Bexar County is in a unique and critical location along the migratory bird North American Central Flyway. The riparian habitats along the San Antonio River and its numerous tributaries here provide the necessary water and fuel sources for these birds. This is one of the first stops in the Spring as they arrive from their flight north across the Gulf of Mexico and the last stop in the Fall before they begin their flight south across the Gulf.
As I mentioned briefly in "A Distinctive Bark," many of the migratory birds, particularly the song birds such as the thrushes and sparrows, rely on the fruit of the Sugar Hackberry trees to provide the necessary energy reserve for their fall migration. There are a number of species of birds that primarily eat insects and other small invertebrates during the nesting season that eat berries and seeds during their migration. The Hackberry fruit are very high in sugar and essential oils and the seeds rich in protein:
Of course, birds aren't the only animals that rely on these berries to help them survive the fall and winter. Numerous mammals, such as possums, raccoons and deer, find them quite appealing. For the most part, people stopped eating these berries after the invention of agriculture, but Hackberry fruit was one of the staples for hunting and gathering societies living where these trees were abundant.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Thursday, October 17, 2013.
The Sugar Hackberry is easily identified solely by the appearance of its bark. There is no other tree that I'm aware of with a knobby bark that looks anything like the Hackberry:
Unfortunately, the Sugar Hackberry has acquired the reputation of being a weed tree, especially in urban landscaping. They reseed easily. The ground along a chain link fence is prime territory for Hackberry seedlings that spring up from seeds in bird droppings. The branches tend to be weak and break off with relative ease, so they are definitely not desirable close to houses or driveways.
On the other hand, the Sugar Hackberry is one of the most valuable trees for wildlife in the United States. Over 200 species of animals depend on the Hackberry. The Hackberry is the larval host for at least four species of butterflies. Migratory birds rely on the Hackberry fruit as a primary source of energy for their fall and winter migration as the fruit and seeds are high in essential oils.
This pair of photographs was taken along the Hondondo Creek Nature Trail in Alamo Heights on Monday, September 9, 2013.
