|After a seven year absence, chimney swifts have returned to our chimney to nest. And, better yet, they have brought a second pair with them to nest for the first time in the silo shaft provided for them in 2015. The evening they arrived, one dived into the house chimney flue that had been used previously. The next evening, after 20 minutes of their typical trio flights interspersed with solo or dual flights while gathering insects, a swift was observed diving into the magical trashcan on top of the silo for the first time.|
|The nest and associated twigs above and below the cup. Neither adults nor nestlings were ever observed using these sticks as an aid in clinging to the wall. But all such swift nests have these seemingly randomly placed sticks. Perhaps they serve a purpose in a chimney or on a smooth rock surface.||The 35’ shaft from below. The swallows built their nest 16’ below the entrance.|
|Both swallows contributed to making a saliva semi-circle as seen here above the nest during the incubation phase. Both adults also participate in incubating and in guarding the nest when incubation is not required. At night, both adults were often on the nest, one incubating and the other hanging on the side.||Given the difficult building material- a random assortment of twigs and a great deal of spit, the nest slowly took shape. At first, watching the swifts fussing with each stick, nest building seemed a very awkward process. But, soon I realized that they were very good at what they do. In all the video of nest building, I only saw one small stick dropped. There were only three short twigs at the bottom of the shaft when the young fledged. And, these may have been broken off during the nesting rather than dropped during construction.|
|The 4 eggs seem rather large for the size of the bird. A semicircle of saliva is spread above the cup during the incubation period. Several sticks have been added to the sides of this circle to further anchor the nest. The purpose of completing the arc is unclear.||The observation port with video cam, temperature data logger, and shelf for an Iphone were positioned directly opposite the nest. Another option, perhaps for next year, would be to mount a camera above their next nest. But, in general, I prefer to view at eye level with any creature, if possible.|
|When not incubating, one, or in this case, both adults often remain near the nest. The adults often spend the night side by side on the nest during the incubation period.||Note the stiff tail feather spines extending beyond the end of the vanes. These spines help prop the bird against the wall.|
|3 day old nestlings with adult below the nest. Eggs were laid every other day.||
4 day old nestlings are noticeably larger. All nestlings hatched within 48 hours.
|8 day old nestlings with eyes still closed. Eyes remained closed until around 15 days.||Eight day old being fed. Swifts, including nestlings, have an incredibly huge gape.|
|The two nestlings on the right have an open gape in response to the second adult’s entrance. The two on the left have just been fed.||Feeding is accomplished by the adult placing a bolus of insects deep inside the nestling’s throat.|
|An adult spends a surprising amount of time near the nest during the day. This was not dependent on bad weather. It appeared that the adult was waiting for the mate to return before leaving. At other times, both adults would arrive and leave together.||The first nestling timidly leaves the nest 16 days post-hatch, clutching the wall with no apparent effort. The other three didn't venture out of the nest until the next day.|
|Here the other three nestlings are 18” below the nest. Note the deeply recessed eyes topped with feather “brows”. Also note the small bill which makes the nestlings’ huge gape even more surprising.||All four are waiting to be fed. They have moved out of the video monitor view so feedings were not recorded at this stage.|
The video links below are of continued nest building during the incubation phase. Several of the videos include an interesting interplay between the two adults and involve some shoving. Acquiring each twig may be the hardest part of the nest building process and a swift returning to the nest with a twig seems to have little patience with its mate not moving over or getting off the nest. Nest building may continue until the eggs hatch.
Swift video 2
swift video 3
Afternoon feeding visits were typically less frequent than in the morning. And, the greatest number of feeding visits was in the evening. The same was true for the resident purple martins and barn swallows. The swifts were the last to retire to their nests, but all three species usually gathered their last mouthfuls of insects right in the back yard and immediate surroundings at the end of the day. They often circled low at this time, perhaps because that is where the insects were or because the proximity to their nests allowed more frequent feedings. Sometimes I would lie on my back in the grass and watch this end of the day aerial display. Looking straight up, there are no terrestrial reference points to orient myself - only wide open sky. With luck, this can sometimes result in mild vertigo, giving the illusion that I am soaring with the birds. (This is safe while lying flat on your back.) While these three species share the same ecological niche, they have evolved their own characteristic abilities of flight. I would claim the swift to be the superior aerial acrobat, even better than a dragonfly. But, a martin might take exception to my opinion and ask me “How many times have you seen me returning to my gourd with a dragonfly in my mouth?” Point taken – all three species are amazing.
The highest temperature reading at the nest during the entire nesting period was 99.5 F (37.5 C). This seemed to have no effect on the nestlings or adults normal behavior. The amount of night incubation was not recorded since I was unable to see whether the adults were incubating or just clinging to the edge of the nest. The infrared lighting on the camera had burned out years ago. But, I found that by tilting the video monitor and viewing the dim image at an approximately 30 degree angle I could see whether one or both adults were present at the nest. Whether one or both spent the night on the nest was not dependent on the temperature. The outdoor temperature was recorded in the shade of the front yard sycamores and would not accurately reflect the air temperature around or inside the silo. Temperature date collected in 2014, upon completion of the shaft, was always slightly cooler in the shaft than in the silo proper. In a future warming world, the fan at the bottom of the shaft could be used to blow in cooler air from the first floor wood shop.
The nest shaft construction in 2014 and the first chimney video in 2001.
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