Minimizing the cost of competition in the black-crested titmouse: status signaling, dominance, and foraging behavior

Status signals allow senders and receivers to minimize the costs of competition by minimizing the need for costly physical fights. While much research has focused on demonstrating that individuals respond to status signals in both breeding and non-breeding contexts, less is known about how the function of status signals may change as resource availability changes seasonally. In this thesis, I provide a basic review of status signaling in birds and report the results of an investigation on status signaling in the black-crested titmouse during different environmental conditions. The black-crested titmouse is a socially monogamous passerine that defends territories throughout the year. This species forms small family groups during the breeding and post-breeding season, which dissolve into mated pairs during the non-breeding and pre-breeding seasons. Using an array of supplemental seed-feeders outfitted with RFID technology, I investigated the relationship between the crest size of adult male titmice and their foraging behavior during the post- and pre-breeding seasons. I also investigated the effect of both crest size and dominance on an individual’s ability to maintain baseline foraging behavior after approximately half of the feeders were removed. I found that birds with larger crests had greater access and monopolization of feeders during the post-breeding season, but not the pre-breeding season. When the number of available feeders were reduced during the pre-breeding season, males that monopolized their most-used feeder the most during baseline, and males that had longer crests, reduced their access to the feeders relatively less than other birds. Taken together, these findings indicate that the crest is used to signal status, particularly during times of increased competition (i.e. due to seasonal fluctuation in resources or increased competition between family groups)

Painted Bunting (\u3cem\u3ePasserina ciris\u3c/em\u3e) Caught in the Web of a Giant Lichen Orb-Weaver Spider (\u3cem\u3eAraneus bicentenarius\u3c/em\u3e)

Orb-weaver spiders weave large webs that are capable of entrapping various species of birds. We report a case of a male Painted Bunting (Passerina ciris) caught in the web of a giant lichen orb-weaver (Araneus bicentenarius). Most cases of bird entrapment in spider webs involve spiders with larger webs (often Nephila sp.) and very small birds, usually hummingbirds. Our case is noteworthy because we report a relatively large bird caught in a relatively small web. Furthermore, the geographic distribution of A. bicentenarius extends beyond the tropics and subtropics, which is where most reported cases of bird entrapment occur. This observation suggests that even small orb-weaver webs may pose a threat to relatively large birds, and that this risk may extend well beyond the regions most commonly associated with entrapment

Seasonal Variation in the Utility of a Status Signaling System: Plumage Ornament Predicts Foraging Success Only During Periods of High Competition

Status signals allow competitors to assess each other’s resource holding potential and reduce the occurrence of physical fights. Because status signals function to mediate competition over resources, a change in the strength of competition may affect the utility of a status signaling system. Status signals alter competitor behavior during periods of high competition, and thus determine access to resources; however, when competition is reduced, we expect these signals to become disassociated from access to resources. We investigated seasonal changes in status signaling of the male black-crested titmouse (Baeolophus atricristatus), a species that experiences substantial changes in population density and competition for food over the annual cycle. We compared the size of the prominent head-crest to foraging success at community-used feeding stations; we tested this relationship when competition was seasonally high, and when competition was seasonally low. We then experimentally decreased the number of feeders to increase competition (during the season of low-competition), and again tested whether male crest size predicted access to feeders. When competition was seasonally high, males with longer crests had greater access to feeders, but this pattern was not apparent when competition was seasonally low. When competition was experimentally increased, males with longer crests were again more successful at maintaining access to feeders. These findings provide evidence of a context-dependent status signaling system, where the status signal only mediates access to resources during periods of high competition. We discuss possible hypotheses for why the signaling system may not be functional, or detectable, during periods of low competition, including that competitors may interact less frequently and so have reduced opportunity for signaling, or that status signals are disregarded by receivers during periods of low competition because signalers are unlikely to escalate a contest into a fight. In any case, these results indicate that resource availability affects a status signaling system, and that the potential for status signaling persists in this system between seasons, even though such signaling may not be overtly present or detectable during periods of low competition

Fracking Up the Future: Recommendations for Hydraulic Fracturing in Gonzales County, TX

Despite its economic appeal, hydraulic fracturing (fracking) has sparked bitter controversy. Allegations of toxic fracking fluids and fracking-induced droughts have made fracking a major public health and environmental concern in the United States. Fracking is dependent on local conditions to a large degree; therefore, we focus on Gonzales County, located within Texas’ Eagle Ford shale region, in order to address county-specific concerns. However, our findings can be applied to help create sustainable practices for fracking in any context. Unfortunately, regulations are limited due to the 2005 Energy Policy Act that prevents federal agencies, including the EPA, from regulating fracking. In order to minimize the external costs of fracking, our research indicates that effective regulations need to be enacted to protect people and the environment from major fracking concerns including overdrawn water sources, wastewater contamination, and chemical releases. We propose that implementing effective regulation will make fracking safer and more profitable for all stakeholders in the long run. Using the catastrophic Deepwater Horizon oil spill in the Gulf of Mexico, we provide a comparison model that is analogous to the current Railroad Commission of Texas’ regulations on fracking. Furthermore, we outline a case study on post-fracking water to demonstrate how a thorough analysis of current practices can create robust recommendations for safer and sustainable fracking practices in the Eagle Ford shale. Finally, our recommendations for fracking in Gonzales County provide possible solutions to many of the concerns associated with fracking

Honesty of a Dynamic Female Aggressive Status Signal: Baseline Testosterone Relates to Bill Color in Female American Goldfinches

Status signals are linked to fighting ability and enable competitors to gain access to resources without risking injury in aggressive combat. The relationship between testosterone (T), a hormone that mediates aggression, and signals of status is well studied in males, but little is known about the relationship between T and female signals of status. Female and male American goldfinches Spinus tristis express a dynamic carotenoid-based orange bill color during the breeding season and previous work has demonstrated that females use orange bill color to communicate competitive ability during intrasexual competition. We test the hypothesis that female bill color reflects baseline T, which would allow receivers to directly assess a competitor\u27s aggressive potential. We found a positive relationship between T and bill coloration in females, indicating that bill color has the ability to signal female competitive status. This finding is consistent with the hypothesis that female bill color is a reliable signal of fighting ability, and indicates that females, like males, may use coloration to signal their hormonally mediated aggressive potential

Data from: Seasonal Variation in the Utility of a Status Signaling System: Plumage Ornament Predicts Foraging Success Only During Periods of High Competition

Status signals allow competitors to assess each other’s resource holding potential and reduce the occurrence of physical fights. Because status signals function to mediate competition over resources, a change in the strength of competition may affect the utility of a status signaling system. Status signals alter competitor behavior during periods of high competition, and thus determine access to resources; however, when competition is reduced, we expect these signals to become disassociated from access to resources. We investigated seasonal changes in status signaling of the male black-crested titmouse (Baeolophus atricristatus), a species that experiences substantial changes in population density and competition for food over the annual cycle. We compared the size of the prominent head-crest to foraging success at community-used feeding stations; we tested this relationship when competition was seasonally high, and when competition was seasonally low. We then experimentally decreased the number of feeders to increase competition (during the season of low-competition), and again tested whether male crest size predicted access to feeders. When competition was seasonally high, males with longer crests had greater access to feeders, but this pattern was not apparent when competition was seasonally low. When competition was experimentally increased, males with longer crests were again more successful at maintaining access to feeders. These findings provide evidence of a context-dependent status signaling system, where the status signal only mediates access to resources during periods of high competition. We discuss possible hypotheses for why the signaling system may not be functional, or detectable, during periods of low competition, including that competitors may interact less frequently and so have reduced opportunity for signaling, or that status signals are disregarded by receivers during periods of low competition because signalers are unlikely to escalate a contest into a fight. In any case, these results indicate that resource availability affects a status signaling system, and that the potential for status signaling persists in this system between seasons, even though such signaling may not be overtly present or detectable during periods of low competition