Text by CVN member Véronique McIntyre. Photos also by Véronique except as noted.
“Hi, Gronk’s sibling. What are you doing?”
“Oh, just looking at some pictures of me some people took. You know I regularly make it onto eBird. People come from far away to take a peek at me here in Deep Bay. Earlier this year it was Kelly Kline with a group of CVN birders from Courtenay.”
“Yeah, I know you are famous, hard not to with you constantly reminding everyone about it.”
“It’s not as easy as you think! I look like any other trumpeter swan, black beak, white, same size… You need to take a closer look to notice that underneath, my beak has a subtle tinge of pinkish orange at the tip, and the above part is adorned with stunning yellow spots like golden flecks, so beautiful. You don’t have those.”
“And why is that? I want some gold on my beak, too.”
“You can’t have any, kiddo. I was born with them; you were born without.”
“Where did those spots come from then?”
“From my parents. You see, my mom was a very special mom.”
“My mom is very special too.”
“True enough, but mine really was a looker. She sported a beautiful orange beak, and her neck! You wouldn’t believe it, but she had such a graceful way of holding it! The shape of an S, not a C like yours or your parents’, or mine. The stuff you make Russian ballets from. Her scientific name is Cygnus olor. Both cygnus and olor mean swan in Latin, although to start with, cygnus comes from Greek. So, my mom belonged to the species considered to be the quintessential swan. Here, look at this picture.”
Fig. 2. Mute Swan. (Photo credit: iStock).
“Wait a minute, I don’t see any golden flecks on her beak. It’s almost completely orange.”
“Yeah, well, the laws of genetics that rule the color of beaks in swans are quite unknown to me, so I can’t explain. Although see under my beak, I have a little bit of orange too.”
“That’s true. And I can see that you hold your head more like my dad. And you don’t have a knob on the top of your bill either like your mom does. Look, here is my dad on the right, and you on the left.”
“Yes, I have a bit of my mom and a bit of my dad in me.”
“Was your mom born here?”
“I’m not sure. One winter in the late nineties she showed up at Windy Marsh on Denman Island with a small flock of trumpeter swans.[1] So, I am inclined to think that she came from somewhere else and simply followed them. I know there are a bunch of swans like her on Salt Spring Island; you can see them in the Ganges harbour.[2] There is also at least one on Bowen Island, a few in Victoria and Nanaimo, a couple more in Vancouver… about 100 in BC in total.”[3]
“Is she a trumpeter swan like me and my parents? Since as you said, she arrived with trumpeters.”
“No, she could not speak like you.”
“Could she speak like you then, that incredibly dissonant croak you utter from time to time? Which is the reason why your sibling on Denman Island is called Gronk?”[1]
“No, she could not speak much at all. A few hisses, grunts, that’s about it. And certainly, no song when she died.”
“Really? She was almost mute then?”
“Yes, that’s what she was called. A mute swan. All her relatives speak like she did.”
“Why did she not sing when she died? Don’t all swans do it?”
“No. Trumpeter swans, and tundra swans, and whooper swans do, as well as cranes and a few other birds, but not mute swans. The swan’s song at death is only the sound of the air escaping the lungs following a tracheal loop within the sternum. It’s the same loop that allows your bugle sound that gave you your Latin name: Cygnus buccinator. My mom’s people don’t have such a loop, so they simply exhale their last breath silently.[4] And they don’t bugle like you do. Me, I probably have a malformed loop, so I can’t speak like either her or you.”
“Oh well, you often see birds of different species in the same flocks. Look at us here, for example. So, a mute swan with trumpeter swans, nothing special there. It’s not worth people being so excited to see you.”
“That’s not the same. You came this fall, and by the spring you’ll be gone back to where you spent your summer, and maybe never come back here, although of course I would look forward to seeing you again next winter. We live together for a little bit, by chance. My mom picked up the best of those trumpeter swans in her flock, my dad. And he picked her as well. Was that a case of mistaken identity?
A bird can lay eggs in the nest of another species. The young are reared by a different species and are imprinted onto their host and grow to prefer them as partners. Was my mom raised by trumpeter swans? Or is it a case of blind love? Love there was for sure. In the spring, when the rest of the flock left for their breeding grounds in the tundra, Mom and Dad stayed behind. You see, here mute swans don’t migrate in the spring and fall like trumpeters, and her new partner, my dad, elected to remain on Denman with her, which shows that migration is not compulsory in trumpeter swans. And it also shows that swans can communicate and negotiate more than humans give us credit for.”
“Then how come I migrate?”
“Simply because you followed your parents and thus learned both the behaviour and the route. Swans are not born with a genetic program to migrate. They learn from their parents. So, if their parents are imported, like my mom’s extended family has been from Europe, or if they are reintroduced, like trumpeter swans were in Eastern Canada in the nineties, you need to find a way to teach them migration. Ultralight planes work with geese, but not with swans—we can only learn to migrate if we take off from water. So, amphibious planes are the answer.[5] As you can guess, neither myself nor my siblings ever migrated since nobody taught us how to.”
“Does your mom have relatives somewhere that can migrate?”
“She has millions of relatives in Europe and Asia. Not all of them migrate, but yes, quite a few do. They travel, for instance, from Ukraine to Italy, 2300 km in straight line, or from northern Sweden to southern Sweden, a good 1600 km.”[6]
“Why was her type introduced here? We are beautiful swans, was that not enough?”
“I guess not. Rich people with estates, zoos, and park keepers all wanted to have some. Beacon Hill Park in Victoria had some, and many were released into the wild or escaped.[7]
Anyway, back to my parents. As you know, we swans are highly sociable. We can communicate with movements of our necks, or by timing our take-offs from water. There was no need for my mom and dad to speak the same language, and they were still able to understand each other beautifully. They mated and my mom built a nest at Windy Marsh on Denman Island, laid eggs and successfully hatched two hybrid cygnets. They did the same the next two years, so I think in total at one point I had four sisters and brothers.[2] Three of them were recorded on eBird in November 2006.”[8]
“Do you have pictures of your siblings?”
“I do, a recent one of my brother Gronk, dated May 4, 2021, who stayed on Denman Island[1] as well as one of three of my siblings in Deep Bay on Nov. 18, 2006.[9] Maybe one day, an old admirer will find another picture of my siblings in their old stash and send me a copy using the CVN site. It would be most gratefully received and forwarded to the CVN membership. I myself have been on eBird a few times since 2016.”[10]
“So only Gronk stayed on Denman Island?”
“Yes, except for Gronk, those of us who were not killed by predators moved to Deep Bay. Very good place, Deep Bay—sheltered, and people feed us when it’s too cold. You’ll see; your parents picked well for your winter vacation. Although, it looks like I am the last one left here. It would make sense, seeing that I am now in my early twenties, which for swans in the wild is quite old. Dogs, racoons etc. can be a plague. Although, swans living in the wild to their early thirties are not unheard of.[11] Mind you, I was smart—look where I live. Close to humans, who protect me and would send me to the MARS rehab centre in Melville if I got sick or injured. There is also the bunch of geese among which we live, and they are excellent at raising the alarm when needed. Did you know they sounded the alarm when some Gauls tried to invade Rome in 390 BC?[12] Anyway, look, I was sent these pictures by a distant cousin of mine who lives on Pocono Summit Lake, Monroe in Pennsylvania. It’s his family on June 10, 2022, and then on December 10, 2023. Mine probably looked very similar.”
Fig. 4. Hybrid swans in Pennsylvania in 2022. (Photo credit)
Fig. 5. Hybrid swans in Pennsylvania in 2023. (Photo credit)
“The young ones are pretty cute, just like me.”
“Yeah, it’s hard to understand why one of us was called the ugly duckling in a fairy tale isn’t it? Look, you are so cute that those birders the other day took a picture of you too. Although your beak isn’t mottled like my cousin’s.”
Fig. 6. Trumpeter Swan born last summer enjoying his winter in Deep Bay.
“And your parents? What became of them?”
“My mom’s carcass was found on Denman Island, most likely killed by a mink, an otter, a dog or a raccoon. My dad left then, reverting to migrating, and if he did not die, he might have found another mate. That’s what swans do when their mate dies. So, I might have a step-mom somewhere. But us, the hybrids, we did not follow him. We were independent by then.”
“Is it normal for individuals belonging to two different bird species to have offspring?”
“No, usually the songs don’t match, or the courtships, or some mechanical difficulty prevents copulation. Fertilization can be impossible if the two species don’t have the same number of chromosomes in their gametes since chromosomes need to pair up to work properly. Even if fertilization occurred, organ development in the egg can be impaired and there is no hatching. And once out of the egg, so many things can develop the wrong way! Having five normal swans like my mom and dad did is really a feat. Mute swans mating with trumpeter swans don’t produce many hybrids—in Canada, eBird records only 153 observations, many of them being myself and my siblings.”[13]
“And could you have cygnets yourself if you found a mate?”
“Any attempt would create second generation hybrids. Given my voice, I think this is bound to fail. And sure enough, neither myself nor my siblings have ever been recorded with a mate, let alone building a nest or laying eggs. And believe me, we have been scrutinized closely by birders. Although, there was a rumour at one time that two of my siblings had found mates. Maybe they did, maybe they didn’t. No, it looks like there won’t be any descendants from us. Part of the problem might come from imprinting. Male zebra finches have been found to prefer to mate with females that look like their moms.[14] Good luck to all my male siblings! There is no mute swan around… of course, my sisters, if I have any, would have a wider choice of mates.”
“Are you male or female?”
“I prefer not to answer this very private question. The only way humans could find out is by seeing me lay eggs.”
“Why did you say “if I have any” talking about your putative sisters?”
“Because of the determination of sex via chromosomes. Humans have a Y chromosome that directs the formation of testes and sperm. Anybody with at least one Y is a male and anybody without a Y is a female, biologically speaking, even if they don’t identify with that sex. The second sexual chromosome in humans is called X. So, most females are XX and most males are XY. X codes for all sorts of traits. If there is a mutation on the X chromosome, it’ll likely be expressed in a male since there he only has one copy, whereas in a female if the other X carries the normal gene, the mutation won’t be expressed. That’s one of the reasons why human males are more prone to genetic diseases than females.
In birds like us it’s the opposite—females carry one Z and one W chromosome, and males carry two Z chromosomes. So, for my sisters, their W chromosome came from my mom, and their Z chromosome came from my dad. For my brothers, one Z chromosome came from each parent. If there is any incompatibility between the sexual chromosomes of mute and trumpeter swans, the viability of my sisters would be lower than that of my brothers. It might well be that I don’t have any sisters.”
“OK, but you didn’t answer my previous question. Assuming you found a mate and managed courtship and copulation, could the eggs produced by your couple be viable?”
“Ah, you are wondering if I could have descendants. You know, it’s a fascinating topic. Species are supposed to be groups of organisms that can mate and have fertile descendants. So, if we could have descendants, maybe the status of mute and trumpeter swans as species could be called into question.
Horses (64 chromosomes) and donkeys (62 chromosomes) can have hybrids called mules (63 chromosomes), but mules are almost completely sterile, so horses and donkeys are seen as two different species. Mules are sterile because they carry an uneven number of chromosomes: 63. 32 from the horse’s gamete and 31 from the donkey’s. You can’t form gametes from an uneven number of chromosomes without losing significant amounts of information.
Mute swans have 80 chromosomes[15] whereas trumpeters have 84.[16] So, their gametes have 40 and 42 chromosomes respectively. Meaning my cells most likely contain 82 chromosomes (40 + 42 at fertilization) but two couldn’t form a pair and thus would be lost at meiosis when my gametes form. Therefore, I am most likely sterile. Even if I had kids, they would be sterile for the same reason as me. So no, we can’t leave descendants past the first and certainly not the second generation of hybrids. No mute swan DNA is likely to enter the trumpeter swan DNA, and vice-versa. Which makes sense, seeing that the common ancestor to both species lived millions of years ago.”
“So, mute and trumpeter swans are really different species then?”
“That sounds correct. At least with the data that is available so far.”
“Did your mom face problems like many migrants do?”
“I think some people believe that my mom’s sort are a bad lot, aggressive and ready to invade and destroy the habitat of other swans here.”
“And is it true? Was she some sort of beautiful gangster?”
“Well, it’s hard to tell. The aggressivity is visible in areas where mute swans are in small ponds, with not enough food for everyone. And of course, just like all of us, during mating season. In Europe and Asia, her kin are fine, predators keep them in check, and so do diseases and parasites, as well as other local birds and grazers. Not so here, so yes, given the chance to reproduce, mute swans could wreak havoc on the grazing grounds. They are said to have enormous appetites. A Maryland study found they ate up to four kilograms a day of submerged aquatic vegetation, removing food and habitat for other species faster than the grasses could recover.[17]
It could well be, but since mute and trumpeter swans are of similar sizes and have similar nutritional needs, we eat similar amounts of food. And we both pull the whole plant out of water. Still, trumpeters are native to North America and mute swans are not. Given that humans literally cover most areas where we can feed with concrete, we end up competing for food, and humans have decided to give trumpeters the priority. That’s typical, instead of deciding to leave estuaries alone and remove all the houses, roads, marinas etc. that infringe on our natural habitat. They are so proud of their brains, and yet they can’t think.
Although, I must add, in Canada all swan species are protected under the federal Migratory Birds Convention Act. This makes the mute swan one of the few non-native species to be afforded a legal protection. That means you just need to ask for a license to kill them. And why favour one bird over the other? We are birds.
One day some mute swans might very well arrive using that old route, the Bering Strait. Who knows? It might have occurred in the past, and there is no trace of them anymore. With humans killing everything in sight….
I spoke too much. I need a drink now. Time for a nap, kiddo. You need to rest before your spring migration.”
References
1. All details on the life of the Mute x Trumpeter Swans couple are courtesy of Dennis Forsyth via personal communication from Kelly Kline to the CVN Birding Group, Jan. 15, 2024, and in this FaceBook post.
2. Scott Denkers (2016). eBird Canada checklist.
3. Government of Canada (2017). Invasive species: mute swan.
4. Wikipedia. Swan song.
5. Bryan Quickmire (undated). Trumpeter swan migration project. National Ultralight Inc. website.
6. P.W. Atkinson et al. (2006). Mute Swan (Cygnus olor) movements. In: S. Delany et al. (eds.). Urgent preliminary assessment of ornithological data relevant to the spread of Avian Influenza in Europe. PDF.
7. Janis Ringuette (undated). The beauty and tragedy of Beacon Hill Park mute swans.
8. Guy Monty (2006). eBird Canada checklist.
9. Guy Monty (2006). Photo of 3 hybrid swans at Deep Bay. flickr.
10. eBird. Mute x Trumpeter Swan (hybrid).
11. Birdfact (2022). How long do swans live? (complete guide).
12. Jack Beckett (2016). How holy geese saved the republic during the first sack of Rome (390 BCE). War History Online.
13. eBird Canada. Mute x Trumpeter Swan (hybrid).
14. Wikipedia. Imprinting (psychology).
15. Animal Genome Size Database. Detailed record for Cygnus olor.
16. Cornell Lab of Ornithology (2020). Trumpeter Swan: Cygnus buccinator. In: Birds of the World [subscription required].
17. Cornell Lab of Ornithology (undated). Mute Swan. In: All About Birds.
