BACKYARD BIRDING IN MERIDA, YUCATAN AND BEYOND-GRUBBERS, STRAINERS, SKIMMERS, AND SHEARERS: DUCK BILLS, MORE OR LESS, PART 1 OF 2

Black-bellied Whistling Ducks

Doesn’t this title sound like cooking utensils found in a kitchen? Instead I will discuss tools for food gathering by duck-like bills as examples.

Have you ever looked at the edge of a duck’s bill or goose or even a flamingo and thought, “What are those tiny ridges? They certainly look like teeth. Hmm, I don’t think birds have teeth.”

White, comb-like lamellae in lower bill of Mallard
Lamellae or teeth-like ridges of upper bill of Mallard
Lamellae ridges of American Flamingo upper and lower bill

You are correct. Birds don’t have teeth. And they don’t need to chew because they can grind their food in their muscular gizzard with help from digestive juices and sometimes grit or stones. (Notice grit is singular. I’m not referring to that buttered kitty litter-like substance or southern food called grits.)

What are those ridges?

Those teeth-like projections on the upper and lower bills, called lamellae, serve as a sieve or strainer for filter feeding in ducks, geese, swans, and flamingos. The lamellae trap seeds, invertebrates and other foods to separate them from dirt and water.  They have varying degrees of flexibility.

Typically most ducks have 50-70 lamellae on their bills. However, Northern Shovelers with their super-sized bills also have a super-sized number of lamellae with 180 on the upper bill and 220 on the bottom!Blue-winged and Green-winged Teals may have 120-130.

Super-sized bill of male Northern Shoveler
Hundreds of white lamellae along upper and lower bills of Northern Shoveler female

So it’s easy to infer these species may feed differently and/or with different diets.

Let’s compare the bills of the Snow Goose to the Canada Goose. From the side, the Snow Goose looks like it’s snarling or giving an Elvis lip. It’s a so-called “grin patch.” The straight Canada Goose bill lacks that.

Short bill of Snow Goose
Snow Goose feeding; note grin patch of bill.
Canada Goose with straight bill

Meanwhile the Snow Goose uproots grasses and sedges with that grin patch to eat plant bulbs and rhizomes. Hence it is a grubber because it digs up roots and tubers. On the other hand, er, bill, the Canada Goose shears off short grasses above ground. They can coexist in the same habitat due to their feeding methods, however, both can graze on grain in agricultural fields. Part 2 will share other feeding methods. (Sometimes we want to fit details into tiny boxes for our understanding, but science is often more complex.)

But wait, there’s more.

Some species have spikes on the sides of their tongues called papillae, which also aid in filter feeding.

Tongue spikes and bill ridges of Canada Goose
Papillae inside mouth of American Flamingo

Papillae and Lamellae.  They sound like a comedy team.

What is the composition of a duck bill?

Light in weight a duck bill is composed of an inner core of spongy bone with solid bone over it. The lining over the bony structure is a hard shell of keratin, which maintains the bill’s shape. This outer layer continues to grow to heal cuts and replace the worn down outer bill parts. (Most of us are familiar with keratin as the protein in human fingernails.)  On the upper bill hardened tip is a nail, which may be used to dig through mud or move food as seen in the Blue-winged Teal image.

Nail at tip of upper bill, Black-bellied Whistling-Duck
Blue-winged Teal feeding underwater

Recent studies indicate the tip of the lower bill contains rows of pits filled with clumps of touch receptors or touch papillae. They vary between wildfowl species but probably can detect food by touch. (Of course taste could be involved too.)

Birds also have a sense of taste and can distinguish between salty, sweet, sour, bitter, and possibly savory but have fewer taste buds than humans. However, typically the taste buds are not on the tongue but along the floor and roof of the mouth. A few taste buds appear close to the tip of the bill.

I am proposing the lamellae of duck bills actually help water-proof their feathers. Recent research indicates how water-proofing doesn’t come from the waxy substance of the preen gland, but rather how the feathers’ smallest structures, the barbules, are aligned with the barbs. Surely those tiny ridges would assist in that. But that’s just my opinion.

Mottled Duck aligns feathers using its bill which aids in water-proofing the plumage

Generally ducks are divided into two groups to obtain food: dabblers and divers.  Dabblers often tip up in water to feed as shown in the next image. Stay tuned for Part 2 to learn more about these two duck groups and the differences in their bills!

PHOTO 15 Bottoms up! Gadwall dabbling, adult male on left

TAKE TIME TO DABBLE IN NATURE

REFERENCES:

Sal a Pajarear Yucatán (Guía de Aves), Birds and Reserves of the Yucatán Peninsula. A Guide to Birds of Mexico and Northern Central America, The Crossley ID Guide: Eatern Birds, What It’s Like To Be A Bird

https://birdsoftheworld.org/bow/home

https://www.allaboutbirds.org/guide/Canada_Goose/lifehistory

https://www.allaboutbirds.org/guide/Snow_Goose/lifehistory#food

https://birdsoftheworld.org/bow/species/cangoo/cur/foodhabits#feeding

https://ebrary.net/97900/health/bill_organs_waterfowl

https://www.ducks.org/conservation/waterfowl-research-science/the-scoop-on-duck-bills

https://www.allaboutbirds.org/guide/Mottled_Duck/id

Cherie Pittillo, “nature inspired,” photographer and author, explores nature everywhere she goes. She’s identified 56 bird species in her Merida, Yucatan backyard view. Her monthly column features anecdotes about birding in Merida, Yucatan and also wildlife beyond the Yucatan.

Contact: all4birdies@gmail.com  All rights reserved, ©Cherie Pittillo



Comments

comments

more recommended stories