Research Objectives:

1. Determine the influence of the impacts on the abundance of birds in relation to distance from the road.
   
   
2. Determine the spatial and temporal influence of the impacts on breeding success and behavior in relation to distance from the road.
   
   
3. Determine the extent to which vocal adjustment or other behaviors is being utilized by birds in response to
   unnatural noise.
   
   
4. As indicated from study results, determine the spatial and temporal extent of impacts to study species caused by the impacts; and make recommendations designed to alleviate negative impact

Management Implications:

1. Changing the daily timing of construction activities
   
   
2. Eliminating or reducing certain activities during the breeding season
   
   
3. Using equipment to muffle the sound of construction equipment

Project Summary:

Noise pollution can mask or distort birds’ songs, which inhibits mating success, predator detection, and parental response to begging calls.  Road noise can cause lowered density, abundance, and reproductive success in songbirds.  Birds may compensate for noisy backgrounds by adjusting the frequency and amplitude of their songs, at higher energetic costs.  Road-noise impacts may increase with the addition of construction noise. 

This study will assess the density, abundance, reproductive success, and vocalization characteristics of golden cheeked-warblers (Dendroica chrysoparia) near active road construction.  Our study sites are located in Real and Uvalde County, Texas along U.S. Highway 83.  We use a reproductive index to evaluate productivity, and automatic recording units to capture and evaluate song characteristics.  The study began in March 2007 and we completed the 3rd field season in June 2009.  We monitor birds on 3 sites:  a road construction site, a road-noise only site, and a control site with no noise or activity.  Reproductive success for the golden-cheeked warbler in 2007 was 90% in the road construction site, 92% in the road-noise only site, and 78% in the control site.  Sixty-two percent of pairs in the road construction site, 93% in the road-noise only site, and 62% in the control site produced at least one fledgling in 2008.  Mean productivity on all sites was 71% in 2008, compared with 88% in 2007.  Birds located in the impact and control sites were 31.5% less productive than birds in the road-noise only site.  During the 2008 and 2009 field seasons we also examined the immediate behavioral response of the warbler to construction noise, and whether the warbler is habituating to construction noise.  We established broadcast stations that simulated construction noise to determine impacts on territory selection and site fidelity.  We placed stations in 3 locations randomly selected from known golden-cheeked warbler territories from the previous year.  We also played recordings of construction noise to individual golden-cheeked and black-and-white warblers in order to examine their immediate behavioral response to introduced construction noise.  In 2008, 2 of the territory centers shifted away from the broadcast units (71m and 27m) and 1 shifted 86m towards the broadcast unit.  Two golden-cheeked and 2 black-and-white warblers responded to playback; these birds were located >200m from the road.  Results of these experiments will determine if golden-cheeked warblers alter behavior in the presence of construction noise, if they have habituated to construction noise in this portion of their range, and whether habituation is hindering productivity. 

In order to evaluate potential changes in vocalization characteristics of golden-cheeked warblers in relation to construction noise, we are collaborating with Zac Loman and Joe Szewczak from Humboldt State University in Arcata, California.  They use Automatic Recording Units (ARUs) to gather audio data on the warblers’ songs and ambient noise.  ARUs are stationed near active golden-cheeked warbler territories throughout the breeding season.  After the season, the long recordings are evaluated using SonoBird™.  This program identifies golden-cheeked warbler vocalizations and allows us to determine whether the birds are using vocal adjustment strategies to compensate for road or construction noise.  Preliminary results show that in 2007 and 2008 there were no differences in vocalizations among birds on the 3 study sites, nor were there differences between vocalizations before 9am v. after 9, early season (before April 15th ) v. late Season (after April 15th),  or between recording year.  However, birds recorded at different locations exhibited significant differences from other individual birds, suggesting that there is individual variation in song between individuals.  The differences in songs between individuals occurred without any apparent consistent tie to noise exposure, distance to highway ROW or transect type.