Research Objectives:

1. Determine whether golden-cheeked warblers us social information in habitat selection.

2. Investigate the relative influence of social information for habitat selection in the context of different habitat vegetation structure and composition.

3. Investigate the fitness outcomes of habitat selection decisions influenced by social information.

Management Implications:

1. Use of social information in habitat selection can drive species distributions within available habitat, potentially leading to patchy, clumped, or aggregated distributions.  Knowledge of the mechanisms influencing bird distributions is essential for understanding current distributions, creating accurate predictive habitat models, estimating population, predicting potential impacts of habitat alteration, and developing effective management strategies. 

2. Social information, in the form of conspecific location cues, may be a useful management tool for establishing occupancy in restored patches of habitat.  But, if this manipulation is applied in habitat that is low quality (e.g., due to high parasitism or predation), it could lead to ecological traps by attracting birds into areas that lead to poor fitness outcomes for adults or yield low reproductive success.  Understanding how social cues influence habitat selections in the context of other habitat characteristics is critical to effective use of this potential management tool.

3. Negative intra-specific interactions, primarily competition, have long been considered the primary force driving species habitat use and distribution.  Investigating the influence of positive intra-specific interactions can lead to better understanding of the behaviors and ecological factors influencing species distributions.

Project Summary:

Researchers investigating species distributions and habitat use have often focused on associations between species presence and vegetative, geologic, and geomorphic habitat characteristics.  Where inter and intraspecific behavioral interactions are considered, research and theory has emphasized the role of negative interactions including negative density dependence and niche in driving assemblage patterns and habitat use.  Positive intra-specific interactions may be important not only for structuring communities, but for influencing habitat use and consequent species distributions. Attraction to the presence of conspecifics may be an efficient strategy for habitat selection.  Migratory birds often have to select a breeding site and establishing a territory within a short time period, during which information about the important limiting factors on these sites may be spatially and temporally difficult to detect.  With incomplete information about the habitat, selecting a breeding site based on the presence of other birds, which can act as indicators of habitat quality, may be an effective strategy.  Additionally, aggregating in groups can provide additional benefits including group vigilance against predators, predation dilution, increased foraging success, increased probability of mating, and increased opportunity for extra-pair copulation.

We are conducting randomized, replicated manipulative experiments to determine if golden-cheeked warblers use conspecific social information to select breeding habitat.  In 2008, we conducted an experiment using broadcast of conspecific vocalizations on sample units during the settlement period in areas identified as optimal habitat that were known to be occupied by warblers in previous breeding seasons.  In 2009, we applied conspecific vocalization treatments to sample units considered suboptimal habitat based on vegetation characteristics to determine if warblers respond to these cues in this habitat.  To determine if warblers use post-breeding social cues for habitat selection in subsequent years across a range of habitat vegetation types, we applied conspecific vocalization treatments to sample units with varying levels of woodland canopy cover; we will measure the response in 2010. We use territory mapping to quantify the number of warbler territories established on treated and control units.  Our preliminary results show a higher territory density on treated units.