An Avian Aphrodisiac

20120808KPMcFarlandDespite the snow pack, there are some early signs of spring around my bird feeder. The Black-capped Chickadees are beginning to use their spring “cheeseburger” song. The Downy Woodpecker is occasionally drumming. But for the American Goldfinches visiting my feeder, the breeding season is a long way off. These finches are some of the latest nesting songbirds here in Vermont, waiting until July before even pondering a nest.

American Goldfinches are the vegans of the bird world. They consume little or no insects, relying instead on a granivorous diet, even when feeding their nestlings. Most songbirds give their chicks food that is high in protein, suggesting that goldfinches must have a special adaptation for getting enough protein from plant seeds. This might be why Brown-headed Cowbirds, infamous for laying eggs in other species nests on the sly, are unable to fully develop in goldfinch nests. They hatch, but when fed a granivorous diet, their growth is slow and they often die before they can fledge.

It has long been known that American Goldfinches nest when thistles have gone to seed in mid- to late summer. As the thistles are flowering, the female goldfinches are building their nests and mating. But what stimulates them to mate and nest so late?

A group of biologists from the University of Western Ontario and the University of California recently presented their experimental work on reproductive physiology of eastern American Goldfinches. In an aviary they exposed groups of finches to hot or cool climates and either blooming, non-blooming or no thistles as the photoperiod increased.

What stimulated the males for breeding? The biologists found a significant effect of flowering thistle. Under warmer conditions, there was a greater testis size and testosterone concentration in birds exposed to blooming compared to non-blooming thistle or no thistle at all. The males also liked it hot. There was no effect of blooming thistle on males in the cooler climate.

A bit of hot weather and a bouquet of thistle is an avian aphrodisiac.

14 Favorites from 2014

Here’s 14 of my favorite nature photographs that I captured in 2014. It might be the story behind the image, or perhaps the image itself that attracted me to it. These may not be my “best” photographs. Rather, they’re my favorite. I hope you enjoy them as much as I do. Visit my photography site to see these images in their full glory.

Snowy Owl – Killington, Vermont – 1 January 2014

He was perched high up in a spruce tree at the base of a very busy ski lift with blasting rock music. I didn’t want to disturb him, so I perched about 100 yards away. Soon I was showing snowboarders and skiers the owl at the top of tree. I heard lots of – dude that is totally awesome – and it was. With a crowd gathered around me the owl suddenly flew and landed just 25 yards away from us on a snow pile, but his back was toward us. My camera was ready on a tripod. I put it in position and then begged him to turn our way. Just as the sun peered from behind the clouds, so did he. He turned his head and stared at us with his bright yellow eyes. After a few minutes, he looked away and then flew back up to the tree. Skiers skied on and I left to get away from the loud rock music. My first bird species in 2014 was a memorable one.

Spring River Fog – Connecticut River, Bradford, Vermont – 20 May 2014

An enchanted early morning with newly arrived migrant songbirds singing all around us in the morning fog.

Goldenrod Crab Spider (Misumena vatia) – Appalachian Trail, Quechee, Vermont – 29 May 2014

I spotted this spider waiting in ambush while watching butterflies visit flowers on the edge of the woods along the trail. They grab prey with their front legs and inject venom into them and then suck their prey dry.

Little Wood Satyr (Megisto cymela) – Woodstock, Vermont – 30 June 2014

This little gem is found fluttering near woodland edges. Its flight seems weak until you approach it for a photograph. It bounces and dodges around the nearest patch of shrubs or into the woods to avoid the lens. After chasing them around for several hours, I finally captured this one on the edge of the dark woods.

Polyphemus Moth (Antheraea polyphemus) – Woodstock, Vermont – 30 June 2014

Hanging with its wings closed at the base of a tree waiting for the night, this striking moth opened its wings when I approached it.

Virginia Ctenucha (Ctenucha virginica) Trapped – North Branch Nature Center, Montpelier, Vermont – 8 July 2014

With its foot stuck in a milkweed flower like a Chinese finger trap, the moth hung lifeless. Unlike most flowers, milkweeds don’t produce tiny grains of pollen to be carried away piece by piece. Instead, the flower produces sticky, orange packets of pollen, called pollinia, which are designed to stick to an insect’s leg. In each of the five slits are two pollinia waiting to be accidentally snagged and carried off. In order for an insect to pick up one of the pollinia from a milkweed flower, its leg has to slip into a tiny slit between the anthers along the side of the flower. As the insect struggles to pull its leg back out of that tiny opening, it might emerge with a pollinia or two stuck to it. If the insect is too small or too weak, the only way it can escape the flowers grip is to leave its leg behind. Read more…

Head Harbour (East Quoddy) Lighthouse – Campobello Island, New Brunswick, Canada – 31 July 2014

While out hunting for whales to photograph (fruitlessly), a ray of sun lit the lighthouse standing before a bank of thick fog looming just offshore.

Skimming Bluet (Enallagma geminatum) - Dewey’s Pond, Quechee, Vermont – 1 September 2014

It is thought that this species is almost exclusively found in lakes containing fish, perhaps to avoid predation by dragonfly larvae that are far more abundant in fishless waters. The female lays eggs unaccompanied by the male in algae and floating debris on the water surface.

Blue Jay (Cyanocitta cristata) Portrait – Mt. Mansfield, Vermont – 17 September 2014

This year marks the 20th season I have been studying birds on Mt. Mansfield, Vermont’s highest peak. After we banded it, I captured a portrait of this Blue Jay before it was released. Feather colors are formed by either pigmentation or structure. Tiny air pockets in the barbs of Blue Jay feathers scatter incoming light resulting in this blue color being reflected back.

Monarch Butterfly (Danaus plexippus) – Woodstock, Vermont – 3 October 2014

The Monarch population is measured in the number of acres they cover in their densely packed winter habitat in central Mexico. There has been a steady decline in numbers of butterflies since 1996, from 15 acres of forest down to 3 last winter. That represents a drop from about one billion butterflies down to 60 million in just the lifetime of my daughter. This year we had an average migration of Monarchs after a dismal migration in 2013. This female was fueling up in the early morning sun. Monarchs in Vermont can be found by the tens to hundreds at times in pastures and hayfields with Red Clover in August and September fueling up for a long flight. Monarchs are the Vermont State Butterfly and Red Clover is the State Flower.

Late Autumn – Woodstock, Vermont – 18 October 2014

WIth most of the leaves already on the ground, mid-morning sun peeking from behind the clouds lit this Sugar Maple on fire.

Northern Saw-whet Owl (Aegolius acadicus) Released – North Branch Nature Center, Montpelier, Vermont – 27 October 2014

One of the most common owls in forests across northern North America during the breeding season, Northern Saw-whet Owls are nocturnal and seldom seen. But you may hear them. Listen for a sharp, high, repeated too-too-too call, reminiscent of the sound a truck makes to warn you it is backing up. During October and November they migrate southward from their northern haunts to spend the winter in dense forests across the central and southern US. Hundreds of biologists are studying their migration and populations across the continent at banding stations, several of them in Vermont. I joined the crew at North Branch Nature Center one night to watch the action. Carol Suich hoped she’d see her first Northern Saw-whet Owl too. She got a better view than she’d imagined. The owl rested on her arm after banding before it flew off into the night.

Bruce Spanworm (Operophtera bruceata) – Marsh-Billings-Rockefeller National Historical Park, Woodstock, Vermont – 9 November 2014

November at dusk with the temperature barely breaking 40 degrees I could see my breath. Yet, all around me moths fluttered through the woods. This cold weather moth is a thermo-conformers. Incredibly, males can fly with air and body temperature ranging from just 27 up to a balmy 77 degrees. Females completely lack wings. When they emerge in October or November, they crawl to the lower trunk of a host tree where they solicit flying males with fine chemistry. Read more… 

Osprey (Pandion haliaetus) – Honeymoon Island State Park, Dunedin, Florida – 28 December 2014

During early evening I found this Osprey feeding on a Sheepshead (Archosargus probatocephalus) not far from shore. The purple clouds in the background and its yellow eye staring at me caught my eye. Ospreys are unusual among raptors in possessing a reversible outer toe that allows them to grasp with two toes in front and two behind. Barbed pads on the soles of the feet help them grip slippery fish.

Winter Blues


I captured this late afternoon scene yesterday while walking the dog. All I had was my iphone and it didn’t exactly capture what my eye did. I edited the image using Efex Color Pro and Lightroom to return some of the vibrant blues of late afternoon winter to the shot that my eyes witnessed.

Red Knot ‘rufa’ Subspecies Declared Threatened in U.S.

Red Knot rufa subspecies at a stopover site during fall migration in the Mingan Archipelago National Park, Canada. / © K.P. McFarland

Red Knot rufa subspecies at a stopover site during fall migration in the Mingan Archipelago National Park, Canada. / © K.P. McFarland

Today, after a 14-month review, the U.S. Fish and Wildlife Service listed the rufa subspecies of the red knot as threatened.



Winter Woods

WInter Woods

WInter Woods

I captured this shot at the end of a winter storm a few days ago with my iPhone. The dark trees contrasting with the fresh white snow caught my eye. I developed this as a black and white in Silver Efex Pro.

Kinglets in the Cold

Biologist Bernd Heinrich made dozens of attempts to follow kinglets to their roosts at night before he finally found a group huddling together.

Weighing less than a nickel and not much larger than your thumb, golden-crowned kinglets are the smallest birds to winter in the New England woods. How does a bird this small stay alive during the long and cold winter night?

Larger animals have a lower surface-to-volume ratio than smaller animals. As a result, they radiate less body heat per unit of mass and are therefore able to stay warm using less energy. In 1847, Karl Bergmann, a German biologist, used this principle to show that within most warm-blooded species, body mass increases with latitude and colder climates.

Kinglets are tiny; their small size seems to break Bergmann’s rule.

To make kinglets even more odd, they only eat insects, even in winter. You’ll never see one at your bird feeder. Nuthatches and chickadees – two of our other small, over-wintering songbirds – eat insects, but they also eat seeds and suet, which are higher in fat and calories than insects. Most insectivorous birds of the North Woods, of course, avoid the problem of staying warm altogether by heading south when insects become scarce. Not kinglets.

Birds generally need to maintain a core body temperature of around 104ºF, year-round. This high temperature allows for powered flight and quick movements and reflexes. But this high temperature also requires a large amount of fuel.

Bernd Heinrich, Professor Emeritus at the University of Vermont, wondered what kinglets were eating during the winter to keep the metabolic flame burning. He found that although they are fairly opportunistic, eating everything from spiders to insect eggs, they subsist primarily on moth caterpillars found over-wintering on trees. He collected some of the caterpillars and kept them in his freezer for the rest of the winter. In the spring, he took them out and thawed them, then raised them to adulthood so that they could be identified more readily. They turned out to be one-spotted variants, a well-known moth whose over-wintering location had not previously been known.

But this was only half the story. Researchers in Virginia calculated that kinglets could only build up enough fat during a day of foraging to fuel their metabolism for half the night. Even with their ability to find plenty of insect food in the seemingly sterile winter woods, they would be unable to stay warm throughout the night based solely on their daytime diet.

Several biologists had suggested that kinglets survive by sleeping in shelters such as old squirrel or bird nests or by huddling together. Enter the ever-inquisitive Heinrich once again. After dozens of attempts to follow kinglets foraging just before darkness fell, one December evening he was finally successful.

Heinrich reported his observation in the Wilson Bulletin, a journal of ornithology. “At 4:20 P.M. I saw three kinglets fly into a brushy white pine. In less than a minute, I found four kinglets huddled together about four meters above the ground under thick branches.”

He returned an hour later with a stepladder and a camera. The birds remained huddled together through the night with their heads tucked into their back feathers and just their tails sticking out of the feathery fluff. The temperature that night dropped to just 14ºF.

Kinglets, like other northern birds, are also able to recapture heat that would otherwise be lost through the skin of their non-feathered legs and feet. In addition to simply tucking their extremities into their thick body feathers while sleeping, birds have a vascular system in which arteries carrying warm blood out to the legs are located close to veins carrying the cool blood back to the body, allowing heat to be retained. The design is so effective that we humans use similar, artificial heat exchangers to recapture heat in all sorts of applications.

Heinrich also found that sleeping kinglets fluff up their feathers to make an inch-thick, downy blanket. His experiments showed that without this down comforter, a naked kinglet would cool 250 times faster than one fully feathered. He weighed the wing and tail feathers, which are primarily used for flying, and compared them to the weight of the body feathers, which are primarily used for insulation. Kinglets have four times more feather mass committed to insulation than to flying.

The smallest winter bird in the North Woods thus transforms itself into a much bigger bird each night, thereby creating a lower surface-to-volume ratio. Puffed-up and cuddling kinglets radiate less body heat per unit of mass, enabling them to conserve energy and survive the long and frosty New England nights.


This article appeared in Rutland Magazine. winter 2014

Wingless Winter Moths


November at dusk with the temperature barely breaking 40 degrees I could see my breath. Yet, all around me moths fluttered through the woods. They were one of two species in the genus Operophtera,  visually drab, but physically magical.

Whether these were the native Bruce Spanworm (O. bruceata) or the introduced Winter Moth (O. brumata), devilishly hard to identify by photograph alone, I couldn’t discern. Either way, both of these small, cold weather moths are thermo-conformers. Incredibly, they can fly with air and body temperature ranging from just 27 up to a balmy 77 degrees. Continue reading →