The Disappearance

When birds are migrating in spring it is fairly easy to notice when a new species arrives.  One day yellow-billed cuckoos are not here and the next day they are.  But in fall migration it is harder to track the disappearance of a species when they fly south.  Since absence of evidence is not evidence of absence, we paid particular attention to the last date we recorded Chimney Swifts and Ruby-throated Hummingbirds in our area.  These small birds undertake heroic migrations in the fall of the year.  Some Ruby-throated Hummingbirds fly non-stop across the Gulf of Mexico and Caribbean Sea to their wintering territories in Mexico and Central America.  Others take the land route around the Gulf through Texas and further south.  Chimney Swifts winter in the Amazon Basin of South America with a hazardous migration similar to that of the hummingbirds. 

We had a hummingbird family in our yard this summer.  A male and a female visited our feeders daily and later in the summer at least one immature hummingbird was with them.  Then in August, the male disappeared.  Did he and the family go south?  Absence of evidence.  In August and into September large numbers of female and immature hummers were in our yard drinking the sugar water.  The number of hummingbirds started to decline in October and we made the final sighting of the year on October 19. 

Chimney Swifts entering a chimney at sunset

Chimney swifts disappeared a few days before the hummingbirds, on October 15.  In the fall of the year, you can find large flocks of migrating chimney swifts around their roosting spots.  Since these birds cannot perch on a limbs or wires, they must cling to a vertical surface, like a chimney, to nest or sleep. Before Europeans entered the new world, Chimney Swifts probably roosted in hollow trees and on cliffs.  

 A local high school has a stack for an unused furnace that is ideal for a chimney swift roost.  We have recorded over 3000 swifts flying into this stack during September.  The swifts begin flying near the chimney around sunset giving their chattering call.  Then the number grows and they begin to form a vortex of swifts hundreds of yard wide.  A half an hour after sunset as the light is disappearing the swifts begin to enter the stack.  The vortex gets smaller and smaller until the last swifts fly into the chimney as total darkness descends.   

We look forward to these birds showing up again next spring.