Microsatellites in the Karoo scrub-robin, Cercotrichas coryphaeus (Passeriformes: Muscicapinae): isolation and characterization of 13 autosomal and two sex-linked loci

Fifteen polymorphic microsatellites were developed for the Karoo scrub-robin, Cercotrichas coryphaeus. Here we describe and characterize microsatellite variation of 13 autosomal loci and two Z-linked loci in 42 individuals from two distinct South African populations. The number of alleles per locus varied from three to 13 and values of observed heterozygosity ranged from 0.318 to 0.900. These loci will be used to test hypotheses relating to fine-scale social structure and mating strategies in this cooperatively breeding species.     

The influence of nest attendance and provisioning on nestling stress physiology in the Florida scrub-jay

Stressful conditions during development may have lasting consequences for an animal's lifetime fitness. We investigated the degree to which parental provisioning and nest attendance influenced baseline levels of the stress hormone corticosterone in nestling Florida scrub-jays. Provisioning rates of male and female breeders and nest attendance of female breeders were recorded during focal watches conducted between days 3 and 5 post-hatch. A small blood sample was taken from each nestling on day 11 post-hatch and used to quantify levels of baseline corticosterone. The proportion of time spent by female breeders at a considerable distance from the nest was positively related to nestling corticosterone levels. Nestling corticosterone was also negatively related to parental provisioning rate, although this effect seemed to be secondary to the effect of the female's time away from the nest. These results indicate that parental behavior contributes to nestling stress physiology, which may in turn direct the formation of the adult phenotype and influence an individual's chances of survival.     

Patterns of nest provisioning and parental investment in the solitary digger wasp Ammophila sabulosa

Abstract.

• 1 In nest-building wasps there is a continuum from species that provision each offspring cell with one large prey item (single provisioning) to species that provision each cell with many small items (multiple provisioning). The significance of number of prey per cell was examined during two seasons in Ammophila sabulosa (L.), a species that provisions between one and five caterpillars per cell.
• 2 There was no difference between the total weight of prey in singly-provisioned and multiply-provisioned cells: individual caterpillars placed in multiply-provisioned cells were smaller.
• 3 Small caterpillars were captured and transported to the nest faster than large ones.
• 4 If the first prey provisioned was large, the cell was usually then permanently closed. If the first prey was small, additional prey were captured, and females appeared to become more selective: additional prey were rarely large.
• 5 It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex. This could be important when available prey sizes vary temporally and spatially.
• 6 There was a male-biased first generation investment ratio. Female-producing cells were provisioned with a higher total prey weight than male-producing cells, and conversion of prey weight to adult weight was more efficient for females.
• 7 Total prey weight provisioned is probably a good indirect measure of parental time investment in A.sabulosa. Other measures, particularly number of prey provisioned, will be less accurate.

     

Aphid reproductive investment in response to mortality risks

Background  

Aphids are striking in their prodigious reproductive capacity and reliance on microbial endosymbionts, which provision their hosts with necessary amino acids and provide protection against parasites and heat stress. Perhaps as a result of this bacterial dependence, aphids have limited immune function that may leave them vulnerable to bacterial pathogens. An alternative, non-immunological response that may be available to infected aphids is to increase reproduction, thereby ameliorating fitness loss from infection. Such a response would reduce the need to mount a potentially energetically costly immune response, and would parallel that of other hosts that alter life-history traits when there is a risk of infection. Here we examined whether pea aphids (Acyrthosiphon pisum) respond to immunological challenges by increasing reproduction. As a comparison to the response to the internal cue of risk elicited by immunological challenge, we also exposed pea aphids to an external cue of risk - the aphid alarm pheromone (E)-β-farnesene (EBF), which is released in the presence of predators. For each challenge, we also examined whether the presence of symbionts modified the host response, as maintaining host fitness in the face of challenge would benefit both the host and its dependent bacteria.     

Influence of temperatures during the nestling period on post-fledging survival of great tit Parus major in a Mediterranean habitat

Survival during the first year is one of the most important factors determining fitness in birds. Birds have poor thermoregulatory abilities during the nestling period when the plumage is not fully developed, thus temperature during the nestling period is a serious candidate to affect post-fledging survival, although it has been usually ignored in previous studies. We analysed the relationship between temperatures and post-fledging survival in a great tit Parus major population in Sagunto (Spain) using capture-recapture data from 12 years. Hatching dates, mass at fledging and temperatures during the nestling period (maximum, minimum and mean ambient temperatures as an estimation of the mean and extreme weather conditions that chicks encountered at the nest) were used as individual covariates. Mean post-fledging survival was 0.13±0.01. Adult survival probability was 0.64±0.02. Multi-model inference suggested that post-fledging survival increased with fledging mass, and decreased as temperatures increased. Furthermore, the effect of mass on survival was less important as temperature was higher. We consider that high temperatures affect nestlings' health due to low thermoregulatory abilities of nestlings. Model selection did not support a relationship between hatching dates and survival once mass and temperatures were taken into account. The results suggest the possibility that the effect of date on post-fledging survival found in previous studies was, at least in part, a consequence of the seasonal pattern of temperature variation.     

Habitat quality, nestling diet, and provisioning behaviour in great tits Parus major

Variation in early nutrition is often a strong predictor of offspring condition and fitness. In the case of woodland passerine birds, nestling diet is determined by the spatiotemporal distribution of prey items such as caterpillars during the nestling period, and is usually quantified as differences in provisioning behaviour between habitats. However, the habitat level does not account for variation between individual territories, the level at which competition and selection are assumed to operate. Here we use nestbox cameras and Radio Frequency Identification technology (RFID) to simultaneously assess variation in both nestling diet (components) and provisioning rates (quantity) among a sample (n=22) of different quality great tit Parus major territories selected from a larger breeding population (n=310 fledged broods) in a single year. Caterpillars were by far the most numerous item provisioned to nestlings (mean=75% of prey items), as expected given the known importance of this food source for this species. Broods raised close to an oak tree, or far from the woodland edge, were provisioned the highest proportion of caterpillars. Provisioning rates declined seasonally and there was a weak association between low provisioning rates and caterpillar rich diets. During the first week of the nestling stage, nestling condition was unrelated to the proportion of caterpillars in the diet, provisioning rates and oak proximity. Condition at fledging was slightly improved in broods fed a higher proportion of caterpillars in the diet and in broods raised close to an oak tree. However, in our data early breeding was the only predictor of recruitment success, although power was low for this test. Analyses of long‐term data (41 years) from the same population confirmed a relationship between oak proximity and fledgling mass, but not recruitment success. Our results suggest that territory level environmental variation can affect offspring condition, probably through observed changes in nestling diet, but that such variation does not necessarily produce discernable effects on offspring fitness.     

Wood thrush nest success and post-fledging survival across a temporal pulse of small mammal abundance in an oak forest

1. Synchronized mass production of seed crops, such as acorns, produces a resource pulse that may have far-reaching consequences for songbird populations through its effects on avian predators. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming rodents numerically respond to seed production and tertiary pulses emerge as generalist predators, such as raptors, numerically respond to rodents. In turn, these two groups reduce nest productivity and juvenile survivorship 1 and 2 years, respectively, after the initial pulse in seed production. 2. At our study site in south-eastern New York, USA, autumn acorn abundance (primary pulse) largely determines rodent abundance (secondary pulse) the following spring. We tested the hypotheses that the population dynamics of a shrub-nesting passerine (wood thrush Hylocichla mustelina), is influenced by rodents through the: (a) direct effect of predation by rodents; (b) indirect effect of rodents on the abundance of raptors (tertiary pulse); and (c) indirect effect of rodent abundance on raptor diet. The latter specifically hypothesizes that a crash in the rodent population in the wake of region-wide failure of acorn production leads to an extreme diet shift in raptors that increases post-fledging mortality in birds. 3. We conducted a 3-year study to examine variation in wood thrush nest success and fledgling survival, using radio telemetry, across a pulse of rodent abundance (i.e. low, medium and high). We also updated and reanalysed regional wood thrush population growth rates as a function of the annual variation in rodent abundance. 4. Fledgling survivorship, but not nest success, varied in relation to annual rodent abundance. Raptors and eastern chipmunks Tamias striatus were the most commonly identified predators on fledglings. Fledgling survivorship was greatest at intermediate rodent abundance consistent with a shift in raptor diet. Regional rate of wood thrush population growth showed a unimodal relationship with rodent abundance, peaking during years with intermediate rodent abundance. This unimodal pattern was due to wood thrush population growth rates near or below zero during rodent population crashes. 5. The telemetry study, pattern of regional abundance and synchronized population dynamics of coexisting thrushes suggest a common mechanism of behavioural changes in raptors in response to declines in rodent prey, which in turn affects thrush population dynamics.     

Parental provisioning, nestling departure decisions and prefledging mass recession in Cassin's auklets

We investigated how parental provisioning and nestling departure behaviour interact to produce prefledging mass recession in Cassin's auklets, Ptychoramphus aleuticus. Under our hypothesis, auklet parents are reluctant provisioners and should be increasingly likely to terminate or reduce provisioning of their single nestling as it matures. For the nestling, remaining in the nest presents a risk of losing mass (if the parent does not provision) but also a possibility of additional provisioning. As the nestling matures and becomes increasingly capable of independence, the benefits of remaining in the nest decrease and nestlings should be increasingly likely to fledge. Nestlings also should be more likely to fledge when the expectation of additional provisioning is low. Data on parental provisioning (based on growth increments) and nestling departure were consistent with our hypothesis. Older and heavier nestlings had smaller growth increments than younger and lighter nestlings, suggesting that parents were reluctant to provision old and heavy nestlings. Older and heavier nestlings also were increasingly likely to fledge. We hypothesized that nestlings might use the intensity of mass loss to gauge parental reluctance to provision, and accordingly, nestlings were increasingly likely to fledge after experiencing a greater amount of mass loss. Copyright 1999 The Association for the Study of Animal Behaviour.     

Parental food provisioning is related to nestling stress response in wild great tit nestlings: implications for the development of personality

Background

Variation in early nutrition is known to play an important role in shaping the behavioural development of individuals. Parental prey selection may have long-lasting behavioural influences. In birds foraging on arthropods, for instance, the specific prey types, e.g. spiders and caterpillars, matter as they have different levels of taurine which may have an effect on personality development. Here we investigated how naturally occurring variation in the amounts of spiders and caterpillars, provisioned to nestlings at day 4 and 8 after hatching, is related to the response to handling stress in a wild passerine, the great tit (Parus major). Broods were cross-fostered in a split-brood design allowing us to separate maternal and genetic effects from early rearing effects. Adult provisioning behaviour was monitored on day four and day eight after hatching using video recordings. Individual nestlings were subjected to a handling stress test at an age of 14 days, which is a validated proxy for exploratory behaviour as an adult.

Results

Variation in handling stress was mainly determined by the rearing environment. We show that, contrary to our predictions, not the amount of spider biomass, but the amount of caterpillar biomass delivered per nestling significantly affected individual performance in the stress test. Chicks provisioned with lower amounts of caterpillars exhibited a stronger stress response, reflecting faster exploratory behaviour later on in life, than individuals who received larger amounts of caterpillars.

Conclusions

These results suggest that natural variation in parental behaviour in wild birds modulates the developmental trajectories of their offspring's personality via food provisioning. Since parental provisioning behaviour might also reflect the local environmental conditions, provisioning behaviour may influence how nestlings respond to these local environmental conditions.

     

Effects of temperature and nest heat exposure on nestling growth,dehydration and survival in a Mediterranean hole‐nesting passerine

Variable environments impose constraints on adaptation by modifying selection gradients unpredictably. Optimal bird development requires an adequate thermal range, outside which temperatures can alter nestling physiology, condition and survival. We studied the effect of temperature and nest heat exposure on the reproductive success of a population of double‐brooded Spotless Starlings Sturnus unicolor breeding in a nestbox colony in central Spain with a marked intra‐seasonal variation in temperature. We assessed whether the effect of temperature differed between first and second broods, thus constraining optimal nest‐site choice. Ambient temperature changed greatly during the chick‐rearing period and had a strong influence on nestling mass and all body size measures we recorded, although patterns of clutch size or nestling mortality were not influenced. This effect differed between first and second broods: nestlings were found to have longer wings and bills with increasing temperature in first broods, whereas the effect was the opposite in second broods. Ambient temperature was not related to nestling body mass or tarsus‐length in first broods, but in second broods, nestlings were lighter and had smaller tarsi with higher ambient temperatures. The exposure of nestboxes to heat influenced nestling morphology: heat exposure index was negatively related to nestling body mass and wing‐length in second broods, but not in first broods. Furthermore, there was a positive relationship between nest heat exposure and nestling dehydration. Our results suggest that optimal nest choice is constrained by varying environmental conditions in birds breeding over prolonged periods, and that there should be selection for parents to switch from sun‐exposed to sun‐protected nest‐sites as the season progresses. However, nest‐site availability and competition for sites are likely to impose constraints on this choice.     

Parental care,nestling growth and diet in a Spotted Eagle Aquila clanga nest

Capsule The breeding biology of the Spotted Eagle was studied and we analysed results from direct observations at a nest in Estonia.     

European starlings: nestling condition, parasites and green nest material during the breeding season

Male European starlings (Sturnus vulgaris) intermingle fresh herbs, preferably species rich in volatile compounds, into their dry nest material. In a field study, we investigated whether these herbs affect the mite and bacteria load of the nests and the condition of the nestlings either directly or via parasite control. We examined the amount of herbs and the number of plant species males carried into their nests, the variation of volatile compounds in the headspace air of the nest boxes and mite/bacteria load of the nests throughout the season. The amount of herb material and the number of plant species, the number of substances emanated by these plants and the infestation of the nests with bacteria and mites (Dermanyssus gallinae) increased with season. In a field experiment, we exchanged natural starling nests with experimental nests with or without herbs. We found that the herbs had no effect on the mites but fewer bacteria were sampled in nests with herbs than in nests without herbs. The body mass of the fledging was not related to the season or the mite/bacteria load of the nests. However, nestlings from nests with herbs fledged with higher body mass than nestlings from nests without herbs. Both bacteria and mite load were related to nestling mortality. In nests containing no herbs, the numbers of fledglings declined significantly with the increasing mite load while the mites had no effect on the number of fledglings in nests with herbs. Thus, the nest herbs counteracted the effect of the mites. In conclusion, it seems that volatile herbs can reduce bacterial but not mite infestation of the starling nests. The positive influence of herbs on nestling growth indicates that herbs either directly (perhaps as immunostimulants) improve the condition of the nestlings and help them cope with the harmful effects of mites, or they provide a nest environment beneficial for the nestlings‘ development by the reduction of germs.     

Intraseasonal patterns in shorebird nest survival are related to nest age and defence behaviour

Nest survival may vary throughout the breeding season for many bird species, and the nature of this temporal variation can reveal the links between birds, their predators, and other components of the ecosystem. We used program Mark to model patterns in nest survival within the breeding season for shorebirds nesting on arctic tundra. From 2000 to 2007, we monitored 521 nests of five shorebird species and found strong evidence for variation in nest survival within a nesting season. Daily nest survival was lowest in the mid-season in 5 of 8 years, but the timing and magnitude of the lows varied. We found no evidence that this quadratic time effect was driven by seasonal changes in weather or the abundance of predators. Contrary to our prediction, the risk of predation was not greatest when the number of active shorebird nests was highest. Although nest abundance reached a maximum near the middle of the breeding season, a daily index of shorebird nest activity was not supported as a predictor of nest survival in the models. Predators’ access to other diet items, in addition to shorebird nests, may instead determine the temporal patterns of nest predation. Nest survival also displayed a positive, linear relationship with nest age; however, this effect was most pronounced among species with biparental incubation. Among biparental species, parents defended older nests with greater intensity. We did not detect a similar relationship among uniparental species, and conclude that the stronger relationship between nest age and both nest defence and nest survival for biparental species reflects that their nest defence is more effective.     

Food limitation in asynchronous bluethroat broods: effects on food distribution, nestling begging, and parental provisioning rules

Scramble competition models of begging predict that junior nestlingswill be more affected by food limitation than seniors. Thesemodels assume that food allocation is under offspring controland, hence, predict that this change in food distribution iscaused by a differential behavioral response by seniors andjuniors. By using the bluethroat (Luscinia svecica svecica)as our model species, we induced food limitation by removingthe male parent temporarily. We found that, as predicted, fooddistribution became more biased in disfavor of juniors whenfood was limited. However, there was no significant differencein the behavioral responses of seniors and juniors (i.e., positioningin the nest or begging postures) to food limitation that couldexplain the change in food distribution. Hence, there was noevidence that seniors controlled food distribution. As predictedif parents preferentially fed seniors, nestling rank affectedfood distribution when controlling for variation in nestlingbehaviors. Furthermore, as expected if the increased skew infood distribution under food limitation was caused by activefood allocation by parents, nestling rank had a greater effecton food distribution under food limitation than under normalconditions. The present study suggests that food distributionin passerine birds is determined not only by nestling behaviors(begging posture and positioning) alone but also by parentalpreferences for seniors based on nonsignaling cues, such asbody size.     

No effect of habitat fragmentation on post-fledging, first-year and adult survival in the middle spotted woodpecker

Despite its relevance for the dynamics of populations, the ecological mechanisms underlying juvenile and adult survival are poorly known in most bird species. This study focuses on the effect of habitat fragmentation on early post-fledging, first-year and adult survival of the middle spotted woodpecker Dendrocopus medius by combining data of radio-tagged and ringed birds. Among juveniles, most deaths occurred during the first three weeks after fledging (survival rate: 0.359±0.077) and were mainly caused by predation. After independence, birds faced another critical period during their first autumn-winter that lowered first-year survival further (0.255±0.044), whereas adult mortality was considerably lower (annual survival rate: 0.786±0.074). We did not find any significant effect of habitat fragmentation (measured as patch size and connectivity) on juvenile or adult survival. Sex ratio at fledging did not differ significantly from parity (proportion of females: 0.513) and was not correlated to patch size. Regardless of age, survival did not differ between the sexes, suggesting that a female-biased mortality was not the mechanism behind the presence of unpaired territorial males in this population. Lighter nestlings underwent significantly higher post-fledging mortality, indicating that conditions in the nest may substantially affect survival later in life.