Mute Swans leaving home

There was a news item yesterday regarding a Mute Swan that had crashed through someone's bathroom window. The swan was treated for cuts and taken for further treatment. The photos suggest that this was a young mute swan. What was it doing to crash in such a way?

Young leaving home 

This time of the year young Mute Swans will be leaving their parents' territories, in search of new homes. Cygnets share their parents territory for a few months, but as the parents start preparing for a new breeding season, the male, called 'cob' becomes more and more intolerant of his offspring, busking to them and trying to keep them out of the water. This blog post was prompted by the arrival of a young mute swan to my local patch, which I saw this morning for the first time. It has possibly dispersed from a nearby lake, where they have bred this year.

A newly arrived Mute Swan at the drain today.

Parents vary in their tolerance to immature swans in their territory, or this may depend on the size of the lake, possibly smaller territories may prompt cobs to chase their offspring earlier. One pair in a local park has two batches of young, the oldest were being chased on Saturday out of the water by the cob.

26th December 2020. Adult pair of swans chase their yearling outside the water.

Cob busking to young, followed by the pen.

Fly practice

Swans are one of the largest flying birds. They are also not amazingly manoeuvrable, and collisions (for example with electric lines) are one of the main mortality causes in swans. Taking off involves paddling on the water while flapping wings, they need a clear length of water to do this and then upon starting their flight they will need to fly up so that they clear any obstacles such as trees and houses on their way. 

Mute Swan in flight.

Watching swans in my local area, I've become aware of practice flying in which young and adults participate. This activity may help the young acquire key flight skills, taking off, landing and strengthen their wings  A short chase by the male may end with several members of the family flying along the lake, to land at the other end, but I've also seen lone young practicing when alone. There is a very good description of practice flying in the blog Swan Life.

 

Cob encourages young to fly. I described the behaviour in my Wild at Hull blog on the 8th December:  "As I got to the lake I saw the Mute Swan family gathered on the north edge of the lake. The adult pair had their two yearlings, born in 2019, and three young born in spring 2020. Usually swans chase their young away from their territory in the autumn, but this pair tolerates their young for much longer, probably because of the large size of the lake and plentiful food. The cob, however, was all fluffed wings and lowered head, a behaviour called 'busking' to one of the two older young. After a short chase, the young started flying, followed by a younger sibling and dad, and all three flew to the other end of the lake. I watched this happened three times while I was there. The swans only needed to drift on the wind to the top of the lake, and then take advantage of the gentle head wind for an easier lift. They yearlings might be getting ready to finally leave their natal lake, practicing taking off and landing".

Another clip of the 'practice flight' next. This is not a take off that failed, the trees and the end of the pond make it impossible that the swan would be able to take off in this direction. Practice flying and landing seems to be the motivation behind it. Note the feet propel the swan over water increasing speed and lift, and are also key to brake when landing.

   

More information

Collins, R. Sex Differences in the Movements and Mortality of Mute Swans. Waterbirds: The International Journal of Waterbird Biology 25, 157–161 (2002).

Frost, D. (2008) The use of ‘flight diverters’ reduces mute swan Cygnus olor collision with power lines at Abberton Reservoir, Essex, England. Conservation Evidence 5, 83-91.

Birkhead, M. and C. Perrins (1986) The Mute Swan.