Visiting the swift tower

Yesterday we did a stop in Oxford on our way south of the UK. After lunch, we quickly popped by the Natural History Museum. This magnificent building holds the swift breeding population that have been studied for several decades. The nests are in adapted nest boxes, which have access from the inside of the building for ringing in the main tower.

A detail of the tower showing the entrances to the nest boxes.

It is quite late in the short Swift breeding season and many fledglings and adults have already left for their African wintering quarters. Every time I see a swift I think it could be the last of the year, so I was not too hopeful of seeing any around the tower.

Birdtrack reporting rate of Swift, showing the main breeding season from May to August.

Then the website revealed that the last Swift nestling in the tower was born a couple of weeks ago (18th July) and hadn't yet fledged. The Museum has set up a live webcam in which you can follow one of the nests. The webcam is now set up onto the latest born nestling. I watched the nestling for a while today and got a couple of screen grabs.

An adult likely after feeding the chick, on the foreground, and the well grown nestling. Young have pale-rimmed feathers on their face, unlike adults.

The youngster resting. It spent some time flapping its wings and grooming. Although is quite feathered, its wing feathers are still quite short. The wing feathers will need to reach beyond the end of its tail before it can leave the nest. You can also see a rejected egg just outside the nest.

As we walked onto the square in front of the Museum and just after taking a few photos, a lone Swift flew overhead. Not the mad noisy chases of dozens of Swifts that usually surround the tower at the peak of the breeding season, but a great end of a lovely visit. 

Eight things I didn't know about swifts

The first Swifts are back! These extremely aerial birds spend just three months of each year with us, from early May to early August - their breeding season - but their continuous flight and noisy chases makes them obvious and fascinating birds to watch. They eat, sleep and mate and collect their nest materials on the wing. I recently read "Swifts on a Tower" by David Lack. A very informative and entertaining book, it is based on the observations of David and Elizabeth Lack and their students. They observed nesting swifts on modified nesting holes in the tower of the Oxford University Museum of Natural History, a building of fame due to being the place where the famous debate on evolution took place between Samuel Wilferforce and Thomas Henry Huxley seven months after the publication of the Origin of Species.

Museum of Natural History (Oxford) the central tower ventilation shafts (10 on each side) are the entrances to the Swift nests. Photo by Michael Reeve, licensed under Creative Commons, from Wikipedia.

Based on this book and more recent research I have compiled this list of facts that I didn't know about swifts.

1. Their young can survive up to 21 days (!!!) with no food. Their growth patterns match the weather so that they stop growing during cold, wet or windy weather. The length of time they take to leave their nests depends as well on the weather, the earliest leave at 5 weeks, the latest at 8 weeks.
2. Eggs can get cold (i.e. left by the adults without incubation) for at least two days and survive.
3. Swifts - and possibly other bee-eating insects - can distinguish drones from bees and drones are the ones they eat, avoiding getting stung by workers.
4. Swifts fight for their nests cavities by grasping each other's claws. The winner is the individual that can get on his back, so that it can push the other out of the nest.
5. Adult healthy swifts can indeed take off from the ground. It is the recently fledged individuals in not so good condition that can't (they leave the nest early and their wings are not fully grown.
6. Once fledged, young swifts are completely independent and receive no further parental care. They return to their summer grounds to breed when they are 3-4 years of age.
7. The young join non-reproducing birds to sleep on the wing high up on the sky.
8. Swifts are the fastest birds during self-powered flight (the peregrine "free-falls" using gravity to accelerate) reaching over 110 km/h in their 'screaming parties'. More info here.

More information:

For an informative article by the 'guardians of the tower' see here.

Henningsson, Per, Johansson, L. Christoffer, Hedenström, Anders (2010) How swift are swifts Apus apus? Journal of Avian Biology, 41: 94-98. Here.

Check the fantastic photos of swifts on flight by Jean-Francois Cornuet here.