Bird Management

The nest box hangs unobtrusively about a third of the way up the light pole in a suburban parking lot. Rutgers University graduate student Phil Stouffer sneaks a ladder up underneath the box, lifts the lid and gently places an unhatched starling egg in the otherwise empty nest inside. The light blue egg is an "orphan" an intruder in the nest (the technical term is "parasite"), placed there as part of a manipulative experiment in starling behavior.

By surreptitiously putting the parasite egg in a nest where it does not belong, Stouffer and his advisor, sociobiologist Harry Power, hope to answer an important question about the behavior of starling "housewives." When the female bird returns to her nest, how will she respond to the presence of the parasite egg? Will she adopt it and hatch it as her own? Will she simply ignore it? Or will she do something that from a human point of view would seem to be almost unspeakable cruel?

Five minutes later the researchers have their answer. As they watch, the female starling returns and dives out of sight into the nest box. Then she emerges seconds later carrying the egg in her beak. When she is a few feet away from the nest, she casually drops the egg from an altitude of about 15 feet. The rejected egg shatters on the pavement below.

In human society, this would be something akin to finding a baby on your doorstep, then dropping it from a 10-story window. But to Power, who has been studying starlings for more than a decade, it is simply one more aspect of the starling’s behavioral repertoire - a repertoire that includes not only the sort of "ovicide" that he has just witnessed, but also house stealing, gang terrorism, rampant promiscuity and even murder. In fact, says Power, when seen in all its conflict, drama and sturm und drang, starling society "makes Peyton Place look like a Sunday School.

A LIFELONG PASSION. Harry Power is a compact, square-jawed outdoorsman in his mid-40s. He looks like a young George C. Scott, but thinks and talks with the speed of a machine gun. His interest in bird behavior dates back to early childhood, when as a five-year-old he spent long afternoons running around his Los Angeles neighborhood with a salt shaker, trying to catch birds by salting their tails. Later, as a Montana high school student, he won a National Science Fair ecology award for pioneering work in the life history of mountain bluebirds - work which he continued to pursue as a post-doctoral student.

But simply observing and cataloguing bird behavior was not enough for Power. He wanted to know how that behavior evolved, how it helped the creatures survive and whether or not there were general principles underlying that behavior that might be applied to other species, even people. To get at those bigger questions, he needed large populations of essentially what he calls "crash-bang experiments" - experiments in which the seamy side of bird behavior can be revealed by, he says, "getting the animal to do something you wouldn’t otherwise see."

Power found bluebirds less than suitable for this kind of experiment. But in starlings - a European bird introduced in the states in the 1890s which since spread to 49 states, northern Mexico and southern Canada - he found the innate "nastiness" he was seeking. He also found the naturally dense populations and the durability that made for more complex experiments - and perhaps, closer analogies with human society. "Starlings are much more like us than bluebirds," he says. "In fact, when we look at them to some extent we’re looking at a morality play of ourselves.

To better understand this morality play, Power began in 1978 to construct what amounted to his own personal starling colony on the Rutgers campus. Over the next 10 years, he and his students augmented an existing colony by building more than 125 new nest boxes and hanging them on light stanchions and telephone poles all over the suburban New Jersey campus. As the starlings took up residence and built nests in the man-made boxes, the scientists kept careful track of the birds by marking and banding them, and even by dyeing each embryo a different color just before it hatched so that they could tell exactly which egg produced each hatchling.

To make a precise determination of which parents had sired which offspring, the researchers did hundreds of detailed biopsies, including sophisticated genetic tests to help establish family lines. And they augmented all this by keeping the nest boxes under steady observation. Over the years these exhaustive procedures enabled Power and his students to compile a virtual encyclopedia of data, information which has allowed them to paint the most detailed picture available of life among the starlings. And, as it turns out, it is a very difficult life.

KEEPING UP WITH THE JONSES. Among starlings, as in many other birds, the nest studies, he explains, "show that the most productive clutch size - the size that produces the most surviving chicks - is six. But the most common clutch size is five. Why the discrepancy? Well, if you start with six eggs and then a parasite comes along, the clutch size goes to seven, and at that size the number of surviving chicks falls way off. But if you only have five eggs and are parasitized to six - you achieve the size that produces the most survivors. I think the birds are in effect leaving space for parasite eggs, not because they want them, but because they want to make sure they don’t get pushed off the productivity cusp."

Although egg parasitism may provide floaters with at least some opportunity to perpetuate their genes, most of these birds would be much more successful if they had nest sites of their own. As a result, many homeless starlings will try to actually steal an already established nest. The technique is simple. "The floater bird invades the established nest, throws all the eggs out and just takes over," says Power.

Attempts at this dual crime - house stealing and mass "ovicide" - occur in about 12 percent of all the nest boxes under Power’s observation, and are sometimes the work not of lone birds but of gangs of up to 13 members. In fact, in one particular group of nest boxes at Rutgers, a sort of gang warfare has been rampant for yeas. "But the success of these gangs," notes Power, "is very low. They’ll come in, lay a few eggs and then some other starling pushes them out."

SEXUAL POLITICS. Obviously, the ongoing struggle for real estate is the source of a tremendous amount of conflict in starling society. But the same is true, Power has found, of sexual politics. He illustrates his point by showing a visitor a rich lawn where hundreds of starling are feeding.

When you look at the birds carefully," he says, "you realize that they’re feeding in male-female pairs, with the male and female not more than a foot apart. In these pairs it’s always the female who leads and the male who follows. What the male is doing is literally protecting her rear - and of course, his genes. If the female gets too far away, or if the male gets distracted, other males will display at her, lunge and attempt to mount her. So the male wants to make sure that she doesn’t pick up any sperm but his."

Starlings rarely stay with a mate longer than one season, and the females are not the only ones with roving eyes. "Once the couple gets back to the nest, and the male is sure the female is secure, he might fly over to the next nest box and try to mount the neighbor’s wife," says Power. The scientist believes that the female’s coquettish availability to other males is an evolutionary strategy designed to keep the male so busy guarding her he has little time for sexual adventuring on his own.

These stratagems do seem to keep the rate of successful cuckoldry surprisingly low. By conducting genetic studies of parents and their chicks in 95 nests, Power determined that only 2 to 8 percent of the offspring were illegitimate. Attempts apparently are legion. "If we had the same frequency of cuckoldry attempts in our society," he says, "you couldn’t trust your wife or husband to go to the market."

Needless to say, however, cuckoldry is relatively inoffensive compared to another common aspect of starling behavior; the killing of their own kind. In winter, for example, starlings will kill for the chance to roost in a nest box, locking their legs around one another and stabbing at each other’s faces until one of the combatants is dead. In fact, one female starling under Power’s observation seemed to have an ongoing propensity for this kind of violence. "Sometimes when we came up to do a nest box census," he recalls, "there she’d be, locked in mortal combat with yet another bird. We must have ‘saved’ her four times in two years."

Because starlings disperse as far as 50 miles after they leave the nest, it is virtually impossible to tell how many of them eventually are killed. But the bodies of dead starlings with telltale beak marks on their faces turn up often enough that Power infers a murder rate among the starlings of as much as 10 percent.

Power is quick to note that none of this seemingly violent behavior is unique to starlings. Wood ducks often practice parasitism, for instance, while cuckoldry is common among bobolinks and egg removal occurs frequently among cliff swallows. What’s more, there are reports of lethal fighting in a variety of bird species.

GOOD BIRD, BAD BIRD. For all its turmoil and strife, starling society has its gentler and more cooperative side. Power notes, for example, that starlings are "very good parents. They’re not easily frightened away from their young, and they take good care of them."

In the end, then, Power tries to avoid making sweeping value judgments. "Nature," he says, "is neither moral nor immoral. To have a realistic view, you have to have an amoral view.

Some critics have argued that Power’s "crash-bang" experiments might produce starling behavior that is something other than the "natural" acts that occur in the wild. But, says the scientist, "we’re not changing the birds’ behavior by giving them things like drugs. We haven’t even increased their natural population density, so the behavior we see is not the result of overcrowding. These birds are doing exactly as they please. Whether or not it’s ‘natural’ is one thing. But it sure as heck is wild!"

 

Massachusetts writer Bill Lawren went starling watching with Harry Power on the Rutgers University campus in 1990. The preceding article was reproduced with permission from the April/May 1990 issue of International Wildlife.