A Goosey Gander – Solving the mystery of Heslington Lake

Recently, I spotted a mysterious and baffling bird.*

I regularly take a lunchtime stroll round the lake on the Heslington West campus of the University of York. As will surprise nobody reading this blog, I enjoy the opportunity it presents to watch plenty of wildlife. There’s a pretty standard array of birds, bar the small flock of Snow Geese (Chen caerulescens) that live there.

Variation in the plumage of Snow Geese Heslington West, York

Variation in the plumage of Snow Geese
Heslington West, York

Foraging Snow Geese Heslington West, York, January 2014

Foraging Snow Geese
Heslington West, York, January 2014

As you may expect, this is not a truly wild population of this primarily North American bird, instead it’s a pretty content feral group. There’s also several of one of my favourite geese, Barnacle Geese:

Barnacle Goose Heslington West, York, January 2014

Barnacle Goose
Heslington West, York, January 2014

Incidentally, if you don’t know the tremendous myth that links Barnacle Geese, Goose Barnacles, and a mad Welsh monk, you should have a read!

So, normally I happily wander round watching the various ducks, geese, coots and moorhens going about their business. But around a week ago something made me stop and stare. An instinct kicked in that something was amiss.

And who might you be?

And who might you be?

It’s the goose in the foreground we’re looking at. Those behind it are all Greylag Geese (Anser anser). But that looks more like a Canada Goose (Branta canadensis). In fact, had it been amongst the many Canada Geese I’d probably not have noticed. But here it is, tucked up happily with a group of Greylag. Once you’ve started to stare, you start to notice more oddities. Here is a Canada Goose:

Canada Goose Heslington West, York, January 2014

Canada Goose
Heslington West, York, January 2014

Notice the colour of the bill? Black. The legs? Black. Now look again at our intruder:

Pink legs, orange bill... what are you?

Pink legs, orange bill… what are you?

Pink legs, not black. Orange bill, not black. The black around the neck and head is actually a grey. And that pattern around the cheeks cuts much closer to the eye. So what’s going on? Just a weird variation on a normal Canada Goose? An unusual, exotic species blown in? Or something else altogether? I was pretty certain I knew the answer.

The Greylags on the right have the pink feet (and do actually have an orange bill too). So we have something that blends characteristics of two species…

Feral goose populations often hang about together, and as the two most common geese around you often get Canada and Greylag Geese in the same flock. So, when two biologically similar and entirely compatible animals are together, at a certain time of year, there is always a possibility of hybridisation. Given this goose is hanging with the Greylag, and given geese tend to stay with their mothers, we can fairly assume our mystery goose is the result of a male Canada Goose mating with a female Greylag Goose. Anser anser x Branta canadensis

A quick hunt around the web revealed a website, Go Birding, that had a dedicated section on hybrid geese, confirming my suspicion.

So there we go, not a new species. Not a mystery migrant. But a satisfying and interesting little mystery anyway.

To end, a few shots of the lovely lake:

IMG_0271 IMG_0272 IMG_0275 IMG_0276

Oh yeah. There’s a daily blog of duck/goose pics from the lakes here: Duck of the Day

* So, yeah, I’ve already blogged about this. But I’m going to just pretend I haven’t!

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7 Responses to A Goosey Gander – Solving the mystery of Heslington Lake

  1. dad says:

    yes i agree i have often seen single canada geese with greylag flocks in the mating season but not the other way round, being a fisherman you tend to notice these things i am sure someone will say it works both ways i have also seen on the river foss in the mating season a canada goose quite happily swimming with a pair of greylags when the male is driving the female to nest when you would normally expect the male greylag to chase him off DAD

    • David says:

      It would be interesting to know if it only works one way, or if male Greylags also go for female Canadas.

      In most wild cases of hybridisation it’s the male that initiates. Less picky I guess!

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I welcome thoughts, comments and questions, so please feel free to share anything at all. Thanks, David

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