Cattle Egrets (Bulbucus ibis) are fairly recent arrivals to the Western Hemisphere. They first arrived in Florida from South America by way of the Caribbean Islands around 1953 and have rapidly spread north and west since then. Cattle Egrets are now well established year round residents in South Texas.
These birds are generally found in large flocks in upland areas particularly where cattle grazing is common as they have a commensal relationship with large, grazing herbivores of all kinds. It is not unusual, however, to find their breeding rookeries close to streams and lakes. With the ecological restoration beginning to take hold along the Mission Reach of the San Antonio River, flocks of Cattle Egrets are beginning to be sighted on and near the banks of the river:
There are at least three distinguishing characteristics that differentiate the Cattle Egret from the other two white egrets, the Great Egret and Snowy Egret, that are also commonly seen along the Mission Reach. Cattle Egrets have red-orange feathers on the top of their heads and the top of their backs. Cattle Egrets have yellow or orange beaks, yellow legs and yellow feet. And Cattle Egrets are almost always seen in large flocks while the other two egret species are generally solitary or in pairs. For comparison, here are a Great Egret on the rock to the left and a Snowy Egret just past the weir to the right:
I probably should note that in the photo of the pair flying close together, it appears as if their feet are black. This pair had just taken off from the muddy river bank, so their feet still have a thin coating of mud on them making them appear darker than they really are.
This set of photographs was taken on my walk along the Mission Reach on Wednesday, July 2, 2014 about a third of a mile or so north of the Loop 410 bridge.
Tuesday, July 9, 2013
Elmendorf Lake Park
Today's photos:
Elmendorf Lake is one of numerous critical ecological resources in the City of San Antonio and the San Antonio River watershed. The Lake and Bird Island serve as a major nesting and breeding site for both year around and migratory birds. The duck, heron and hawk species that winter over in Bexar County have flown to their summer nesting grounds. Cattle Egrets, Green Herons and Cliff Swallows have settled in for the summer.
The ecosystem around the Lake is capable of supporting a diverse biological community in spite of numerous water quality and invasive plant issues that have plagued the Lake for decades. The Elmendorf Lake Improvement Project will preserve the bird habitat, including Bird Island, and address the ecological issues. The Project also provides an added benefit of creating an excellent resource for watershed ecology education.
- The first photo is a view looking across the Lake with Bird Island in the foreground. The beautiful Sacred Heart Conventual Chapel and the twin spires of the Main Building at Our Lady of the Lake University are in the background.
- The second photo is a detailed view of Bird Island. The high population of egrets and cormorants is clearly evident in this photo.
- The third photo is of a Broadleaf Cattail inflorescence. Cattail are monoecious plants having separate male and female flowers on the same plant. The female flowers here are the easily recognized "cat tail." The male flowers are higher on the stalk at the top of the photo. The cattail are widely distributed native plants that have a tendency to dominate a wetland habitat creating a monoculture if not controlled. There is an over abundance of cattail growing along the bank of the Lake.
- The fourth photo is a Creeping Water-Primrose (Ludwigia peploides (Kunth) Raven). This is a different species of Water-Primrose than the one I have photographed along the San Antonio River which is Ludwigia octovalvis (Jacq.) Raven.
- The fifth photo is a Green Heron.
- The sixth through ninth photos are of a Neotropic Cormorant taking flight from the surface of the Lake.
- The tenth through twelfth photos are of Trumpet Creeper. This vine is growing on a Black Willow tree on the bank of the large island.
- The thirteenth photo is one of beautiful, large Bald Cypress trees growing along the bank of the large island.
- The fourteenth photo is a Red-eared Slider Turtle swimming in the Lake.
- Also in the fourteenth photo: One of the ecological problems in the Lake is the tendency to have algal blooms, especially in the summer, due to the lack of water circulation and the high levels of nutrients from runoff following rain events. The very high concentration of algae is clearly visible in this photo. The decaying algae falls to the bottom and rapidly depletes the dissolved oxygen creating dead zones below the water surface.
- The fifteenth photo is a Fox Squirrel munching away on Bald Cypress cones.
- The sixteenth photo is a view of Bird Island as seen looking east from the SW 24th St bridge.
- The seventeenth through twentieth photos are Cliff Swallows flying out over the Lake from their nests under the SW 24th St bridge.
- The twenty-first photo is of two Double-crested Cormorants sitting on top of a tree on Bird Island. According to multiple sources, Double-crested Cormorants are rarely seen in Bexar County during the summer, but I have seen several both here at Elmendorf Lake and along the San Antonio River the past couple months.
- The twenty-second through twenty-fourth photos are Cattle Egrets with their very distinctive breeding plumage. There are also Great Egrets and Snowy Egrets nesting on Bird Island, but the Cattle Egrets currently are the most numerous.
* I am resisting the temptation to take While on a Walk in a distinctly academic direction. I have given much thought to the concept of "Critical Ecological Resources" this week. I realized this evening, I have another book to add to my list of "Books in Progress."
