Pedernales Falls State Park Prothonotary Warbler Nest Box Study: Nesting Blue Grosbeaks & Nest Box Updates

Prothonotary Warbler Occurrence In Texas

Central Texas draws the western line for the Prothonotary Warbler range. This species occupies much of eastern North America up to the southern boarder of Ontario Canada.
Prothonotarys' nest in natural cavities but also readily use nest boxes located on or near water. Flooded swamps represent ideal habitat but they will also nest along rivers or small bodies of water.
In May 2007 I saw a brightly colored male Prothonotary Warbler at Pedernales Falls State Park bird blind. After some research I learned male birds have been seen building nests in neighboring counties to Blanco County. Further research revealed a pair of Prothonotary Warblers successfully nested at Heard Wildlife Sanctuary in McKinney, Texas.
In December 2007 I decided to undertake a nest box study at the park. January through February 2008 I hiked the entire Pedernales River and tributaries within park boundaries, in an effort to choose the best sites. Habitat selection proved a challenge do to high flood levels along the river.
Five sights were eventually selected where two nest boxes each were placed. Most boxes were attached to trees however two were attached to metal poles. These boxes were monitored from March through June 2008 on a weekly basis. A Breeding Bird Study was conducted at each nestbox location in 2008 and will be continued in 2009.

Thursday, May 29, 2008

Nesting Blue Grosbeaks & Nest Box Updates

Today was a treat being out at the park surveying breeding birds during the week. The campground and trails were quite peaceful with few visitors. Once again I had Common Nighthawks active through mid morning. The highlight was finding a pair of Blue Grosbeaks building a nest near the Pedernales River and Twin Falls Creek. This male is a first year bird with only a blue head.
I found the Rufous-crowned Sparrow for the second week in a row along Wolf Mountain Trail at the location pictured with my mountain bike. This sparrow has a beautiful song.

The flowering Yucca is a Twisted leaf Yucca in bloom and visible along many roads in the Texas hill country.
Today I opened each nest box to see what critters were occupying them. They almost all turned out to be in the Insect order, other than one Arachnid.
A wasp species was found in six nest boxes, three boxes were entirely empty, three had the Organ-Pipe Mud Dauber Wasp, and one had Cock Roaches. The Mud Dauber is docile. It paralyzes a spider, places it in a vertical mud cylinder, then lays an egg never to return to the nest.

The Acadian Flycatcher is still present at Tobacco Creek. There are four species of warbler nesting along the river at nest box sites, the Louisiana Waterthrush, Black & White Warbler, Northern Parula, and Golden-cheeked Warbler. Water levels in the Pedernales River continue to drop from lack of rain. I snapped this photo, a tranquil river scene from East Park Boundary.