Book Review: Sea Room by Adam Nicolson

Published by North Point Press, copyright 2001, 401 pages

 

The ebbing tide over-powered her desperate strokes toward the island and carried the swimmer steadily and surely away from land.  Her distraught husband on the shore knew that her rescue was impossible.  It took two strong adults to launch the heavy scow pulled high up the beach and the only other inhabitants on the small island were their infant children, safely asleep in the cabin.  All he could do was call out his love, over and over.  She did the same until just a speck in the vast sea, finally succumbing to a cold watery fate.  “The sea invites and the sea destroys”.

The Hebrides                                    photo courtesy of A. Sternick

This, and many other accounts of life and death on the Shiants, three small isolated islands in the Hebrides off the western coast of Scotland, form the basis of this wonderful book.  The author knows of what he speaks since he owns the Shiants, inheriting them from his father, who bought them for a meager sum as a young man in the 1930’s, and then passed them on to his son 40 years later.  Who would want them, four miles from the nearest port across an unpredictable and dangerous passage, bordered by steep cliffs, rocky shores, and poor anchorages?  For the author these islands “at times…have been the most important thing in my life”.

Double-crested Cormorant, Phalacrocorax auritus

This book represents the author’s twenty year quest to uncover everything about the 550 acre Shiant Islands.  How were they formed and will they survive?  Who were their Stone Age, Viking, and more recent inhabitants?  Did they thrive or merely survive?  He sought to understand the flora and fauna, especially the birdlife with myriad seabirds nesting on the steep cliffs.  Although this is not a birding book per se, the birds figure prominently in the author’s love affair with the islands, “moated by the sea”.  Nicolson enticed archeologists, geologists, ornithologists, and social historians to help him reconstruct the island’s colorful past.

Atlantic Puffin, Fratercula arctic                            courtesy of A. Sternick

His initial excursions to the islands were on fishing boats but Nicolson needed his own boat, something in the Norse tradition, that he could sail single-handedly.  He found John MacAulay, a salty shipwright, who designed and built him “Freyja”, a sixteen foot, stout, open cockpit, rowable sailboat, perfect for his needs. The only problem was that the author did not know how to sail.  As a sailor, I shake my head in amazement as Nicolson relates his crash nautical education and solo ventures into the rip-tides and dangerous waters of the Minches.  History reports dozens of shipwrecks and lost seamen here, but the author and “Freyja” surprisedly prevailed.

Peregrine Falcon, Falco peregrinus

Birders will enjoy the descriptions of the abundant avian life of the Shiants.  The Skua are the “Viking birds, heroic, bitter northern, aggressive, and magnificent modern invaders whose nests are littered with bits and pieces of Puffin and Kittiwake”.  He describes the graceful headfirst dives of the sharp-billed Gannets, one piercing the floorboards and hull of one unlucky fisherman who was smart enough to keep the bird and bill plugging the hole until safely in port.  There are descriptions of Eagles, Ravens, Falcons, Guillemots, Shearwaters, and Fulmars, “the most effortless of all the seabirds” while the social wintering Barnacle Geese mark spring each year when they leave for their nesting grounds on Greenland.

Brant, Branta bernicla

The quizzical Puffins are the island’s avian stars, wonderfully portrayed by the author, whereas the Shag or Cormorants with their evil green eyes are his “trash birds”.  I’m somewhat embarrassed to admit that the Puffin is still one of my nemesis birds (a life bird yet to be seen).  This book has inspired me to head north, at least to the coast of Maine and the maritime Canada provinces to correct that deficit.  Someday I may even make it to the Hebrides, if not the Shiants themselves.  We’ll see.

John J. Audubon’s Puffins

The Shiants have many abandoned ruins of various ages.  The study and excavation of them allowed the author and others to begin to reconstruct the social history of the islands.  It’s amazing how archeologists can discern patterns of human behavior from mere fragments of pottery, tools, stone ruins, or a bronze age golden torc dredged up by a Hebridean fisherman.  A discovery of special importance was a loaf-sized stone found buried beneath the floor of some ruins.  Upon rolling it over the archeologists discovered it was a deeply carved four-armed cross with circular border, likely the work of a saintly hermit of the first millennium seeking shelter, solace, and peace on the island.

Buller’s Shearwater, Puffinus bulleri

Sheep herding and even cattle grazing occurred on the grassy plateaus.  At its peak some 50 people inhabited the Shiants but by the late 19th century only one family remained.  The Campbells were a hardy clan of father, deaf mute son, and two beautiful daughters who were the toast and envy of the Hebrides.    The staid and determined mother tried, but failed to guard her daughters from visiting fishermen.  Even the Campbells left in 1901, leaving the islands to the sheep and birds.

Common Murre, Uria aalge

This is a fascinating book about eons of birds, plants, and later humans including the author, all eking out a spartan existence in this beautiful but challenging land.  There is a somewhat melancholy conclusion as Nicolson’s trips to the islands seem to be numbered.  Will his young college-aged son accept and cherish his inheritance as his grandfather and father had?  What will be the effects of climate change and progressive civilization on the island’s ecosystem?  For me, the lesson of the book is the inevitability of change.  Nothing ever remains the same, but life in some form will cope and persist, even on the weather-battered Shiants.

Don’t You Wish You Could Molt?

Osprey, Pandion haliaetus

 

The late August birding in my patch was slow, very slow.  When that happens you can always resort to photographing butterflies, moths and plants, but where were all the birds?  There were several possible explanations.  Fighting over territories, mates, and nesting sites were yesterday’s battles.  The birds are now more interested in fattening up for winter or migration.  Almost all the new birds had already fledged while the swallows had left the patch and were flocking inland prior to their trip south.  The maniacal keeehahh of the perching Red-tailed Hawk may have had something to do with the quiet, but it was more a threat to the squirrels and rabbits who were having a banner year, than to the songbirds.

Red-tailed Hawk, Buteo jamaicensis

Then it occurred to me.  Maybe they were molting, molting in private, hiding in their embarrassing and more vulnerable states.  I don’t know about you, but molting has always confused me.  Consider this post as a back-to-school course, Molting 101; my attempt to shed some light on this critical avian process.

Tiger Swallowtail, Pterourus glaucus

American Painted Lady, Vanessa virginiensis

Canada Thistle, Cirsium arvense

Feathers are dead appendages with no innervation or blood flow.  They are an amazing and complex adaptation for flight, insulation, and display, but their fragility necessitates periodic replacement.  They can be preened, cleaned, and rearranged, but they cannot be repaired.  Every feather has a rudimentary replacement in its follicle waiting for a stimulus to grow and push out the worn, frayed, precursor.  The simple annual cycle for birds is to breed, molt, and survive the winter or migration, and then start the same cycle next year, all over again.

Magnolia Warbler, Dendroica magnolia

Two sets of terminology are used to describe molting and the resultant plumages.  This adds to my confusion.  The traditional, used since 1900, describes the adult’s two plumages as “winter” and “breeding”.  Shortcomings of this system occur since many of our birds winter and may breed in South America where it is actually summer.  And other young birds in breeding plumage may not actually breed for several years.  Thus, in 1959 the second and preferred terminology was proposed.  In this system adult birds molt into their “basic” plumage just after breeding, and then in spring will molt into their “alternative” plumage, prior to breeding.

Verdin, Auriparus flaviceps

But it gets more complicated as each bird species has its own molting schedule and various numbers of yearly molts depending on its lifestyle.  Sedentary arboreal birds may stick to the standard molting script, whereas birds attempting long difficult migrations, or those living in harsh environments such as a desert or the Arctic, may undertake more frequent molts.  Birds wintering in cold climates may add up to 50% more feathers to their basic plumage compared to the alternate garb.  All this for added insulation and winter survival.

Chestnut-sided Warbler, Dendroica pensylvanica

Then there are the juveniles who molt out of their natal down into a juvenile plumage before fledging, and later molt into the adult basic plumage.  The progression to adult may occur in the first year for many, or may be spread over several years as seen in the gulls. They molt into first, second, and third winter, and for some even fourth winter plumages before obtaining the basic plumage.

Black-throated Green Warbler, Dendroica virens

Birds have evolved two major molting strategies.  Ducks, loons, grebes and others are called synchronous molters and get it done, all feathers, all at once.  This results in a month of flightless vulnerability often spent on an isolated pond or lake away from predators, but does not interfere with flight or life for the remainder of the year.  The other strategy is to gradually molt a few feathers at a time in a defined reproducible sequence, specific for each species.  This method has a minimal impact on flight and other routines of life.

American Goldfinch, Carduelis tristis

Molting is one of the most energetically costly events in a bird’s life.  It generally, therefore, does not overlap with the other demanding activities of reproduction and migration.  There are some examples, however, when molting does occur simultaneously with egg laying and incubation, but in these circumstances the molting process is much prolonged.  Very little is known about what factors trigger a molt.  A single lost feather is rather quickly replaced, but what triggers a generalized molt?  One theory suggests it is related to the changing length of daylight.

American Wigeon, Anas americana

My philosophy for understanding molting, and just about everything else is “KISS” (Keep It Simple Stupid).  So with that in mind, just remember that most of our birds have their most important molt in late summer, after breeding, replacing all their flight and body feathers with basic plumage in preparation for either winter or migration.  They will also undergo a second, partial, prenuptial molt in spring, often into a striking, colorful alternative plumage, enhancing their breeding opportunities.

American Robin, Turdus migratorius (in juvenile plumage)

Don’t you wish you could molt, or maybe you do?  I keep one basic and practical wardrobe, only requiring some minor cleaning and preening, and the alternative wardrobe for “date night” or other special occasions.  This latter plumage, like the birds, is colorful and designed to impress and turn heads.  Don’t I wish.

 

Our Flying Feathered Dinosaurs

Brown Pelican, Pelecanus occidentalis

 

 

The guttural squawk of the spooked Great Blue Heron as he arose from the shore of the brackish swamp took me back 200 million years, until my ringing cell phone jarred me back to the present.  I suspect that the heron somewhat resembles its Mesozoic ancestors;  large bird with wide wingspan and slow, flapping, straight line flight.  But who knows for sure?  The fossil record is spotty and the origin of birds has been hotly debated in academia for centuries.  This is not a “settled science”.

Great Blue Heron, Ardea herodias

Remember the Genesis story.  Then God said, “Let the waters swarm with fish and other life.  Let the skies be filled with the birds of every kind, each producing offspring of the same kind”…And God saw that it was good.   It was and is very good.

GBH, click on any to zoom

In the 18th century some thought that fish and their scales were the precursor of the birds and their feathers, but by the mid 19th century scientists began to notice the many reptilian characteristics of birds.  Note the common three fingers hidden by the wing, and just substitute the heavy teeth with a lighter beak, add some feathers, and you have a bird.  But its not that easy.

Green Heron, Butorides virescens

 

A big break came in 1861, just two years after the publication of the “Origin of Species” by Darwin, when Archaeopteryx (Greek for “ancient wing”) was uncovered in a limestone quarry in Bavaria.  This 150 million year old Crow-sized fossil had the tail, spine, and claws of a reptile, but the wishbone and feathers of a bird.  Was this the transitional link?  Let the debate begin.

Archaeopteryx lithographica

The fossilization of birds is a very rare event.  Birds have thin, hollow bones and delicate feathers.  For a fossil to form the sediment must be oxygen-free and very fine in order to bring out the subtle detail of soft tissues and feathers.  That’s why Archaeopteryx was so exciting.  Later, in 1926 Heilmann published “The Origin of Birds” which suggested that birds and dinosaurs were related and shared a common bipedal reptilian ancestor 230 million years ago, but birds did not evolve from dinosaurs directly.

Great Egret, Ardea alba

Feathers evolved long before flight so clearly they must have offered some other survival advantage.  Many of the early feathered dinosaurs were much too heavy for flight and lacked other skeletal features that flight required.  The symmetrical dinosaur feather (birds have an asymmetric feather with a hollow core) were more likely used for insulation or for courtship display.  What female dino could possibly resist a male feather dance, or was it the female doing the dancing?  We’ll never know.

Great Black-backed Gull, Larus marinus, with unfortunate songbird in its talons.

Luckily there were numerous fossil discoveries in China and Spain in the late 20th century that shed new light on the origin question.  As a result, the current consensus is that birds did indeed evolve directly from Theropod dinosaurs, a group that includes the ferocious Tyrannosaurus Rex, but also a group of smaller, lighter, bipedal, raptor-like “dromeosaurs” that share many characteristics with early birds.

Buff-breasted Sandpiper, Tryngites subruficollis

The early to mid Cenozoic Era (37 to 65 million years ago) was a heyday for the birds.  The evolution of angiosperms (flowers) and grasses, and the mild climate were ideal.  Its been estimated that since their origin in the Mesozoic Era the Earth has hosted 150 thousand different species of birds.  There were two mass extinctions, however, that severely thinned the ranks.  The earlier was in the Cretaceous Period and took out many groups of toothed, aquatic birds along with all the dinosaurs.  The latter was in the Pleistocene epoch, 1.5 million years ago, a time of great climate upheaval with ice and glaciers covering vast areas of North America.  Of the 21 thousand bird species present at the outset of that epoch, only 10 thousand remain today.

By 20 million years ago most of the modern bird families and genera had appeared, but what are the most ancient birds?  Which are the true “early birds” that have survived the longest?  Only two major bird groups date back to the late Cretaceous Period in the Mesozoic Era, 65+ million years ago.  They are the Suborder Charadrii (shorebirds and gulls), and the Super Family Procellarioidea (albatrosses and petrels).  The others all came later onto the scene.

Black-footed Albatross, Phoebastria nigripes

There’s something about the dinosaurs that fascinate children, including me.  They learn the long names in kindergarten and play with their plastic models.  Maybe its their size or power, or maybe its because they ruled the Earth for so long and then disappeared so quickly and mysteriously.  Was it a comet strike or something else?  In any case, I’m so happy that some of their feathered offspring survived and continue to bring us newcomers, Homo sapiens, much pleasure today in the Cenozoic Era, Quaternary Period, and Holocene Epoch.

Bird Bones and the Injured Goose

 

Since spring there has been a sad sac Canada Goose waddling around the yard, dragging an injured right wing behind.  I plead guilty to chasing it away from the pool deck and dock where it likes to deposit its fruits of digestion.  When chased it obviously can’t fly away with its friends but instead does a fast waddle to the riverbank and tumbles over the rip rap to the safety of the water.  It seems to have no problem swimming.  My initial annoyance with the goose has slowly changed to toleration and even a little respect as it strives to survive.

Canada Geese, Branta canadensis

I don’t know the story of the “accident”, or even if this is a resident or migrating goose as it was first seen before the spring migration when both types of geese were here.  Most likely it was wounded during hunting season by a poorly aimed shotgun, but that is all conjecture.  When I first noticed the injured fowl I did not give it much of a chance for survival with its dragging wing and the abundance of Red Fox, Bald Eagles, Vultures, and Great Horned Owls in the neighborhood.

Bald Eagle, Haliaeetus leucocephalus

But in May and June it was still here and even seemed to participate in the care of several broods of goslings hatched along the cove.  These, however, have matured and moved on.  The wounded bird is now usually seen alone, feeding on the lawn.  Who knows what awaits the bird this autumn and winter?

Great Horned Owls (juveniles), Bubo virginianus

Being a radiologist I would love to x-ray this bird’s wing and diagnose the exact problem.  Which bone is fractured or is it just dislocated?  Is there evidence of early healing?  And what is the prognosis for future flight?

Black Vulture, Coragyps atratus

The avian wing, the equivalent of our arm, is a magnificent structure formed for maximum strength and efficiency, while maintaining lightness for flight.  The upper arm or humerus bone is relatively shorter and thicker than ours and bears the major torque of the flapping wing.  The more distal paired radius and ulna are the equivalent of the human forearm, and like ours can be rotated or twisted.  This allows fine tuning of the wing attitude during flight.  Small bumps along the trailing edge of the ulna are the attachment sites of the secondary feathers.

Rock Dove Left Wing, from “Manual of Ornithology” by Proctor and Lynch.

Its in the wrist and hand bone where one sees the most deviation from the human skeleton.  The bird has two small carpal bones while we have eight.  They have three fused metacarpals to our five.  Distally they have three digits or fingers while most of us have five.

Brant, Branta bernicla

The pectoral girdle or shoulder of the bird is also very different from ours.  Just think of function.  The demands of flight require a  stout bracing for the large flight muscles and a strong attachment of wing to body, whereas the human shoulder is designed for flexibility and finer movements.  The bird’s oversized sternum and coracoid are obvious flight adaptations.  The “wishbone” or furcula is felt to be a flexible bone the bends downward with each wing beat and then springs upwards, aiding the flapping motion of flight.

Snow Geese, Chen caerulescens

Most bird bones are hollow and highly pneumatized with air sacs that actually communicate with the respiratory system.  Internal struts give the light, hollow bones added strength, but not enough to withstand the trauma of the shotgun pellets.

Canada Goose and goslings, Branta canadensis

Getting back to our injured goose, I’ve decided not to intervene.  I’m not going to sneak the bird into the hospital’s x-ray department at night for a wing film, or try to splint the ailing wing, nor will I consult the humane society.  Instead my goose’s fate will be up to nature, its survival skills, and/or some higher power. I must admit that I admire its dogged fight for life and am rooting for it as it faces the coming colder months.  You might even catch me scattering some corn when no one is looking.  We’ll see.

My injured goose

The Birds & The Bees

 

Great Blue Herons, Ardea herodias

 

Birds do it, bees do it,

Even educated fleas do it.

Let’s do it, let’s fall in love.

Cole Porter

You don’t have to be an astute observer to notice that something’s up in the avian world right now.  It’s springtime and once the birds have recovered from the stress of migration or the burdens of winter, their raison d’etre becomes reproduction. The hormones from brain and adrenal glands rule the roost and result in both physical and behavioral changes, all focused on reproducing and preserving their species.

Rose-ringed Parakeets, Psittacula krameri

Claiming a territory is step one in this process.  In my neck of the woods this is most noticeable with the boisterous Red-winged Blackbird, perched on the tallest reed, sporting his bright red and yellow epaulets, warning other males to stay clear and beckoning females to come and check him out.  He hopes they are attracted by his beauty, health, and strength.

Red-winged Blackbird, Agelaius phoeniceus

There are numerous avian signs of courtship, some common and others quite bizarre.  The common include colorful breeding plumage, such as the striking migrating Warblers and their melodious songs, all evolved to attract a mate.  The more bizarre include the Magnificent Frigatebird’s inflation of his giant red throat (which other jealous males attempt to puncture), the water ballet of courting Grebes performed in perfect unison, or the Baryshnikov-like leaps of the Sandhill Crane.

Burrowing Owls, Athene cunicularia

There are the gentle offerings of food and mutual grooming, or the spectacular flight and airshows of the Hawks, or the lower nighttime air dance of the Woodcocks.  I don’t quite get the courtship practice of the male Parrot vomiting into the mouth of the female, allowing her to sample the prospective mate’s taste in food, nor do I condone the Mallards’ gang rape of a cornered female, so common with that specie.  But these are all signs of spring, evolved over millions of years to recreate and preserve life.

American Wigeons, Anas americana

As a Radiologist I have a special interest in the comparative anatomy of humans and birds.  First for the male, the avian testes, the producers of sperm, are located high in the abdomen, near the upper poles or the kidneys–male birds have no scrotum.  The sperm travel down through the deferent duct and seminal vesicles and empty into the cloaca at mating.  As with mammals, sperm require lower than normal body-temperatures to mature.  Birds solve this by lowering their body temperature at night and by storing sperm in the cooler seminal vesicles in the lower pelvis.

Copulating Black-necked Stilts, Himantopus mexicanus

Most male birds have no penis.  Mating occurs with “kissing cloaca”, the brief and often repeated contact of the male and female cloacae.  But a few male birds including Ducks, Storks, Flamingos, and Ostriches do have an erectile penis arising in the cloaca.  In the mating duck this is quite large and has a corkscrew configuration while the complementary female anatomy has a reverse corkscrew shape to accept it.  Some have said that these birds, who often mate in water, use this penetrating copulation to prevent water from washing the sperm away.

Red-shouldered Hawks, Buteo lineatus

The most interesting aspect of bird anatomy is that most female birds have only left-sided internal genitalia–the right sided structures are involuted or completely absent.  There are a couple potential explanations for this.  It may serve to reduce body weight and make flight easier, and it also prevents bilateral ovum forming simultaneously with opposing eggs obstructing each other in their passage to the lower genital tract.

Cactus Wrens, Campylorhynchus brunneicapillus

The ovary is positioned high in the abdomen, similar to the testes, and its eggs pass to the cloaca via the oviduct, uterus and vagina.  Grossly these three structures appear to be a continuous tortuous tube, but microscopic anatomy reveals differing functions.  At ovulation the soft ovum enters the upper oviduct and becomes coated with albumin and keratin as it proceeds downward.  The limey shell and egg coloration is added in the uterus and the finished egg is stored in the vagina.  It appears that the fertilization with sperm occurs in the upper oviduct.  The entire process from ovary to cloaca takes about 24 hours.

Greater Yellowlegs, Tringa melanoleuca

The structure and function of the avian egg is a fascinating topic by itself, but best left for a later posting.  Just as a trailer however, consider that a bird’s egg must be strong enough to withstand the weight of the incubating parent but fragile enough to allow the hatching chick to escape.  It must be a protective barrier, but also porous enough to allow oxygen transport and respiration.  It must also contain all the nutritional and energy requirements of the developing embryo.

Hooded Mergansers, Lophodytes cucullatus

So as you head out this spring remember the raging hormones have expressed themselves in many ways, some visible and some unseen.  The males are carrying testes that have increased their volume 100 times and are trying to find and impress a mate in any way possible.  The female, her own genitalia markedly enlarged for the season is the egg producer, primed and ready, hoping to find a worthy mate.  If successful, the real work will have just begun.

Osprey, Pandion haliaetus

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

Where Have All the Swallows Gone?

Tree Swallow

Barn and Tree Swallows

Gliding, diving, graceful birds

Acrobats in flight.

On a boring day in May, June, or July you can always sit on the porch with a cool drink and watch the swallows.  This year the Tree Swallows won the annual competition for the birdhouse down by the creek, the one with the water view, and the Bluebirds were again relegated to the other two houses along the driveway.  I don’t pick favorites as both have great appeal.  The birdhouse by the water does have some issues as the smart Fish Crows from the neighbor’s trees are always poking their large bills through the hole, trying to snag a hatchling for lunch.  The parents do a brave job driving off the much larger crows, but I fear they are not always successful.  That doesn’t seem to stop the swallows from coming back here year after year.

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Barn Swallow, Hirundo rustic,                   click on any photo to zoom

The entertainment is their airshow.  Swooping, sharp corners, straight up, diving low over the grass and river, catching insects, eating and drinking, even in flight.  In my book only the terns can rival the swallows in aerial acrobatics.  The Tree Swallows arrive first in the spring to stake out a nesting cavity, and stay later in the fall since they are the only swallow that can also feed on berries when the bugs are no longer plentiful.  The later arriving Barn Swallows almost exclusively build their mud nests on man-made structures–in my yard that’s the underside of the boat dock.

Eastern Bluebird

Eastern Bluebird at the “loser’s” house

The “Barnies” are the only North American swallow that has that deeply forked swallow tail.  It, plus the chestnut colored throat make the ID easy.  The Tree Swallows are striking birds with pure white below and metallic blue or green above, depending on the light.  These are the most common swallows in the East, but keep an eye out for the Bank S. with its dark chest band, the less sociable and more bland Northern Rough-winged S., and an occasional Cliff S. with its buff rump and forehead.

Tree Swallows

Tree Swallow flock

Then one evening in late July you notice they’re gone.  No fanfare or goodbyes, just gone, show’s over.  The birdhouse and dock are vacated.  And why did they leave so early?  There are still plenty of bugs, warm weather and sunshine, and maybe even enough time to raise another brood.  But I’ve learned that they are not gone.  The swallows haven’t really left for the season yet, but have changed their venue.  Just travel a few miles east to the inland fields with power lines or the vast tidal marshes along Delaware Bay and you’ll find them again.  You’ll see flocks, sometimes huge mixed flocks of swallows, no longer interested in breeding but now more intent upon consuming large volumes of insects and storing up energy for the coming fall.

Northern Rough-winged Swallow

Northern Rough-winged Swallow, Stelgidopteryx serripennis

The fall migration is a much bigger deal than its spring counterpart.  A successful breeding season will swell the flock many times over the number of birds that arrived the previous spring.  But there’s danger ahead.  Its been reported that the mortality rate for songbirds during the fall migration and at the wintering sites may be as high as 85% due to disease, predators, accidents, weather, etc.

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Tree Swallows, Tachycineta bicolor

 Flocking prior to and during fall migration, and continuing all winter, may in part be a safety mechanism to confuse predators with visual overload.  As opposed to most songbirds the swallows migrate in these large flocks during daylight, perhaps relying on visual clues for guidance.  This also allows them to feed on the fly.  The Tree Swallows will actually undergo a gradual molt during the trip to South Florida, the Gulf coast, Cuba, or Mexico, whereas the “Barnies” wait to molt until they have arrived at the wintering grounds in South America.

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Coastal flock prior to fall migration

So the swallow’s sojourn in their summer breeding grounds appears to be a two part affair.  First mate, nest, and raise the young.  But when that’s accomplished congregate in great numbers, fellowship, teach the juveniles advanced flying skills, and build up fat reserves for migration.  And when the mysterious word is spoken, whether it’s hormonal, sunlight, or temperature, be ready to head south en masse.  Their return in the spring will not be in massive flocks but rather in smaller groups of survivors, coming north to start the cycle all over again.

Do Birds Retire?

Red-shouldered Hawk

Red-shouldered Hawk, Buteo lineatus

 

As I approach that golden age of retirement my birding hobby causes me to look to the avian world for guidance.  Do birds retire and perhaps seek that perfect habitat where food and water are plentiful and the temperature ideal all year long?  Do they give up those long migrations and the work of nesting and breeding?  Do they recreate with other aging birds, have more time for song, or perhaps help with raising of the grand and great-grand chicks?  Birds, I know do not crave a large nest egg; for them that just signifies the nefarious work of a parasitic cowbird and means another large mouth to feed.  (See earlier post “Birds Behaving Badly / Brood Parasites”, 8/22/2015)  In short, is there a golden age for birds?

Ruby-crowned Kinglet

Ruby-crowned Kinglet, Regulus calendula (click on any photo to zoom)

There seems to be two distinct approaches to this issue in humans; those who want to keep working or must work until they die in the saddle, and those who crave and can afford the free-time of retirement.  You can’t explore these issues for birds until you figure out how to determine the bird’s age, and they don’t make that easy.

Indigo Bunting

Indigo Bunting, Passerine cyanea

Bird size is not a reliable dating tool, nor is bird song.  Some have observed that second year males often have weird or incomplete versions of the adult song, but you can’t rely on it for dating.  Early dating by plumage is straight forward, using natal down and the rapid progression to juvenile plumage, which is usually duller than the adult’s and often spotted or striped.  But by late summer, fall, or early winter, depending on the species, the “first winter” plumage develops which is usually very similar to the adult.

White-eyed Vireo

White-eyed Vireo, Vireo griseus

Judging the age of adult birds then becomes much more difficult.  The annual or biannual molt makes the shabby and worn out feathers all new again, like repairing the wrinkles of age.  Wouldn’t a yearly face-lift or tummy tuck be great?  Luckily some birds, gulls in particular, have a yearly progression of plumages allowing first year, second, third, and adult age designations.  Learning these variations is difficult and requires a good guidebook or an experienced colleague.

Brown Pelicans

Brown Pelicans, Pelicans occidentals (adult above and juvenile below)

Another dating technique is called skulling.  One can observe the air cavities in the bird’s skull by wetting and separating the feathers.  The maturing skull apparently goes through a specific and progressive pattern of pneumatization and maturation, visible through the bird’s thin skin.  This is obviously a tool for ornithologists–don’t try this at home.  That leaves banding, the most definitive technique in determining the birds age, but again a technique for the experts.  These basic facts are now known:  birds in the cooler temperate zones live shorter lives than those in the tropics, rural birds live longer than urban birds, large birds live longer than small birds, and young, inexperienced juveniles have the highest mortality rate of all.

Mottled Duck & Ducklings

Mottled Duck & Ducklings, Anas fulvigula

I was surprised to learn that the annual mortality of passerines was 70% in the temperate zones.  The longevity record for the Bald Eagle and Osprey is 22 years, 16 years for a Northern Cardinal, and 7 years for a House Wren.  But these were the lucky ones.  Message to birds:  avoid risky juvenile capers, leave the city and head to the tropics and stay there, and don’t volunteer to be a canary in a coal mine or a clay pigeon.

House Wren

House Wren, Troglodytes aeon

D.J. Holmes and others, writing in “Experimental Gerontology”, has noted that birds have relatively longer life spans compared to similar sized mammals, especially given their warm body temperatures, rapid heart rates, high glucose levels, and high metabolic rates.  These are usually harbingers of rapid aging, but not so with birds.  Some seabirds in particular age very slowly and actually increase their reproductive activity with age.  Apparently birds have evolved specific adaptations to offset the cell damage caused by oxidative and glycosylative compounds, mechanisms not found in mammals.  Is there a hidden “Fountain of Youth” under all those feathers?

Dark-eyed Junco, AKA Snowbird

Dark-eyed Junco, Slate-colored, Junco hyemalis (AKA Snowbird)

So it turns out that birds do not retire and enter a life of leisure but rather press on or even increase their activity and fecundity with age.  That is until they just drop, fly into a window, or are snatched away by a more agile hawk or owl.  I’m sorry to learn this, but maybe we humans can adapt some of their techniques for staying young.  Life in the tropics sounds good, so I for one will become a “snow bird” and head south this winter.  I’m also interested in those avian chemical adaptations.  Maybe there’s an investment opportunity lurking here.

What’s Up With the Martins?

Purple Martin

Purple Martin, Progne subis

The last of April and early May were remarkable for the cold, wet weather here in Maryland and throughout the Mid-Atlantic.  I heard we had 14 straight days of measurable rain and the thermometer was clearly forgetting that the spring equinox was six weeks ago.  As we pulled into our rural road, returning from a hot supper out, there was a good-sized flock of Purple Martins, maybe 25 or 30, blocking our way.  As I slowed down surprisingly only a few flew away and even those birds quickly landed a short distance further down the road as if to claim it for themselves.  I ran an obstacle course through them trying hard to straddle as many as possible.  What was going on?  These were not the usual energetic, swooping, and vocal swallows one usually sees each spring.  The next morning the martins were still on the road, but now there were several squashed bodies of those that had refused to yield to traffic.  This went on for several days and the body count mounted until the survivors finally disappeared.

Purple Martin

Martin roadblock; note the droopy tail and wings

About this same time I was at a party where friends of mine recounted another episode of strange martin behavior occurring about the same time in the cold and drizzle.  This couple are bird lovers and astute observers of the flora and fauna in their yard. They noticed a martin with unusually droopy wings perched on the porch of their Purple Martin house.  He flew away when they investigated with a ladder but one of the apartments was jammed with five other stuporous martins.  The entry to another apartment was blocked by a dead bird, and when he was removed another five birds flew out the now open door.  What’s going on?

Purple Martin

male

As you probably know Purple Martins are long distance migrants. The older scouts first arrive in the Chesapeake region in the second half of March, seeking their prior year’s nesting site.  The younger birds make the long trip from South America up to four weeks later.  The martins are the largest New World swallows and the only swallows displaying sexual dimorphism–the sexes look different. The eastern subspecies has the unusual trait of almost entirely depending upon man-made cavities for nesting.  Hundreds, perhaps thousands of years ago Native Americans in the east started hanging hollowed-out gourds to attract the sociable martins.  European settlers noticed this and expanded the practice which we continue today.  After thousands of generations of birds using these man-made nesting sites the eastern martins have essentially abandoned the use of natural cavities.

Purple Martin

Click on any photo to zoom

The concept of long distant and massive bird migrations has not always been known.  This makes sense since until the end of the 15th century we weren’t even aware of the distant continents themselves.  There was a general idea that the disappearing fall birds were hibernating somewhere, just like the frogs, turtles, and some mammals.  I’ve read old accounts of torpid spring martins that were assumed to be waking up from their winter’s sleep and wonder if they were describing the same behavior of our martins last month.

Purple Martin

Progne subis

So here’s my theory of what’s going on with the martins.  They are tough birds but after a two thousand mile migration their body weight is significantly reduced and the birds are vulnerable.  The ill-timed cold snap and rains greeted them in their already weakened state making it difficult to fly, or even avoid an oncoming car.  Martins usually forage during flight, but if they are too weak to fly hunger will compound their plight.  Possibly the flying insects they feed on were also in short supply due to the inclement weather.  I’ll bet they were huddled in the apartment and on the dark road in a last desperate search for warmth.  In the open they were clearly easy prey for predator hawks as well as the squashing cars.

Let me know if you’ve noticed similar behavior or if you have any additional thoughts.  It may well be a tough breeding year or two for the martins, at least in our neck of the woods.