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.
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.
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.
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.
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.
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.
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.”