Vaux’s Swift Migration

Vaux’s Swifts have been roosting in the Rio Lindo Adventist Academy chimney since 1989, the first year the school’s boiler wasn’t producing steam year-round. The chimney is still used in the winter when the boiler generates heat for the school campus, but that is after the fall migration. The first small groups of migrating birds usually appear in mid-August. The numbers increase and generally peak between September 10 and 20. In an average year, the count peaks between 5,000 and 10,000 birds for a few evenings. The highest numbers that have been observed were in 2015 when a couple evenings the estimate was above 35,000 birds. The lowest was in 2005 when the highest count was only 300.

The incredible sight of thousands of birds flying in a tornado-like pattern against the dusk sky is simply incredible. Bird and nature enthusiasts travel from all over to see this unforgettable phenomenon. Most years, the birds arrive the first week of August and leave at the end of September. Check back with this website as numbers are posted on a regular basis.

Videos can be seen here from KQED’s California Report.

Visitors Welcome

We are glad to welcome visitors to our campus to see the swifts. We only ask that you remember this is a boarding high school campus with students present 24 hours a day, seven days a week, which means no smoking or alcohol is allowed on the campus. Please keep dogs on a leash, even friendly ones. Also, please stay in the area of the chimney and do not roam the campus. Keep in mind that we do not know exactly when they will arrive for the evening or when they will begin to enter the chimney. Generally the best time to arrive on the campus is 30 minutes before sundown. We have observed that the time they begin to enter the chimney is sensitive to the air temperature (the colder it is the earlier they enter the chimney), sundown, and the number of birds here entering the chimney (the higher the number the earlier they begin to enter).

Swifts are counted by timing from the moment the swifts enter until they finish and multiplying the number of minutes by 360, which is determined by a video calculation that was performed by the Audubon Society in the early 1990s. The number is only an estimation and not precise.

Swift Count for 2016

Date

Number of swifts

Aug. 7 100
Aug.14 240
Aug. 16 750
Aug. 20 1070
Aug. 27 6,900
Sept. 1 3,400
Sept. 2 2,700
Sept. 3 1,100
Sept. 4 3,600
Sept. 5 2,600
Sept. 6 1,000
Sept. 7 2,200
Sept. 8 3,100
Sept. 9 3,600
Sept. 10 4,500
Sept. 11 8,500
Sept. 12 29,000
Sept. 13 14,000
Sept.14 11,000
 Sept. 16 11,000
Sept. 17 6,300
Sept. 18 4,500
Sept. 19 1,900
Sept. 21 3,300