Harns Marsh Preserve and the Swamphen Saga

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Harns isn’t listed with the famous birding destinations in south Florida (Corkscrew, Ding Darling, the Everglades, and Big Cypress) but maybe it should be.  This is a 578 acre preserve in Lehigh Acres set aside in 1985 for stormwater control along the Orange River.  Half is an open water lake but the more interesting half for birders is the shallower marsh and surrounding trail.  If you bird in the morning the sun will be at your back and allow some great shots of the waders and flyovers.  Bring a scope as many of the birds tease you from a distance.

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Sandhill Crane, Grus canadensis

In my experience Harns is the best place to see Snail Kites.  The imposing Sandhill Cranes approached me so closely I was a little worried about their intention, but it did allow some great closeups.  The abundant non-native Apple Snails also attract Limpkins, while Bald Eagles, Harriers, Red-shouldered Hawks, Bitterns, and Vultures galore complemented the usual Florida waders.  My personal life list here is 37, but locals report up to 100 species at Harns.

Black Vulture

Black Vulture, Coragyps atratus

The reason for our recent visit was to chase the unusual Grey-headed swamphen (Porphyrio poliocephalus), listed on eBird as a rarity at this location.  “Porphyrio” is Greek for purple, “polio” is Greek for grey, and “cephalus” is Latin for head.  I had previously seen the bird only once at great distance and it was a life bird for my colleague.  The large purple and blue bird was easily spotted among the grasses almost as soon as we arrived.  The grey head was subtle if present at all.  Apparently it is most obvious on the male; the female head is blue.

Grey-headed swamphen

Grey-headed swamphen, Porphyrio poliocephalus

The swamphen saga in Florida is either one of escape and survival, or invasion and alarm depending on your point of view.  The Purple swamphen is a native of Turkey, India, China, and Thailand and has recently been split into 6 separate species, the Grey-headed being one.  There are two stories of the origin of this large tropical rail in south Florida.  One account claims they escaped from the Miami Metro Zoo during hurricane Andrew in 1992.  The other story blames careless aviculturalists allowing them to roam freely in Pembroke, Florida at about the same time.  In any case the birds were sprung and made the most of their new freedom.

Tricolored-heron

Tricolored-heron, Egretta tricolor

This bird has been described as “a Purple Gallinule on steroids”, it being much larger but otherwise quite similar to its native cousin.  The non-migratory rail has quickly adjusted to the good life in the freshwater marshes of sunny Florida, primarily feasting on plants and supplementing the diet with mollusks, and small animals.

Red-shouldered Hawk

Red-shouldered Hawk, Buteo lineatus

Up the food chain their threats are from alligators, large mammals, birds-of-prey, and for a while, man.  The swamphens often raise several broods a year and their population has grown.   With some alarm regarding their potential threats to the natives, authorities started a program of eradication, shooting 3100 birds over 27 months.  This campaign ended in 2008 with the birds still  surviving and thriving.

Grey-headed swamphen

Grey-headed swamphen, Porphyrio poliocephalus

What do you think about the non-natives moving in?  My feelings are colored by the Mute Swans that almost took over our tributary of the Chesapeake Bay several years ago.  At their peak I could count several hundred of these alien, aggressive, non-migratory birds on the river with multiple nest along the shoreline.  They were displacing the native, migratory, and more humble Tundra Swans and devouring the vital submerged grasses, roots and all.  They clearly went too far when they attacked us in our canoe, (I fended them off with the paddle), and played chicken with me on the riding mower.  Thankfully an eradication program ended all this and I have not seen one on the Chesapeake in years.

Belted Kingfisher

Belted Kingfisher, Ceryle torquatus

The jury’s still out on the swamphen.  Can they assimilate and play well with others, or will they follow the lead of the Mute Swans and try to take over and dominate the Florida marshes?  The bird is clearly a survivor.  I admire that and so far I am not aware they have caused any substantial damage, but only time will tell.  In the meantime, check out this photogenic bird and the other avifauna at Harns Marsh Preserve.

Bird Digestion

Florida Scrub Jay

Florida Scrub Jay, Aphelocoma coerulescens

 

I know this may be an unappetizing topic for some, but being a physician I find the comparative anatomy and physiology of avian digestion fascinating.  Don’t confuse my title and posting with the venerable and recommended periodical “Bird Watchers Digest”, mainly for their sake.  Check it out at http://www.birdwatchersdigest.com.

Herring Gull with lunch

Herring Gull with crab, Larus argentatus

I reckon that a bird spends the majority of his life eating or hunting for food.  Even the apparent sedentary perching owl or hawk is likely planning his next attack and contemplating the next meal.  And this is time well spent since the survival of these warm-blooded, active birds, with very high metabolic rates requires a constant source of energy.  Reproduction (breeding, nest building, and rearing of the young) along with migration are also time consumers, but take a back seat to eating and daily survival.

Piping Plover

Piping Plover, Charadrius melodus

Given the requirements of flight, birds do not have the luxury of storing heavy layers of fat or foods internally, with the one exception being the preparation for migration.  For this some songbirds increase their body weight by 40% and need every last ounce and calorie for the rigors of migration.  But generally most birds need a steady and constant inflow of food and energy to survive.  This is even more critical in the cold of winter.

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Little Blue Heron, Egretta caerulea

Luckily birds have evolved a rapid and efficient digestive system, able to cope with a varied diet.  For some birds and food types the transit from beak to cloaca can be as rapid as 30 minutes.  The beak and toothless mouth are for stabbing, carrying, crushing, and tearing the food, quickly sending it downstream to the tubular esophagus.  Fortunately, given their diet, birds have a small tongue with few, if any taste buds.

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Gull demonstrating the edentulous mouth, small tongue, and no taste buds.

Many have a widened area in the mid-esophagus called the crop.  This is the site of short-term parking for a big meal as is often demonstrated by the tell tale neck bulge of the heron who recently swallowed the large fish, always head first.

Great Blue Heron

Great Blue Heron, Ardea herodias

The bird stomach is very different than ours.  It is a two-part affair with a glandular first sac called the proventriculus.  Strong acid, enzymes, and mucus start the digestive process here, before transporting the food to the second part called the gizzard.

Snowy Egret

Snowy Egret with large insect, Egretta thula

The gizzard is a thicker muscular sac with a rough sand-like lining, perfect for grinding and mixing.  Some contain sand and stones further aiding the process.  Pellets containing the non-digestible waste such as bone fragments, hair, shells, and feathers are passed and often mark the roosting sites of owls and other birds-of-prey.

Peregrine Falcon

Peregrine Falcon eating a Lesser Black-backed Gull, Falco peregrinus and Larus fuscus

The actual absorption of nutrients occurs in the small intestine where food is mixed with the enzymes from the pancreas.  Birds-of-prey have a relatively short small bowel, whereas herbivorous birds have a longer one, needed for the slower digestion of the tougher cellulose-rich food.  Multiple small sacs off the small bowel are called caeca and harbor beneficial bacteria, further aiding digestion.

Limpkin with Apple Snail

Limpkin with Apple Snail, Aramus guarauna

A bird’s colon or large bowel is short, just serving as a conduit to the final cavity, the cloaca.  The cloaca empties to the outside world via the vent, sometimes onto the unsuspecting birder.  As you know the cloaca is the common chamber for both sexes receiving the products of the gastrointestinal, urologic, and genital tracts.  The close and rapid contact of the vents and cloacae is when and where the genetic material is exchanged.

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Its a Blue-gray Gnatcatcher so it must be eating a gnat. Polioptila caerulea

The Cattle Egret below was finally fed up with his diet of insects and mice and got in the drive-thru lane at McDonalds thinking that they might offer a better menu.  I’m not so sure.

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Cattle Egret, Bubulcus ibis