Thursday, April 30, 2015

Bill Size and Shape

One of my favorite things to do, during migration season is to identify birds.  Many aspects of bird watching combine to make this the world’s number one hobby; the hunt through the binoculars for that wind-blown leaf you thought was a bird;  the sudden realization that you’re facing the wrong direction in a valley; following a song for an entire afternoon just to get a glimpse of that fellow who sings his heart out. 

When I do finally see that special bird, I have to take quick mental notes on size, color, foot type (if I see a bird feeding), bill type, and behaviors.  Although behavior is a really big part of identification, I enjoy using bill type as a guide for those really tough ones.  This is especially true when you consider that many species depend mostly on a specific food for survival.  Whether it feeds on seeds, insects, nectar, or other animals, its bill will be specially adapted for feeding.

Members of the parrot family have beaks that are designed for gripping and cracking seeds and nuts.  (photo: Leigh French)

Seedeaters need to have a bill that is strong enough to crack through the thick hard hulls to get to the meaty fruit inside.  Their bills are often thick and arrow shaped having hard ridges to aide in grip, like a wrench.  Parrots are a great example of this.  Their bills are very thick and their upper mandible has serrations on its underside, out near the tip, so that they can grip nuts and crack them.  Also, cardinals have a thick, strong bill for smaller seeds.

Shorebirds are a wonderful example of diversity within a habitat.  Gulls and terns have bills adapted for fishing.  They dive into the water from the air or from floating on the water. 

Roseate Spoonbills have a bill shaped for shoveling around in the lake bottom debris for their food. (photo: Gay Schroer)

Some Ducks and wading birds have a specialized bill for shoveling around in the water for invertebrates. 

This Scarlet Ibis has a very specialized beak for probing for food in soft mud and under plants (photo: Gay Schroer)

Birds like the sandpipers, oystercatchers, godwits, turnstones, and plovers have bills that are shaped for finding invertebrates that have tunneled into the sand or mud.  Their bill is sort of shaped like the prey for which they forage. 

Herons and egrets use their bill as a spear.

This Great Blue Heron uses his bill as a spear and then swallows the fish whole (photo: Gay Schroer

…whereas this Yellow-crowned Night Heron snatches his preferred diet of crayfish with his long pointed bill

…and then turns it, pinchers side out, and crushes it with the powerful upper portion of his bill before swallowing it

Moving away from the shore, there are other smaller birds that flit about after tiny gnats and flies.  These birds have small bills and are a bit more difficult to identify because they are usually small and fast.  These are typically gnatcatchers and flycatchers. 

Prothonotary Warblers have small thin bills for catching insects and snails which they pry out of their hiding places

Ruby-crowned Kinglets are such tiny little birds and they are the most difficult for me to see clearly.  That’s when I listen to any calls or songs they may be making.  Woodpeckers have a bill that is like a chisel.  They bang away at trees looking for insects crawling under the bark and inside the wood.

Finally, I think crows and ravens are a good transition into birds of prey.  They are very adept and intelligent.  They hammer and poke and tear and pull their food.

Meat eaters are probably more diverse because they may feed on certain animals based on their habitat.  Owls, hawks, and eagles have bills that are great for tearing meat.

The Eurasian Eagle Owl has a beak that is supremely well adapted for tearing meat (photo: Gay Schroer)

So, when you are having trouble narrowing down that bird species, perhaps you can get a good look at the bill to figure out a bit about it.

The next time you visit the World Bird Sanctuary, pay particular attention to the different beak shapes that you will see on our display birds and the birds that visit our bird feeders.  Try to guess what each bird’s preferred food would be.

Submitted by W. Leigh French, World Bird Sanctuary Naturalist

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