repeated west nile virus epidemic transmission in kern county, california, 2004-2007.west nile virus (wnv) has remained epidemic in kern county, ca, since its introduction in 2004 through 2007 when the human case annual incidence increased from 6-8 to 17 per 100,000, respectively. the 2007 increase in human infection was associated with contradicting surveillance indicators, including severe drought, warm spring but cool summer temperature anomalies, decreased rural and urban mosquito abundance but increased early season infection in urban culex quinquefasciatus say, moderate av ...200919198528
mites of the genus torotrogla (prostigmata: syringophilidae) from north american passerines.five new quill mite species of the genus torotrogla kethley, 1970 (acari: syringophilidae) are described from north american passerines: t. aphelocoma sp.n. from aphelocoma californica (corvidae) and t. cardinalis sp.n. from cardinalis cardinalis (cardinalidae) in texas; and t. coccothraustes sp.n. from coccothraustes vespertinus (fringillidae), t. cyanocitta sp.n. from cyanocitta stelleri (corvidae), and t. piranga sp.n. from piranga ludoviciana (thraupidae) in california. a key to females of a ...200919351069
house finch (haemorhous mexicanus) conjunctivitis, and mycoplasma spp. isolated from north american wild birds, 1994-2015.sampling wild birds for mycoplasma culture has been key to the study of house finch (haemorhous mexicanus) conjunctivitis, yielding isolates of mycoplasma gallisepticum spanning the temporal and geographic ranges of disease from emergence to endemicity. faced with the challenges and costs of sample collection over time and from remote locations for submission to our laboratory for mycoplasma culture, protocols evolved to achieve a practical optimum. herein we report making m. gallisepticum isola ...201627285414
differential impact of west nile virus on california birds.the strain of west nile virus (wnv) currently epidemic in north america contains a genetic mutation elevating its virulence in birds, especially species in the family corvidae. although dead american crows (corvus brachyrhynchos) have been the hallmark of the epidemic, the overall impact of wnv on north america's avifauna remains poorly understood and has not been addressed thoroughly in california. here, we evaluate variation by species in the effect of wnv on california birds from 2004 to 2007 ...200920589226
detection of persistent west nile virus rna in experimentally and naturally infected avian determine whether west nile virus (wnv) persistent infection in avian hosts may potentially serve as an overwintering mechanism, house sparrows and house finches, experimentally and naturally infected with several strains of wnv, and two naturally infected western scrub-jays were held in mosquito-proof outdoor aviaries from 2007-march 2008. overall, 94% (n = 36) of house sparrows, 100% (n = 14) of house finches and 2 western scrub-jays remained wnv antibody positive. when combined by species, ...201222826479
sequence capture of ultraconserved elements from bird museum dna sequencing technologies are allowing researchers to explore the genomes of the millions of natural history specimens collected prior to the molecular era. yet, we know little about how well specific next-generation sequencing (ngs) techniques work with the degraded dna typically extracted from museum specimens. here, we use one type of ngs approach, sequence capture of ultraconserved elements (uces), to collect data from bird museum specimens as old as 120 years. we targeted 5060 uce loc ...201626391430
the effect of within-year variation in acorn crop size on seed harvesting by avian hoarders.spatial and temporal variation in resource distribution affect the movement and foraging behavior of many animals. in the case of animal-dispersed trees, numerous studies have addressed masting-the synchronized variation in seed production between years-but the fitness consequences of spatial variation in seed production within a year are unclear. we investigated the effects of variable acorn production in a population of valley oaks (quercus lobata) on the composition and behavior of the avian- ...201626809620
western scrub-jays allocate longer observation time to more valuable information.when humans mentally reconstruct past events and imagine future scenarios, their subjective experience of mentally time travelling is accompanied by the awareness of doing so. despite recent popularity of studying episodic memory in animals, such phenomenological consciousness has been extremely difficult to demonstrate without agreed behavioural markers of consciousness in non-linguistic subjects. we presented western scrub-jays (aphelocoma californica) with a task requiring them to allocate ob ...201424322875
western scrub-jays do not appear to attend to functionality in aesop's fable experiments.western scrub-jays are known for their highly discriminatory and flexible behaviors in a caching (food storing) context. however, it is unknown whether their cognitive abilities are restricted to a caching context. to explore this question, we tested scrub-jays in a non-caching context using the aesop's fable paradigm, where a partially filled tube of water contains a floating food reward and objects must be inserted to displace the water and bring the food within reach. we tested four birds, bu ...201626925331
counting on your friends: the role of social environment on quantity discrimination.quantity discrimination has been established in a range of species. however, most demonstrations of quantity discrimination control for social factors by testing animals individually. i tested whether sociality affects quantity discrimination in the wild by comparing the performances of the highly social mexican jay (mj; aphelocoma wollweberi) and the territorial western scrub jay (wj; aphelocoma californica). the birds were given a choice between two lines of peanuts that differed in initial qu ...201627036232
western scrub-jays (aphelocoma californica) solve multiple-string problems by the spatial relation of string and reward.string-pulling is a widely used paradigm in animal cognition research to assess what animals understand about the functionality of strings as a means to obtain an out-of-reach reward. this study aimed to systematically investigate what rules western scrub-jays (aphelocoma californica) use to solve different patterned string tasks, i.e. tasks in which subjects have to choose between two or more strings of which only one is connected to the reward, or where one is more efficient. arranging strings ...201627470204
speciation in western scrub-jays, haldane's rule, and genetic clines in secondary contact.haldane's rule, the tendency for the heterogametic sex to show reduced fertility in hybrid crosses, can obscure the signal of gene flow in mtdna between species where females are heterogametic. therefore, it is important when studying speciation and species limits in female-heterogametic species like birds to assess the signature of gene flow in the nuclear genome as well. we studied introgression of microsatellites and mtdna across a secondary contact zone between coastal and interior lineages ...201424938753
social cognition by food-caching corvids. the western scrub-jay as a natural corvids hide food, but such caches are susceptible to pilfering by other individuals. consequently, the birds use several counter strategies to protect their caches from theft, e.g. hiding most of them out of sight. when observed by potential pilferers at the time of caching, experienced jays that have been thieves themselves, take further protective action. once the potential pilferers have left, they move caches those birds have seen, re-hiding them in new places. naive birds that ...200717309867
rooks perceive support relations similar to six-month-old babies.some corvids have demonstrated cognitive abilities that rival or exceed those of the great apes; for example, tool use in new caledonian crows, and social cognition, episodic-like memory and future planning in western scrub-jays. rooks appear to be able to solve novel tasks through causal reasoning rather than simple trial-and-error learning. animals with certain expectations about how objects interact would be able to narrow the field of candidate causes substantially, because some causes are s ...201019812083
translational research into intertemporal choice: the western scrub-jay as an animal model for future-thinking.decisions often involve outcomes that will not materialise until later, and choices between immediate gratification and future consequences are thought to be important for human health and welfare. combined human and animal research has identified impulsive intertemporal choice as an important factor in drug-taking and pathological gambling. in this paper, we give an overview of recent research into intertemporal choice in non-human animals, and argue that this work could offer insight into huma ...201525225036
nutritional deficits during early development affect hippocampal structure and spatial memory later in life.development rates vary among individuals, often as a result of direct competition for food. survival of young might depend on their learning abilities, but it remains unclear whether learning abilities are affected by nutrition during development. the authors demonstrated that compared with controls, 1-year-old western scrub jays (aphelocoma californica) that experienced nutritional deficits during early posthatching development had smaller hippocampi with fewer neurons and performed worse in a ...200516300442
western scrub-jays conceal auditory information when competitors can hear but cannot see.western scrub-jays (aphelocoma californica) engage in a variety of cache-protection strategies to reduce the chances of cache theft by conspecifics. many of these strategies revolve around reducing visual information to potential thieves. this study aimed to determine whether the jays also reduce auditory information during caching. each jay was given the opportunity to cache food in two trays, one of which was filled with small pebbles that made considerable noise when cached in ('noisy' tray), ...200919605383
studies of trichomonad protozoa in free ranging songbirds: prevalence of trichomonas gallinae in house finches (carpodacus mexicanus) and corvids and a novel trichomonad in mockingbirds (mimus polyglottos).this study refutes the accepted dogma that significant pathogenic effects of trichomonas gallinae are limited to columbiformes and raptors in free ranging bird populations in north america. trichomonads were associated with morbidity and mortality amongst free ranging house finches (carpodacus mexicanus), mockingbirds (mimus polyglottos) and corvids (scrub jay: aphelocoma californica; crow: corvus brachyrhynchos; raven: corvus corax) in northern california. prevalence of trichomonad infection wa ...200919278788
field and laboratory evaluation of diagnostic assays for detecting west nile virus in oropharyngeal swabs from california wild birds.three diagnostic assays for detecting west nile virus (wnv) in avian oral swabs were evaluated in california in 2004 and 2005: two commercial antigen-capture assays, vectest and rapid analyte measurement platform (ramp), and reverse transcriptase-polymerase chain reaction (rt-pcr) of oral swabs in a specialized viral transport medium (vtm). results from this study demonstrated that vtm was excellent for transportation and maintenance of wnv in avian oral swab samples and allowed for detection by ...200616796516
role of corvids in epidemiology of west nile virus in southern california.the invasion of different southern california landscapes by west nile virus (wnv) and its subsequent amplification to epidemic levels during 2004 enabled us to study the impact of differing corvid populations in three biomes: the hot colorado desert with few corvids (coachella valley), the southern san joaquin valley (kern county) with large western scrub-jay but small american crow populations, and the cool maritime coast (los angeles) with a large clustered american crow population. similar su ...200616619622
comparing alternative models to empirical data: cognitive models of western scrub-jay foraging behavior.animals often select one item from a set of candidates, as when choosing a foraging site or mate, and are expected to possess accurate and efficient rules for acquiring information and making decisions. little is known, however, about the decision rules animals use. we compare patterns of information sampling by western scrub-jays (aphelocoma californica) when choosing a nut with three decision rules: best of n (bn), flexible threshold (ft), and comparative bayes (cb). first, we use a null hypot ...200414970927
avian host and mosquito (diptera: culicidae) vector competence determine the efficiency of west nile and st. louis encephalitis virus transmission.the ability of the invading ny99 strain of west nile virus (wnv) to elicit an elevated viremia response in california passerine birds was critical for the effective infection of culex mosquitoes. of the bird species tested, western scrub jays, aphelocoma coerulescens, produced the highest viremia response, followed by house finches, carpodacus mexicanus, and house sparrows, passer domesticus. most likely, few mourning, zenaidura macroura, or common ground, columbina passerine, doves and no calif ...200515962789
planning for the future by western scrub-jays.knowledge of and planning for the future is a complex skill that is considered by many to be uniquely human. we are not born with it; children develop a sense of the future at around the age of two and some planning ability by only the age of four to five. according to the bischof-köhler hypothesis, only humans can dissociate themselves from their current motivation and take action for future needs: other animals are incapable of anticipating future needs, and any future-oriented behaviours they ...200717314979
a comparison of four corvid species in a working and reference memory task using a radial maze.birds were tested in an open-room radial maze with learned spatial locations that varied from trial to trial (working memory) and locations that remained spatially stable (reference memory). three of the species, the clark's nutcracker (nucifraga columbiana), pinyon jay (gymnorhinus cyanocephalus), and western scrub jay (aphelocoma coerulescens) store food to varying degrees. the other species, the eurasian jackdaw (corvus monedula) does not. pinyon jays and scrub jays performed better than the ...200011149538
hint-seeking behaviour of western scrub-jays in a metacognition task.metacognitive processes during memory retrieval can be tested by examining whether or not animals can assess their knowledge state when they are faced with a memory test. in a typical foraging task, food is hidden in one of the multiple tubes and the subjects are given an opportunity to check the contents of the tubes before choosing the one that they thought contained food. following the findings from our previous study that western scrub-jays (aphelocoma californica) can make prospective metac ...201626267805
the effects of low levels of light at night upon the endocrine physiology of western scrub-jays (aphelocoma californica).florida scrub-jays (aphelocoma coerulescens) in the suburbs breed earlier than jays in native habitat. amongst the possible factors that influence this advance (e.g., food availability, microclimate, predator regime, etc.), is exposure to artificial lights at night (lan). lan could stimulate the reproductive axis of the suburban jays. alternatively, lan could inhibit pineal melatonin (mel), thus removing its inhibitory influence on the reproductive axis. because florida scrub-jays are a threaten ...201323970442
re-caching by western scrub-jays (aphelocoma californica) cannot be attributed to stress.western scrub-jays (aphelocoma californica) live double lives, storing food for the future while raiding the stores of other birds. one tactic scrub-jays employ to protect stores is "re-caching"-relocating caches out of sight of would-be thieves. recent computational modelling work suggests that re-caching might be mediated not by complex cognition, but by a combination of memory failure and stress. the "stress model" asserts that re-caching is a manifestation of a general drive to cache, rather ...201323326366
eurasian jays (garrulus glandarius) overcome their current desires to anticipate two distinct future needs and plan for them appropriately.western scrub-jays (aphelocoma californica) have been shown to overcome present satiety to cache food they will desire in the future. here, we show that another corvid, the eurasian jay (garrulus glandarius), can distinguish between two distinct future desires and plan for each appropriately, despite experiencing a conflicting current motivation. we argue that these data address the criticisms of previous work, and suggest a way in which associative learning processes and future-oriented cogniti ...201222048890
visual coverage and scanning behavior in two corvid species: american crow and western scrub jay.inter-specific differences in the configuration of avian visual fields and degree of eye/head movements have been associated with foraging and anti-predator behaviors. our goal was to study visual fields, eye movements, and head movements in two species of corvids: american crow (corvus brachyrhynchos) and western scrub jay (aphelocoma californica). american crows had wider binocular overlap, longer vertical binocular fields, narrower blind areas, and higher amplitude of eye movement than wester ...201020803204
cognitive representation in transitive inference: a comparison of four corvid species.during operant transitive inference experiments, subjects are trained on adjacent stimulus pairs in an implicit linear hierarchy in which responses to higher ranked stimuli are rewarded. two contrasting forms of cognitive representation are often used to explain resulting choice behavior. associative representation is based on memory for the reward history of each stimulus. relational representation depends on memory for the context in which stimuli have been presented. natural history character ...201020708664
ten years of research into avian models of episodic-like memory and its implications for developmental and comparative cognition.episodic memory refers to the ability to remember specific personal events from the past. ever since tulving first made the distinction between episodic memory and other forms of declarative memory in 1972, most cognitive psychologists and neuroscientists have assumed that episodic recall is unique to humans. the seminal paper on episodic-like memory in western scrub-jays (aphelocoma californica) by clayton and dickinson [4] has inspired a number of studies and in a wide range of species over th ...201020600352
the development of caching and object permanence in western scrub-jays (aphelocoma californica): which emerges first?recent studies on the food-caching behavior of corvids have revealed complex physical and social skills, yet little is known about the ontogeny of food caching in relation to the development of cognitive capacities. piagetian object permanence is the understanding that objects continue to exist even when they are no longer visible. here, the authors focus on piagetian stages 3 and 4, because they are hallmarks in the cognitive development of both young children and animals. our aim is to determi ...200919685971
geographic variation in the community structure of lice on western scrub-jays.parasites are incredibly diverse. an important factor in the evolution of this diversity is the fact that many parasite species are restricted to 1, or just a few, host species. in addition, some parasites exhibit geographic specificity that is nested within their specificity to a particular species of host. the environmental factors that restrict parasites to particular regions within the host's range are poorly understood, and it is often difficult to know whether such patterns of geographic s ...200918576864
why does the yellow-eyed ensatina have yellow eyes? batesian mimicry of pacific newts (genus taricha) by the salamander ensatina eschscholtzii xanthoptica.color patterns commonly vary geographically within species, but it is rare that such variation corresponds with divergent antipredator strategies. the polymorphic salamander ensatina eschscholtzii, however, may represent such a case. in this species, most subspecies are cryptically colored, whereas e. e. xanthoptica, the yellow eyed ensatina, is hypothesized to be an aposematic mimic of highly toxic pacific newts (genus taricha). to test the mimicry hypothesis, we conducted feeding trials using ...200818248632
serial reversal learning and the evolution of behavioral flexibility in three species of north american corvids (gymnorhinus cyanocephalus, nucifraga columbiana, aphelocoma californica).in serial reversal learning, subjects learn to respond differentially to 2 stimuli. when the task is fully acquired, reward contingencies are reversed, requiring the subject to relearn the altered associations. this alternation of acquisition and reversal can be repeated many times, and the ability of a species to adapt to this regimen has been considered as an indication of behavioral flexibility. serial reversal learning of 2-choice discriminations was contrasted in 3 related species of north ...200718085920
the control of food-caching behavior by western scrub-jays (aphelocoma californica).western scrub-jays (aphelocoma californica) did not show extinction when caching behavior was never rewarded and they had no choice of where to cache the food. however, when the jays had the choice of caching items in 2 different locations or during 2 successive episodes, and only 1 of each was always rewarded at recovery, they rapidly learned to cache in the rewarded location or episode. when the jays had learned during training trials that their caches were always moved to 1 of 2 locations the ...200717924785
no evidence of temporal preferences in caching by western scrub-jays (aphelocoma californica).humans and other animals often favour immediate gratification over long-term gain. primates, including humans, appear more willing to wait for rewards than other animals, such as rats or pigeons. another group displaying impressive patience are the corvids, which possess large brains and show sophisticated cognitive abilities. here, we assess intertemporal choice in one corvid species, the western scrub-jay (aphelocoma californica). these birds cache food for future consumption and respond flexi ...201424378212
experimental infection of california birds with western equine encephalomyelitis and st. louis encephalitis viruses.a total of 27 bird species from the san joaquin and coachella valleys of california were inoculated subcutaneously with sympatric strains of western equine encephalomyelitis (wee) and st. louis encephalitis (sle) viruses. overall, 133 of 164 birds inoculated with wee virus developed a viremia detected by plaque assay; significantly greater than 72 of 163 birds inoculated with sle virus. host competence was calculated as the average number of days that each avian species had a viremia > or = 2 lo ...200314765678
temporal predictability in food availability: effects upon the reproductive axis in scrub-jays.florida scrub-jays (aphelocoma coerulescens) in a suburban environment with year-round access to multiple sources of abundant, human-source foods consistently breed earlier each year and have lower baseline levels of circulating corticosterone (cort) than jays in a nearby wildland setting. these findings suggest that food supplies influence cort levels, which in turn may partially determine the timing of reproduction. however, wildland birds with access to high-quality supplemental foods did not ...200918756528
food-caching western scrub-jays keep track of who was watching when.western scrub-jays (aphelocoma californica) hide food caches for future consumption, steal others' caches, and engage in tactics to minimize the chance that their own caches will be stolen. we show that scrub-jays remember which individual watched them during particular caching events and alter their recaching behavior accordingly. we found no evidence to suggest that a storer's use of cache protection tactics is cued by the observer's behavior.200616709747
independent effects of food and predator-mediated processes on annual fecundity in a songbird.we investigated the relative importance and interaction of ecological processes affecting annual fecundity in birds by simultaneously manipulating food availability and nest predation risk in a small songbird, the wrentit (chamaea fasciata). from 2000 to 2002 we provided supplemental food to individual wrentit territories, and during 2002 we altered nest predation risk by providing supplemental food to their principal predators, western scrub-jays (aphelocoma californica). these experiments were ...200616634307
is the western scrub-jay (aphelocoma californica) really an underdog among food-caching corvids when it comes to hippocampal volume and food caching propensity?food caching has been linked to better performance on spatial memory tasks and enlarged hippocampal volume in both birds and mammals. within food-caching birds, it has also been predicted that species less reliant on stored food should have inferior spatial memory and a smaller hippocampus compared to species that depend heavily on food caches. several comparisons suggest that north american corvids have a significantly smaller hippocampus and overall brain volume compared to the eurasian corvid ...200616219995
effects of nutritional restrictions during post-hatching development on adrenocortical function in western scrub-jays (aphelocoma californica).altricial birds grow rapidly during post-hatching period and are developmentally sensitive to variations in food supply. limited food results in elevated corticosterone levels in chicks of semi-precocial birds but it is not clear whether altricial songbirds show similar adrenocortical stress response to nutritional restrictions during early development. it is also unknown how nutritional stress during early development affects the adrenocortical function later in life in altricial birds which sh ...200616102756
west nile virus-related trends in avian mortality in california, usa, 2003-12.west nile virus (wnv) is an arbovirus transmitted enzootically by culex mosquitoes among avian hosts. since 2000, the california dead bird surveillance program (dbsp) has tracked avian mortality reported by the public on a telephone hotline and website and measured the prevalence of wnv infection in dead birds. we summarize herein wnv prevalence in dead birds tested and variation of wnv transmission over time and space with the use of dbsp data from 2003 to 2012. prevalence among dead birds was ...201525919466
food caching by western scrub-jays (aphelocoma californica) is sensitive to the conditions at recovery.western scrub-jays (aphelocoma californica) cached perishable and nonperishable food items, which they could recover after both short and long retention intervals. when perishable items were always degraded at recovery, jays decreased the number of perishable items cached and increased their caching of nonperishable items, relative to a control group whose caches were always fresh at recovery. jays reduced the number of nonperishable items cached, however, when highly preferred food items were d ...200515839770
cache protection strategies by western scrub-jays (aphelocoma californica): hiding food in the the presence of conspecifics, food-caching western scrub-jays (aphelocoma californica) implement a variety of strategies to reduce the chances of cache theft. this experiment aimed to determine whether the jays could exploit an environmental variable, the level of ambient light, to reduce the transfer of visual information to potential pilferers. each jay was allowed to cache non-degradable food in two trays, one of which was well lit, whereas the other was in shadow. in some trials the birds ...200415801583
western scrub-jays ( aphelocoma californica) use cognitive strategies to protect their caches from thieving caching birds hide food and recover the caches when supplies are less abundant. there is, however, a risk to this strategy because the caches are susceptible to pilfering by others. corvids use a number of different strategies to reduce possible cache theft. scrub-jays with previous experience of pilfering other's caches cached worms in two visuospatially distinct caching trays either in private or in the presence of a conspecific. when these storers had cached in private, they subsequently ...200412827547
interacting cache memories: evidence for flexible memory use by western scrub-jays (aphelocoma californica).when western scrub-jays (aphelocoma californica) cached and recovered perishable crickets, n. s. clayton, k. s. yu, and a. dickinson (2001) reported that the jays rapidly learned to search for fresh crickets after a 1-day retention interval (ri) between caching and recovery but to avoid searching for perished crickets after a 4-day ri. in the present experiments, the jays generalized their search preference for crickets to intermediate ris and used novel information about the rate of decay of cr ...200312561130
clark's nutcrackers (nucifraga columbiana) are sensitive to distance, but not lighting when caching in the presence of a conspecific.we examined the caching behavior of the clark's nutcracker (nucifraga columbiana), a relatively asocial corvid bird, during social and non-social conditions with conspecifics. past work by dally et al., (2004, 2005a) has found that the related but more social scrub jay (aphelocoma californica) caches food in locations that are far away or that are more dimly illuminated when in the presence of an observer. here, we used procedures comparable to those of dally's group to examine if the less socia ...201626581321
effects of vasoactive intestinal peptide on plasma prolactin in passerines.vasoactive intestinal peptide (vip) is a potent releaser of prolactin (prl) in domestic fowl, turkey, and ring doves. however, few comparative studies have investigated this in wild species. we tested the effects of intravenously administered chicken vip on plasma prl concentrations in four passerine species: the white-crowned sparrow (zonotrichia leucophrys gambelii), the dark-eyed junco (junco hyemalis), the florida scrub-jay (aphelocoma coerulescens), and the western scrub-jay (a. californica ...199910068494
efficacy of three vaccines in protecting western scrub-jays (aphelocoma californica) from experimental infection with west nile virus: implications for vaccination of island scrub-jays (aphelocoma insularis).abstract the devastating effect of west nile virus (wnv) on the avifauna of north america has led zoo managers and conservationists to attempt to protect vulnerable species through vaccination. the island scrub-jay (aphelocoma insularis) is one such species, being a corvid with a highly restricted insular range. herein, we used congeneric western scrub-jays (aphelocoma californica) to test the efficacy of three wnv vaccines in protecting jays from an experimental challenge with wnv: (1) the fort ...201121438693
sex, estradiol, and spatial memory in a food-caching corvid.estrogens significantly impact spatial memory function in mammalian species. songbirds express the estrogen synthetic enzyme aromatase at relatively high levels in the hippocampus and there is evidence from zebra finches that estrogens facilitate performance on spatial learning and/or memory tasks. it is unknown, however, whether estrogens influence hippocampal function in songbirds that naturally exhibit memory-intensive behaviors, such as cache recovery observed in many corvid species. to addr ...201526232613
corvid caching: insights from a cognitive model.caching and recovery of food by corvids is well-studied, but some ambiguous results remain. to help clarify these, we built a computational cognitive model. it is inspired by similar models built for humans, and it assumes that memory strength depends on frequency and recency of use. we compared our model's behavior to that of real birds in previously published experiments. our model successfully replicated the outcomes of two experiments on recovery behavior and two experiments on cache site ch ...201121639668
can animals recall the past and plan for the future?according to the 'mental time travel hypothesis' animals, unlike humans, cannot mentally travel backwards in time to recollect specific past events (episodic memory) or forwards to anticipate future needs (future planning). until recently, there was little evidence in animals for either ability. experiments on memory in food-caching birds, however, question this assumption by showing that western scrub-jays form integrated, flexible, trial-unique memories of what they hid, where and when. moreov ...200312894243
testosterone and social and reproductive behaviour in aphelocoma jays.when there is a direct relationship between testosterone level and payoff in reproductive success through aggression, testosterone levels should be elevated. elevated testosterone, however, has fitness costs, particularly a decreased tendency to display parental care. thus the pattern of testosterone secretion in males should vary with the social and mating system. western scrub-jays, aphelocoma californica woodhouseii, form monogamous pairs on territories during the breeding season. mexican jay ...199910564596
geographic variation in mexican jays (aphelocoma ultramarina): local differentiation, polyphyly or hybridization?studies of genetic variation within highly variable taxa can provide valuable insight into the factors influencing biological diversification. we examined six microsatellite loci, a nuclear intron and the mitochondrial control region to determine if the mexican jay subspecies aphelocoma ultramarina couchii and a. u. potosina have hybridized with western scrub-jays (a. californica). we suspected hybridization because these mexican jay populations resemble scrub-jays in several traits. we sampled ...200415315684
surveys for antibodies against mosquitoborne encephalitis viruses in california birds, 1996-2013.from 1996 through 2013, 54,546 individual birds comprising 152 species and 7 orders were banded, bled, and released at four study areas within california, from which 28,388 additional serum samples were collected at one or more recapture encounters. of these, 142, 99, and 1929 birds from 41 species were positive for neutralizing antibodies against western equine encephalomyelitis virus (weev), st. louis encephalitis virus (slev), or west nile virus (wnv) at initial capture or recapture, respecti ...201626974395
california scrub-jays reduce visual cues available to potential pilferers by matching food colour to caching substrate.some animals hide food to consume later; however, these caches are susceptible to theft by conspecifics and heterospecifics. caching animals can use protective strategies to minimize sensory cues available to potential pilferers, such as caching in shaded areas and in quiet substrate. background matching (where object patterning matches the visual background) is commonly seen in prey animals to reduce conspicuousness, and caching animals may also use this tactic to hide caches, for example, by h ...201728724689
differences in relative hippocampus volume and number of hippocampus neurons among five corvid species.the relative size of the avian hippocampus (hp) has been shown to be related to spatial memory and food storing in two avian families, the parids and corvids. basil et al. [brain behav evol 1996;47:156-164] examined north american food-storing birds in the corvid family and found that clark's nutcrackers had a larger relative hp than pinyon jays and western scrub jays. these results correlated with the nutcracker's better performance on most spatial memory tasks and their strong reliance on stor ...201323364270
abundance and bloodfeeding patterns of mosquitoes (diptera: culicidae) in an oak woodland on the eastern slope of the northern coast range of california.the abundance and bloodfeeding patterns of mosquitoes was studied from 2008 to 2010 at an 18 ha. oak woodland in lake county, ca. host-seeking females were collected weekly from sunset to sunrise by paired dry-ice-baited cdc style traps, whereas resting females were aspirated from paired walk-in red boxes. sequences of the coi gene amplified from bloodmeals from engorged resting females were used to identify the bloodmeal hosts. aedes sierrensis (ludlow) and aedes increpitus dyar complex mosquit ...201728874011
western scrub-jays anticipate future needs independently of their current motivational state.planning for the future has been considered to be a uniquely human trait [1-3]. however, recent studies challenge this hypothesis by showing that food-caching western scrub-jays (aphelocoma californica) can relate their previous experience as thieves to the possibility of future cache theft by another bird [4], are sensitive to the state of their caches at recovery ([5] and s. de kort, s.p.c.c., d. alexis, a.d., and n.s.c., unpublished data), and can plan for tomorrow's breakfast [6]. although t ...200717462894
spatial variation in host feeding patterns of culex tarsalis and the culex pipiens complex (diptera: culicidae) in california.west nile virus (family flaviviridae, genus flavivirus, wnv) is now endemic in california across a variety of ecological regions that support a wide diversity of potential avian and mammalian host species. because different avian hosts have varying competence for wnv, determining the blood-feeding patterns of culex (diptera: culicidae) vectors is a key component in understanding the maintenance and amplification of the virus as well as tangential transmission to humans and horses. we investigate ...022897051
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