Complex sentence: They are even observed to occasionally share nest sites with other species of swallows, such as Barn Swallows, particularly in north central Mexico and increasingly in the United States with the use of highway culverts as nesting sites.
Split into simpler sentences: They are even observed to occasionally share nest sites with other species of swallows, such as Barn Swallows. This occurs particularly often in north central Mexico and increasingly in the United States with the increased use of highway culverts as nesting sites.