood had been artificially reducedto two young responded to the dummy with less defense than dida control group with their pre-test brood size left intact.The nature of defense was qualitatively the same as that elicitedby a live woodpecker. Parents confronting the owl near theirbrood decreased their response with an artificial reductionin brood size much less. Because the owl used poses a seriousrisk to the defenders, as compared to the woodpecker, the resultlends powerful support to the "total loss" version of the modelof unshared PI; it predicts brood size to affect unshared PImore strongly when there is less risk to the parent. This interpretationis correct to the extent that one premise of the model, namelythat of uncompromised parentage, can be relaxed; great tit broodscontain a sizeable number of extrapair young. Males defendedtheir brood more strongly than did females. Sex and brood manipulationadded up linearly when affecting defense level, i.e., therewas no interaction.     

Aestivation in Pieris brassicae (L.) affects the parasitoid load caused by Cotesia glomerata (L.)

The large white butterfly Pieris brassicae (L.) (Lepidoptera: Pieridae) undergoes a unique aestivation in southern Spain. Its pupae remain dormant for three months in summer, emerging in early September. Its main parasitoid, Cotesia glomerata (L.) (Hymenoptera: Braconidae), shows no such diapause behavior and is thus deprived of its main host for this period and has to switch to less suitable host species. To study the effect the aestivation has on the parasitoids, caterpillars were collected from the region in May and September and levels of parasitization were determined. Results show that parasitoid attacks decrease clearly after the summer diapause. The number of parasitized butterfly clutches in September was only one third as the number in May and the infestation rate of an attacked clutch decreased by 55% after aestivation. The distribution of brood sizes of C. glomerata showed clear signs of superparasitism before but not after the diapause. Therefore, the butterfly generation after summer diapause has to deal with distinctly diminished numbers of parasitoids. This increases the survival rate of the caterpillar and thus improves the fitness of the butterfly.     

The genetic map of the B system of cattle blood groups as observed in French breeds

40 cases of irregular inheritance of phenogroups in the B system of cattle blood groups, that were presumed to have arisen from single crossing-over, have been used to establish a partial genetic map of this system. In addition, the relative positions in the map of several antigenic factors were inferred from relationships observed between particular phenogroups occurring in French breeds.
The tentative map thus obtained shows an overall similarity to that established by Ruiterkamp et al. (1977) in Dutch Friesian cattle. This result, in addition to other arguments, supports the hypothesis that the genetic structure of the B system of cattle blood groups is basically the same in all taurine breeds.
Evidence is given, for the first time, for the occurrence in the B system of genetic events other than single crossing-over (double crossing-over or gene conversion, and possibly deletion).
The rate of recombination between the genetic determinants of the terminal factors of the system, Q and I', was calculated in the progeny of some Normande bulls heterozygous for these two determinants (447 gametes); a value of 1.34 centimor-gan¹ was obtained. However complementary data indicate that 0.7 centimorgan would be a better estimate.