Download Crayfish - Colorado Field Ornithologists

THE HUNGRY BIRD
Crayfish
Dave Leatherman
Introduction
My restaurant-manager friend Nia, born and raised near New Orleans, says the best way to eat them is from a roadside stand, fresh boiled
in proper seasonings, maybe a couple pounds worth. “You hold the bug
in both hands, and at the same time pinch off the head and tail, throwing away the body. Suck the head, get all the good juice out, then toss
it. Next you lift the tail meat a little with one thumb, pinch the tip with
the other hand, and that pops the meat out. Eat the tail meat, take a bite
of potato and a bite of corn (on the cob). Wash it all down with Abita
Amber (beer), or if you’re a hardcore local, an Abita Turbodog. Grab
another bug. Repeat. Makes me homesick just talkin’ about it.” She was
visibly emotional.
Down on the Gulf they call them “bugs” or “mudbugs.” We Ohio kids
caught “crawdads.” In Australia they’re “yabbies.” Throughout most of
the U.S. they are known as “crawfish” or “crayfish.”
Regardless of what name they go by, humans; many other vertebrates
like raccoon, mink, otter, fish and, yes, birds find them highly edible.
To highlight the degree to which humans enjoy eating crayfish, in the
early 2000s more than 500,000 acres of Louisiana, supplier at the time
of over 90% of the world’s crop, had been flooded for the production
of crayfish. The 2004 harvest was more than 58,000 tons (Anonymous
2009). That’s a lot of head-sucking and tail meat. More information will
follow regarding the influence of
southern U.S. crayfish farming on
birds (Huner 2000, Anon. 2009).
Crayfish are in the Phylum Arthropoda, Subphylum Crustacea,
Class Malacostraca, Order Decapoda and Superfamily Astrocoidea.
All the species in Colorado are in
the family Cambaridae.
As decapods they have 10 walking legs, the first pair modified into
pincers. Their bodies are divided
into two major regions, the cephalothorax and the abdomen, that
A large crayfish specimen (Orconectes sp.) together are comprised of 20 segfrom Claymore Lake in Laporte (Larimer ments, each with a pair of appendCounty), CO. Photo by Dave Leatherman ages. Besides walking forward, the
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various appendages aid in directing water to the gills, reproduction (including egg holding in females), swimming backward and various other
functions.
If you like the charm and detail common to scientific writing before they put something in the water at research institutions, check out
Thomas Huxley’s famous late 19th century treatise (available in its entirety in the “further reading” section of the Wikipedia entry for crayfish
on-line). Here we learn “cray” is an Old English derivative of “crevis”
or “crevice.” These terms are thought to come from either the French
“ecrevisse” or the Low Dutch “crevik,” by which the crayfish is known
in these languages. Both obviously refer to general lifestyle of these
animals. Huxley is not sure which etymology is correct and charmingly
deduces the term crayfish, or “crevicefish”, is either the result of the
Norman Conquest or comes from the natural assimilation of Angles and
Saxons into the English culture (Huxley, 1880).
Certain species of crayfish can live up to 15-20 years. They are generally born in the spring and take a few years to reach sexual maturity.
Young crayfish enlarge by molting their exoskeleton 2-3 times per year.
Later in life, molting is annual, with very old individuals shedding only
every few years. They eat a wide range of dead matter, mostly plant but
some animal. The pincers, for which they and their lobster relatives are
known, aid food manipulation, courtship and defense. Of course, the
crayfish existence is generally aquatic, but they are capable of living out
of water for short periods. During times of low water or hot weather,
they often burrow into soft mud or retreat to mini-caves along the bank.
Almost all crayfish species like relatively unpolluted, moving water that
does not freeze completely throughout its depth (Huxley 1880).
Colorado Crayfish Distribution and Status
Looking at the literature, the occurrence and status of Colorado
crayfish would appear to be a moving target, depending on the species.
This is in part due to taxonomic issues, the general lack of systematic/
periodic (including recent) surveys, collection records not being published and the volatility of human introductions via reckless handling or
purposeful release of live bait. That said, the following is a concerted attempt at pulling things together. Colorado hosts, or has hosted, at least
eight species of crayfish (Walker 2013, Unger 1986). Six of these are
considered native to at least one drainage in the state, with two being
wholly introduced. This compares with the roughly 350 species occurring in North America, the southeastern U.S. being richest in diversity
(Unger 1986).
The current status and distribution of the eight Colorado species is as
follows (Walker 2013, Unger 1986, Foutz per. comm.):
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Cambarus diogenes (devil crayfish) was native to the South Platte
River, now considered extirpated.
Orconectes virilis (virile crayfish) was native to the South Platte River
and presently is known from the South Platte, Arkansas, Colorado and
possibly Rio Grande Rivers.
O. nais (water nymph crayfish) was native to the Arkansas, South
Platte, Rio Grande and North Fork of Republican Rivers. Presently it
is known from the Arkansas, South Platte, Republican and Rio Grande
Rivers.
O. immunis (calico crayfish) was native to the South Platte and Arkansas Rivers. Presently it is known from the South Platte, Arkansas
and Colorado Rivers.
O. neglectus neglectus (ringed crayfish) was native to the Republican
River and is now known from the Republican and Arkansas Rivers.
Procambarus simulens (southern plains crayfish) was possibly native
to the North Fork of Smokey Hill River (south of Burlington) but, if
present there, has since been extirpated. It presently resides in the Arkansas River, where introduced.
O. rusticus (rusty crayfish) is considered an introduced invasive that
presently is known to reside in parts of the Colorado and Rio Grand
Rivers. It has the potential to spread and negatively affect native crayfish, fish and aquatic plants.
O. propinquus (northern clearwater crayfish) has been introduced in
the Arkansas River.
Summarizing the status of crayfish in Colorado, seven species are
thought to presently reside with the borders of Colorado. The eastern
plains represent what is likely the western range limit of species native to the East. The Rocky Mountains are a barrier, and any crayfish
found west of the Continental Divide represents human introduction.
No species native to the far western U.S. has occurred here. In Colorado at present it appears only a few species are at all plentiful, widely
distributed and/or exhibit habits that would make them significant as
prey for birds. That said, a considerable number of Colorado bird species
are reported to have eaten crayfish at some place and time within their
established ranges.
Crayfish and Birds
Even considering our less than robust diversity, sooner or later any
birder who spends time by a variety of water bodies in Colorado will see
a bird eat a crayfish, often gulls, diving waterfowl or waders. But other
species, including dabbling ducks and so-called “land birds,” will take a
crayfish if the opportunity presents itself.
Apparently birds eating crayfish is a popular subject for outdoor en
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thusiasts with cameras. When I did a search for “birds eating crayfish,”
no less than 23 species were represented in the still photo portfolio (including two non-North American species: Great Crested Grebe and
White-faced Heron). I also found videos including a charming episode
of a parent Common Loon feeding a chick; a Barred Owl parent feeding a crayfish to its owlet named “Wallace;” a male Hooded Merganser,
crayfish in beak, being hounded by either a female or young conspecific
and an American Coot dining on crayfish in an exclusive New York
City eatery named Central Park.
No less than 88 species currently on the Checklist of the Birds of
Colorado (plus Mottled Duck, which may soon be added, and Mute
Swan, perhaps a future qualifier) are known to consume crayfish (species in bold are particularly notable for their routine or episodic eating
of crayfish). Another 25 or more would likely eat crayfish under the
right circumstances. The list of known crayfish-eating species that have
been seen in our state is as follows: Fulvous Whistling-Duck, Blackbellied Whistling-Duck, Wood Duck, Gadwall, Mallard, Blue-winged
Teal, Cinnamon Teal, Northern Pintail, Green-winged Teal, Harlequin
Duck, Surf Scoter, White-winged Scoter, Black Scoter, Long-tailed
Duck, Bufflehead, Common Goldeneye, Barrow’s Goldeneye, Hooded Merganser, Common Merganser, Red-breasted Merganser, Ruddy
Duck, Common Loon, Pied-billed Grebe, Horned Grebe, Red-necked
Grebe, Eared Grebe, American White Pelican, Double-crested Cormorant, American Bittern, Least Bittern, Great Blue Heron, Great Egret,
Snowy Egret, Little Blue Heron, Tricolored Heron, Cattle Egret, Green
Heron, Black-crowned Night-Heron, Yellow-crowned Night-Heron,
White Ibis, Glossy Ibis, White-faced Ibis, Roseate Spoonbill, Wood
Stork, Common Black-Hawk,
Red-shouldered Hawk, Redtailed Hawk, Crested Caracara,
Merlin, King Rail, Virginia Rail,
Sora, Purple Gallinule, American
Coot, Sandhill Crane, Whooping Crane, Piping Plover, Killdeer, Black-necked Stilt, Greater
Yellowlegs, Upland Sandpiper,
Whimbrel, Long-billed Curlew,
Long-billed Dowitcher, Wilson’s
Pied-billed Grebe attempting to eat a crayfish Snipe, Franklin’s Gull, Mew
at Bosque del Apache NWR, New Mexico on Gull, Ring-billed Gull, Cali25 November 2009. All but one claw, which fornia Gull, Herring Gull, Cascame off in a vigorous bout of thrashing, was pian Tern, Black Tern, Barn Owl,
swallowed. Photo by Bill Schmoker
Western Screech-Owl, Eastern
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Screech-Owl, Great Horned
Owl, Barred Owl, Belted
Kingfisher, Red-headed Woodpecker, Loggerhead Shrike, Blue
Jay, American Crow, Common
Raven, Tree Swallow, Brown
Thrasher, Rusty Blackbird,
Common Grackle and Greattailed Grackle.
Comparing the above list to
the total Colorado checklist,
there are species missing that
might seem likely to consume
crayfish: Osprey, Brown Peli- Rusty Blackbird male with small crayfish taken
can, the Aechmophorus grebes, from Boulder Creek east of Boulder, CO on 22
Neotropic Cormorant, both December 2013. Photo by Bill Schmoker
scaup, Ring-necked Duck, Reddish Egret, certain hawks, Black Rail, certain large plovers, many large
“white-headed” gulls and Forster’s Tern. However, available species accounts contain no mention of crayfish.
Crayfish are eaten by birds in many ways, mostly depending on the
size and condition of the prey and the type of bird. Strategies for dealing with/avoiding the hard crayfish exoskeleton include discarding the
hardest sections or pulling meat/viscera out of cracked or decayed sections of this casing (gulls, for example); grinding it in the crop after ingestion (Hooded Merganser, for example) or regurgitating it in bits via
pellets (kingfishers, owls and ibis, for example). Crayfish captured alive
and eaten whole are usually eaten tail-first, in deference to the claws
and/or simply choosing the path of least resistance based on crayfish
anatomy (streamlined in this direction, a tangle of barbed wire in the
other). Birds attempting to eat particularly large crayfish, or that just
prefer not to eat them whole, usually remove the claws. This has been
my experience with gulls, particularly Ring-billed, Franklin’s and California Gulls at eastern plains reservoirs in late summer/autumn. In such
places the beach can be heavily littered with beautiful blue and orange
pincers. To each crustacean-eater his own. Presented with a plated lobster, we humans covet the tail and claw “meat” (the latter mostly made
up of the adductor muscle used to close the pincers). Birds consuming
much smaller crayfish most-highly value tail meat and internal viscera.
Apparently, little nuggets of meat entombed within hard chitin pincers
are just not worth it for most birds. Birds that scavenge dead crayfish,
such as shorebirds and gulls, will pick and probe for any and all soft
morsels they can find.
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Interesting tidbits from the literature
pertaining to birds and crayfish
• The diet of King Rails in Arkansas
rice fields was 61 percent by volume crayfish in spring, 22 percent in summer, 3 percent in fall and 7 percent in winter. In this
study smaller specimens were eaten whole,
while larger ones were hacked to pieces
(for a particularly large one, this latter process took seven minutes) (Poole 2005).
• Mew Gulls nesting near inland
lakes in British Columbia relied heavily
on crayfish (Vermeer 1986).
• Mottled Ducks nesting in Louisiana rice fields eat at least some crayfish
Western Screech-Owl fledgling, envious (Weeks 1969, Stutzenbacker 1988).
• With the acceleration of comsibling at its side, swallows a crayfish
tail provided by a parent. Lake Forest mercial crayfish farming in the South,
Park, WA. Photo by Gregg Krogstad many waders including herons, egrets
and ibis were assigned “pest” status due
of a drawing by Tony Angell
to their predation on the “crop,” a label
that threatened them in ways reminiscent of the millenary trade in the
late 1800s and early 1900s (Ryder 1994, Martin 1985, Fluery 1995).
• The two crayfish types grown for human consumption, and now
prominent in the diets of many southern waders, are Procambarus
clarkii (red swamp crawfish) and P. zonangulus (white river crawfish).
These species make up 70-80 percent and 20-30 percent respectively
of the commercial harvest (Huner 2000). Their introduction into
other parts of the world, Africa particularly, has proven problematic.
• White-faced Ibis employ two methods when foraging in water:
the “ranging” method, which involves walking back and forth and
pecking like a chicken, and the “stationary” method of standing in
one spot and swinging the bill side to side. Ranging is used for crayfish and stationary for midge larvae (Belknap 1957).
• Rusty Blackbirds have been known to submerge their heads entirely to acquire crayfish (Forbush 1927, Avery 2013), while Western
Screech-owls (not wanting to mess up a “good facial disk day?”) will
only stick their legs into the water (Cannings 2001).
• An Aplomado Falcon once stole a crayfish from a Little Blue
Heron (Clark 1989).
• Selenium concentration in crayfish is one of the threats to the
population of the Yuma Clapper Rail in the Lower Colorado River
area (Rusk 1991).
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• Sora rail chicks raised in
captivity from birth will readily
take dog food, but those brought
in from the wild will not eat dog
food until crayfish and dragonfly bits are mixed in (Kaufman
1987).
• Of all the species that feed
on crayfish, White Ibis perhaps
depends on them most. Inland
freshwater Florida studies found Wood Duck male with crayfish at Long Pond,
crayfish provided 60-72 percent Fort Collins, Larimer County, Colorado on
of the total energy this bird ob- 20 March 2013. Photo by Rachel Hopper
tained from feeding (Kushlan
1979). Another inland Florida
study lists the contents regurgitated from 50 young White
Ibises as: 352 cutworms, 308
grasshoppers, 602 crayfish and
42 small snakes (Baynard 1912).
Perhaps a very surprising consumer of crayfish (O. virilis), from
a report in Ontario, is Tree Swallow. In this instance, swallows ate
crayfish just prior to breeding sea- White-winged Scoter preparing to swallow a
son, presumably to boost calcium crayfish tail-first, Thomas Reservoir, Boulder
levels needed for eggshell produc- County, Colorado on 29 December 2008.
Photo by David Waltman
tion (Winkler 2011).
While not involving consumption of crayfish per se, at least three Colorado birds, Piping Plover (Elliott-Smith 2004), Killdeer (Kull 1977) and Caspian Tern (Bent
1921), utilize crayfish exoskeletons, including claws, in their nests. The
plovers construct simple “scrapes,” while the tern, not a known breeder
here (Wickersham, pers. corr.) produce a ground nest built-up enough
to have a rim (which is where claws are incorporated). Presumably these
function to camouflage the nest from predators.
Lastly, a story from my Grandview Cemetery haunt in Fort Collins
where an irrigation ditch filled in summer with water diverted from the
Poudre River runs through the eastern part. Over years of frequent visitation, I have come to learn that Common Grackles utilize this ditch
quite a bit. In it they dunk dry food obtained elsewhere, and they find
prey along or in it quite often. On 10 May 2011 I became interested in a
male grackle flushed from tall dry grass along the bank. After I retreated
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20 yards, the bird quickly returned to
the flushing location. Grackles can
be quite wary, so I feigned indifference and then very slowly swung my
optics to watch what happened next.
To my surprise, although perhaps I
shouldn’t have been had I paid better
attention the first 62 years of my life,
the grackle was poking at, stabbing
and otherwise subduing a large crayfish. The captured creature had been
dragged from the water onto the lower ditch bank, and was flailing claws
like a lone fan in the stands trying to
get “the wave” started. After subduing the creature, the grackle removed
its tail, pecked at the tail meat, and
Common Grackle preparing to eviscerate a then focused on the contents of the
crayfish it captured and killed along the ditch “torso”. With the meal on its back,
at Grandview Cemetery, Fort Collins, Col- the grackle positioned itself beside it,
orado. Photo by Dave Leatherman
beak pointed away from the head to
start. Then it looked down and thrust
its beak inside the tube of chitin. For minutes it pulled out chunks of internal organs, basically leaving only a hollow casing with orange-tipped
claws attached.
About 10 months earlier on 31 July 2010, I photographed a young
crayfish scavenging tissue from the skeletal remains of a snake lying under water on the bottom of the same ditch mentioned above. As I write,
having witnessed many grackles that wash or soak their prey in water,
the above grackle episode with the crayfish, and a 9 June 2013 incident
that involved a grackle eating a garter snake in the same ditch, I now
wonder if it all just kind of goes together in this big, bad, wonderful
natural world of eat and/or be eaten. Like Nia said, to do it right, first
you pull off the head, then you pop out the tail meat, take a couple bites
of other stuff, and wash it all down…
Acknowledgments
Thanks go to Bill Schmoker, David Waltman and Rachel Hopper for granting use of their photographs. Tony Angell was most generous to share his
screech-owl drawing that will appear along with others in his book The
House of Owls (scheduled for 2015). Gregg Krogstad photographed Tony’s
drawing and emailed the file in timely fashion. Randy Foutz, Native Aquatic
Species Biologist with Colorado Parks & Wildlife, was very helpful in providing access to Pete Walker’s unpublished CPW crayfish report. Duane Nel-
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son kindly responded promptly to my request for local knowledge of crayfish occurrence
east of Pueblo. Janeal Thompson provided a helpful review. Lynn Wickersham confirmed
Caspian Tern is still not known to have bred in Colorado. John and Joan Schmid let me
catch the crayfish (pg. 153) in the ditch near their home.
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