Inverted dimorphism

This is the last story article dedicated to my trip to Lapland and Varanger, back in June. We will have a wrap-up post later on, and then we will be done with it. I have some more photographs from Finland and France I want to show you (many I haven’t edited yet…), and of course there will be more content from New Zealand, as I travel further.

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Several animals look different depending on whether you’re looking at a male or a female. Think of the lion: males have a mane, which females lack. Think of the Paradise shelduck (Tadorna variegata): females are orange and white, while males are essentially dark grey.

Paradise shelduck (Tadorna variegata)

That’s called sexual dimorphism: these species have two forms (“morphs”), depending on the sex. Many species don’t show that at all. For instance, both sexes of European robin (Erithacus rubecula) look alike.

European robin (Erithacus rubecula)

In general, males have the most flamboyant livery. They have to show to potential mates that they are the strongest, the healthiest, the best fitted to produce offsprings that will survive and ensure the species’ survival. They engage in courtship display, sometimes in fight with other males, to show this. On the other hand, females might be nondescript to hide in their environment and raise chicks discreetly.

However, some species have turned this pattern around, and it’s females that are brighter and more colourful than males. I encountered two such species far north, and thus this article was born.

Red-necked phalarope (Phalaropus lobatus)

In Vadsø, I was lucky enough to spend some time surrounded by Red-necked phalaropes (Phalaropus lobatus), and could study their behaviour as they completely ignored me. Light as the air, they darted on the water’s surface from left to right, catching unwary insects in a mesmerizing dance. Finns call them “water swallows” (vesipääsky), a fitting name given how this feeding behaviour looks like a swallow’s own aerial hunt for insects. For waders, it’s unusual to feed that way, but I saw no competition for them up there, so I guess they evolved to occupy this unused niche.

Red-necked phalarope

Red-necked phalarope

Anyway, we were talking about inverted dimorphism, and phalaropes are a fine example of it. Males and females look similar, but the latter are larger and more colourful. They display, and the males raise the chicks. Look below: the first picture is that of a female, while the second one shows a male.

Red-necked phalarope

Red-necked phalarope

As I lay on the muddy shore, a phalarope came to me, settled there and started to preen, not even a meter away from my front lens. Very confiding, it barely noticed me moving to get into a better position. So, male or female?

Red-necked phalarope

Red-necked phalarope

The second species to show inverted dimorphism is subtler, and even looking at the pictures, I’m not sure who is who.

Eurasian dotterels (Charadrius morinellus) nest in the Arctic tundra like the one that covers the fells of Lapland. When I first went to Kiilopää, I was successful with the Rock ptarmigan (Lagopus muta) but couldn’t find any dotterel. It was too early, snow had just melted. Two weeks later, I was back to close the loop. I opted for Kaunispää, for it’s more accessible (there’s a road to the top 😉), and I had seen many people had observed them there in recent days.

Eurasian dotterel (Charadrius morinellus)

I was there at 4 in the morning, when the sun was already high in the sky but hidden behind clouds. It was cold, maybe a few degrees above zero with a freezing wind. I could hear the birds, it was then all about finding them. For such colourful buggers, they are pretty good at hiding in the heath, but I located one, then two more. Painfully, I lowered myself onto the wet vegetation, and crawled, doing my best to close on them without scaring them away. The sun hit, offering a crude, unpleasant light, but it was the first time I saw these birds (my fourth lifer on this trip), so I did my best to go home with nice images, if not the best.

Eurasian dotterel

Can you guess which one is the male and which one is the female?

Eurasian dotterel

While I was there, a European golden plover (Pluvialis apricaria) landed nearby. That species shows sexual dimorphism in a classic way, and the bird that had landed was a splendid male in breeding plumage, showing why it’s named “golden plover”. From my experience, they are shy birds, and the best way to approach them is by car, for they will often not fly away if you drive by. This one had probably not noticed me, and it started to call, a glorious sight with the forest as a soothing backdrop.

European golden plover (Pluvialis apricaria)

European golden plover

That’s basically how I ended my Nordic adventure. I spent the rest of the day in Ivalo, practising my Finnish with Ritva while watching birds at her feeder. I was exhausted, and glad to fly back to Helsinki to enjoy the warm weather that had settled there.

Previously in this series:

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BIRD INVENTORY

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