Tuesday, March 3, 2015

Come flop down on the beach with Black Skimmers!

Black Skimmer
A very relaxed Black Skimmer. Crown Point Park, Mission Bay, California. February 16, 2015. Greg Gillson.
There is nothing wrong with the Black Skimmer pictured above. They often rest with their heads on the beach like that! In fact, the Sibley Guide to Birds depicts one of the the birds exactly like this.

They are in an order of birds (Charadriiformes) that also includes the families of plovers, sandpipers, gulls, terns, skuas, and auks, among many other similar birds around the world. They all share skull similarities, webbed feet, and vocal structures.

But even though they are like these other birds, they are also different. Skimmers are just weird. They are very unusual--in many ways.

The lower mandible is much longer than the upper. They skim the water--and even the sand--with their bill as they fly slowly along with deep wing strokes primarily above the horizontal and head held down. As the bill contacts fish or crustaceans the head pulls back and then up as the bird swallows the food and then the head is dipped down again.

The eye of the skimmer has 5 times more rods than cones--enabling it to see well in low light conditions. Not surprisingly, they often feed at dusk/dawn, even at night, during low tides. However, since they often rest on bright sandy beaches in the sun, their pupils constrict greatly. Again, unique, their pupils contract in vertical slits like cats, and are not round as in other birds.

You may notice a metal band on the leg of the bird above. I think they are Mexican bird bands--they start with the word "Aves" (rather than "USGS"), and have some numbers, but I can't see the entire band to read it all.

Black Skimmer
A more respectable resting posture?

Black Skimmer
Is it my imagination, or do these look like horizontal penguins with Candy-Corn bills?

Black Skimmer
Short legs with webbed toes, but they rarely swim. Skimmers are just weird.

Black Skimmer
What's up with the nostril down on the side of the upper mandible rather than on top?

Additional photos from a post in December 2013 are here: Black Skimmers at Mission Bay