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Effect of predation risk and food availability on parental care and nest survival in suburban and wildland Florida Scrub-Jays
Title
Effect of predation risk and food availability on parental care and nest survival in suburban and wildland Florida Scrub-Jays.
Creator
Niederhauser, Joseph, Jenkins, David, Fedorka, Kenneth, Bowman, Reed, University of Central Florida
Abstract / Description
Individual organisms often use cues from their natural environments to determine many behavioral and life-history (")decisions.(") These (")decisions(") are usually adaptive, i.e. a response to selection, because the environmental cues on which they are based reliably correlate with increased fitness over time. When the selected behavioral response to a natural cue no longer provides a fitness benefit, then selection for a new response may occur but individuals maintaining the previously...
Show moreIndividual organisms often use cues from their natural environments to determine many behavioral and life-history (")decisions.(") These (")decisions(") are usually adaptive, i.e. a response to selection, because the environmental cues on which they are based reliably correlate with increased fitness over time. When the selected behavioral response to a natural cue no longer provides a fitness benefit, then selection for a new response may occur but individuals maintaining the previously selected response may suffer reduced survival and reproduction. Especially in human-modified landscapes individuals making a maladaptive behavioral or life-history choice based on those formerly reliable environmental cues may be faced with an (")evolutionary trap("). In urban, or suburban, environments many factors have been altered in ways that could lead to evolutionary traps. Inappropriate behavioral responses by many individuals could lead to reduced demographic performance of urban populations relative to their wildland counterparts and to the decline of entire urban populations. In birds, maladaptive patterns of nest provisioning or vigilance may occur (a) when human-provided adult foods are easier to feed young because they are more abundant and predictable than foods appropriate for nestlings, or (b) when birds' perception of predation risk, which can be influenced by human disturbance, is greater than the real risk. By provisioning or attending their nests more or less than what is appropriate given the environmental level of resources and risks, the behavior of suburban parents may be contributing to high levels of nest failure during the nesting stage. To determine whether maladaptive parental care influences nest survival during the nestling stage, I conducted an experiment using Florida Scrub-Jays (Aphelocoma coerluscens). Suburban scrub-jays have lower nest survival during the nestling stage but higher survival during the incubation stage relative to wildland jays. Both predators and food abundance vary greatly between suburban and wildland scrub. The suburbs have a greater abundance of predators that may prey on both adult scrub-jays and their nests and more foods appropriate for adults but less nestling-appropriate food. This variation in risks and resources should affect the parental care behavior of suburban scrub-jays, which in turn may affect patterns of nest survival. In pre-treatment observations, I found that suburban females spent more time brooding than wildland birds but suburban males did not provision any more than wildland males. Experimentally increasing the perception of adult predation risk reduced parental care in both suburban and wildland females. Increasing the availability of nestling food reduced parental care in suburban females but had no effect in wildland females. Increasing food availability, but not predation risk, decreased call rates but increased call frequency in nestling scrub-jays from both habitats. However, neither parental care nor food availability had much influence on nest survival during the nestling stage. Instead, side nest concealment and the presence of helpers were the most important variables in nest survival analyses prompting other explanations besides maladaptive parental behavior or lack of nestling food resources for the habitat-specific difference in nest survival during the nestling stage.
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Date Issued
2012
Identifier
CFE0004219, ucf:49015
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004219
DEMOGRAPHIC CONSEQUENCES OF MANAGING FOR FLORIDA SCRUB-JAYS (APHELOCOMA COERULESCENS) ON AN ISOLATED PRESERVE.
Title
DEMOGRAPHIC CONSEQUENCES OF MANAGING FOR FLORIDA SCRUB-JAYS (APHELOCOMA COERULESCENS) ON AN ISOLATED PRESERVE.
Creator
Lyon, Casey, Stout, I. Jack, University of Central Florida
Abstract / Description
Many species naturally occupy discrete habitat patches within a mosaic of habitats that vary in quality. The Florida scrub-jay (Aphelocoma coerulescens) is endemic to Florida scrub, a habitat that is naturally patchy and greatly reduced in area over recent decades owing to development and urbanization. Because of this habitat loss, future management of Florida scrub-jays will focus on smaller, fragmented tracts of land. My study examines such a tract, Lyonia Preserve, southwest Volusia County...
Show moreMany species naturally occupy discrete habitat patches within a mosaic of habitats that vary in quality. The Florida scrub-jay (Aphelocoma coerulescens) is endemic to Florida scrub, a habitat that is naturally patchy and greatly reduced in area over recent decades owing to development and urbanization. Because of this habitat loss, future management of Florida scrub-jays will focus on smaller, fragmented tracts of land. My study examines such a tract, Lyonia Preserve, southwest Volusia County, FL. This preserve was unoccupied by scrub-jays prior to habitat restoration. The preserve is now frequently managed exclusively for scrub-jays as a habitat island surrounded by development. Management of the preserve includes roller chopping, root raking, timbering, and "oak stripping" where islands of oak patches are left intact while the rest of the area is roller chopped. I investigate what, if any, demographic consequences may be associated with the habitat management and the spatial setting of the preserve. I used population data collected in this area since 1992 to examine population growth and responses to habitat restoration within the preserve and habitat destruction outside the preserve. I mapped territories and measured survival and recruitment of scrub-jays, and dispersal into and out of the study area, for two and a half years. Since restoration, the population has shown logistic growth, with the area supporting higher than average densities of scrub-jay family groups. Observed density of the population and territory size varied between study years. Breeder survival values were positively related to territory size and significantly lower during periods of highest observed density. However, recruitment (yearling production) showed no relationship to territory size. Dispersal to isolated habitat patches was observed; likewise, several failed dispersal events were noted. No immigration into the study area was observed; however these data may be underrepresented since not all scrub-jays in and outside of the preserve were banded, and data collection was limited during the initial colonization period. High densities inside the preserve may therefore be both a result of frequent habitat management in the form of mechanical treatment as well as crowding of individuals due to outside habitat destruction. The results indicate that carrying capacity of habitat for scrub-jays may be raised by frequent, mechanical management; however, if the area is isolated, management may result in high densities and negative demographic consequences, e.g., reduced breeder survival. Negative effects of management may be avoided by subjecting smaller areas to mechanical treatment with increased time between treatments. Land managed for Florida scrub-jays should be contiguous or connected with other scrub habitats so that surplus birds from the managed areas have a refuge and do not contribute to increased densities. Regulatory officials should use caution when allowing for "take" of scrub-jay habitat as the effects may extend beyond the local habitat being destroyed.
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Date Issued
2007
Identifier
CFE0001769, ucf:47280
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001769
HATCHING ASYNCHRONY OCCURS AS A BYPRODUCT OF MAINTAINING EGG VIABILITY
Title
HATCHING ASYNCHRONY OCCURS AS A BYPRODUCT OF MAINTAINING EGG VIABILITY.
Creator
Aldredge, Robert, Noss, Reed, University of Central Florida
Abstract / Description
For many organisms, embryonic development begins directly after an egg (ovum) has been fertilized by sperm; however, some organisms delay the onset of embryonic development until conditions are favorable for raising young. This delayed onset of development could occur by delaying implantation of fertilized ovum on the uterine wall, as seen in many mammals. Birds delay embryonic development by laying a set of fertilized ova over a period of consecutive days. These fertilized ova are protected...
Show moreFor many organisms, embryonic development begins directly after an egg (ovum) has been fertilized by sperm; however, some organisms delay the onset of embryonic development until conditions are favorable for raising young. This delayed onset of development could occur by delaying implantation of fertilized ovum on the uterine wall, as seen in many mammals. Birds delay embryonic development by laying a set of fertilized ova over a period of consecutive days. These fertilized ova are protected from the ambient environment by an exterior shell, and it is in this shell outside of the female's body that embryonic development occurs, but only when females initiate incubation. The number of fertilized ova (eggs) that can be laid by a single female in a single clutch varies among and within bird species, and understanding this variation remains a vital, unanswered question in ornithology. A latitudinal gradient in clutch size is widely recognized, but the reason for this pattern is unclear. Some birds lay relatively large clutches over many days, thus we should expect that eggs could withstand fairly long exposure to ambient temperature and remain viable. However, recent evidence suggests that egg viability declines with increased exposure to ambient temperatures. The egg viability hypothesis predicts that eggs will fail to hatch if exposed to warm ambient temperatures for prolonged periods. I conducted a natural experiment to determine whether egg viability can explain site-specific variation in hatching failure. Hatching failure is higher in a suburban population of Florida Scrub-Jays than it is in a wildland population, possibly because suburban scrub-jays lay larger clutches. Scrub-jays, like many bird species, lay one egg per day and begin incubation with the last-laid egg, thus first-laid eggs in the larger suburban clutches should be exposed to the warm ambient temperatures of sub-tropical Florida longer than first-laid eggs in the smaller clutches typical of the wildland population. As predicted, I found hatching failure is higher in first-laid eggs in the suburbs, and these eggs experience increased exposure to warm ambient temperatures. At both sites, females appear to begin incubation earlier in the laying period as ambient temperatures increase seasonally, possibly to minimize exposure to warm ambient temperatures and minimize hatching failure in first-laid eggs. However, early onset of incubation causes eggs to hatch asynchronously (> 24 hours between the first and last-hatched egg), and hatching asynchrony increases within-brood size-asymmetries, which leads to an increased frequency of brood reduction (the nonrandom loss of last-hatched young because of starvation). Thus, a tradeoff may exist between beginning incubation earlier in the laying period to minimize hatching failure in first-laid eggs and delaying the onset of incubation to minimize hatching asynchrony and brood reduction. This tradeoff can have profound effects on avian clutch sizes, and may potentially explain the widely known negative relationship between latitude and clutch size.
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Date Issued
2008
Identifier
CFE0002473, ucf:47706
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002473
Juvenile Ornamentation: Its Evolution, Genetic Basis, and Variation Across Habitats
Title
Juvenile Ornamentation: Its Evolution, Genetic Basis, and Variation Across Habitats.
Creator
Tringali, Angela, Noss, Reed, Bowman, Reed, Fauth, John, Fedorka, Kenneth, University of Central Florida
Abstract / Description
Ornamental traits are considered honest advertisements of fitness, and their evolution is usually explained in terms of sexual selection. This explanation remains unsatisfactory in some instances, for example, juvenile birds whose plumage is molted prior to adulthood and breeding. I first evaluate whether juvenile plumage reflectance signals dominance status in the Federally Threatened Florida scrub-jay (Aphelocoma coerulescens) using a combination of observational and experimental methods....
Show moreOrnamental traits are considered honest advertisements of fitness, and their evolution is usually explained in terms of sexual selection. This explanation remains unsatisfactory in some instances, for example, juvenile birds whose plumage is molted prior to adulthood and breeding. I first evaluate whether juvenile plumage reflectance signals dominance status in the Federally Threatened Florida scrub-jay (Aphelocoma coerulescens) using a combination of observational and experimental methods. Then I estimate the heritability, non-genetic maternal and environmental effects, and strength of selection on juvenile plumage reflectance using archived feather samples and a pedigree constructed from historical nest records. Finally, I compare plumage reflectance and its use as a signal between a wildland and suburban population of scrub-jays. I conclude that plumage reflectance is a signal of dominance, and that social selection can also drive the evolution of sexually dimorphic traits. In this species, plumage reflectance is heritable and influenced by maternal effects, but environmental effects are inconsequential. Although this trait appears to have an important function, only mean brightness and female hue are associated with lifetime reproductive success. Plumage reflectance was more UV-shifted in the suburban birds, but there is no reason to believe that urbanization decreases the value of this plumage as a signal. However, these plumage differences may facilitate dispersal from suburban areas, contributing to the decline of suburban populations.
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Date Issued
2013
Identifier
CFE0005431, ucf:50413
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005431