A Freaky Fisherman – the Osprey

Have you heard an unbelievable fact yet today?  Here’s one: there are currently 10,585 species of birds in the world – a world which is 70% covered in wet stuff – and only one single species has evolved to hunt fish by plunging into the water feet-first.

Don’t believe me?  Take a mental walk through the ranks of the world’s fish-eating birds and you’ll find they generally fit into one of four categories1.  Birds like loons, mergansers, puffins and penguins fish while swimming, by chasing on the surface or underwater.  Herons and egrets, on the other hand, spear or grab their fish from a standing position.  More spectacular are the gannets, boobies and terns who dive beak-first from high in the air.  Finally we have the fishing eagles and owls who artfully snatch fish from the water’s surface with their talons.2

No, the feet-first plunge is not a popular move.  It might be because most birds don’t have the feet for it, and those that do don’t tend to be gifted swimmers (hence a preference among eagles and owls for the stay-dry snatch technique).  But there is one bird that ignores the obvious arguments against and forges its own path into the fishing world.  It’s specialized.  It’s sophisticated.  It’s freaking weird.  It’s the Osprey.

osprey
The one and only Osprey, doing what it does best.

Like any bird with a one-off survival strategy, the Osprey is necessarily unusual.  At first glance you would presume it a hawk, and the hawks are indeed its closest relatives.  But it is not a hawk, nor an eagle, nor any other sort of bird.  It is an Osprey, and that is that.

For not the first time on this blog we are looking at a bird that is the sole representative of its family, in this case the family Pandionidae.  It does share a basic body plan with its cousins in the neighbouring Accipitridae (the hawks and eagles), but with some notable alterations which adapt it to its special hunting strategy.

It is most obviously distinguished from the hawks by its long, narrow, elbowed wings.  This shape seems to equip the Osprey for soaring, like its cousins, but also for hovering over the water while it searches for its prey.  Perhaps they also assist in the dive itself, stretching back behind the Osprey’s body creating a slick, streamlined silhouette to facilitate slicing through both air and water.

Entering the water brings its own challenges, and so the Osprey is outfitted with dense, oily plumage to prevent waterlogging and allow takeoff from the water’s surface.  It can also close its nostrils to keep the water out of its lungs – this being a useful talent for all air-breathing aquatic creatures.

Once in the water the Osprey must secure its quarry and this can itself be difficult, what with fish being so slippery and generally not wanting to be eaten.  For this the Osprey has some of the most fearsome feet in the raptor realm.  Its talons are especially large and sharply curved3.  Its outer toe can rotate to the back, to place a talon on every side of its meal4.  The soles of its feet are covered in sharp spicules which facilitate gripping slimy prey.  A better-adapted pair of fish-grabbers you simply will not find.

osprey
An Osprey on the hunt, weapons at the ready.

Finally, prey in-hand (er, foot), the Osprey must carry its catch to solid ground in order to make a meal of it.  It does this using a bit of brute force, but also by taking advantage of the naturally hydrodynamic (and consequently aerodynamic) shape of its cargo.  Upon takeoff, the Osprey carefully positions its prey so that it flies face-first through the air, providing the least resistance and conserving energy for the weary hunter.

As a consequence of its adaptions – and perhaps for other reasons not entirely clear – the Osprey is a bit of an odd-looking critter.  Something about its body seems inherently disproportionate, and it is forever making a goofy expression.  It’s no beauty-contest winner, is what I’m getting at.

Nevertheless the Osprey’s unique life strategies have worked well for it, as it is one of only three raptor species that inhabits all of the world’s non-Antarctic continents5.  It seems to occupy a niche with little viable competition, and so wherever you find fish near trees you are likely to find an Osprey.  Provided it’s warm out anyway, as migration turns out to be an absolute necessity for fish-eaters in cold climates6.

Should you find yourself on the search for this not-so-elusive creature, a trip to the nearest fish-bearing water body is in order.  Osprey can often be seen circling overhead as they hunt, or perched in trees along the bank.  Their high-pitch, chirping, surprisingly wimpy call can give them away, as can the presence of their characteristic nests.  Built high in an open tree or on a human-made structure7 these large stick-nests are typically easy to see, and watching Osprey raise their young is a favourite pastime of vacationers everywhere.

If you’re not familiar with the Osprey, I implore you to get out and meet one of our most accessible one-word-birds.  They have all the strange quirkiness that a one-word name should be attached to, with the convenience of probably living right next-door.  What better toe-dip into the world of one-word-birds could you ask for?


1Not official categories, making this up as I go along.
2Sorry skimmers, there was no room for you here.  Weirdos. 
3Like fishhooks.  Get it?
4This condition – shared with owls – is called zygodactyly.  You’re welcome.
5Name the other two for a nickel?
6You’ll never guess why…
7Like a hydro pole, utility tower or dedicated platform.

Photos:
Top: The author.
Bottom: By NASA – http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=23019, specifically 04pd1258.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=111931

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