Nighthawk speciation

Speciation in the Common and Antillean Nighthawks

The ranges of the Common Nighthawk (Chordeiles minor) and Antillean Nighthawk (Chordeiles gundlachii) meet in the Florida Keys, with Antillean being primary a Caribbean species, and Common widespread in continental North America. The two species expanded their ranges into the Florida Keys in the 1960s, likely tied to the clearing of land for human development, so this contact zone between the two species represents a recent case of secondary contact that is of great research interest. We are studying these two species and the area of contact for insights into how new species form and how they are maintained once they regain contact (i.e., secondary contact).

Common and Antillean Nighthawks look nearly identical, but sound extremely different. However, where their ranges meet in the Florida Keys, birdwachers have noticed and sound recorded vocally intermediate birds.

Undergraduate student researchers have led the charge on this research project, conducting analyses of vocalizations using data from the Macaulay Library of Natural Sounds and Xeno-Canto. They have also conducted behavioral experiments in the field by broadcasting sounds of the same and the different species and measuring the responses of wild birds to these sounds.

These two species of nighthawks are of further interest because in addition to species-specific vocalizions, the males of both species perform impressive aerial displays to attract females, in which they produce a mechanical sound with the wing feathers, coloquially known as a “boom”.

On the left, Dr. Johnson, and undergraduate researchers Malena Sellen and Abby Knepprath, sound conduct behavioral experiments on nighthawks on Big Pine Key. On the right, a photo sequence of a displaying Antillean Nighthawk on Big Pine Key. Both nighthawks dive from a great height and produce a "booming" mechanical sound with feathers of their wings at the bottom of the dive.

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