The females come back a month or more later than the males. They are cryptic (camouflaged) and easy for the human eye to miss, but the males are alert to them. I often saw one female with four to six males in swift flight behind her. The males’ intense pursuit and the female’s equally intense evasive maneuvering looked like an act of aggression in progress, but these chases did not end in aggression. According to the classic picture the female could have been shopping around, examining the then-established male territories to find the one with the best resources, before deciding where and with whom to settle and raise a family; and when she entered a male’s territory, its owner should have courted her, and perhaps even offered food, to impress her with the resources to be found there and to lure her to stay. What I saw did not match this picture. These females acted as though they were doing their best to get away and hide in the dense low vegetation.
Could the males’ pursuit of the newly arrived females be related to mating? Perhaps, but I had never seen either copulation or fights at the end of such chases. Supposedly the females were looking for territories to settle in, and after they chose, the territory holders would mate with them. But the timing was off: birds normally mate at or just before egg laying, which would not begin until three to five weeks later. And when I did see copulations later, they were not preceded by chases. Thus, neither the males’ territorial behavior nor the females’ responses to the males seemed to fit the expected schedule.
That said, I also saw spectacular male-on-male chases. But rather than in March when the males arrived at their territories, these occurred in late May, when eggs had been or were being laid. Some went round and round the entire bog. According to theory, the “fittest” males secure the best territories, and in deciding where to settle a female chooses not only the direct benefits of occupying the best territory but also, indirectly, the male’s fitness. So it pays a male to fight other males and exclude them from his territory. But these chases extended across the territories of several males.
The scheme of territorial defense makes intuitive sense and has excellent experimental support. For example, as previously mentioned, when researchers inserted a stranger in the form of a stuffed male mounted on a pole into a territory, the territory holder attacked the interloper. This is convincing evidence of territorial defense, but using a stuffed male for the test automatically introduces an unfamiliar potential rival, one that the resident males will not recognize as a neighbor. Resident males in the marsh often stay several meters apart and pay no apparent attention to one another—and these are territorial males that are displaying their red epaulets! The fact that even at the end of May, when the females were completing the laying of their clutches, I sometimes saw a group of males violently chase another male hundreds of meters into distant territories at another end of the marsh suggests male cooperation among at least some neighbors.
From the studies summarized by Searcy and Yasukawa we know that redwing territory holders return to the same territory in successive years. This may explain the lack of aggression I saw among just-returned males: the individuals may know each other and may have already established boundaries. They may be neighbors that have traveled together when outside the home marsh. The males they chase out of their marsh may be the floaters, who are complete strangers. However, in the chases after females that I observed, the object of the chase never left the marsh but instead appeared to try to hide in low vegetation, and the reason for the chasing was more obscure.
Ironic as it may seem, as intensity of competition increases, one of the standard evolutionary solutions to it is more cooperation. We humans are a prime example. Local squabbles exist in any group and in any relationship, but a common threat unites by the common interest it creates, and can cause differences to seem less important. A main factor making cooperation possible is that the individuals know one another or at least know they share some identifying characteristic (such as the specific scent of a particular social-insect colony). Red-winged blackbirds can distinguish among individual humans—as researchers found out when the birds preferentially attacked those people who “raided” their nests (to band the young).
Many of the nests in the beaver bog I later found prematurely empty. I usually did not see the raiders, but the redwings would have, and having identified them, they regularly flew up out of the marsh to attack ravens, crows, and any passing blue jay, bird species that routinely take the eggs and young of other birds. Specific humans who have threatened their young receive the same treatment.
Cooperation among the male redwings was often evident. On the evening of June 8, 2007, I was surprised to see two otters playing in our beaver pond. The next morning they were in the bog next to the pond, and a mob of red-winged blackbirds and grackles (both of which had eggs and young in their nests in the cattails) were diving at them and making a huge ruckus. The mixed-species mob advanced across the bog, keeping up with the otters below. The male redwings from most if not all of the marsh had aggregated within perhaps a dozen square meters. All the birds were scolding loudly and taking turns diving at the otters, thereby notifying others that the intruders represented a hazard. On another occasion I witnessed the birds mobbing a mink. I sometimes lost sight of their target as it was obscured by vegetation, but I could easily plot its progress through the marsh by watching them keeping pace with it. At no time during these episodes did one redwing male attack another. The No Trespassing convention had been waived in the face of communal danger. The red-winged blackbirds’ behavior illustrates what behavioral ecologists have come to call the “dear enemy” phenomenon, in which territorial residents display less aggression toward familiar neighbors than toward strangers.
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Phoebe Seasons
WHEN JOHN JAMES AUDUBON WAS COURTING HIS FUTURE wife, Lucy Bakewell, near Mill Grove, Pennsylvania, the two became fascinated by a pair of eastern phoebes nesting in a cave. They often watched these relatively tame birds, and Audubon wrote that the sight of the freshly laid eggs was to him “more pleasant than if I had met with a diamond of the same size,” and that it “filled my mind with as much wonder as when, looking towards the heavens, I searched, alas! in vain, for the import of all that I saw.” The eggs hatched, the young grew up, and Audubon (presumably with Lucy holding them in her hands) tied silver thread onto their legs. The next spring (1803) he found two of the banded birds returned from their winter residence. He is credited with the first recorded bird banding in America.
Audubon’s words seem personal to me. Just as his early love of the natural world was colored by phoebes (then known as peewee flycatchers), my history was heavily influenced by another flycatcher, the pied flycatcher (Ficedula hypoleuca), a pair of which nested in a bird box on my family’s cabin in the Hahnheide woods in northern Germany, where I lived six years as a young boy. The birds caught my eye, and I experienced a soothing feeling of comfort to have them so close, almost living with us. And when eventually the light blue eggs appeared they evoked the same kinds of emotions Audubon described. Then when my family came to Maine, finding the phoebes nesting here immediately made this place our home. By that time they were much more common than in Audubon’s day because of an increase in the number of manmade nesting sites. They were nesting in our barn, our outhouse, and our shed. Much later, phoebes nested on our house in Vermont, and they were and still are a fixture at my new home in Maine. Phoebes invoke the joys of spring and domestic harmony, and although they are not scientifically classified as “songbirds,” their vocalizations bring me more cheer than those of any canary.
Arriving back at our woods in Maine on April 21, 2012, we expected to see the (not necessarily always the same) pair of eastern phoebes near their nest on a log above a window and under the roof of my original cabin, where I had lived seasonally before we moved into the new cabin fifty meters away. The ponds were still frozen over, and the steep path up to the cabin was covered with thick ice with meltwater gushing over it. As usual
at this time, the snow in the shaded woods was still crusted in the morning and hard enough to walk on. The yellow-rumped warblers were migrating through and visiting the first flowering red maples, possibly for nectar or small insects. Blue-headed vireos were singing and tree swallows were fighting for a nest box. In the evening a woodcock displayed on and over the clearing, and later at night a grouse drummed in the moonlight.
To my great joy and comfort, a pair of phoebes that I considered old friends were back. The next morning one of them perched beside my window, swiveling its head and flicking its tail up and down in the phoebe’s singular salute. Occasionally it sallied to the ground to catch an insect, then flew up to perch in a birch or a sugar maple whose branches brushed up against the cabin. The birds gave an occasional soft cheep, but not once did I hear them make the typically loud and emphatic phee-bee and cheer-vreet calls, which often alternate in the males’ territorial advertisement songs. I expected them to start nesting shortly. However, for the next two weeks the weather was cold and wet. No insects flew, and the phoebes and many other birds left or became silent.
A phoebe and nest containing four phoebe eggs and one cowbird egg.
Nesting activity resumed or began on May 7. The tree swallows were carrying dry grass into their nest box, and the phoebe pair examined the old nest site on the old log cabin where a pair of phoebes had nested every spring since it had been built twenty-seven years before. But the phoebes also flew in and out of the cellar space under the new digs. They had not yet started nest building but were enthusiastically inspecting possible locations.
After another of their forays under the new cabin, one of the pair flew high into the air, rising above the tallest maple trees at the edge of the clearing, performing what looked like a poor imitation of a woodcock sky dance. Immediately afterward they began carrying mud onto a small board shelf I had tacked to a beam in the space, the “cellar,” under the floorboards. The female made trip after trip, bringing first mud and then moss from the edge of my rock-lined well about a hundred meters downslope. Her mate accompanied her on these trips but did not carry anything himself. The nest was finished by May 19, and two days later it held two eggs. But to my surprise I saw a phoebe inspecting the area under the eaves at the old log cabin as though still checking for potential nest sites. Phoebes are territorial: two pairs could not live this closely together. Subsequent observations deepened the mystery.
I had been able to watch the pair closely during nest building and egg laying because the opening to the cellar was conveniently below my window and because they perched nearby, on the still-bare branches of a white birch tree three meters from me, or on the tops of dry mullein stalks in the clearing just beyond the tree. At this time, well into nesting, they were usually not vocally demonstrative except at dawn.
The next day, when she added the third egg to the still-incomplete clutch (the typical clutch is five), I heard extraordinary, animated vocalizations. The male appeared to be “singing” as phoebes usually do at the beginning of the nesting season; he made two kinds of phee-bee calls but, oddly, again performed a sky dance over the cabin and the trees while making them. Unable to think of a reason for this sudden display in the normally rather secretive egg-laying period, I checked the nest that afternoon. I reached in and felt with my fingers—the nest was empty except for some eggshells!
Throughout that day and well into the evening the male called repeatedly and continued his fluttering display flights over the clearing. I had heard and seen such activity in early spring, and once on the day the young fledged, but never at this stage. Since the nest disturbance I had seen only one bird, never two at once, and I realized that the female was missing—probably killed on the nest by a predator that had also destroyed the eggs—and that the male’s continuous calling and his sky dancing had to do with her absence. Flycatchers are classified as suboscines, a moniker that distinguishes them from the oscines or “true” songbirds. They are not melodious like thrushes and warblers, but I’m not sure why their vocalizations, given in the same contexts as those in which oscines sing, are not considered songs, regardless of their subjective tonal effect on us. What emotion may prompt their utterances is not for us to say. I suspect that, for them as for us, context matters: we may cry when we are hurt or sad but also shed tears of joy; we may scream in terror or in rejoicing.
The next morning we awoke before daylight to the phoebe’s loud and constant calling. But as the calls continued all morning and well into the afternoon, they became muted. Finally at 4 p.m. the calls stopped.
On the third day the male at first stayed around the cabin and still called from the treetops, then frequented low perches and started to capture one insect after another. I wondered: Might he be fueling up for a long trip? At the next dawn the silence felt deafening, and we did not hear or see him again that summer.
Fall and winter passed. Hoping the male might return, we awaited his arrival anxiously in early spring of 2013. Would he come with a new mate, or would he come alone and advertise for one here?
The year had so far been unusual: we had had little snow in the winter, and instead of a long cold wet period in the spring there was a heat wave. In mid-March temperatures reached near 30°C and all the snow melted. Phoebes are one of the earliest migrants to return, and I thought they would come even earlier this year.
On March 19 I saw a lone phoebe. It was silent except for occasional cheeps. I expected a potential mate to arrive soon and nest building to begin.
Two mornings later there was still only one, almost silent, phoebe around the cabin. At 1:10 p.m., though, he suddenly erupted into nonstop song, making the phee-bee and cheer-vreet calls alternately, with an occasional lower trill. After eight minutes of calling he caught a large insect, pounded it on a branch, and swallowed it. After that, without making any more calls, he left, flying high into the air toward the east. I expected him to come back soon.
The weather then made an abrupt turn. It snowed, and temperatures on March 26 were below freezing in the daytime and far below freezing at night. Winter was not over. However, he or another phoebe had returned just before it snowed. He was not vocalizing and stayed near the ground. There could have been no insects to catch on the wing.
By March 30, after several centimeters of fresh snow, the bird was gone, and by April 7 there was still no sign of a phoebe at the cabin. But nine days later I saw two of them. I could not tell if they were male or female from their appearance, because to our eyes the sexes look identical. One repeatedly checked the old nest site under the cabin roof. It fluttered near the tattered old nest, landed there, and made soft churring sounds. It landed on another ledge under the roof, then flew back and forth between the two, each time sweetly chittering as if excited. The second bird hung back and kept some distance from the cabin, but whenever it came near, the first immediately fluttered to the potential nest sites as if to either draw attention to them or defend them. Sometimes one flew after the other.
The next dawn a lone phoebe continuously broadcast his song from the treetops. Around 7:30 a.m., when another phoebe arrived, he stopped singing and again visited the nest sites. He would seemingly squat on each site for a few moments, then fly to a nearby maple twig, shake his wings and wag his tail vigorously, and flit back to the nesting spots. Sometimes he suddenly flew from the nest area and attacked the other bird. Once the two tangled in flight and dropped to the ground before separating. Several times one chased the other in fast flight through the woods, but quickly came back to repeat the behaviors at the potential spots for placing a nest. Their standoff continued all morning and into the early afternoon, with one squatting at the nest sites and attacking whenever the other came near. They were rivals fighting for possession of a place to nest in this territory. By 2 p.m., one male was singing vigorously and still flying to and from the possible sites, but the other had left.
The next morning, April 18, with the other bird apparently chased off, the victorious phoebe devoted less
time to site visiting and much more time to attention-getting singing from conspicuous high perches in the tops of the trees near the cabin.
At 7:25 a.m. another phoebe arrived. This one was unobtrusive but remained near the cabin. The then-resident male instantly left his singing perch and hovered at one potential nest site after another, choosing spots under the roof overhang where there was sufficient ledge to attach a nest. Next he landed on the cabin roof over one site and then the other. He made excited-sounding short chip calls and cheeps and buzzing calls, and sometimes sang from directly on a nest site, something I had never seen him do before. He carried on crazily around the roofed sites. Never once did he fly at the visitor, nor did either bird attempt to attack. I gathered that this newcomer was a female, and that he was showing her where she might choose to build a nest and thereby become his mate.
She seemed unimpressed, though, and after less than a minute flew away toward the east. There had not been one aggressive interaction. Shortly after she left he too flew in that direction, and soon I heard him singing in the distance, far from the nest sites. He came back in a few minutes, aggressively swooped at a yellow-rumped warbler, and resumed singing around the cabin.
One Wild Bird at a Time Page 15