Every winter my feeder birds are mostly the same, both in species and numbers. But usually there is at least one surprise, even in winters when no northern finch irruptions occur.

A blue jay on a feeder in Montgomery County, PA

A blue jay on a feeder in Montgomery County, PA (Photo by Brian Henderson on Flickr, Creative Commons license)

Last winter was the year of blue jays, often nicknamed “jaybirds” because of their calls.

We live tucked away by ourselves atop a mountain so we’ve never had more than a couple blue jays at our feeders over the 46 years we’ve lived here, and many winters none at all. But beginning in early December last year, blue jays started appearing in greater numbers, just as the cold and snow set in.

On December 16, with the thermometer at three degrees Fahrenheit, I counted 10 blue jays at our feeder area. From then until late January, numbers varied from seven to a high of 11 on January 16 when they blanketed the ground with their electric blue color.

Usually they stayed on the ground to feed, sparring with each other and the gray squirrels while the mourning doves and the smaller songbirds hung out in the periphery or visited the feeders, which, in turn were dominated by a pair of red-bellied woodpeckers.

A blue jay feeding with a red-bellied woodpecker in Danville, PA

A blue jay feeding with a red-bellied woodpecker in Danville, PA (Photo by fishhawk on Flickr, Creative Commons license)

At least some of the blue jays roosted in our Norway spruce grove and sounded their clarion “jay-jay” calls whenever I neared it on my daily walks. In mid-February, when blue jay numbers at the feeders had diminished, I found a trail of plucked blue jay feathers in the grove as well as plenty of “white wash” on the tree branches. I suspected a barred owl had been feasting on the blue jays, but whether it was death, the unseasonable warm weather, or some other reason, I last recorded five blue jays at the feeders on February 20 and then no more.

Despite being common birds that almost anyone can identify, these clever members of the Corvid family are not as easy to study as other corvids, such as American crows, because they are secretive and quiet during the spring and summer when they are courting, mating and raising their families.

But as acorns ripen on oak trees, these forest denizens announce their presence here, picking and eating acorns and beechnuts before they fall to the ground. Last autumn both the red and white oak complexes produced a huge crop of acorns, and no matter where I walked I could hear blue jays.

A blue jay with an acorn

A blue jay with an acorn (Photo by Tom Shockey on Flickr, Creative Commons license)

They also cache acorns to eat in the winter and spring, tucking two to three acorns in their expandable throat and upper esophagus, a fourth one in their mouth and a fifth in their bill and carrying them as far as a mile to cache in more open areas. They do the same with beechnuts.

Writing in The Second Atlas of Breeding Birds in Pennsylvania, Douglas Gross (Game Commission Endangered and Nongame Birds Section supervisor) calls the blue jay the “keystone bird of eastern deciduous and mixed forest of North America because of its habit of caching tree seeds, inadvertently planting deciduous trees, especially oaks and beeches…”

Like most caching birds, blue jays have excellent memories for where they hid their nuts, but a few are always missed. In Blacksburg, Virginia, researcher Susan Darley-Hill found that in 28 days approximately 50 blue jays carried and cached 150,000 acorns, which was 58% of the total nut crop from a mere 11 pin oak trees. Furthermore, they were capable of choosing sound acorns that had not been affected by weevil larvae.

Blue jay close-up with an acorn

Blue jay close-up with an acorn (Photo by Kenneth Cole Schneider on Flickr, Creative Commons license)

With those numbers, I can only imagine how many acorns blue jays transported from our forest last autumn. Still, I wondered if the huge crop of acorns was harvested by our resident blue jays or by those that had migrated from other areas.

Like most aspects of blue jays’ lives, their migration patterns are also puzzling. The northernmost subspecies of blue jays (Cyanocitta cristata bromia, our northern blue jay) lives as far north as Canada in the southern half of Ontario, Quebec, and New Brunswick. Sometimes northern blue jays may migrate south since thousands, moving in flocks from five to 250 birds, have been observed over the Great Lakes, including Lake Erie.

In Pennsylvania hawk watchers on our mountain ridges east of the Allegheny Front have reported migrating blue jays from the third week in August to the second week in November, although the greatest numbers migrate in mid-September to mid-October.

While blue jays winter in every Pennsylvania county, the jays are a mixture of resident and migrant birds. Researchers used to think that young jays were the migrants, but more recent studies show that jays of any age may migrate. Furthermore, it looks as if individual jays decide on a year to year basis whether to stay put or move south. Most likely it relates to either food sources, weather conditions or both.

A blue jay on a nest in Codorus State Park, Hanover, PA

A blue jay on a nest in Codorus State Park, Hanover, PA (Photo by Henry T. McLin on Flickr, Creative Commons license)

During spring in Pennsylvania blue jays migrate north from late April until mid-May. By the fourth of May, our resident blue jay males have already engaged in courtship displays with their monogamous partners, which continue as they select their nest sites and construct their nests. Usually they settle on a tree or bush as high as 25 feet from the ground, preferring an evergreen, but settling for whatever is available. They may even use rural mailboxes or occupy the nests of American robins.

Both sexes build their cup-shaped nest of twigs, small roots, moss, lichens and bark as well as human detritus such as light-colored tissue, cloth, paper, string, and wool. The male feeds the female as she sits on the three to seven bluish or light brown, spotted eggs for 17 to 18 days, beginning in late May in Pennsylvania. Then she broods her young for half their 17 to 21 days in the nest before she joins her mate in finding food for their offspring, although the male continues to provide most of the food.

A juvenile blue jay

A juvenile blue jay (Photo by Carolyn Lehrke on Flickr, Creative Commons license)

After their nestlings fledge, usually by July, the family remains together for another month or two. Then the young are on their own, while their parents sustain their bond for their lifetime.

Blue jays eat a wide variety of material including 22% insects during the breeding season. They are known for “anting,” rubbing ants against their feathers to remove the formic acid, not, as previously believed, to rid themselves of parasites, but so they can eat the ants, according to a recent study which found that 10 ants equals one egg in nutritional value.

Blue jays also consume human-based food—cultivated grains (especially corn) and fruit, bread, and dogfood—in addition to hard mast (43%) except in July and August. Their reputation for eating birds’ eggs and nestlings is highly overrated, and most studies put such food at one to two per cent of their diet if that.

Blue jays have their own predators to guard against. As adults they are the victims of Cooper’s, broad-winged and red-tailed hawks, great horned and barred owls and eastern screech-owls. Gray and fox squirrels kill and eat young fledglings, and nest predators include American and fish crows, squirrels, black rat and northern black racer snakes, raccoons and opossums.

Blue jays are known for their wide variety of calls and use them to mob hawks, large snakes, raccoons, domestic cats, and large owls. The video embedded below illustrates the variety of calls made by blue jays. These “songbirds without a song,” as Donald Kroodsma labeled them in his The Singing Life of Birds, use many sounds. After observing a pair on their nest near his home in Amherst, Massachusetts late in April, he noted that “the jays seem infinitely expressive, capable of transforming the simplest of jay sounds into a diverse array. At one extreme, the harsh ‘jay’ becomes a single, fine pure whistle, often with harmonics. Sometimes only one voice box will be engaged, sometimes two, creating special tonal effects.”

Altogether, in three and a half hours, he heard from those jays and others that visited them, five different ‘jay’ variations, two ‘squeaky-gate’ calls, melodious ‘bell calls’ and from the female on the nest ‘rattle’ calls.

“How little we know about these jays—that’s what my brief experience with them has taught me,” he concluded.

In Pennsylvania, blue jays increased from the first to the second atlasing periods with their highest numbers in Montgomery, Lehigh and Bucks counties in scattered woodlots. Because blue jays are able to adjust to changing land practices and airlift tree seeds to open areas, they will remain valuable “ecosystem engineers,” in the eastern United States by “increasing their caching effort after fires and selecting canopy gaps as cache sites,” according to a Cornell Lab press release of a study entitled “Jays and Crows Act as Ecosystem Engineers.”

Even renowned Philadelphia naturalist William Bartram, back in the early nineteenth century, recognized that blue jays “alone are capable, in a few years’ time, to replant all the cleared land.”


Bird Brains

Don’t call anyone a bird brain unless you are complimenting them. In the last couple decades, researchers worldwide have been discovering how amazing bird brains are. That should not be a surprise since feathered winged animals that fly have been evolving on earth for more than 150 million years, according to recent genetic analyses.

Neuroscientists Suzana Herculano-Houzel and Pavel Nemec recently published a paper entitled “Birds have Primate-like Numbers of Neurons in the Forebrain,” in which they write that the brains of birds are organized much like those of primates.

“We found that birds, especially songbirds and parrots, have surprisingly large neurons in their pallium: the part of the brain that corresponds to [our] cerebral cortex, which supports higher cognition functions such as planning for the future or finding patterns.”

To truly understand how intelligent birds are, researchers study how a species behaves in the wild, conduct experiments with captive birds, and compare what they see in the field with what they learn in the lab about a species’ genes and cells.

Some bird species seem to learn as little as possible to get along. Others are bird Einsteins. Most are in between. But relatively few of the more than 9000 species of birds worldwide have been studied in detail. And in much of the last century, even though people had been reporting anecdotally what appeared to be the intelligent actions of some birds such as crows and ravens, scientists had not begun any systematic studies of birds’ brains.

An American crow on a fence post

An American crow on a fence post (Photo by Joe McKenna on Flickr, Creative Commons license)

While some of us have watched parrots dance to music and New Caledonian crows solve problems on You Tube, many of our common birds are just as clever. American crows, for example, are adept at problem-solving. One researcher observed an American crow carrying water in a Frisbee to dampen its dried mash and another one using the end of a plastic slinky toy to scratch its head while it was perching.

According to research by John Marzluff in Washington State, American crows can recognize human faces, using the same parts of their brains to do this as we do. They plan ahead when they find and then leave a gift for a human who has been feeding them. In addition, they will delay gratification if they think they will be offered something better (usually food) at a later time.

Common ravens are socially adept, remembering other ravens they were friendly with before they paired for life, recalling those special friends even after they have been separated for three years.

A blue jay with an acorn

A blue jay with an acorn (Photo by Jeff Hart on Flickr, Creative Commons license)

Still another member of the Corvid family, our blue jays, can accurately select fertile acorns 88% of the time and can count to five. They also mimic red-shouldered and red-tailed hawks. Blue jays often mimic the latter on our mountain and fool us. Some scientists hypothesize that they do this to trick other blue jays into thinking that there’s a raptor in the area and they need to leave, giving the blue jay imitating the red-tail time to harvest acorns without competition.

Another scientist noticed that a blue jay was smart enough to rub red ants on its body to get rid of the ants’ formic acid before eating them.

Because more than 80% of bird species are socially monogamous, staying with one partner for a season or even, in some cases, for life, they have developed “relationship intelligence,” which is an ability to understand what their partners want or need and respond in order to successfully breed and raise their young.

But apparently 90% of both sexes also sneak off to copulate with others without getting caught by their partners. This results in more healthy offspring.

In autumn, birds that store food for the winter, such as black-capped chickadees, grow new cells in their brain center (the hippocampus) which deals with spatial memory. This allows them to remember where they hid seeds months later.

A brown-headed cowbird female in Codorus State Park

A brown-headed cowbird female in Codorus State Park, near Hanover, Pennsylvania (Photo by Henry T. McLin on Flickr, Creative Commons license)

Brood parasites such as brown-headed cowbirds, especially the females, have large hippocampuses, because they are the ones that must lay their eggs in other species’ nests. They must find, remember, and revisit the nests they parasitize.

And invasive bird species, such as house sparrows and European starlings, have larger brains, are innovative, and have more flexible behavior because they must adapt to a foreign environment.

But our brainiest birds may be hummingbirds, because their brain is the largest brain relative to its size, a whopping 4.2% of their total body weight. Their hippocampus is five times larger than that of songbirds, seabirds and woodpeckers. They can remember every flower in their territory and how long it takes them to refill with nectar after they feed from them.

A ruby-throated hummingbird at a feeder

A ruby-throated hummingbird at a feeder (Photo by likeaduck on Flickr, Creative Commons license)

From year to year at home and in migration they also remember where every feeder is. They even learn which feeder people are responsible or irresponsible and have huge episodic memories that allow them to plan when and where to feed on hundreds of flowers a day.

The females watch older females making nests to learn how to do this because female hummers are on their own once they have bred. They must build their nests, brood their eggs, and feed their young alone.

Hummingbirds have the ability to move backwards, forwards, and sideways because they have more complex brains. In the part of their brain that responds to visual stimuli, instead of the usual back-to-front preference most animals and humans have, hummingbirds have no preference and can move in any direction.

A ruby-throated hummingbird at a flower

A ruby-throated hummingbird at a flower (Photo by chrisdupe on Flickr, Creative Commons license)

During their mating flights, which we’ve watched with awe from our front porch, they make instantaneous course corrections much faster than a fighter jet. Thus, their brains can move efficiently in three dimensions, which some scientists believe makes their tiny brains the most complicated of any vertebrate species.

Hummingbirds have not been considered songbirds, but biologists Claudio Mello and Erich Jarvis have found that hummingbirds have the same areas in their brains that control song learning and production as songbirds and parrots. They do sing in a higher pitch than songbirds, but their songs are amazingly rich, and in some species, complex.

Neurobiologists have been comparing birdsong with human speech and language. Like human children, young birds listen to other birds of their species to learn songs. They imitate and practice, seemingly using the same brain structures and genes to learn songs as children use to learn language. Some birds even stutter.

There is incredible variety in birdsong, as various as the 4,000 songbirds on our planet. And if you listen as carefully as Donald Kroodsma, who has been studying birdsong, especially in the eastern United States, for more than 40 years, you might be able to hear the 30 to 40 songs of a Carolina wren, the 50 to 100 of an eastern bluebird, the song and mimicking calls of a white-eyed vireo, the 30 to 40 songs of the ethereal wood thrush, the 200 to 400 different mimicking songs and calls of a gray catbird, the 100 songs of a northern mockingbird, and the 2,000 of the mimic champion—the brown thrasher.

Then there is the hermit thrush whose song has been compared to human musical scales with trills and slides reminiscent of a woodwind instrument. Some ornithologists have claimed that hermit thrushes sing major, minor and pentatonic (five note) scales.

But composer Emily Doolittle and biologist Tecumseh Fitch didn’t believe it. Still, using recordings of 14 hermit thrushes from the Borror Laboratory at Ohio State University, they started analyzing the pitches of 114 song types. When they slowed them down, they could hear their harmonies.

A hermit thrush singing

A hermit thrush singing (Photo by Yankech gary on Flickr, Creative Commons license)

“They jumped out at us,” Doolittle said, adding that 70% of the hermit thrushes’ songs were harmonic.

And maybe most miraculous of all to us are our songbirds that migrate. Scientists have found that at first they rely on genetic information for both direction and distance until they gain experience. Then they use their own brain maps to find their way. They build up magnetic maps during migration and some may use odor to help guide them. Some researchers even think they may hear a landscape infrasonically, especially the ocean, to help navigate. But to do all that and more they must possess fantastic spatial memories.

Every day, it seems, more is being revealed about the brains of birds. It’s a hot topic. For instance, researchers have recently found that the bird that is closest to its dinosaur ancestors is our own wild turkey. That’s because, since the days of feathered dinosaurs, the wild turkey’s chromosomes have had fewer changes than those of other birds. And, as any hunter knows, wild turkeys are wily and smart.