Complex sentence: It ranges from South Texas (where it is rapidly expanding) to northern Colombia; west and north of the Isthmus of Tehuantepec it is limited to the Atlantic slope, except for a population around Oaxaca City that probably originates from escaped cagebirds.
Split into simpler sentences: It ranges from South Texas (where it is rapidly expanding) to northern Colombia; west and north of the Isthmus of Tehuantepec. It is limited to the Atlantic slope, except for a population around Oaxaca City that probably originates from escaped cagebirds.