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. 

Ice-breaking Mute Swan

The ponds and lakes in town are all covered on ice after the last frosts. The other day I watched as part of a family of swans landed on ice on their lake, the young walking tentatively on the slippery ice. Today a pair of swans reached the edge of the ice and the cob seemed determined to move on. It pushed its chest onto the ice and broke it, moving forward each time. I noticed how after each break, it did a tail shake, as they often do after landing. I wonder if the swan feels like it is in unchartered territory and is nervous while breaking the ice. Tail shaking is something waterfowl do after an exciting event (mating, landing). The cob fed under where the ice had been, but then it decided to turn round to its partner.

Cob mute swan ice breaking.

Often lakes that have swans have some open water, as the large, heavy swans are able to break the ice. If they can't and the lake becomes fully iced over, then all waterfowl leaves in search of some open water. 

These are some photos of a mute swan family in a different lake.

Initially one of the young was on its own.

Its family had landed on the other side of the lake, on the ice, and it flew towards them.

The young was then keen to return to the open water.

The pen was happy to stop to preen and rest on the ice.

Mute Swan acoustic communication

I've said it before, Mute Swans are not really mute, they have a repertoire of calls and sounds. They also use movements of their head and neck to communicate. There is a quick head bowing movement, and a courting movement in which the feathers at the top half of the neck are ruffled, while those at the bottom are not, while the swan bows his head alternatively to left and right; and the aggressive 'busking stance' of the territorial male. In this post I focus on sound communication. I have trawled through Xenocanto, an encyclopaedic website with thousands of bird calls, to compile the following selection of Mute Swan sounds. I was prompted to write the post after listening to an odd distant call, which I didn't recognise to start with, and I was surprised to find out that it was a mute swan's. I heard the call again today, young swans calling to a swan flying overhead. It is not straightforward to distill the 'meaning' of a call, but the context can helps.

1. Snort

A short grunt or snort, often uttered when the swans are relaxed, and appears as a contact call while feeding, between members of a family, but also a greeting call. A lone young swan snorted when I walked by a lake near him.

2. Begging call

A soft repeated whistle typical call of young. Mute Swans don't 'feed' their young by putting food in their bills, but they help the young to obtain their food by paddling with their feet to  disturb the sediments or by pulling underwater plants. Even fully grown immature swans carry on whistling.

  3. Wing-beat Sound

This loud sound produced by the mute swan's wing-beats is really eery, especially when it takes you unawares until you realise that is coming from a swan. It carries very well and appears to replace the trumpeting contact calls of other swans.

4. Hissing

An aggressive sound, usually uttered by the female she has small young and a danger (human, dog) approaches. The bill is open and the swan adopts an upright stance towards the danger source.

5. Contact all

A two-note contact call reminiscent of other swan's flight call. I heard this call when a pair was separated, maybe during landing (one ended up in the river, the other one in a lake). Also when a Mute Swan flew over a family, the juveniles used this distance call.

6. Courtship calls

A range of snorts and grunts during courtship.

 Have I missed any? Let me know in the comments.

Mute Swans drying and tucking foot

Mute swans often stick one foot in the air as they swim (top shot) easily steering themselves with the other foot. I had often wondered what the purpose of this habit was.
  The two Mute Swans in my local park have afforded close observation in the last couple of months. Last week I noticed that sometimes they have one of their legs tucked under their flank feathers, virtually invisible, only a bit of the 'knee' showing, while swimming with the other leg. This behaviour probably results in keeping one leg quite warm under the plumage.
Yesterday I put both behaviours together by watching how the young swan took one foot out of the water, shook it and left it out for a while. Then it behaved like it wanted its leg dry before tucking it under its feathers: it tucked his leg under the feathers, but seemed not to be happy about it and it stuck it out again and shook it a bit more before finally tucking it in for good.
 I had noticed that cygnets, even before they have feathers, have this habit of tucking a leg out of the water over their body. I just had never realised the adults would do it too, preceded by the leg-stuck-out while drying.
This behaviour has also been reported in other swan species and although thermoregulation seems to be the underlying reason, both cooling and drying/warming have been proposed as explanations for the behaviour.
 The next series of photos illustrates the sequence of behaviour.

The following photo is from 21 June of 2015, taken in a local fishing lake. A young downy cygnet a few weeks old. You can notice how its right leg is tucked by its body, outside of the water, while it preens. When it grows feathers, the same position results in a leg completely covered with feathers.

More information

Why do some swans only paddle with one leg, with the other leg tucked up under the wing?

The Whooper Swan. Here. p 93-94.

A story of ringed Mute Swans

Last Wednesday 1st of November I went to Pickering Park. There were six Mute Swans. The resident cob (841 yellow ring), followed by the resident pen (ringed 842, top shot) was busy busking towards a white swan in the lake, who tried to avoid him and ended up preening on the bank at one end. It was a polish variant one, possibly a young of last spring, and when it came out to the shore I could see it was also ringed (red 182Y).
There were also three brown-feathered young swans, starting to moult into adult plumage. Just one of them was ringed (red 537). I assumed they were offspring of the resident pair. One of the brown young kept near the polish one being chased, joining it on the shore.

182Y at Pickering on the 1st of November.

The brown swan accompanying 182Y at Pickering.

The resident pen at Pickering.

***

On Sunday 5th I went to Pearson Park. I was pleasantly surprised to find a mute swan, brown, not ringed. After a while I realised that there was another mute swan, white, on the other side of the pond. The small lake at Pearson Park has very rarely held swans, and not for too long. The last one I saw there was a juvenile from November 2005 to March 2006, when another two appeared in the park before all departed. I casually checked for rings, as I often do, and after some trying I managed to read it. I was surprised to find that the white one was the same that was being chased at Pickering Park, 182Y! The brown young wasn't ringed, but its plumage development is consistent with the one keeping near 182Y at Pickering, so both birds must have left the lake together, possibly an incipient young couple? 

182Y now at Pearson Park. I was able to read the ring as the swan swam.

The brown unringed young at Pearson park.

Both swans at Pearson Park. The white swan showed some aggressiveness towards the brown one, pecking it when it got close.

The swans are getting a lot of attention at Pearson Park. I think the brown one is a male, as it occasionally fluffs up its neck which looks thick in comparison to the other. Still there today, being fed by locals. There is currently a good empty breeding territory at Oak Road lake, it would be good if these two moved there!

A lucky front shot of a male Mute Swan on a local park. He was with his polish variety partner, and ringed and approached me as I walked around the lake.

The Mute Swan

I recently purchased The Mute Swan, by Mike Birkhead and Christopher Perrins, after a visit to a local fishing lake where a pair of swans holds territory year round. It has been an interesting, informative read, especially the historical aspects, although I would have liked to read a little bit more on behaviour. Some aspects are dated, for example, lead weights have been banned since 1987, and the mute swans populations have recovered, probably also helped by milder winters (BirdTrends). Mute Swans are the heaviest British birds, with males over 10 kg in weight and 2.20 m wingspan.

Variation
There is an unusual colour variety called immutabilis or 'Polish swans' in which the young are white when downy and moult into white feathers, instead of the usual brownish feathers of the juvenile. The feet of the immutabilis form are pinkish grey instead of dark grey or blackish. Read more here.

A normal juvenile with its parents

An immutabilis juvenile (pink bill) with parents.

An immutabilis cygnet (left) with its normal sibling.

Calls
Mute Swans get their name from their relative lack of calls, especially in flight, and in stark contrast to their vocal relatives the Trumpeter, Whooper and Bewick. Although relatively quiet, Mute Swans are not mute. They have a repertoire of vocalisations, which, although weak and not carrying long, are quite obvious when at close quarters: they snort, a pig-like call; they hiss loudly like geese, a threat call to predators or people approaching too much, especially when young are about, and they have a short, quiet two note call reminding of rooks'.

A hissing swan

Their wingbeats, however, are loud and make a whistling noise that is audible, it is said, from over a mile. This sound might have replace the flight contact calls of the other swan species.

A pair of Mute Swans in flight.

Moulting
Non-breeders migrate to safe waters to moult in the summer, often congregating in large numbers. Moulting in breeding pairs is different. They moult when they are breeding: the female moults first, and then the male, once the female's feathers are fully grown. This way, there is always an adult with grown wings, which play an important role in the cygnets defence.

A moulting flock of non-breeding swans at Hornsea Mere

A semi-domestic bird?
At some point in history most if not all adult British swans, and most likely those from other European countries, were pinioned, and therefore, unable to fly. They were a heavily managed species, as it was regularly eaten, and it is likely that this management saved it from extinction from overhunting. The spectacle that is the sight of flying swans would have been much rarer, and restricted to movements involving young birds. In the early XX century, the custom of eating swans disappeared, and, management in most areas was much reduced. In a way, we can see swans as a once domestic, now feral species.

Food and the swan's neck
Swans have a record number of bones (vertebrae) in their necks for a bird: 25. Their long necks allow them to exploit aquatic plants and tubers much deep than other water birds. They use several feeding techniques, shallow feeding in which they keep their neck folded to up-ending, when they use their body and neck to reach deep levels, about a meter deep. They also use their feet in a paddling movement to disturb the bottom sediments and being able to filter out small particles or loosen roots and tubers. Swans might migrate some distances if their territories ice up in the winter.

These feeding swans attracted numbers of coots and various ducks, most likely benefiting of the swans disturbing and pulling deep aquatic plants.

A swan uses its long neck to feed from a hole in the ice

Courtship
I have never seen the courtship of the mute swan, which appears to have nothing to envy to the Great Crested Grebe's (watch a video here). It involves the pair facing each other with smoothed, dipped wings, and engaging in synchronised, repetitive head dipping and flank rubbing, swimming in circles and, after copulation, both partners paddle and raise their bodies together, with their necks arched and bills pointing down.

Territorial defence

A pair of breeding swans defend their territory, in a lake or river, fiercely: sometimes over the winter if enough food is available and there is no ice. They will chase other swans, with flapping wings being used as a threat, and use a threat display, busking, which I have covered at The Rattling Crow before, in which they swim with strong pushes of both feet together towards intruders, their secondary wing feathers kept high up, neck arched and neck feathers ruffled.

an approaching busking swan.

high intensity busking just before wing flapping and chasing of an intruding juvenile.

Both males and females participate in territory guarding and defence. This pair approached a juvenile busking, chased it away and then swam around the perimeter of their lake.

Nesting

Nests are often very visible as they are built from surrounding plants, creating a gap in reed beds or river margins. Swans lay 4-7 eggs that only the female incubates while the male keeps guard nearby.

Incubating female swan.

Parental behaviour
Like geese, which are the closest relatives of swans, both parents are involved in caring and defending the young. Adults will carry the young downy cygnets on their backs, often only the cygnet's heads showing over the parents wings, to suitable feeding areas. The male is more involved in territorial and brood defence, often chasing other birds like mallards or coots away. When little, the cygnets are unable to reach aquatic plants at the bottom of the lake, but parents will often disturb the water with their legs, or pull vegetation for the young.

Male swan (cob) chasing a mallard away.

Female with cygnets

Mute swans often swim with one leg, keeping the other dry out of water (cygnet on the left). The cygnet on the right is feeding by up-ending.

Up-ending adult pulling food for cygnet

Independence
Normally young disperse in September, once they have grown their first year plumage. Then they leave their parents territory and join a flock of non-breeding birds. However, some young stay with their parents until the spring. The local lake couple seem very tolerant of their young, and they often let them stay until the spring.

Last years first year swan moulting into adult plumage (23/1/15) still in its parents territory.

Non-breeding flocks
Mute Swans do not normally breed until they are 3-4 years old. Young swans unable to secure a breeding territory are more sociable and form non-breeding flocks.

Busking Mute swans

In a visit to a local fishing lake, we find the swan family, the pair and a young from last year. The male kept his wings arched high over his body, staying between the shore, where several dogs were running around, and the other two swans. This behaviour is a mild form of threat display called busking (yes, another type of street performance if you like). Swans not only use it to deter potential predators, but also as a threat against intruding swans, before lunging or chasing them out of their territory. In its highest intensity, the display involves the swan arching its neck, and keeping its head low under his wings, while they lunge forward to the intruder swimming fast, propelling themselves with both feet at the same time. It is a most impressive sight.

Male swan busking a juvenile, note the front wave he is creating! (North Cave wetlands, 3/3/14).

The young one has a pink, instead of orange bill, and will probably stay around until the pair start nesting in the spring.

Today, at some point the dogs got too close to the shore and the female approached...

...also displayed. 

The male, or cob, swan.