How to Eat a Sea Star

by | Jan 26, 2022 | Blog, Conservation, Science

By Sharon Wada

Fill

Quick Note: This blog calls a gull a seagull… do we care? Not at all! So enjoy this wonderful piece and later explore Seagull or Gull: Who really cares?
Early morning is my favorite time of day to go for a walk with my camera.  I traverse the same route and never get bored because I’m usually not looking for a particular type of bird.  When I see a creature or some activity that captures my attention, I just stop and hang out from a distance so that it will act naturally and do its thing.

Last September during golden hour, I set out along the West Seattle shoreline hoping to catch the sunrise.  As I walked toward Elliott Bay, I noticed that the usual suspects were starting their daily activities:  soaring, calling, preening, or foraging.

Just as the sun’s rays started to peek over the horizon, I spotted this Glaucous-Winged Gull (Larus glaucescens) right next to the shore.

An Anna's Hummingbird hovers amidst falling snow.

Gull © Sharon Wada

I had never seen a bird eat a sea star (or starfish as they’re commonly called).  And after the wasting disease hit Puget Sound several years ago, I rarely see sea stars like this Evasterias troschelli, so the pairing was unusual.  I crouched down and waited to see what the gull would do after successfully hunting down one of the slowest moving prey species in Puget Sound.

Here is a 7-step primer on how to eat a sea star as depicted by a very determined seagull and interpreted by one of our local seabird scientists, Tom Good, Research Fisheries Biologist at the Northwest Fisheries Science Center.

 

STEP 1:  Bring the prize to higher ground.

Gull © Sharon Wada

After wrestling with its prize while waves lapped at its feet, the gull hopped up onto the drier rocks above.  After all, one needs a proper dining surface to enjoy such a fine meal, right?

 

STEP 2:  Scarf down as much as possible in one swallow.

Gull © Sharon Wada

This behavior really surprised me.  While I had seen gulls eat fish whole, the rough, stiff and spindly arms of this sea star seemed to be fraught with challenges.

During past field observations, Tom has seen this behavior and said that it’s not unusual for seagulls to eat sea stars.  “Sea stars which are echinoderms related to sea urchins, have a high water content,” Tom noted.  “So, while the skin of the sea star looks rigid, water is supporting its structure.”

 

STEP 3:  Rest for about 10 minutes and try not to feel too much regret.

Gull © Sharon Wada

At this phase, the sea star was moving down the throat to the gull’s esophagus and beyond.

“Seagulls have incredibly strong muscles in their digestive tracts,” Tom explained.  “Food moves down the esophagus to its crop which is a sort of a holding tank before the stomach juices of the gizzard begin to break it down.  As it ingests the sea star, the gull is continuously squeezing and weakening the creature so that its hydrostatic skeleton becomes more pliable.” 

 

STEP 4:  Attempt a second inhale.

Gull © Sharon Wada

The seagull shuddered as it forced the sea star farther in.  Imagine the inner power it takes to pull in a large and unwieldy living creature down what must be a very forgiving food pipeline.

 

STEP 5:  Take another short break and look like you’re eating a handful of kielbasa sausages.

Gull © Sharon Wada

In this image, you can actually see how the water inside the sea star is being squeezed out into its now bloated arms.  Also, notice how wide the gull’s mouth was stretched.

“Birds have different strategies for different prey items,” Tom mentioned, “And because it can be difficult for the gull to break apart the sea star with its beak, it has become adept at swallowing certain types of prey whole.”

 

STEP 6:  At this point there is no going back so hammer down the rest.

Gull © Sharon Wada

Unlike humans, birds can breathe and swallow at the same time.  Notice the gull’s distended tongue and widening neck which contains esophageal (digestive) and tracheal (respiratory) “pipes” that are not attached and can shift apart from each other.  While scientists have encountered birds like herons that choked to death on a prey item that was too fat and too long, this isn’t commonly observed because fish-eating bird anatomy has been honed to accommodate sizeable and supposedly delectable meals just like this.

 

STEP 7:  Feel wonky for a while but not too long.  There’s a whole day of foraging ahead!

Gull © Sharon Wada

After the final swallow, the sea star continued its ill-fated journey, eventually landing in the bird’s crop until the stomach started to digest it.  “After digestion, most birds including gulls cough up the undigestible parts of their prey like shells and bones,” Tom noted.  “But the sea star is an invertebrate with a soft skeleton that can be digested in entirety.”

I left this gull on the rocks along Elliott Bay in what looked like a very uncomfortable state.  It had consumed the entire sea star in 20 minutes!

I felt grateful to have witnessed this incredible feat.  If I had been in a hurry or looking for a particular critter, I could have easily walked right past this guy.  So, the next time you’re on a nature walk, be sure to keep your eyes and mind open to the antics of even the most common birds and pause to watch their behaviors.  You’ll surely gain a new appreciation for how they manage to survive in our urban jungle.  Have fun exploring!

 

Author’s Note: A special thank you to scientist Tom Good PhD (tom.good@noaa.gov) for teaching me about this seagull and its sea star encounter.  Tom is both a field and seabird ecologist.   He has conducted research on diet, foraging behavior, and breeding success of seabirds in New England (herring gulls, great black-backed gulls) and in the Pacific Northwest (western gulls, glaucous winged gulls, and their hybrids, Caspian terns, rhinoceros auklets, tufted puffins, and double-crested cormorants).  Tom works on a variety of seabird-fisheries interactions, including seabird bycatch in West Coast groundfish fisheries and avian predation on Pacific salmon.
Sharon Wada

Sharon Wada

Seattle Audubon Board Member

A native Seattleite and graduate of the University of Washington, Sharon enjoyed a decades long career in healthcare information technology, including 25 years managing her own independent consulting firm.  Sharon is an avid photographer but fairly new to birding.  She considers it a privilege to observe and capture images of birds in nature. 

Glaucous-winged Gull © Sharon Wada

Gulls of Washington State

Related Articles

Join Our Science Committee

Join Our Science Committee

May 11, 2023

Do you believe conservation and education should be informed by science? Consider volunteering on our Science Committee.

Birds of Incarceration

Birds of Incarceration

May 4, 2023

No longer a barrier, our new name represents an open door for new communities to join us in our mission to advocate and organize for cities where people and birds thrive.

Intro to Urban Birds

Intro to Urban Birds

Apr 26, 2023

Conflicts over Short-Eared Owls, other birds, and access to habitat in Bow, Washington, prompted the Washington Department of Fish and Wildlife (WDFW) to update access rules to the Samish River Unit of the Skagit Wildlife Area.