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.