George Burritt Sennett, businessman and naturalist, the only child of Pardon and Mary (Burritt) Sennett, was born in Sinclairville, New York, on July 28, 1840. The family later moved to Erie, Pennsylvania, where Pardon Sennett was engaged in the iron-smelting industry. George received his formal education at Erie Academy and at a preparatory school in Delaware County, New York. He spent four additional years traveling in Europe, where he informally studied literature and languages. In 1865 Sennett returned to the United States and assumed the management of his father's ironworks in Meadville, Pennsylvania. His father died around 1879, leaving George heir to the family interests. During the 1870s and 1880s Sennett helped form the Meadville Library, Art and Historical Association and served as president of the Meadville Natural History Society and the Meadville Glass Company, and as mayor of Meadville. In 1896 he moved his factory to Youngstown, Ohio.
Sennett is best known for his studies of Texas birds, particularly those of the lower Rio Grande valley. He made collecting trips to Texas in 1877, 1878, and 1882, and thereafter secured specimens from Texas and Mexico by means of paid collectors. His extensive collection, accumulated between 1877 and 1900, is deposited in the American Museum of Natural History in New York City. During the spring of 1877 Sennett and his assistant, Frederic Smith Webster, collected briefly at Galveston, Corpus Christi, and Brownsville, and then at Hidalgo, their base of operations. The published account of the 1877 expedition consisted of an annotated list of 150 species, including the description of Sennett's olive-backed warbler, and the first records of the northern ferruginous owl, the white-fronted dove, and Weid's crested flycatcher in the United States. Sennett was assisted on his 1878 trip by Elbert Jasper Newton Sanford. On March 19, 1878, the two men arrived in Corpus Christi, where they collected along the coast. They arrived at Port Isabel on April 3 and traveled to Lomita Ranch, eight miles above Hidalgo, where they continued to collect until May 25. They recorded 168 species on this trip, two of which were new subspecies, the Rio Grande turkey and the Lomita wren, and four of which were species new to the United States: the Texas kiskadee flycatcher, the groove-billed ani, Sennett's white-tailed hawk, and the beardless flycatcher. The total number of specimens collected during the 1877 and 1878 expeditions totaled about 1,000 bird skins, 2,400 eggs, numerous insects, and a few mammals, reptiles, and fish. After 1878 Sennett continued to receive specimens from J. B. Burbois at Lomita Ranch, and from February 1880 through May 1881 Marston Abbott Frazar collected for Sennett in Hidalgo, Starr, and Cameron counties.
In 1882 Sennett made his third journey to Texas. He arrived on April 21 at Corpus Christi, where he met the naturalist Benjamin Franklin Goss from Pewaukee, Wisconsin. Accompanied by two assistants, the naturalists collected for several days near Corpus Christi. The results of the 1882 trip were never published. John Marion Priour assisted Sennett and Goss in 1882, and by 1886 Priour was providing Sennett with specimens on a regular basis. In the spring of 1887 Priour collected between Corpus Christi and the Brazos River. The numerous specimens he provided enabled Sennett to establish new breeding records for several coastal birds, as well as material for descriptions of three new subspecies: Merrill's pauraque, the chestnut-fronted titmouse, and the Texas tufted titmouse. During 1887 collections made by William Lloyd in the Trans-Pecos provided the specimens from which Sennett described Lloyd's bushtit. During the spring of 1888 Sennett financed a collecting expedition by John Priour and Charles E. Grover to Tampico, Tamaulipas. In 1889 Priour, accompanied by his brother Isadore, again returned to Mexico to collect specimens around Monterrey. The results of the collections made in Mexico were never published.
In 1883 Sennett became one of the original members of the American Ornithologists' Union, and in 1886 he was elected chairman of the Committee on the Protection of North American Birds, a position he held until 1893. In 1887–89 he also served as president of the Linnaean Society of New York. Sennett labored for several years to prepare a monograph on the avifauna of the lower Rio Grande. As he became more involved with business during the 1890s, however, his scientific productivity began to decline, and the work remained uncompleted upon his death. In seventeen articles comprising over 175 pages, Sennett described two new species and eight new subspecies of Texas birds. He is also memorialized by four subspecies of Texas birds, a species of rodent, and a moth that are named in his honor. In the mid-1860s Sennett was married to Sarah Essex, a union to which one daughter was born. Sennett died on March 18, 1900, in Youngstown, Ohio.