Performing Department
Wildlife Ecology and Conservation
Non Technical Summary
Objective 1) Causes of vocal complexity in family Paridae (chickadees and titmice). Fundamental questions in the study of communication relate to signal complexity. Why is there incredible diversity in signal complexity? What factors select for signal complexity? Several hypotheses offer potential insight into these questions. A recent hypothesis to explain signal complexity in animals is the Social Complexity Hypothesis (Freeberg and Krams 2015) and my colleagues and I are testing this hypothesis rigorously for a vocally prodigious family of birds, chickadees and titmice (family Paridae). According to this hypothesis, species or populations that form complex social groups require more complex signaling systems and generally have greater cognitive capacities than species or populations that form simpler social groups (Sewall 2015). My colleague and Co-PI, Todd Freeberg, is the leading proponent of the "social complexity determines vocal complexity hypothesis" and we are currently addressing this hypothesis in a regionally comprehensive research study with parids that also addresses key alternatives. Together with Jeffrey Lucas of Purdue, Todd and I are testing all three of the following hypotheses with experimental and comparative approaches. Aiding us in this endeavor here in Florida is Michael Avery (USDA / APHIS). Social Complexity Hypothesis - Individuals in more complex flocks (e.g., larger or more diverse relationships) produce calls with greater complexity than individuals in simpler flocks. Habitat Constraint Hypothesis - Individuals in habitats that are more open produce calls with greater complexity than individuals in more closed habitats. Predator Pressure Hypothesis - Individuals exposed to a greater number or diversity of predators produce calls with greater complexity than individuals exposed to fewer predators.Objective 2) Consequences of hardwood canopy removal on avian communities. Game bird managers across the southeastern US have converged on a major hypothesis concerning how to increase productivity of bobwhite (Colinus virginianus) in managed pinelands. They refer to this hypothesis as the 'Open Ground' hypothesis (OGH), and testing this hypothesis is the goal of this Objective. There is not much in the white literature on this hypothesis (DeMaso et al. 2014) but landowners in the Red Hills region of N. Florida have accumulated practical observations of positive Bobwhite quail population responses to hardwood canopy thinning (Terhune, pers. comm.; Jones et al. 2009). Research ongoing at Tall Timbers Research Station explores mechanisms whereby this could be occurring, including both top down (hawk and owl predation release) and bottom up (herbaceous regeneration) factors. I am co-advising a graduate student who is testing the hypothesis that the OG effect derives from a reduced numerical and functional predation pressures on selected avian prey (Martin 1993; Gregg et al. 1994). In this case the idea (overall hypothesis) is that reduction of hardwood structure and mast resources will reduce several predator guilds at once: from predatory hawks that perch and nest in the oaks to omnivorous nest predator species dependent on overwinter oak mast such as raccoons, rodents, and (indirectly) their generalist predators (foxes, snakes, etc.; Mixon et al. 2009). In order to test this multi-predator species hypothesis, the team is tracking responses of all of these species in order to test for their linkages to predicted (previously observed) positive responses of grassland birds (Bachman's sparrow, Peucaea aestivalis, and bobwhite) to hardwood reduction (e.g., Wilson et al. 1995). No study has tackled the system-wide linkages and level of trophic complexity that this project is attempting. In collaboration with Tall Timbers, the department of Wildlife Ecology and Conservation is supporting student research to address the predator and avian prey responses to large-scale hardwood removal in a replicated (two large properties) BACI experimental design (before-after-control-intervention). One doctoral student (Kristen Malone) is dedicated to the project already in 2015 and is completing her first intensive field season. Oak removal began in 2015 and will be completed in 2017 such that Malone will have the full range of BACI study periods to analyze. She will continue collecting data through 2018, at least for her dissertation, and TTRS will continue after that
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
Objective 1) Causes of vocal complexity in family Paridae (chickadees and titmice). My objective here is to test three current hypotheses in order to explain the extremely high complexity and information encoding capacity of parid vocalizations. This work is collaborative and ongoing under NSF-IOS Animal Behavior # 1353308 to K.E. Sieving 2014-2018 with Todd Freeberg, Jeff Lucas, and Michael Avery. I will provide the largest amount of detail on this objective for this proposal, as I will be spending the majority of my efforts here and on related topics for the next 5 years.Objective 2) Consequences of hardwood canopy removal on avian communities. Under a cooperative agreement between WEC/UF and Tall Timbers Research Station (TTRS), I am supporting work addressing avian community changes caused by experimental and large-scale hardwood canopy reduction. This work is supported by various competitive, UF, and TTRS funding sources, and as it forms the substance of Kristen Malone's PhD thesis (a student under my advisement).
Project Methods
Objective 1) In FL, the study areas are Ordway-Swisher Biological Station, San Felasco State Park, and Tall Timbers Research Station. Within each population, we work in 5-15 independent flock territories in order to achieve sampling in a total of 90-135 independent flocks. For each flock, we obtain over 100 calls per sample in each 2-month sampling period, in unmanipulated naturalistic settings (after Freeberg and Harvey 2008; Freeberg 2012). This will allow us to assess normative (ambient) call variation, giving us a robust sampling of calls to characterize vocal complexity. Flocks are situated in a variety of habitats with different vegetative densities and this provides the comparative design for assessing the habitat complexity effects on call complexity variation. Additional approaches, described in greater detail below, involving predator stimulus presentations will be used to document vocal complexity in the anti-predator responses of the birds. These field trials will allow us to address the predator complexity hypothesis with a comparative design. Testing the effects of social complexity on call complexity will occur in the field by a comparative design; when flocks are being recorded we will characterize the social structure regarding hetero- and con-specific composition of winter flocks. The hypotheses we will test - Social Complexity, Habitat Constraint, and Predation Pressure - are not mutually exclusive. However the three regions of our studies vary in ways that will allow us to tease the relative importance of each factor apart. For example, conspecific flock sizes for both chickadees and titmice are larger in TN than in FL. Avian predator pressure appears to be greatest in FL and lowest in IN. Comparative Studies: At each research site (Indiana, Tennessee, and Florida) we are collecting calls from flocks of varying social complexity, recordings of playbacks of parid calls along transect points at increasing distances from playback speakers in habitats with different structural complexity, and we are using playback stimuli to elicit the full range of anti-predator call complexity across the three states (varying in predator community complexity). Experimental Studies - Aviaries: Both the Predator and Social complexity hypotheses will be tested experimentally in aviaries at two sites (FL and TN). In 6 aviaries at each site, we will construct flocks of different social composition. Beginning in Year 2 (July 2015 - June 2016), we will bring in chickadees and titmice from wild flocks (that are not part of our field studies described elsewhere). Birds will be housed in the aviaries for periods of 1-2 months. Spectral imaging analyses: Testing predictions deriving from each of these 3 hypotheses requires a variety of acoustic analysis approaches. Measures of vocal complexity require objective categorization of different vocal units. Our inter-observer reliability in scoring of notes of chick-a-dee calls has ranged from 78 - 99% agreement (using conservative Cohen's kappa statistics). We will test inter-observer reliability throughout the proposed work. Vocal complexity here will be analyzed at two levels. First, we will address vocal complexity of the chick-a-dee call in terms of its note composition, as done in recent studies by our labs and others (e.g., Freeberg et al. 2012) and in other parid species (Ficken et al. 1994). Second, we will analyze the note composition diversity of the total call sample from each flock, using uncertainty (bits of information) conveyed by signals (Weaver & Shannon 1963). One uncertainty measure relates to note use, and assesses the diversity and proportional frequency of signal units. This is measured as -Σ[Pilog2(Pi)]. Pi is the probability of each of the i note types occurring in the call sample obtained for each flock. Real uncertainty at this level typically is lower than the maximum possible uncertainty, as note types are not used with equal frequency (Ficken et al. 1994; Bloomfield et al. 2004, 2005; Charrier et al. 2004). The other uncertainty measure relates to note pair use, and assesses the diversity and proportional frequency of ordered pairs of signal units. This uncertainty is measured as -Σ[Pijlog2(Pj i)]. Pij is the probability of the ij sequence of note types, and Pj i is the conditional probability of the j note type occurring in a call given the i note type has just occurred. Calls will be analyzed using Avisoft SASLab Pro, using the Automatic Parameter Measurement function and identical settings across our labs.Objective 2) - no space to describe.