I was idly looking at my page this morning & thought, it might be quite fun to tell you the story behind the picture (yes, that really is me; my husband took the photo in nineteen-mumbley-mumble). That is, how (& why) did I become mother to a bunch of little swans? It's a long story…
I ended up with the cygnets because I was doing my PhD on the behaviour & ecology of black swans. To begin with, this involved an awful lot of swan-watching from a hide among the raupo at the edge of a dune lake. And this generated heaps of data on the swans' behaviour. But I got interested in how the various social behaviors I was seeing developed in cygnets, & this was next to impossible to look at from a distance, especially because the very young broods spent a lot of time hidden away in the raupo. What to do??
Well, the first thing was to get permission from the Department of Conservation to keep a group of cygnets in captivity. The next was to work out where to keep them – there wasn't really anywhere suitable at the university where I was studying, so in the end we decided to keep them at home… It was a very old flat! On a large & very private section.
So, when I had captured a group of 6 cygnets, from 2 to 7 days old (their ages varied because they came from several different families), they came home to a very comfortable set-up. They spent their nights in a room lined with black plastic, with a raised platform where they could sleep (under a heat lamp when they were very young – I did draw the line at brooding them at night!) & one of those metal-framed kids' paddling pools (& every morning I siphoned the water out into the flowerbed, which grew very well that year). During the day they were outside in the back yard, eating grass (& silverbeet, dandelions, & lots of other healthy greens) and swimming in a pond dug in what had been a rather unsuccessful vege garden. And for the next two & a half months I looked after them, watched them, & took notes & photos.
For me, one of the most exciting things about this project was that I was finding out things that nobody else knew about. For example, those cygnets followed me because they had imprinted on me. But this wasn't the rapid process that I'd thought it was, based on what I'd been reading. It took about a week before they started regularly following me and sharing a greeting ceremony with each other & with me. Now, you'd expect that this lengthy period of learning to recognise 'mum' would see a lot of brood mixing. But in fact, on the dune lake where I was studying them, the breeding pairs were very territorial and there wasn't really any opportunity for the cygnets to intermingle with other broods. Where black swans nest colonially, eg on Lake Ellesmere, broods may intermingle & form creches – up to the point where the cygnets are about 14 days old. After this the adults will attack strange cygnets and drive them away.
When you're studying for a PhD one of the things you need to do is integrate your findings with what other people in the field have discovered (a bit like Scholarship, in a way!). So, how did what I'd found, with my cygnets in their vege-garden pool, fit with & extend our knowledge of swan behaviour?
Different species have different 'sensitive periods' for imprinting, & these differences are often related to differences in nesting habits. If the chicks are precocial (ie they're mobile straight away, like chickens, ducklings & cygnets) then the imprinting process is very short – unless the broods are kept isolated (or there are benefits in mixing). With altricial birds (like sparrows and kakapo) the chicks stay in the nest for quite a long time, and the imprinting period is similarly extended.
The long imprinting period that I found in Black swans is also found in the other swan species & in geese. Other swans are strongly territorial (like the dune-lake Black swans I watched), so that broods don't get the chance to intermingle and there's no disadvantage in having a lengthy period of imprinting. Although Black swans in Australia, and parts of NZ, breed colonially, I concluded that territorial breeding was probably the ancestral pattern in Black swans and that colonial nesting was a relatively recent adaptation to a particular set of environmental conditions.
What happened to the cygnets, in the end? Eventually they grew too large to keep where they were – & also they were getting ready for flying, which could have led to a lot of awkward explanations if they'd landed in someone else's back yard! So they went to live on a farm in the Wairarapa, where the farmer had a permit to keep wildfowl on his pond. And as far as I know, they all lived happily ever after.