Offspring retention in the Siberian jay {Perisoreus infaustus): the prolonged brood care hypothesis

We examined aggressive behavior in Siberian jay groups containingboth retained offspring and immigrant juveniles during winterfeeding and during breeding. Selective tolerance of retainedoffspring by parental birds in winter suggests that cooperationevolved through kin selection. Parents exhibited a self-restraintin aggression towards retained offspring at food in winter.Comparatively, nonkin immigrants were aggressively preventedfrom sharing food by the local pair. Parental tolerance in wintercould bring inclusive fitness gains through the direct kin componentif retained offspring experience relaxed competition and enhancedsurvival. Parental tolerance would then favor the evolutionof delayed dispersal. There is no evidence that delayed dispersalamong Siberian jays should have evolved because of indirectfitness benefits to retained offspring from helping to raiseyounger siblings. Offspring retained by parents did not participatein incubation, feeding or nest defense.     

Comparative manipulation of predation risk in incubating birds reveals variability in the plasticity of responses

The evolution of different parental care strategies is thoughtto result from variation in trade-offs between the costs andbenefits associated with providing care. However, changingenvironmental conditions can alter such fitness trade-offsand favor plasticity in the type or amount of parental care provided. Avian incubation is a form of parental care whereparents face changing environmental conditions, including variationin the risk of nest predation. Because parental activity candraw attention to the location of the nest, a reduction innest visitation rates is a predicted response to an increased,immediate predation risk. Here, we experimentally increasedthe risk of nest predation using model presentations at nestsof five coexisting species that differ in their ambient levelsof nest predation. We examined whether individuals detect changesin nest predation risk and respond by reducing visitation tothe nest. We also tested whether this behavioral response differsamong species relative to differences in their ambient risk of nest predation. We found that males of all species detectedthe increased predation risk and reduced the rate at whichthey visited the nest to feed incubating females, and the magnitudeof this change was highly correlated with differences in therisk of nest predation across species. Hence, as the vulnerabilityto nest predation increases, males appear more willing to trade the cost of reduced food delivery to the female against thebenefit of reduced predation risk. Our results therefore suggestthat nest predators can have differential effects on parentalbehaviors across species. We discuss how the comparative natureof our results can also provide insight into the evolution of behavioral plasticity.     

Isolation and characterization of 100 polymorphic microsatellite loci for the Siberian jay (Perisoreus infaustus)

We describe primers and polymerase chain reaction conditions to amplify 100 microsatellite loci from the Siberian jay (Perisoreus infaustus). The primers were tested on two geographically separated Finnish populations. The developed primer pairs yielded an average of 4.72 alleles per locus (range one to 17) and an average observed heterozygosity of 0.55 (range 0.04 to 1).     

Genetic evidence for male-biased dispersal in the Siberian jay (Perisoreus infaustus) based on autosomal and Z-chromosomal markers

Sex-bias in natal dispersal patterns can have important genetic and evolutionary consequences; however, reliable information about sex-biased dispersal can be difficult to obtain with observational methods. We analysed the sex-specific patterns of genetic differentiation among three Siberian jay (Perisoreus infaustus) populations, using 11 autosomal and six Z-chromosomal microsatellite markers. Irrespective of marker-type and indices used (viz. F(ST), average pairwise relatedness and effective number of immigrants), all analyses provided strong evidence for male-biased dispersal. Population structuring at autosomal loci (F(ST) =0.046, P<0.05) exceeded that at Z-chromosomal loci (F(ST) =0.033, P<0.05), and levels of introgression were inferred to be significantly higher for Z-chromosomal when compared to autosomal loci. Of the three populations studied, levels of genetic variability were the lowest in the southernmost fringe population, despite the fact that it harboured a group of divergent Z-chromosomal haplotypes that were not found in the other two populations. In general, the results provide strong genetic evidence for male-biased dispersal in Siberian jays, where observational data have previously suggested male philopatry. The results also highlight the utility of Z-chromosomal markers for gaining insights into the genetic diversity and structuring of populations.     

Sex‐Specific Parental Care in Response to Predation Risk in the European Roller,Coracias garrulus

Sublethal effects of predation constitute an important part of predation effects, which may modulate prey population and community dynamics. In birds, the risk of nest predation may cause a reduction in parental activity in the care of offspring to reduce the chance of being detected by predators. In addition, parents may modify their parental food allocation preferences within the brood in response to predation risk. Our aim in this study was to evaluate the effects of risk of nest predation on parental care and within‐nest food allocation in the European Roller (Coracias garrulus), an asynchronously hatching bird. We manipulated brood predation risk by placing a snake model near the nests that simulates the most common nest predator in the Mediterranean region. Our results show that males but not females increased their provisioning rate when they were exposed to the model and that despite this, nestlings’ body mass decreased in response to this temporary increase in predation risk. We did not find evidence that parents changed their food allocation strategy towards senior or junior nestlings in their nests in response to predation risk. These results show that the European roller modifies parental care in response to their perception of predation risk in the nest and a sex‐specific sensitivity to the threat, which suggests a different perception of offspring reproductive value by parents. Finally, our results show that changes in parental behaviour in response to nest predation risk might have consequences for nestling fitness prospects.     

Floating and fidelity in nest visitation byCrawfordapis luctuosa (Hymenoptera: Colletidae)

We studied nest visitation behavior of the ground-nesting beeCrawfordapis luctuosa (Colletidae) at the Monteverde Cloud Forest Preserve, Puntarenas Province, Costa Rica. Some females entered many nests, while others consistently entered only one nest. Multiple nest entry was exhibited by bees we called floaters, and those bees that consistently entered only one nest were provisioning bees. Provisioning bees abandoned their old nests after provisioning periods and became nonprovisioning bees that floated over the nesting area. Floating behavior was a nest-searching behavior typified by oscillating flights just above the ground (<15 cm). Floaters investigated available nests and were not observed to interact aggressively with nest owners. Upon establishing a new nest, floaters became provisioning bees.     

Conspecific nest parasitism is associated with inequality in nest predation risk in the common goldeneye (Bucephala clangula)

Previous studies of the role of nest predation in conspecificnest parasitism have not taken into account the possibilitythat predation risk may not be randomly distributed among nestsites and that breeding individuals may use different cues toassess the risk and adjust their reproductive tactic betweenyears accordingly. Especially in cavity-nesting species, therole of nest predation in conspecific nest parasitism has beendownplayed, while the role of nest site limitation has beenhighlighted. Using both observational and experimental data,I show that in the common goldeneye (Bucephala clangula), acavity-nesting species in which conspecific nest parasitism iscommon, predation risk varies considerably between nest sitesand does not follow a random expectation. The inequality inpredation risk between nest sites also showed up in the occurrenceof parasitized nests in an experimental setup. Nests parasitizedin year t were more frequent in those nest sites that were notdepredated during the previous nesting attempt in year t - nthan in nest sites that were depredated and in control nestsites that had not been used for nesting before. A nest siteaddition experiment revealed that conspecific nest parasitismwas not associated with nest site limitation. My findings givesupport for the hypothesis that nest predation is an importantecological factor explaining conspecific nest parasitism ingoldeneyes.     

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providingcare is costly, reducing parental growth and survival and, thereby,compromising future reproductive success. To determine if anexotic benthic predator might be affecting parental care bynest-guarding smallmouth bass (Micropterus dolomieu), we comparednest-guarding behavior and energy expenditures in two systems,one with a hyperabundant recently introduced predator, the roundgoby (Neogobious melanostomus). In Lake Erie, USA, smallmouthbass vigorously defended their nests from benthic round gobies.In Lake Opeongo, Canada, smallmouth bass were exposed to fewerand predominantly open-water predators and were less activein their nest defense. From scuba and video observations, wedocumented that nest-guarding smallmouth bass chased predators(99% of which were round gobies) nine times more frequentlyin Lake Erie than in Lake Opeongo. This heightened activityresulted in a significant decline in weight and energetic contentof guarding males in Lake Erie but no change in Lake Opeongomales. Bioenergetic simulations revealed that parental careincreased smallmouth bass standard metabolic rate by 210% inLake Erie but only by 28% in Lake Opeongo. As energy reservesdeclined and offspring became increasingly independent, malesin both lakes consumed more prey and spent more time foragingaway from their nests; however, nest-guarding smallmouth bassconsumed few prey and, in Lake Erie, rarely consumed round gobies.Therefore, increased parental care costs owing to the presenceof round gobies could affect future growth, reproduction, andsurvival if smallmouth bass approach critically low energy reserves.     

Nest defence by Magpies(Pica pica) and the brood parasitic Great Spotted Cuckoos(Clamator glandarius) in parasitized and unparasitized nests

Summary Nest defence is a frequent and widespread parental behaviour which enhances brood survival. We have found that in a Spanish Magpie population which is heavily parasitized by the brood parasitic Great Spotted Cuckoo, Magpies defend (1) unparasitized more frequently than parasitized nests, and (2) at the end of the nestling period more frequently than in other stages of the breeding cycle. Great Spotted Cuckoos are brood parasites, which means that their eggs are incubated and their nestlings are raised by members of a host species. Brood parasites are not thought to take care of their own offspring. However, we have found that Great Spotted Cuckoos sometimes scolded us on our regular visits to parasitized magpie nests (but never on those to unparasitized nests). Frequency of nest defence by cuckoos differed significantly among years, being significantly higher at the beginning of the study. Although sporadic observations of adult brood parasites feeding juveniles have been recorded, nest defence has not previously been suggested for any brood parasite.

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Nestverteidigung von durch den Häherkuckuck(Clamator glandarius) parasitierten und unparasitierten Nestern bei Elstern(Pica pica)

Zusammenfassung Nestverteidigung ist ein häufiges und weit verbreitetes elterliches Verhalten zur Erhöhung des Bruterfolges. In einer spanischen Elsterpopulation, die sehr intensiv vom Häherkuckuck parasitiert ist, wurden unparasitierte Nester häufiger verteidigt als parasitierte, und zum Ende der Nestlingsperiode wurden Nestern häufiger verteidigt als zu früheren Phasen des Brutzyklus. Häherkuckucke sind Brutparasiten, deren Eier von den Wirtseltern bebrütet und die Nestlinge von ihnen aufgezogen werden. Solche Brutparasiten kümmern sich im allgemeinen nicht selbst um ihre Nachkommen. Manchmal jedoch haßten Häherkuckuck auf uns, wenn wir parasitierte Nester der Elster kontrollierten, während an unparasitierten Nestern ein solches Hassen niemals erfolgte. Die Häufigkeit dieser Nestverteidugung der Kuckucke variierte zwischen Jahren und war signifikant häufiger zu Beginn unserer Untersuchung. Zwar wurde gelegentlich schon Füttern der Jungvögel durch elterliche Brutparasiten beobachtet, die hier festgestellte Nestverteidung ist bisher aber von keinem Brutparasiten beschrieben.

     

Parental nepotism enhances survival of retained offspring in the Siberian jay

The evolutionary payoff accruing to parents from breeding offspringcould be an incentive for prolonged investments in the offspring.Enhanced survival for offspring as a result of such a prolongedparental investment would increase the value of remaining inthe natal territory for the offspring. Here we show that first-yearsurvival in Siberian jays is higher in the company of theirparents. Two observations point to that the enhanced survivalof retained offspring is due to nepotistic parents rather thanto the quality of a shared habitat. First, winter survivalis higher only for those retained offspring whose parents havesurvived too ; this precludes the possibility that the linkbetween timing of dispersal and survival should reflect a higher phenotypic quality of retained offspring in general. Second,there is no support for the more parsimonious explanation thatthis link between the survival of parents and retained offspringreflects habitat quality of a shared territory. We could, withhigh statistical power, reject the possibility of a correlationbetween the survival of parental birds and unrelated immigrantsto the territory. Such a correlation would have been expectedif survival reflected habitat quality and not kinship. Our data instead suggest a direct fitness gain to retained offspringin enhanced survival through parental nepotism (parental facilitation).The behavior of parents in allowing retained offspring accessto food that is denied to immigrants is one proximate mechanismmediating a benefit of delayed dispersal.     

Predation risk affects trade-off between nest guarding and foraging in Seychelles warblers

The fitness costs of egg loss for Seychelles warblers (Acrocephalus sechellensis)on Cousin Island are considerable because warblers have a single-eggclutch and no time to lay a successful replacement clutch. Onthe islands of Cousin and Cousine, with equal densities of Seychellesfodies (Foudia sechellarum), nearly 75% of artificial eggs placedin artificial nests were predated by fodies after 3 days. OnAride Island with no fodies present, loss of artificial eggswas not observed. Female warblers incubate the clutch, and malewarblers guard the clutch when females are absent. Deterrenceof fodies by male warblers is efficient: loss rate of eggs fromunattended warbler nests was seven times as high as from attendednests, and the more nest guarding, the lower the egg loss andthe higher the hatching success. Egg loss is independent ofthe amount of incubation by females. There is no trade-off betweenincubating and foraging by females. Nest guarding competes withforaging by males, and this trade-off has a more pronounced effecton egg loss when food availability is low. The transfer of breeding pairsfrom Cousin to either Cousine with egg-predating fodies or toAride without fodies allowed us to experimentally investigatethe presumed trade-off between nest guarding and foraging. OnCousine, individual males spent the same amount of time nestguarding and foraging as on Cousin, and egg loss was similarand inversely related to time spent nest guarding as on Cousin.Males that guarded their clutch on Cousin did not guard theclutch on Aride but allocated significantly more time to foragingand gained better body condition. Loss of warbler eggs on Aridewas not observed. Time allocation to incubating and foragingby individual females before and after both translocations remainedthe same.     

Testing sources of variation in nestling‐stage nest success of Florida Scrub‐Jays in suburban and wildland habitats

Human modification of habitats can reduce reproductive success by providing novel cues to which birds may respond with behaviors that are actually maladaptive in those environments. Ad libitum human‐provided foods may provide the perception that urban habitats are food‐rich even as natural food availability decreases. Similarly, human activity may increase the perception that predation risk is high even as natural predators may decrease in abundance. In response, birds may reduce parental care with a subsequent cost to successful reproduction. Florida Scrub‐Jays (Aphelocoma coerulescens) in suburban areas have lower nest success during the nestling period than do wildland jays, possibly the result of such maladaptive responses, but maybe because of ecological differences with wildlands. We manipulated adult perception of predation risk and the availability of nestling foods in suburban and wildland areas to determine if these factors influenced parental care and nestling begging, and if the behavioral responses of adults influence nest survival during the nestling stage. Experimentally increasing perception of predation risk reduced parental care by both suburban and wildland females, but did not influence care by males. Increasing food availability, but not predation risk, had little influence on parental care, but resulted in decreased nestling begging rates and an increase in the frequency (pitch) of begging calls in both habitats. However, neither parental care nor food availability influenced nest survival during the nestling stage. Instead, the presence of helpers was the most important variable in nest survival analyses, suggesting that habitat‐specific differences in nest survival during the nestling stage were not simply the result of maladaptive parental behavior or shortage of nestling food resources in the suburban habitat. The lack of helpers combined with ecological differences, such as the abundance of nest predators, may be why fewer nests of Florida Scrub‐Jays survive during this stage in suburban areas.     

Phenotypic lability and the evolution of predator-induced plasticity in tadpoles

The hypothesis that predator-induced defenses in anuran larvae are maintained by divergent selection across multiple predation environments has not been fully supported by empirical results. One reason may be that traits that respond slowly to environmental variation experience a fitness cost not incorporated in the standard adaptive model, due to a time lag between detecting the state of the environment and expressing the phenotypic response. I measured the rate at which behavior and morphology of Rana temporaria tadpoles change when confronted with a switch in the predation environment at two points in development. Hatchling tadpoles that had been exposed during the egg stage to Aeshna dragonfly larvae were not phenotypically different from those exposed as eggs to predator-free conditions, and both responded similarly to post-hatching predator treatments. When 25-day-old tadpoles from treatments with and without dragonflies were subjected to a switch in the environment, their activity budgets reversed completely within 24-36 h, and their body and tail shape began changing significantly within 4 days. The behavioral response was conservative: Tadpoles switched from high-risk to predator-free treatments were slower to adjust their activity. The study confirmed that behavioral traits are relatively labile and exhibit strong plasticity, but it did not reveal such a pattern at the level of individual traits: Morphological traits that developed slowly did not show the least plasticity. Thus, I found that differences in lability of traits were useful for predicting the magnitude of plasticity only for fundamentally different kinds of characters.     

Nutritional physiology of the Santa Ana sucker (Catostomus santaanae): A threatened freshwater fish endemic to Southern California

The herbivorous fish Catostomus santaanae is a federally “threatened” freshwater fish species endemic to southern California and is the centre of legal battles over water use. Because little is known about the nutritional ecology of this species, we investigated the nutritional physiology of C. santaanae to better understand their dietary and energetic needs with the goal of generating data useful in conservation efforts. Individuals of C. santaanae were raised for six weeks on an algal diet in the laboratory. They digested approximately 45%, 55% and 80% of protein, soluble carbohydrate and lipid, respectively, from the algal diet. Their metabolic rate (~0.0024 mg O₂ min^?1 g^?1) suggested they would need to eat more than their body mass per day of an algal diet to thrive. Digestive enzyme activities of the laboratory‐reared and wild‐caught fish showed patterns typical of a “plug‐flow reactor” gut with high intake and rapid gut transit. However, lipase activities remained elevated throughout the gut, and this result, coupled with the lipid digestibility data, and evidence of feeding selectivity on specific diatom taxa in nature, suggests that C. santaanae targets diatoms as it grazes and that diatom lipid may be crucial to their survival. Our data set provides parameters that can be used in conservation modelling efforts towards habitat restoration.     

Size-assortative nest preference in a paternal brooding blenny Rhabdoblennius ellipes (Jordan & Starks)

Field and laboratory studies were conducted to clarify the processes contributing to the size-assortative nest use by males of a paternal brooding blenny Rhabdoblennius ellipes . The use of natural and artificial nests by males in the field was highly size-assortative; males used smaller nests even when larger nests were available. Aquarium nest choice experiments without a competitive male strongly suggested that the size-assortative nest use by males is not the result of male–male competition for larger nests, but male preference for size-matched nests. Males were likely to choose nests on the basis of the nest entrance size rather than nest length and volume, suggesting that the size-assortative nest preference in this species is an adaptation to predation pressure against eggs and resident males.     

Flow‐mediated plasticity in the expression of stickleback nesting glue genes

Nest construction is an essential component of the reproductive behavior of many species, and attributes of nests – including their location and structure – have implications for both their functional capacity as incubators for developing offspring, and their attractiveness to potential mates. To maximize reproductive success, nests must therefore be suited to local environmental conditions. Male three‐spined sticklebacks (Gasterosteus aculeatus) build nests from collected materials and use an endogenous, glue‐like multimeric protein – “spiggin” – as an adhesive. Spiggin is encoded by a multigene family, and differential expression of spiggin genes potentially allows plasticity in nest construction in response to variable environments. Here, we show that the expression of spiggin genes is affected significantly by both the flow regime experienced by a fish and its nesting status. Further, we show the effects of flow on expression patterns are gene‐specific. Nest‐building fish exhibited consistently higher expression levels of the three genes under investigation (Spg‐a, Spg‐1, and Spg‐2) than non‐nesting controls, irrespective of rearing flow treatment. Fish reared under flowing‐water conditions showed significantly increased levels of spiggin gene expression compared to those reared in still water, but this effect was far stronger for Spg‐a than for Spg‐1 or Spg‐2. The strong effect of flowing water on Spg‐a expression, even among non‐nesters, suggests that the increased production of spiggin – or of spiggin rich in the component contributed by Spg‐a – may allow more rapid and/or effective nest construction under challenging high flow conditions.     

Phenotypic plasticity and integration in response to flooded conditions in natural accessions of Arabidopsis thaliana (L.) Heynh (Brassicaceae)

Flood response is a crucial component of the life strategy of many plants, but it is seldom studied in non-flooded tolerant species, even though they may be subjected to stressful environmental conditions. Phenotypic plasticity in reaction to environmental stress affects the whole plant phenotype and can alter the character correlations that constitute the phenotypic architecture of the individual, yet few studies have investigated the lability of phenotypic integration to water regime. Moreover, little has been done to date to quantify the sort of selective pressures that different components of a plant's phenotype may be experiencing under contrasting water regimes. Genetic differentiation and phenotypic plasticity at the single-trait and multivariate levels were investigated in 47 accessions of the weedy plant Arabidopsis thaliana, and the relationship of plastic characters to reproductive fitness was quantified. Results indicate that these plants tend to be highly genetically differentiated for all traits, in agreement with predictions made on the basis of environmental variation and mating system. Varied patterns of apparent selection under flooded and non-flooded conditions were also uncovered, suggesting trade-offs in allocation between roots and above-ground biomass, as well as between leaves and reproductive structures. While the major components of the plants' multivariate phenotypic architecture were not significantly affected by environmental changes, many of the details were different under flooded and non-flooded conditions.     

The role of variation and plasticity in parental care during the adaptive radiation of three‐spine sticklebacks

Phenotypic plasticity might influence evolutionary processes such as adaptive radiations. Plasticity in parental care might be especially effective in facilitating adaptive radiations if it allows populations to persist in novel environments. Here, we test the hypothesis that behavioral plasticity by parents in response to predation risk facilitated the adaptive radiation of three‐spine sticklebacks. We compared the behavior of fathers across multiple ancestral (marine) and derived (freshwater) stickleback populations that differ in time since establishment. We measured behavioral plasticity in fathers in response to a predator found only in freshwater environments, simulating conditions marine males experience when colonizing freshwater. The antipredator behavior of males from newly established freshwater populations was intermediate between marine populations and well‐established freshwater populations. In contrast to our predictions, on average, there was greater behavioral plasticity in derived freshwater populations than in ancestral marine populations. However, we found greater individual variation in behavioral reaction norms in marine populations compared to well‐established freshwater populations, with newly established freshwater populations intermediate. This suggests that standing variation in behavioral reaction norms within ancestral populations might provide different evolutionary trajectories, and illustrates how plasticity can contribute to adaptive radiations.     

Horn polyphenism in the beetle Onthophagus taurus: larval diet quality and plasticity in parental investment determine adult body size and male horn morphology

In a wide range of taxa, individuals are able to express strikinglydifferent morphologies in response to environmental conditionsencountered during development. Such polyphenisms have receivedparticular attention from evolutionary biologists because thecondition-dependent expression of alternative morphologies isbelieved to reflect the existence of discrete sets of adaptationsto heterogeneous ecological or social conditions, which precludethe evolution of a single, optimal phenotype. Correct interpretationof the adaptive significance, if any, of facultative trait developmentrequires a solid understanding of the determinative regime governingmorph expression. Here I explore the environmental variablesdetermining male morphology in the horn-dimorphic beetle Onthophagustaurus. I demonstrate that natural variation in both the quantityand quality of food that larvae receive from their parents determinesbody size in males and females, and, by means of a thresholdresponse, the presence or absence of horns in males. In addition,results suggest that parent beetles adjust the amount of foodthey provision for their offspring according to diet quality,which may help to compensate for environmental variation inducedby differential resource quality in the wild. I use these resultsto further characterize the selective regime responsible forthe evolution of male polyphenism in onthophagine beetles anddiscuss its significance for understanding the origin and maintenanceof morphological variation in the genus Onthophagus.