Osprey

 

The osprey is about two feet long with a five-foot wingspan. This one is hovering while hunting. It eats mainly fish, which it catches by diving feet-first into water, sometimes to a depth of more than a foot. Not surprisingly, it is also called a fish hawk. Click to enlarge.

The osprey is not one of my backyard birds. But there is a nest on the Delaware River that is close enough to my house that I can walk there to watch them. 

The male catches fish in the river, carries them to the nest, then flies out again. 

And again. 

This shaggy character is one of this year's young. So... well done, osprey parents! 

Sea Hawk vs. Seahawk

This is an osprey, Pandion haliaetus, sometimes called a river hawk, sea eagle, or sea hawk. It nests near water and eats fish, diving with a dramatic splash and then rising with a fish in its talons.  
             Click on the picture to enlarge. 

I have a $20.00 bet on the Seattle Seahawks in today's Superbowl game, so I am on their side. Nevertheless, I want to point out that the live raptor they use as a mascot, the one that flies across the field just before the team runs on, is an Augur hawk, a bird native to Africa. It eats mammals, snakes, lizards, and birds -- it's really a land hawk.

OK, back to beer and nachos.

Ospreys

A pair of osprey, Pandion haliaetus. Click to enlarge.

This osprey nest platform is at the Edwin B. Forsythe National Wildlife Refuge in Oceanville, New Jersey. The female on the nest is in a crouched and open-winged posture soliciting copulation. The male is approaching, ready to comply. Want to see what happens next? Click here. 

Summer Birds, Winter Birds

An osprey, Pandion haliaetus. Click to enlarge.

Some birds fly south away from us in winter. Others fly south to us.

Osprey leave the Forsythe National Wildlife Refuge in New Jersey, where the above picture was taken, in early September. They spend the winter along the coasts of Central America and southern North America, and throughout much of South America.

Two male northern pintail ducks, Anas acuta. 

Northern pintail ducks breed in summer in Northern Eurasia, Alaska, and across Canada. They fly south to spend the winter along the east and west coasts of North America and across the southern half of the United States and into South America. Some pintails, like the ones in this photo, end up at the Forsythe Refuge in south Jersey.

The ospreys are gone, but the pintails are back. Yay!

Bird droppings...

Like humans, birds defecate the undigested remains of things they eat. Also like humans, they excrete the metabolic waste products that are left over after food is broken down for use by cells; that's mainly nitrogen. Humans excrete waste nitrogen as urea in urine -- it takes lots of water to make the dilute solution.

Birds can't be burdened with heavy water-filled bladders, and they need their metabolic water reserves for other things -- like long distance flights. They excrete nitrogen as a chemical called uric acid. It is excreted in a concentrated form with no dilution necessary. So birds stay light for flight. And uric acid excretion works fine inside eggs. The metabolic waste produced by a developing shell-bound bird fetus can be neatly stored within until hatching.

The white pasty part of bird droppings is uric acid. The dark part, sometimes brightly colored from the bird's diet, is feces. Birds simultaneously evacuate uric acid and feces from an opening just under the tail that is called the cloaca or vent. The cloacal sphincter muscle can provide ejaculatory force, as demonstrated by the defecating osprey in the photo below.

An osprey expels waste in a white stream with enough force to clear the nest. Click to enlarge!  

Some raptorial birds, like ospreys and owls, eat whole organisms. Ospreys eat fish and digest almost but not quite everything. They vomit the scales and other indigestible bits in compact "pellets." Owls regurgitate pellets of hair, bones, claws, and undigested parts of the small animals they eat. Both end up without much solid waste in their droppings, just a lot of white uric acid. The areas around their nests and eating perches get covered with droppings called "whitewash." Pellets can often be found on the ground below whitewash.

A royal tern in an indelicate moment. That's a little Forster's tern on the right, discretely averting its gaze.