The secret and baffling life of the blue jay

I wake every morning to a few birds swooping around the oak tree and shrubs lining the fence in my backyard. One of the most common residents is Cyanocitta cristata, or the blue jay. It may well be that these brilliant colored birds are the only ones I recognize in my early morning daze. The blue jay is white-breasted with blue feathers. It has a distinguishing blue crest, black collar, and black beak, with plumage that does not vary with sex or season. As I pour myself a cup of coffee, my roommate and I watch the magnificent-looking bird perch on a tree branch, then swoop down and chase off a smaller bird.

Like all members of the corvid family (crows and ravens), the blue jay has a fairly complicated social system. However, in comparison to other New Word jays it is relatively simple. As Racine and Thompson discuss, for the most part, blue jays are monogamous and so the breeding pair forms the cornerstone of the social structure. However, blue jays are not territorial and so it is not uncommon to find multiple pairs of jays sharing the same feeding ground. Oddly enough, blue jays will form large flocks toward the end of breeding season (late summer). Many jays from the northern US will migrate south during the winter. However, there is a small group that stays throughout the year. In a bird sanctuary in central Massachusetts, Racine and Thompson found that groups of blue jays form stable groups during the winter. Banded jays returned to the same feeding station over successive winters. Further, the offspring of known banded jays also returned to the same feeding station. Racine and Thompson speculate that the group bonding extends beyond feeding behavior. Even with alternative feeding stations, the same jays returned to the original location. The migratory patterns on blue jays are not well understood. Stewart found in his meta-analysis of over 8,000 recaptured blue jays in banding stations in the Atlantic Flyway (Florida, Massachusetts, New Jersey, and New York), there is no one defining factor determining which jays migrate south and which stay in their nesting area. As he discusses, the migration pattern of the blue jay is under dispute. Some ornithologists asserting that young jays predominantly migrate in hopes of having better luck finding food during the winter months, but other ornithologists claiming that older and younger jays migrate at equal rates.

Males are almost exclusively the dominant members of the breeding pair. Tarvin and Woolfendon’s four-year study looking at the dominance behavior of blue jays in south-central Florida found that of 316 interactions between males and females, less than 1% were won by the female. In general, males are larger than females and this difference in body size may be responsible for their unwavering victories. However, the authors noted that in this study, the males were only 5% bigger in most of the measured characteristics. They attribute the dominance to the males more aggressive nature. Males are more likely, in general, to be involved in interactions. Interestingly enough, immediately before breeding season (March), males became markedly less aggressive and females became more aggressive. The authors attribute this to “nesting phenology” and a shift in the energy demands as females needed to consume more nutrients for the nesting season. This did not shift the dominance, though, and females were still subordinate to males. It is very hard for me to see this hierarchy from my window, though, because from a distance, male and female blue jays look exactly the same. In fact, many professional ornithologists cannot even tell the difference without an up-close inspection!

One of the most interesting aspects of the blue jay is its resourcefulness. One study found that blue jays raised in a lab at the University of Massachusetts were able to make and use a tool to gather food. First, a single jay used pieces of newspaper lining the bottom of the cage to gather food pellets, otherwise out of reach with its beak. When presented with a paper clip, plastic bag tie, feather, and straw grass, the bird was able to successfully use these as tools to gather the out-of-reach food pellet. When the researches presented the other jays in the colony with the same materials, they found that 6 out of the 8 blue jays were able to use tools to gather food in the same manner. Fascinating!

Blue jays have a variety of calls and have been known to imitate other bird’s calls. Lofton and Clench report two such examples in Florida and Texas, respectively. In each case, a blue jay imitated a red-shouldered hawk in an effort to con other birds out of their food. The blue jay perched near a feeding bird and mimicked the hawk’s call. The bird feeding heard the call, thought a hawk was nearby, and flew away. The blue jay then swooped down and ate the food left by the bird. It is not know if Jays developed this unique ability mainly as a protective measure to warn others that a hawk is in close proximity or solely as a manipulative devise. Either way, it is very clever.

Typically, I only think of squirrels as collecting and storing nuts. Apparently, birds do this too. Johnson discusses the blue jay’s active role in distributing nuts. As a conservative estimate, he cites that 5-6% of a nut crop may be dispersed by jays. In fact, many researches consider the blue jay as primarily responsible for the widespread dispersal of certain beech trees after the glacial period in the eastern US. Blue jays routinely collect nuts and acorns and cache them in the ground for a later date when food is scarce. A single jay may cache many thousand nuts each year. Jays will forget about the food they stored and the nuts germinate and grow, extending the tree population up to several hundred meters per year. Blue jays are odd amongst birds that practice this behavior because they will transport the nuts several thousand meters!

My high school mascot was a blue jay and I used to think it was rather weak in comparison to large mammals and birds of prey. Now, though, I have gained a newfound respect for the blue jay. Although not always highly regarded by ornithologists because of their domineering behavior and mimicry calls (which can be confusing if you are actually looking for a hawk!), the blue jay leads an interesting, but not well-understood life. I used to admire them only for their beautiful blue plumage. Now, I am going to pay much more attention to the finer points of their behavior as I watch them flying around in my backyard while drinking my morning coffee.

References:

Stewart PA. 1982. Migration of Blue jays in eastern North America. North American Bird Bander 7:107-112. http://elibrary.unm.edu/sora/NABB/v007n03/p0107-p0112.pdf

• This paper describes the migrations patterns of blue jays from north to south. It discusses possible reasons why most blue jays are partly migratory.

Racine RN and Thompson NS. 1983. Social organization of wintering blue jays. Behaviour 87:237-255. http://www.jstor.org/stable/4534305

• This paper discusses the group formation of blue jays during the fall and winter months as opposed to mating pairs in the spring and summer.

Tarvin KA and Woolfenden GE. 1997. Patterns of dominance and aggressive behavior in blue jays at a feeder. Condor 99:434-444. http://www.jstor.org/stable/1369950

• This paper discusses a study conducted on the dominance behaviors among blue jays. I mainly pulled from the male-female interactions section.

Jones, T.B. and Kamil, A.C. 1973. Tool-making and tool-using in the northern blue jay. Science 180, p. 1076-1078. http://digitalcommons.unl.edu/bioscibehavior/66

• This paper describes a case of blue jays using tools in the lab to gather food outside of their cage.

Lofton, RW. 1991. Blue jay imitates hawk for kleptoparasitism. Fla. Field Nat. l9(2): 55. 1991. www.fosbirds.org/FFN/PDFs/FFNv19n2p55Loftin.pdf

• This paper and next describe case reports of blue jays imitating birds of prey in order to scare birds and steal their food.

Clench, MH. 1991. Another case of blue jay kleptoparasitism. Fla. Field Nat. 19(4): 109-110. http://www.fosbirds.org/FFN/PDFs/FFNv19n4p109-110Clench.pdf

Johnson, W.C. and Webb, T. III. 1989. The role of blue jays (Cyanocitta cristata) in the postglacial dispersal of fagaceous trees in eastern North America. Journal of Biogeography16: 561–571. http://www.jstor.org/stable/2845211

• This paper talks about the integral part blue jays play in spreading acorns and nuts of certain tree species while they cache food.

Table from University of South Florida study (Tarvin & Woolfenden, 1997) on dominance relationships in blue jays. Males are almost exclusively dominant over the females. However, males are also much more often involved in interactions with both females and other males.

Figure from University of Massachusetts study on blue jay tool use (Jones & Kamil, 1973) depicting the frequency of tool use as a function of time (food deprivation). Circles represent type of behavior (solid is paper manipulation, divided is thrusting the paper through the cage). Line type denotes presence of food (food is present outside the cage with solid lines, no food pellets were present with dashed line). Blue jays become most resourceful when food is present and they are hungry.

Blue jay using paper as a tool to gather food outside the cage (Jones & Kamil, 1973)

perched blue jay in snow. http://upload.wikimedia.org/wikipedia/commons/0/04/Cyanocitta-cristata-004.jpg

blue jay with peanut. http://upload.wikimedia.org/wikipedia/commons/f/fa/Blue_Jay_with_Peanut.jpg

A map of the blue jay’s distribution throughout the United States: yellow is summer-only, blue is winter-only, and green is year-round. http://upload.wikimedia.org/wikipedia/commons/9/93/Blue_Jay-rangemap.gif