One Wild Bird at a Time

by Bernd Heinrich

  As I made myself comfortable in the grass to settle down for a long watch, the dogs and the goslings lay down beside me while the bantam rooster scratched in a raspberry patch. I pulled a folded sheet of paper out of my back pocket and started scribbling notes that I would later transcribe over a cup of coffee at the kitchen table.

  If the flycatchers’ commotion was odd, I soon noticed something even more surprising: one of them often followed another. This late in the breeding cycle the pair would usually stay separate, independently foraging in the woods to feed the young, rather than carrying on with each other near the nest. Could there be, as I thought I briefly saw, a third bird? Soon there was no doubt about it—three flycatchers were flying together. Had the young morphed and fledged overnight? That prospect was remote, but I had to eliminate the least likely possibility first, so I got my stepladder and, as I had done several times before, climbed up to lift the lid on the nest box and peer in. As expected, the five young were still there. Again they hunkered down, and again one snapped its beak at me. The three adults, which had been paying very close attention to one another for at least a half-hour, ignored me.

  An hour later the adults finally started carrying food to the nest box. Curiously, though, even when one arrived with an insect in its bill, it would linger for minutes at a time, perching on a vine by the box while scanning in all directions, before slipping into the nest box to feed the young.

  Note taking, after three almost full days of continuous watching, was becoming increasingly tedious, but I needed to record as much information as I could, because I knew nothing about what was going on and therefore could not tell what might be important. The process of getting data, mining inferences, and comparing hypotheses to try to solve a puzzle is seldom predictable and almost never straightforward. With luck a pattern emerges so one of several hypotheses can click into place. Finally I realized that some of the data I had collected was relevant to judging a hypothesis. My first inference was that the excitement was due to the sudden presence of a third party, another great crested flycatcher. But why would a third bird have arrived, and why would it stay? Did it want to usurp the nest cavity for its own use? That didn’t make sense: What would it want with a nesting place near the end of the breeding season? Also, if the bird was an intruder, the pair would surely attack it, and I had seen no attacks. I doubted my own eyes: Was I really seeing a third bird interested in this nest? Maybe it had simply been attracted to the commotion, or to something else, such as the red-winged blackbirds that had recently converged in a meadow. The redwings had focused their attention on the ground, and as I ran over to investigate, a mink ran by my feet in the thick grass. So the riddle of the blackbird crowd was solved in seconds. I had also just seen a mob of birds—robins, cedar waxwings, kingbirds, and catbirds—flying together. They were chasing a blue jay caught in the act of raiding a robin’s nest in the birch tree directly in front of me. In these examples the causes of the disturbances were obvious. But for the flycatchers’ unusual behavior I could see no cause, and nothing made sense. By now I was convinced, however, that there were three birds, or possibly more since I could not distinguish them as individuals.

  The parents, which came and went hunting insects for the young, brought primarily dragonflies, of at least three species. On that afternoon they delivered five dragonflies in three hours. I had the impression that they made fewer trips to the nest than before. But impressions don’t count. Numbers do.

  I was out to watch the flycatchers by 5 a.m. the next morning, and saw the pair. But a half-hour later a second pair flew in, and almost immediately there were chases, during which I heard the high-pitched staccato calls that were different from others I had heard before. These were all-out chases, but the chased birds were unwilling to leave. One pursuit culminated in two birds’ tangling in midair and then falling straight down in a fluttering ball and landing in a dense patch of goldenrod. No more were the flycatchers merely shouting from the treetops. Instead, they were duking it out after what had apparently been a long test or buildup period. But what was the quarrel about? Were the newcomers a second pair wanting to kill the young and take over the nest box?

  At 8:03 a.m. I got another surprise. A flycatcher arrived with a dragonfly, perched at the nest box, and called. A second bird answered from the top of a neighboring tree. The first bird entered the box, emerged without the dragonfly, and called again, then the two left together. All was quiet for a minute or so. But then suddenly a single bird, which remained silent, flew in with something in its bill. It too landed next to the box and hesitated, and while I was trying to identify its prey (a beetle?), it flew off, still silent, without having entered the box. Just as it flew into low bushes, two other adults appeared as if out of nowhere. Neither of these two carried food, but they called loudly. It seemed as though the previous bird had tried to escape them. Was the pair trying to repel a bird that had come to help them rear their young—to be a helper at the nest? The idea seemed preposterous. However, my subsequent observations eventually left no doubt that one or both of the newly arrived birds were not only trying to feed but actually succeeding in feeding the others’ young.

  The resident pair generally stayed together as a couple, with one perching high in the trees and calling often while its mate flew low into the woods and bog to hunt. Whenever one returned with food, the other perched high and called while the first landed on the grapevine in front of the nest box and called, then entered the box with the food. The pair always maintained a conversation” by calling back and forth. One entered the box, fed the young and came out, stayed awhile and called, and then the two left together. Often soon after their departure a lone flycatcher showed up with an insect in its bill, slipped quickly into the nest box, emerged minus the food, and left. It did all this in silence, although another flycatcher called from a distance.

  The second two flycatchers (rather than just one, as I had by now thought likely) came mostly when there was silence around the nest. Occasionally the two pairs’ visits overlapped and violent chases ensued. But the chases gradually became milder; the pairs seemed to reach an accommodation, perhaps mainly by avoiding each other. The net prey brought in per hour increased from just one insect on the first morning to eight, twelve, seven, fourteen, and then eighteen on subsequent days.

  By the third day, when I could by behavior distinguish the residents from the others, there were no more fights and no more chases. The second female had become a true helper, whereas her mate hung back from the nest. Of one day’s total of eighteen insects, she brought in ten. Perhaps the parent birds tolerated her by then because she was useful, or perhaps (as I think is more likely) they had simply become habituated to their helpers.

  As usually happens, answering one question leads to another. The obvious next question was why a second pair had arrived to help raise another pair’s young. Given what we know about birds we can make educated guesses, and my guess was that they were neighbors whose nest had been destroyed and who were playing out their parental instincts on the young of the other pair. The parents at first perceived their interest in the nest as an intrusion but eventually became used to them, and/or the second pair became more skilled at approaching the nest. But additional and almost inadvertent observations made after all the young fledged on June 23 suggested another possible twist.

  With the young gone, I could examine the nest. It was clean, so the scat must have been carried out as soon as it was produced. On a whim I pulled out the now-useless nest to see what it was made of, and was surprised that it consisted almost solely of the long dry needles shed by white pine trees. Curiously, there was an intact great crested flycatcher egg under the top layer of the nest. This was strange, because birds generally do not cover up their own eggs unless they leave the nest for a long period. When I put the egg in a bowl of water it floated; it was therefore either spoiled or incubated. Once I opened it, some still-intact yolk and a lack of blood vessels made clear that it had not been incu
bated, but was spoiled.

  The rejected egg interested me greatly as a possible clue to the riddle of the shared nest duties: it could have belonged to a pair other than the one that fledged young. Perhaps the helping pair had been at the nest box first, long enough to produce one egg, after which the now-resident pair had arrived and driven them off. The new occupants would have gone through their whole nest-building repertoire regardless of what was in the nest at the time; they would have covered up any existing egg or eggs as though they were debris. The evicted pair would then have been without a nest hole to start a new family (suitable nest holes are often rare). Perhaps they did not find one and eventually came back to check their former nest, only to find ready-made babies.

  The day after the young fledged, the adults no longer called near the nest box, but at times I still heard both their demonstrative calls and the young’s begging in the distance. However, five days later, at 9:35 a.m. on June 28, two adults arrived. One chased the other for at least a half-hour, making staccato rattling calls. The chased bird did not want to leave.

  The flycatcher parents’ attempts to keep the interlopers from caring for their young was most likely related to the avian evolutionary strategy of reducing nest parasitism, while the other two were probably motivated by a strong drive to feed their own young. Both pairs were following their usual adaptive scripts, which in this case were off the mark because of changed circumstances. A friend told me about a similar situation: a pair of house finches (Carpodacus mexicanus) nesting in a cranny on her porch had a nestful of young, and a pair of English or house sparrows (Passer domesticus) were not only feeding them but also carrying off their poop, whereas house finches normally let the wastes collect where they may. The reason this switch in behavior may at first seem dubious is that house sparrows are well known to viciously fight other birds at nesting sites, evict the others’ eggs and young, then lay their own eggs and raise their own young there. Why had they not done so here but instead become apparent altruists?

  The likely answer is the same for the sparrows as for the flycatchers: they were expressing their parental instincts after their own nest and young had been destroyed. This parenting instinct is so strong that it can be uncritical and can be misdirected, as when it induces a small warbler to feed a parasitic cuckoo nestling that may be several times its own size and looks nothing like its own young.

  14

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  Red-winged Blackbirds Returning

  THE CLASSIC DEPICTION OF THE RED-WINGED BLACKBIRD IS one of male fighting, dominance, territoriality, polygamy, harems, and the females’ attraction to resources or to the males that have them. But this bird also has popular appeal through its showy conspicuousness and almost universal familiarity. In northeastern America redwings are one of the first bird species to return in the spring, and many springs I have eagerly awaited their arrival at a beaver bog in Vermont. The males usually appear quite suddenly on sunny days when the snow starts melting in the first week of March.

  In early March of 2011, I was expecting to see male redwings show up at the beaver bog next to our house, but instead, at dawn on March 7, two males were perched in a spruce outside my study window in a white-out snowstorm, and within minutes they were picking up sunflower seed spilled from a birdfeeder that during the winter had been visited only by chickadees, nuthatches, and blue jays.

  Every spring, red-winged blackbird males arrive in a group, usually appearing a month or more before any females. In previous springs the males had also fed on sunflower seed, and had flown back and forth between the bog and the feeder (females never came to the feeder). But these two did not fly into the bog. They continued to shuttle between a red spruce tree by my window and the adjacent snow-covered ground under the feeder. Perched under a branch covered with a thick cushion of snow, using it as a roof, they made an attractive picture that induced me to watch and sketch them. They were excellent models, giving me their whole day and wearing their finest garb, their breeding plumage. But unlike the popularly depicted male redwing plumage, theirs showed not the tiniest hint of bright flaming red. They hid their red badges of maleness under their black wing feathers, leaving visible only the light yellowish edge that bordered the red.

  The two remained silent all day in the continually falling snow, shuttling between the feeder and their shelter under the spruce bough, where they perched fluffed out and side by side. Occasionally one flicked his tail and stretched a wing. When one flew down, the other immediately joined him, and when he came back up to the perch he again sat next to the other. They stayed all day, until an hour before dusk they finally left together.

  Nighttime temperatures dropped to 0°F that week, and it was not until the evening of March 13 that I finally saw a flock of about thirty male redwings perched in a tree several kilometers from our house. The next morning males had arrived in our wetland and were yodeling again and again, producing their cheerful-sounding oog-la-yee territorial advertisement. The snow had then been melting for several days but was still a meter deep in the woods. Crows were cawing, and groups of them came flying overhead in a northerly direction.

  By the end of March, when the male redwings in our wetland in Vermont had long since established their territories, others were still on the move elsewhere. On March 26, as I was heading east to Maine, I met a flock of twenty males at a spot near Mt. Washington where there is almost unbroken forest in all directions. These redwings were passing over the road in front of me, flying into a strong wind from the northwest. Their resolve to buck this wind and fly as a group to an apparently agreed-on place, which at this time would be a wetland to nest in, hinted at unanimity of purpose, not aggressive rivalry. How had these birds met and become a flock? Given the two males I had seen previously that acted like close friends, and given what I had observed in my casual watching of redwings in earlier years, it seemed not impossible that these twenty or so individuals could be a community of birds, perhaps returning to a common home area they had shared before and would share again. If so, how would that jibe with the classic story of male dominance and territoriality?

  Red-winged blackbirds are close relatives of grackles and orioles. They belong to the family Icteridae and are one of the most social of songbirds. Social behavior is part of their genetic heritage. In our beaver bog wetlands, the common grackles come as a flock, stay as a loose flock, often nest near one another, and in the fall aggregate into flocks of thousands that sweep through the forest like huge rolling waves. To varying degrees, the different species of icterids form communal roosts of thousands of individuals in the non-breeding season, and some, like the Oropendolas (a group of several genera of South and Central American icterids), nest in colonies.

  Long after making my own observations I read two monographs on blackbirds. The first, by Gordon H. Orians of the University of Washington, dated from 1980, when the scientific literature on the topic amounted to about 170 works. The second, a 1995 report by William A. Searcy of the University of Miami and Ken Yasukawa of Beloit College that focused almost exclusively on red-winged blackbirds (Agelaius phoeniceus), listed 440 scientific publications. The authors stated: “The behavior of red-winged blackbirds in the wild has been studied as extensively as that of any species of bird in the world.”

  A red-winged blackbird male displaying its red epaulets.

  The reason for the abundance of studies is simple: redwings are one of our most common birds, and they are highly visible because they live in open habitat, such as cattail marshes and wet fields. Redwings populate almost the entire North American continent from Alaska through Central America and from the Atlantic to the Pacific. And because of their wide distribution and conspicuousness, almost anyone can have access to them.

  These older publications, with anecdotes and observations not focused on current theoretical problems, made what I saw interesting, at least to me.

  During the breeding season the redwing males are, according to these monographs, “strongly territo
rial” (Orians) or “classically territorial” (Searcy and Yasukawa); they reside preferentially in cattail marshes, where they occupy plots “more or less exclusive” of other males. Redwings are one of the few songbird bird species that are polygynous (several females may share the same male or, as conventionally stated, “males have more than one female”), whereas the majority of birds are socially monogamous. A female chooses a mate indirectly by choosing the territory that a male holds. These females also mate with males of other territories, but not with floater males, which do not have territories. Males do not build nests or incubate eggs, and for the most part don’t feed the young. But they are fierce defenders of the home turf. As Searcy and Yasukawa put it, those who study redwing breeding behavior are “familiar with the sensation of being struck on the back of the head by a male who has just performed a power dive.” I’ve never experienced this myself, but then I have also not studied territoriality, though I’ve spent much time in their territories.

  Redwings’ territorial behavior has been experimentally examined using male redwing taxidermy mounts set up in redwing wetland. The results are dramatic: territory holders attack these mounts, rip them apart, even tear out their eyes. Despite the seeming consistency of the classic picture, what I had seen in my wetland in Vermont left me scratching my head. Context is obviously important, if not everything, but it still seemed incongruous to me that males who traveled back to their home bogs in small groups, apparently tolerating one another, would become enemies after they got home. In the days after the males returned to the bog they spread out over the bog, but in the evenings flew together to a roost. In their daytime displays from the tops of bushes or cattail stalks, they were at times within several meters of one another, vocalizing and prominently displaying their red wing badges, but without any apparent interactions despite close proximity to each other.