Venus, FL, United States
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Wilcoxen T.E.,University of Memphis | Boughton R.K.,Avian Ecology Laboratory | Schoech S.J.,University of Memphis
Behavioral Ecology and Sociobiology | Year: 2010

In species that undergo actuarial senescence, the value of current reproduction is predicted to increase relative to the value of future reproduction with age, as the probability of survival to another reproductive event is reduced. Therefore, life history theory predicts that aging animals should increase their investment in reproduction. However, an increase in reproductive investment may carry significant costs to the breeding individuals. We recorded provisioning rates of Florida scrub-jay male breeders, followed by their immediate capture to assess body condition and collect blood for an in vitro test of immunocompetence and an assay of baseline corticosterone for a measure of stress. Older males provisioned offspring and brooding mates at the highest rates. There was no evidence of any physiological deficits in males with high provisioning rates, independent of age. It appears that birds that survive to old age are high quality birds that maintain good physiological condition, which complements the value of experience and permits maximal investment in offspring. © 2010 Springer-Verlag.


Wilcoxen T.E.,University of Memphis | Boughton R.K.,Avian Ecology Laboratory | Schoech S.J.,University of Memphis
Biology Letters | Year: 2010

Opportunities to investigate selection in freeliving species during a naturally occurring epidemic are rare; however, we assessed innate immunocompetence in Florida scrub-jays before the population suffered the greatest overwinter mortality in 20 years of study. Propitiously, three months prior to the epidemic, we had sampled a number of male breeders to evaluate a suite of physiological measures that are commonly used to estimate the overall health-state of an individual. There was a significant, positive selection gradient for both Escherichia coli bacterial killing capability and body condition, suggesting that directional selection had occurred upon each of these traits during the disease epidemic. © 2010 The Royal Society.


Kulahci I.G.,Avian Ecology Laboratory | Kulahci I.G.,Princeton University | Bowman R.,Avian Ecology Laboratory
Ethology | Year: 2011

Food caching animals depend on their caches at times of low food availability. Because stored food is susceptible to being stolen or degraded, many species employ cache protection strategies such as ceasing caching in the presence of others or avoiding storing perishable items for long periods. Several species frequently recover their caches and recache, which may reduce pilferage or degradation of cached items. We studied the food handling decisions of Florida scrub-jays (Aphelocoma coerulescens) after cache recovery to determine the roles that social and ecological environments play in post-recovery decisions. Instead of reducing recaching in the presence of others, recovering jays flew away from the recovery site, allowing them to eat or recache a recovered item regardless of the social context. Microhabitat type and soil moisture of the recovery sites had a significant influence on whether recoveries were eaten or recached; most items that were recached had been recovered from bare sand sites or sites with low soil moisture. Taken together, our results suggest that food store management of Florida scrub-jays are unaffected by the social context, but are strongly affected by the habitat conditions that influence the quality of caches. © 2011 Blackwell Verlag GmbH.


Wilcoxen T.E.,University of Memphis | Wilcoxen T.E.,Millikin University | Bridge E.S.,University of Oklahoma | Boughton R.K.,Avian Ecology Laboratory | And 3 more authors.
Ibis | Year: 2011

Hatching failure within clutches of eggs occurs to varying degrees in many avian species. We investigated predictors of hatching failure in a population of Florida Scrub-Jays, for which hatching success has been monitored for 15 years. We assessed whether hatching failure was related to parental traits (e.g. age, experience as a pair or body condition), lay date, social structure (e.g. number of helpers), environmental conditions, or some combination of these. We used linear mixed models and Akaike's information criterion to determine the models that best explain observed patterns of hatching failure. The best model showed that increased hatching failure was associated with below-average rainfall during the breeding season, and was more common for newly established breeding pairs than for pairs that had previously produced one or more clutches together. Other contributing models suggested that hatching failure was greatest for the youngest and oldest female breeders. Some aspects of our findings are consistent with conclusions drawn from other species. However, as a whole, our analyses suggest that hatching failure in the Florida Scrub-Jay is influenced by a complex set of environmental and parental factors. © 2010 The Authors. Journal compilation © 2010 British Ornithologists' Union.


Urbanization changes habitat in a multitude of ways, including altering food availability. Access to human-provided food can change the relationship between body condition and honest advertisements of fitness, which may result in changes to behavior, demography, and metapopulation dynamics. We compared plumage color, its relationship with body condition and feather growth, and use as signal of dominance between a suburban and a wildland population of Florida Scrub-Jay (Aphelocoma coerulescens). Although plumage color was not related to body condition at either site, suburban birds had plumage with a greater proportion of total reflectance in the ultra-violet (UV) and peak reflectance at shorter wavelengths. Despite the use of plumage reflectance as a signal of dominance among individuals in the wildlands, we found no evidence of status signaling at the suburban site. However, birds emigrating from the suburban site to the wildland site tended to be more successful at acquiring breeder status but less successful at reproducing than were immigrants from an adjacent wildland site, suggesting that signaled and realized quality differ. These differences in signaling content among populations could have demographic effects at metapopulation scales and may represent an evolutionary trap whereby suburban immigrants are preferred as mates even though their reproductive success relative to effort is lower. © 2015 by the author(s).


McClure C.J.W.,Auburn University | McClure C.J.W.,Boise State University | Rolek B.W.,Avian Ecology Laboratory | Hill G.E.,Auburn University
Condor | Year: 2012

Information regarding microhabitat, here defined as small-scale vegetation structure, is often useful in predicting use of habitat by birds. Quantifying microhabitat, however, is expensive and labor intensive compared to assessment of habitat at a larger scale, possibly from remotely sensed imagery. To assess the importance of microhabitat information in constructing predictive models of habitat occupancy, we compared occupancy models built on the basis of macro- and microhabitat together and separately. We based our models on counts of wintering migratory bird species and vegetation surveys within Tuskegee National Forest, Alabama, completed during winter 2009. Models built from macrohabitat data only outperformed models built from microhabitat data only for five of the six species analyzed. however, the best model for every focal species included both macro- and microhabitat covariates. Pine forests-excluding plantation-were the only land-cover classification important to our focal species, and measures of density of vegetation were important in predicting occupancy. Our results suggest that migrants wintering at our study site select habitat at multiple scales-specializing in certain types of cover and then preferring specific structural aspects of vegetation within them. We conclude that microhabitat information is important for inference into use of habitat by wintering migratory birds. © The Cooper Ornithological Society 2012.


Tringali A.,University of Central Florida | Bowman R.,Avian Ecology Laboratory
Animal Behaviour | Year: 2012

Although sexual selection is undeniably important in the evolution and maintenance of ornamental traits, it remains an unsuitable explanation for juvenile ornamentation. Male-male competition has been important in the evolution of UV-blue plumage ornamentation in birds, suggesting that this type of plumage may signal status more generally. In the present study, we compared dominance status of juvenile Florida scrub-jays before and after experimental plumage manipulation and found that plumage reflectance signalled status. Male-male competition is important in maintaining UV-blue plumage ornamentation in adults of other species. However, our evidence shows that sexually dimorphic ornamentation can also mediate competition over food resources in juvenile Florida scrub-jays. Understanding status signalling among juveniles may yield insights into differences in fitness, especially in species with cohesive social systems where early interactions are likely to influence future competitions over resources or mates. © 2012 The Association for the Study of Animal Behaviour.


Rensel M.A.,University of Memphis | Boughton R.K.,Avian Ecology Laboratory | Schoech S.J.,University of Memphis
General and Comparative Endocrinology | Year: 2010

Nestlings of altricial species undergo a period of substantial growth and development in the nest after hatching. The hypothalamic-pituitary-adrenal axis regulates the release of stress hormones such as corticosterone, which in adults is critical in allowing an animal to respond to a stressor. However, activation of this axis in young birds may be detrimental to growth and possibly survival. The developmental hypothesis predicts that altricial nestlings should display a dampened corticosterone response to stress as a means of protection against the potentially harmful effects of elevated corticosterone. We examined this hypothesis in Florida scrub-jays, a cooperatively breeding species with altricial young. Blood samples were collected from nestlings, nutritionally independent young, and yearlings for measurement of corticosterone levels. Baseline corticosterone levels did not differ between age-classes; however, stress-induced corticosterone levels were highest in yearlings, intermediate in independent young, and lowest in nestlings. The nestling stress response was also of a shorter duration than the response in independent young and yearlings. This variation in stress responsiveness across ages may be an adaptive mechanism to protect the developing bird from the negative effects of corticosterone on growth and cognitive development. © 2009 Elsevier Inc. All rights reserved.


Tucker Jr. J.W.,Avian Ecology Laboratory | Schrott G.R.,Avian Ecology Laboratory | Bowman R.,Avian Ecology Laboratory
Southeastern Naturalist | Year: 2010

We measured densities of Solenopsis invicta (Red Imported Fire Ant) mounds at sites occupied by Ammodramus savannarum floridanus (Florida Grasshopper Sparrow), a federally endangered subspecies, at Avon Park Air Force Range (APAFR), Kissimmee Prairie Preserve State Park (KPPSP), and Three Lakes Wildlife Management Area (TLWMA). Our objective was to compare densities of fire ant mounds among areas with active cattle grazing programs (two areas of native dry prairie habitat at APAFR and a tamed pasture at KPPSP) and areas without active grazing programs (native dry prairie habitat at KPPSP and TLWMA). Densities of fire ant mounds differed among the five areas examined and were greater in areas with active grazing programs than in areas without active grazing programs. We measured densities of fire ant mounds inside and outside of a cattle exclosure, but the total numbers detected were insufficient for analysis. We also placed bait stations inside and outside the exclosure. Fire ants were detected at 50% fewer bait stations inside the exclosure, but these differences were not significant.


Tringali A.,Avian Ecology Laboratory | Bowman R.,Avian Ecology Laboratory | Husby A.,University of Helsinki
Ecology and Evolution | Year: 2015

Sexually dimorphic plumage coloration is widespread in birds and is generally thought to be a result of sexual selection for more ornamented males. Although many studies find an association between coloration and fitness related traits, few of these simultaneously examine selection and inheritance. Theory predicts that sex-linked genetic variation can facilitate the evolution of dimorphism, and some empirical work supports this, but we still know very little about the extent of sex linkage of sexually dimorphic traits. We used a longitudinal study on juvenile Florida scrub-jays (Aphelocoma coerulescens) to estimate strength of selection and autosomal and Z-linked heritability of mean brightness, UV chroma, and hue. Although plumage coloration signals dominance in juveniles, there was no indication that plumage coloration was related to whether or not an individual bred or its lifetime reproductive success. While mean brightness and UV chroma are moderately heritable, hue is not. There was no evidence for sex-linked inheritance of any trait with most of the variation explained by maternal effects. The genetic correlation between the sexes was high and not significantly different from unity. These results indicate that evolution of sexual dimorphism in this species is constrained by low sex-linked heritability and high intersexual genetic correlation. © 2015 John Wiley & Sons Ltd.

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