In a short amateur video, filmed in a Brussels street in the bright, early hours of one of the first days of May, the camera points towards the gable of a house, a corner that would not usually catch one’s eye. We suddenly hear and glimpse ten or so small, black birds sweeping over the house in quick flight. The filmmaker comments: “7:53 AM. After feeding for an hour, first attempts to find the holes.”¹ Some of the birds suddenly plunge into the gable, just under the edge of the roof, and charge the spot, violently hitting their bodies against it before bouncing back. A few seconds later, they strike against the freshly rendered wall. During the five videos filmed there that day, we see the birds coming back, again and again, persisting in trying to enter holes that are no longer there. Each spring, they used to return from their nine-month-long migration in sub-Saharan Africa to that same cavity. Now they find it cemented over.

These “amusive” birds, called common swifts (Apus apus, hereafter swifts), are admired for flying “with an astonishing lightness and with the speed of the wind”, and for the way they appear to “swim slowly in the air”.² They spend most of their life in flight through the immensity of the sky (fig. 1). However, less famous than their flight is their vital need to cram themselves into small dark holes during the breeding season. Their extreme speed makes it hard to catch sight of them as they enter their nesting hole, that is, if there is still a hole for them to enter. Whether through negligence or deliberate efforts, in recent decades their nesting sites have been increasingly destroyed by changes in the construction and renovation of buildings.

When Buildings Prove Fatal

Records of swifts continually crisscrossing the clouds in Brussels date back to 1921, but their relationship with the city is much older than that.³ Swift experts estimate that these birds have specialized in nesting in the holes and cracks of human-made houses for 10,000 years, as long as these structures were built over four metres tall. In Europe, their population expanded together with the edification of monuments during antiquity and their construction techniques.⁴ In the nineteenth century, they were called “wall swifts” (“martinets de muraille”), since they inhabited old edifices in the crevices of church towers or ancient castles (fig. 2).⁵

In Belgium, swifts mostly live in cities, of which Brussels is one of the most significant. In contrast with many other birds, they still inhabit the city centre and other historic districts densely populated by humans. In the early 2000s, between 1,200 and 2,400 breeding pairs were estimated to live in the city. Cavities are hardly visible from the ground, and this makes the inventory of breeding sites difficult and the numbers imprecise.⁶ Recent monitoring has indicated that between 1992 and 2020 the number of swifts in Brussels dropped by 42 per cent, and a similar decline has been observed across Europe.⁷ Scientists attribute this decline to several phenomena. First, their migration towards south-east Africa is perilous and may be even more so depending on the climate conditions. Moreover, the fact that swifts are away nine months of the year plays to their disadvantage. Their places are too easily neglected and destroyed during their long absence. If a pair’s traditional site is no longer available, adopting another breeding place is extremely difficult for them. Second, as numerous studies suggest, insectivorous bird species such as swifts also depend on abundant insect populations to feed themselves and their young, and so to ensure successful breeding.⁸ Starvation may thus be another cause of death, as flying insects have significantly declined due to intensive industrial farming and the use of insecticides, or in cities where insect populations are made vulnerable due to the lack of adequate vegetation, or light pollution.⁹ When undernourished, swifts become much more vulnerable to predators, such as falcons, sparrowhawks, owls, martens, weasels, or cats. Third, swifts’ vital dependence on human buildings is seen, in many places, as a major reason for their decline.¹⁰ The evidence for this lies in the observation that all urban bird species that depend on man-made structures have seen their numbers plummet, as the evolution of current construction techniques and materials offer fewer nesting opportunities in comparison to older buildings. The most recent reports indicate that the number of birds breeding in cavities in Brussels has dropped by an average of 74 per cent between 1992 and 2018.¹¹

Indeed, when the swift’s decline was first detected in Brussels, it was particularly districts where lots of renovations had been carried out that were affected.¹² These renovations entail the replacement of old buildings with edifices whose flat surfaces are made of concrete, manufactured panels or glass, without recesses or protrusions.¹³ These buildings’ minimalist style leaves no room for other cavity-nesting birds or nonhuman animals that have been making their homes in the crevices of our buildings for centuries.¹⁴ Plus, next to public urban renewal programmes that have been implemented since the late 1970s, the thermal insulation of the walls and roofs of existing houses has become a focus of public authorities. In Brussels, the regulation dealing with the reduction of energy consumption in the construction sector became more apparent in the first decades of the twenty-first century,¹⁵ and the recent energy crisis prompts a massive insulation of most residential buildings.¹⁶ Although the need for renovation and to reduce carbon emissions through insulation techniques and regulations is important, its current form of implementation undermines other forms of life than human ones, regardless of their crucial dependency on the materiality of buildings.

In short, whereas swifts’ vulnerability certainly stems from their migratory and insectivorous character, urban observations foreground the destruction of their nesting site as a major threat to their disappearance. Swifts’ vital dependence on the human-built environment, together with their discontinuous but loyal and barely noticeable presence in its holes, have rendered them highly vulnerable to the loss of their homes.

Caring for Storied Places

In a previous issue of this journal, philosopher Thom van Dooren and anthropologist Deborah Bird Rose proposed the notion of “storied-places”. With that notion, the authors call for an attentiveness to the nonhuman storying of a place; that is, how animals “understand and render meaningful the places they inhabit.”¹⁷ As they frame it, a story is not necessarily a verbal or written account, nor must it involve chronological descriptions. A story can also be developed by weaving connections between events while experiencing a world meaningfully. These connections emerge, for instance, on Sydney’s shorelines, when penguins faithfully return to their breeding sites, which have become lost places; when they adapt their burrows to local rock crevices; or transmit their practices of place-making to subsequent generations. From this perspective, urban places are more-than-human worlds: they’re multispecies achievements, being “co-constituted in processes of overlapping and entangled ‘storying’, in which different participants may have different ideas about where we have come from and where we are going.”¹⁸ To speak of “storied-places” is a plea against human exceptionalism, since it contends that the ability to inhabit a meaningful world is not exclusive to humans. The notion also requires deeper consideration than that of “habitat”, which limits the focus to the biophysical attributes of the sites that birds occupy.¹⁹ In this way, van Dooren and Rose’s proposition claims a greater “conviviality” with nonhuman animals in cities: an ethics that would acknowledge alternative ways of inhabiting and making a place meaningful, in a more equitable city, perhaps especially for those whose lives are endangered.

This proposition has fuelled my concern for the swifts, their nesting sites in Brussels and their destruction. The notion of “storied-places” calls for taking more seriously the swifts’ meaningful engagements with, or worlds within, the particular places they inhabit. But the case of swifts leads me to expand the proposition by adopting a slightly different focus, which raises some different questions. Swifts have intimately embedded their storying of places in human-made buildings. For generations, they have entangled their sense of place with ours. In Brussels and elsewhere in Europe, the destruction of their breeding places has engendered a commitment to maintaining or remaking these places in ways that the birds would best accept them. In other words, the situations I have found in Brussels involve the specific relationships that the birds have formed with particular places, but also the persistent efforts by devoted people to provide nesting sites that swifts will hopefully adopt. Those efforts are the focus of this paper. I articulate swifts’ storying of their places along with the practices of people who are learning to care for them. If swifts have different ideas about the human-made buildings they inhabit, then there’s a lot to learn from the people who are discovering these ideas and dwellings, and the responses they call for.

I therefore explore the actual situations in which a more careful attention takes shape between the birds, the buildings, and the people who encounter them there. My relational thinking comes from a body of work that focus on care practices, informed by science and technology studies. These ethnographic studies focus on the relationships that develop between different beings — people, technical things, animals, and others — and examines what these relationships produce in ongoing attempts to improve fragile situations.²⁰ In these studies, care is not all about warm, nice, and infinitely supportive relationships. Caretakers rather try out specific ways of operating within those situations, notably by (re)arranging the spaces.²¹ Here, by focusing on the forms of care for other species involved in practices of place-making, I bring out how attentive practices emerge between swifts, their storied-places and the human caretakers who learn about them. How can animal spatial practices and meanings, in this case involving swifts, be supported in the (re)making of a place? How might an attentiveness develop along with these care practices? And which tensions or contradictions do they carry?

In Brussels, conservation efforts for swifts and their nesting sites rely heavily on volunteers. Martine Wauters, who filmed the video I mentioned earlier, is a leading figure among them. Since 2010 she has been increasingly committed to the fate of these birds, to such an extent that it has become the central activity of her life, albeit unpaid. After having read the many observations she posts on her blog, “Martine(t) News”,²² I conducted a series of interviews with her and I then observed her interventions on-site. While these direct observations were fruitful, in order to get a deeper sense of the situations at stake I completed them with archival research and recent grey literature about the swifts in Brussels (monitoring reports, maps or local observations), documentary research into Brussels’ building types, ornithological studies about swifts spanning other European regions (natural history, descriptive biology, ethology), and technical manuals about buildings or nest boxes. In other words, this method is less predefined and more guided by the situation under scrutiny: by what this situation requires me to learn to better understand and reflect on the worlds that take shape in those places and multispecies encounters. This method leads me to refer to the natural sciences, as well as other, non-scientific ways of knowing, while remaining critical about certain knowledge practices, in order to weave a tale proper to the social sciences.²³ This tale articulates how urban sites in Brussels matter for swifts and people, where their respective values and practices of place-making may entwine, clash or be reinvented.

In what follows, I describe how swifts’ storied places involve the social creation of distinct cavities. Next, my attention centres on people’s engagements with specific sites, where they develop certain ways to notice, to recuperate historical artefacts, and to use technologies such as nest boxes and audio recordings. More than merely providing suitable habitats, those engagements are forms of care through which people learn about the birds’ storying of places and propose plots, in the materiality of buildings, in the hope that they continue or reshape these storying practices. In the final section, I discuss how “paying attention” occurs as the birds and caregivers draw each other into their worlds, through tangible interventions as much as imaginative work. In my view, these emerging modes of attention and of imagination, and worlds that materialize in buildings, map some of the more liveable paths through the more-than-human city.²⁴

Swifts’ Stories: The Social Creation of Distinct Cavities

Each summer, swifts animate the sky over several neighbourhoods in Brussels with tireless sarabandes. Swifts are very much at home in the air, eating, drinking, and even sleeping, grooming, and mating in flight. But one thing they can hardly do on the wing is lay eggs. For that, they need a grounded place, and so they seek out particular streets, houses, holes, and the darkness therein. This is where they will settle down for the summer months. Once a hole is adopted, the nest built, and two or three eggs have been laid, the parents take turns brooding them and will then feed the nestlings with numerous airborne insects hunted beyond the colony’s territory (fig. 3). Approaching the end of July, nestlings strengthen their wings and hesitantly scrutinize the outside world before entering their aerial lives. As for the parents, they take their leave for Africa soon after the last juvenile has left the nest. If they are lucky, the pair will return to the same cavity throughout their entire lifetime, which might be many years or even decades. The oldest known resident has been returning to the same nesting site for twenty-one years.²⁵ While swifts’ nesting places are without a doubt indispensable to their reproduction, the significance of the holes goes beyond their being useful for breeding. How do the birds inhabit them? Through which experiences and connections do they render these holes meaningful? In other words, what do we know of the way that they “story” these places?

“The discovery of a suitable nesting site,” writes Ulrich Tigges, “undoubtedly is the most important event in the life of a swift.”²⁶ As he observes in Berlin, the borders of a colony’s territory align with the streets’ spatial layouts, such as the rows of houses that frame a few blocks. The sociality of a colony is thus first and foremost aligned with the built environment of a neighbourhood. In turn, the city block, while becoming a territory, contributes to the social invention of swifts as neighbours. Indeed, they transmit its frontiers across generations. Over the summer, swifts’ flying parties involve high-pitched, piercing screams that indicate the locality to the youngest members of the colony. While analysing these “screaming parties”, Rosanne van Oudheusden found that variation in calls occurs between individuals, but also between different geographical locations. Although this observation invites further research, it suggests that a territory may well be distinctive in its vocalization.²⁷ Once drawn to that location, at dusk the youngest swifts engage in an aerial display for which ornithologist David Lack coined the term “banging”: a bird alone, or sometimes followed by several others, will loop and brush against the holes in a building.²⁸ As soon as the banging activity starts, older members of the colony come back to their cavities, sit at the entrance and scream at the potential intruder in order to signal their occupation. While passing and passing again in front of the holes and nests of the colony, the youngest in fact map which ones are occupied and who is living where within the colony’s territory.²⁹ They engage in these jubilant rituals with great energy and screaming, but will not nest in their own cavity before coming back the next year. Thus, they sharpen their sense of place through these banging movements and screams, among the swifts of a colony and the blocks that they inhabit. This emplaced sociability appears even more valuable when one knows that, during their migration, the birds make very little contact with each other.³⁰ The relations between older and young members of the community take shape together with the transmission and recreation of their territory, bounded by the spatiality of a neighbourhood.³¹ And while adult swifts remain loyal to their cavity summer after summer, the youngest birds prospecting for new sites are more inclined to adopt new kinds of holes. They therefore appear as more hopeful settlers to the people who try to attract them to other crevices or nest boxes.

Then, within such a territory, swifts’ storying involves cavities and their interior. While back from migration adult swifts meet their partner in the same cavity as the previous year, which thus becomes a rendezvous point. When first adopting a new nest, a swift learns to enter it with ease and quickness, and then trains its partner by demonstrating the appropriate movements.³² It takes several days of training for flight movements to be successfully attuned to a particular entrance. Partners then arrange their nest with a degree of “architectural dexterity”³³ in the darkest side of the hole. They collect light materials carried up by the wind over the colony site or near it, like bits of straw, feathers, small leaves, pieces of plastic, grass, scraps of paper, sometimes petals, and damselflies or butterflies whose vivid colours sparkle.³⁴ More than a collection of materials, the nest of a pair of swifts consists, too, of secretions from their own bodies. They stick these materials with their saliva and shape their nest by turning around it, moulding it to fit the interior contours of the cavity.³⁵ They keep building the nest when the eggs are laid and stop when they hatch, and non-breeding pairs continue the nest-making process throughout the whole summer, preparing for the years to come. Thus, each nest is unlike any other: swifts create a distinct relationship with them through the attunement of their flight to the entrance and interior arrangement with their own collection of materials and secretions.

But swifts’ cavities are not only singular within the territory of a colony or in its interior design. The birds also demonstrate the importance of their home through their stubbornness in defending it. Not only do they scream out when a potential intruder passes by, but when resident swifts find a stranger in their hole (conspecifics or otherwise, such as starlings or sparrows), a fight ensues that can last more than five hours.³⁶ Serious injuries, and in some rare cases death, may result from these vigorous fights, although playacting is not excluded from these encounters.³⁷ These battles are another manifestation of how much swifts’ distinctive homes matter to them. And these conflicts are contingent upon “our” buildings as well: the scarcer the holes, the greater the chance of fights.

From this glimpse into swifts’ connections with their dwelling places, it is notable how much their storying is imbued with sociability, and results in the creation of a distinctive place: while becoming a neighbour within the territory of a colony, transmitting its boundaries across generations, discovering which cavities are available or inhabited, and by whom, attuning their vocalizations to a location, being reunited with one’s partner after an incredibly long journey, building a nest together, defending the place with sheer stubbornness and, last but not least, sustaining a lifelong fidelity to the only site where they ever dwell. Swifts’ involvement with their nesting places also occurs through a familiarization with the space of a singular cavity, through their bodily training to enter it quickly, or when shaping the nest according to the layout of a hole. What to a human might seem like nothing more than dark, dusty little cavities into which the birds crawl to raise their young, in fact carry social importance and distinct familiarizations. In a text entitled “More-than-Human Sociality”, Anna Tsing calls for critical descriptions that extend our curiosity into the social worlds of nonhuman others, which are not understood through human social standards.³⁸ With these socialities belonging to other species, Tsing evokes the way landscapes can carry multiple contingent histories, in which humans and their plans remain important but are far from being the only agent. I will come back to the conjoint histories of a site. For now, I would simply like to point out how swift sociality, as they put it in motion within a colony, a pair, or interspecies interactions, is intimately entangled with, and created by, the singular built environment in which they learn to dwell, from the configuration of a city block to the shape of a cavity.

Cracks and Colonnades: Noticing, Learning, Conveying

The collection of swift photographs and anecdotes that Martine shares on her blog draws readers in with an attentive curiosity for these unexpected sites. The documentation of her observations and interventions is a practice through which a form of noticing emerges.³⁹ She sometimes says that she now looks at the city “with swift eyes”. As we will see, in practice this expression can mean shifts in focus and different ways of noticing.

The older posts on her blog show pictures of houses, often poorly maintained, which are zoomed in on the holes and cracks around which she first heard screams and, looking up, spotted swifts’ cavities. Non-breeding swifts brushing the tops of houses when banging often provide the first clues to the presence of a colony. But swifts’ nesting sites are hard to see because their entrances are impossibly small — a crack between two bricks, the slight gap in the eaves — and because the swift’s flight in and out is so quick that one must watch with undisturbed patience to perceive it.

Soon after she started to collect observations, Martine engaged in technical arrangements in order to protect nesting sites or to install new ones. Whether tending to emergencies or not, she is constantly alert and ready to go to sites of concern. On the map she shared with me in 2020, I counted 130 interventions she made in Brussels, under or inside eaves, in holes or walls. She also established the volunteer working group, whose members monitor colonies or help to carry out awareness-raising actions. Her knowledge, then, comes from the accumulation of these situated experiences. Importantly, it is also supported by a network of swift enthusiasts from countries across Europe. The network consolidates learning and support, allowing members to give advice, share new scientific knowledge, and to meet up regularly and invite each other to visit sites abroad.⁴⁰ Such a community of knowledge allows learning that is both based in locality and travels across territories, where the dwellings of birds often reveal new details about the suitability of particular places. In this way, swift lovers have learnt to pay attention to the birds while becoming affected by what matters to them. I became aware of the potential of such attentiveness when reading Vinciane Despret’s study about birds’ territories and the ornithologists who multiply the many ways in which they are experienced, felt, and made significant. Learning to pay attention, she writes, is a process of “attunement” (“accorder de l’attention”): it is both “giving one’s attention” and acknowledging how other beings are attentive; “it is another way of acknowledging importance”.⁴¹ In other words, when birds make territories, they create modes of attention to which ornithologists may in turn become attuned. This makes the birds more interesting and opens up significant differences, not only between perspectives or hypotheses, but between territories, ways of living, and ways of world-making. Returning to Martine, I recognize this attunement of attention to that of the birds in the way she learned to notice swifts’ places through an accumulation of observations of local colonies, enlarged by those of connoisseurs from abroad. She also used to watch over her interventions, checking to see if the birds would come back and that nothing bothers them. Yet in recent years, the volume of requests has become so overwhelming that little time remains to see if all goes well in those places.

Moreover, the process of noticing and learning is sometimes not enough. The work of preserving or providing homes for swifts requires conveying this field knowledge and its importance to unfamiliar interlocutors. This occurred as we were sitting in the construction site cabin, behind a monumental art and history museum (Musée du Cinquantenaire), together with the site managers of the governmental organization managing the state’s properties (Régie des Bâtiments). This museum is a persistent mark left by Belgium’s colonial power and displays a collection of archaeological artefacts and artworks from non-European cultures. In 2015, ornithologists discovered a colony of swifts living in the cracks in the curved colonnade on either side of the museum (fig. 4a & b).

There, swifts offer an impressive spectacle, with their acrobatic flights around the mosaics and their cries that reverberate among the stones of the colonnade. Since their presence has been documented, it was also mentioned in the planning permission, which subsequently requires a meeting in order to see if the upcoming restoration of the colonnade will affect the birds. The roof is prone to leaking, but before the necessary repairs can be undertaken, it is necessary to ascertain that they will not disturb the nesting sites.

For Martine, the stakes of this meeting are even higher than protecting the nests. Not only does she care about this astonishing colony, but, knowing the numerous, huge buildings that the Régie manages, she also envisions the possibilities that may arise if her interlocutors were to be receptive to the matter of urban wildlife. She thus attempts to magnify the meeting’s importance. From the outset, she has placed on the table two wooden artefacts — a swift and a square with a hole in it — along with her laptop featuring blog posts about previous interventions, and annotated pictures of the building and its colonnades (fig. 5). With these objects she concretely explains the situation: she talks about the birds, their needs, the specific holes where their presence has been documented. Her arm dives down and then swoops back up and turns around. She is showing swifts’ movements as they would leave and enter the holes, and the space they require to do so.

The meeting goes well: all agree to make sure that no works will occur during the breeding season, and that no remaining infrastructure will prevent access to the cracks. I am surprised to discover how these site managers listen at length about swifts, look at leaflets about the birds’ ethology, and become interested in different forms of nesting boxes. I am moved by the feeling that something comes to truly matter, which did not an hour ago. We then go up under the colonnade to take a closer look in situ, which manifested even more care. Martine indicates the nesting sites, and where and how the swifts fly. In doing so, she stirs her interlocutors’ imaginations: she creates a “fictional presence” of the birds while they are away. From there we can also notice the actual sizes of the cracks and how spotlights aimed at the mosaics may be disruptive for the birds. The meeting concludes with further commitments. They envisage the installation of nest boxes on the museum’s vast roof for black redstarts or grey wagtails, these birds having been documented on the site. They also extend their concerns to other buildings managed by the Régie. The organization includes a service devoted to sustainability, yet the reduction of energy consumption is, again, a leading priority.

But that meeting may induce earlier changes. I observed how the site managers’ interest took shape, along with Martine’s budding joy when sensing her interlocutors’ responsiveness. She managed to make this happen, when she mimicked the birds’ movement, talked about their ways of life, used objects that gave a concrete idea, showed existing solutions, or the birds’ behaviour when on site and, when necessary, shifted from these stirs of imagination to a technical and architectural language. It was through these concrete ways of doing that a sense of importance was passed on to the others. Of course, such a sense of importance is not always so readily manifested and conveyed. And perhaps my presence as an observer also amplified it. But when it does, these ways of doing foster significance. Conveying, here, is not simply communicating information, but, as its popular Latin root conviare reminds us, it offers an invitation “to accompany on the way”. These approaches foster commitment in people; they spread and amplify concerns, first embedded in that building and situation, then opening on to others.

Putlog Holes and Towers: Reactivating Heritages

Certain historical artefacts belong to the architectural specificities that Martine and other swift lovers have learned to notice. In the nineteenth century, Brussels saw tremendous development with the erection of the characteristic terraced townhouses that swifts, among other birds, came to particularly enjoy. Most of these maisons bruxelloises were built between the 1850s and the 1930s, at a time of great industrial prosperity. These houses are hospitable to swifts, mostly because they offer more spaces and cracks, but also due to a detail of their architecture.

Below the eaves of the maisons bruxelloises, a series of holes have been inserted at regular intervals, called “putlog holes” (“trous de boulins”, fig. 6a). These holes have existed at least since the Middle Ages, and were particularly common in nineteenth century constructions in Belgium and northern France. Until the inter-war period, they were mandatory in most municipalities in Brussels. Putlog holes were first and foremost used to insert the ends of beams, to support scaffolding for finishing touches or repairing façades, and occasionally to insert pulleys for raising furniture (fig. 6b). “Putlog covers” (“cache-boulin”) were often placed over the holes, to be removed when the holes were needed. At first, putlog covers were made of cork, but from the 1870s they were attached by a hinge at the top, as large-scale and inexpensive production developed models either in cast iron or in stamped or molten zinc (fig.6c).⁴² Putlog covers are shaped as ornaments featuring stars, rosettes, and often mascarons such as frightening human or animal faces (here mostly lions or dogs), originally intended to frighten away evil spirits. If the covers were not stolen to be sold for scrap metal, they were often slightly ajar or corroded by rust, leaving open a small passage to the hole. From the turn of the twentieth century, architects’ tastes led them to leave the holes fully open and to play with polychromed materials for embellishing the borders. Nowadays, putlog holes and their covers are little known. They are hardly appreciated as cultural heritage, and literature about them is scarce. Yet, once brought to your attention, they are noticeable everywhere in the suburbs of Brussels.

To begin noticing putlog holes is to begin looking at Brussels’ houses with swifts’ eyes. Almost always more than five metres above street level — a swift’s minimum requirement — putlog holes are very popular among the birds. While swifts are sensitive to light at the nest, they find obscure cavities in putlog holes, as they are about thirty centimetres deep. Owing to the covers, their entrances may be quite narrow, making the hole a safe refuge by keeping bigger birds out. Smaller models (five to eight centimetres in diameter) are also interesting to swifts as corridors to reach spaces under roofs. In all cases, an opening of three centimetres makes the hole perfectly suitable for swifts to enter with their straight flight, or when swooping out (fig. 7).

Other cavities in Brussels’ buildings are good candidates for becoming swifts’ dark quarters. Watching the city “with swifts’ eyes” means noticing entrances that look tiny to humans. Mostly, eaves provide large boxes that the birds first explore from their side edges. Yet swifts may also find shelter in ventilation holes whose grates have fallen off, in cracks under or above lintels or windowsills, and under fascia boards, where narrow spaces are left between the end of the wall and the side of the roof. More rarely, swifts have dwelled in roller shutter boxes, although such spaces are difficult to access for them. Martine notes that there are some “cultural” differences between Brussels’ swifts and those belonging to other landscapes, as well as between colonies, since some of them favour one sort of cavity over another.⁴³ Putlog holes in particular are architectural technologies that are culturally, historically, and geographically specific. Today they are not well known, but swifts have long found them suitable. Their storying of places has emerged with these specific artefacts that are culturally situated. This is the case for different kinds of cavities, such as eaves, but putlog holes show even more forcefully how swifts converted a highly specific historical technology into a dwelling place. As Dominique Lestel argues, if technical skills and the use of tools are cultural attributes among human societies, then the making of private spaces by animals (such as nests or burrows) are part of their cultures too.⁴⁴ In this way, putlog holes lie at the interface between local human and swift cultures. Swifts’ conversions of these holes, like other specific human-made artefacts that have come to suit their preferences, form a historical and cultural entanglement between their world and ours. Thus, swifts and their defenders do not engage with “human constructions” in general, but with these discrete, specific heritages that have become meaningful in the swift’s world, and now gain new attention and meaning for people in their encounters with them.⁴⁵

Another form of architectural heritage to which swifts draw our attention are towers. Not modern skyscrapers, as we have seen, but lower and older towers such as those of churches or castles. These towers are more than suitable technologies. When a colony lives in the top walls or roof of a tower, the group circles round the column, seemingly chasing each other. As discussed above, these collective “screaming parties”, together with the looping play of young birds, are central to swifts’ social, territorial, and intergenerational lives. Swifts also engage in these flying screaming parties along streets, with the houses of their cavities at the centre of their flight trajectories. When this house is a tower, they circle around it. It seems that a tower perfectly suits swifts’ circling patterns, possibly even enhancing the pleasure these parties provide.⁴⁶ The noisy, circling flights around the rising part of the building appear to be a dazzling performance for those partaking and for those observing. The swifts’ acrobatic flight is a recurrent fascination among scientists and enthusiasts. Their social choreographies awaken a sense of grace with their aerial slides, the agility of their dives and bounces, and the thrill of excitement while pursuing each other. As philosopher Etienne Souriau contends, these aesthetic movements are not simply instinctive and mechanical repetitions. When animals play with their driving forces and try to find the right rhythm, their sensitivity is at stake.⁴⁷ Hence, such aesthetic experiences do not happen just for the appreciative observer, but for the aerobatic birds as well. I would add that the possibility of an aesthetic encounter also involves the towers that mediate the birds’ circling movements and their captivating expression.

Such spectacles have been a common sight in northern Italy for centuries. The use of “swift towers” (“torri rondonare” in Italian) most probably spread among medieval fortified buildings from the fifteenth century, possibly even the thirteenth century, onwards. As Mauro Ferri describes, artificial nests were installed in tower houses (“casa torre”), and then in belfries, farmhouses, palaces, bell towers, and so on. Up until the twentieth century, turrets were also added on existing roofs. They were made of rows of cells embedded in walls, which the birds could reach through little corridors. The rows of holes added regular touches to the sober architecture (fig. 8). At the back of each cell, a wooden plug could be removed in order to capture nestlings before their first flight, once they were fattened and would taste like “small butter pancakes”.⁴⁸ Young swifts were cooked, canned, and stored for gastronomic occasions or offered as highly valued gifts. The delicacy was rare, since the selection of nestlings had to be carefully carried out, on the condition that the captures would not harm the colonies. Ferri found regional variations for coping with that condition: either the first brood was completely spared, or only one bird was taken; or else, for each brood, “one chick had to be spared so that the parents were not upset”.⁴⁹ The birds’ breeding places were thus a means for exploiting their chicks as food and involved moral obligations within a strongly asymmetrical relationship. Whereas swifts were offered shelter at the expense of (a part of) their progeny, humans got a delicious dish with little inconvenience. Nowadays, hundreds of these towers are still standing but left in ruins since the practice faded in the early twentieth century, as little birds were not considered food anymore. Ferri has been fighting to preserve this heritage, which he thinks may be rediscovered to support the species, along with the novel “swift towers” that have recently mushroomed across Europe.⁵⁰

Back to Brussels, and for those like Martine who have witnessed swifts’ screaming parties around Italian towers, watching the city “with swifts’ eyes” also means that towers spark the imagination. She now notices certain towers in the city that emerge as good candidates for future transformation. She has integrated nest boxes in some of them located in schools, churches, or in industrial buildings such as a former brewery, in an effort to match the architectural style of the towers. The success of these operations depends on swifts adopting the next box, circling around it, and amplifying its aesthetic. However, this is not always easy, as with the Tomberg tower in eastern Brussels. This tower was part of a municipality building listed for its 1930s Art Deco style. At a time when its restoration was planned, Martine had already spotted that tower and got ideas from the Italian swift spectacles. She joined meetings to propose swift boxes for the design project. First approved by the municipality, the Historic Monuments and Sites Department, the architect and the contractor, the boxes were later excluded from the project due to overwhelming concerns about finding the right aesthetic style in harmony with local heritage. Here the concern about the exclusive conservation of an architectural heritage dispelled the possibility of an aesthetic multispecies encounter.

Yet, a change is underway: today putlog holes and (certain kinds of) towers compel attention because they are at the crossroads of swifts’ and human cultural heritage. While the former called to swifts’ ingenious agency in converting an architectural artefact into a home, the latter started as a technology for food exploitation and persists as an architectural artefact that intensifies the encounter through the pleasures of joyful circles around rising brickwork. Ultimately, engaging with swifts’ meaningful connections with putlog holes and towers involves the possible reactivation of these technical and aesthetic heritages.

Risky Nest Boxes

Lastly, a great deal of Martine’s interventions to install nest boxes consists of going up to rooftops via scaffolding or a lift, sometimes with the support of the municipality. The placement of artificial nest boxes, and their possible adoption by swifts, is a widespread practice across Europe. For the human novices who discover them, the nest boxes appear as devices through which forms of proximity with birds are invented. The making of artificial nests for swifts includes the deployment of many technical details that adapt the boxes to their needs, for instance, by using thermos-regulator materials, designing a slanting roof that prevents predators from landing, an entrance that discourages other dwellers, or by inserting a cup in the nesting area that spares them time in building a whole nest (Fig. 9 a & b).

Yet, for swifts to adopt new nesting sites, installing boxes is only the first step. Once the boxes have been correctly installed (e.g. at a sufficient height, avoiding the threat of overheating due to a south-westerly orientation, at irregular intervals to prevent swifts from mistaking “their” entrance and the ensuing fights, etc.), further effort is required to lure the birds to them. It typically takes years before swifts select a box and make it their home, so recordings of their vocalizations are used to attract them.⁵¹ As such, nest boxes cannot be reduced to the mere solution of installing and improving a technology in itself. The boxes require ongoing attention and care, therefore more volunteers, and more of their patience and stamina. Artificial nest boxes offer the promise of rejoicing when catching a glimpse of a swift flying towards the hole, but this is not guaranteed. The success of these nest boxes is a risky affair: it requires the refinement of these technologies to make them more inviting to the birds, the creation of a “fictional presence” of swifts using sound, and the boxes must be watched over while letting swifts choose whether to respond to those tricks.

But installing nest boxes runs greater risks than being seen as solutions in themselves and forgotten about after being placed. Martine told me a story with some unease, in which she evoked the construction of a huge package distribution centre on a vast wasteland of twelve hectares along the Brussels canal. From 1930 to 1993, the site was host to a gas plant that produced and delivered town gas, coke, and derived products for the carbon-chemical industry. As a result, it was estimated to be the most polluted site in the Brussels region.⁵² Like many former industrial sites, in the decades since the plant closed down, the area had become a marsh where many animals and plants had come to dwell. The wasteland was quite famous among Brussels’ naturalists. For birds alone, they reported about sixty different species living on the site, both endemic and migratory. In order to compensate for the loss of habitat, the company proposed to install eight nest boxes for swifts, but without much care about how it would be done. In short, placing the boxes provided an alibi for a cynical greenwashing operation. Following a public inquiry, environmental organizations lodged objections during the authorization procedures, but without going to court.

An ambivalence pervades Martine’s account: like other environmentalists, she sorely regrets the loss of the wasteland, but since the mega-depot was going ahead with its eight nest boxes anyway, she provided advice on how to better integrate them so that swifts could actually adopt them. Again, what was at stake for her was the conveying of importance. The negotiation opened a big door for her to become an advisor for Citydev, a public organization that plays a central role in the development of real estate housing projects and businesses across the city. There is a success for Martine and the swifts here: the increasing importance of integrated nest boxes throughout the city. However, I cannot help but see a contradiction in the use of the nest boxes for the construction on the wasteland. Placing the boxes requires few engagements: they are not expensive, do not bother the human residents, and may give the construction project an unearned positive image. In other words, since swifts are unobtrusive dwellers in human buildings, interventions to install nesting sites may help to justify construction projects and draw attention away from the way these projects destroy other living beings’ places. With cautious use, the boxes are technologies that create proximity and meaningful possibilities for the birds, but these objects are also dangerous since they can be easily mobilized as instruments for greenwashing.

Watching the City “with Swifts’ Eyes”

In their storying of places, swifts have an astute knowledge of our buildings that illuminates a world made of generational transmissions, scream dialects and looping parties, flight attunements to particular entrances, hole arrangements, and fierce fights. These dwelling practices involve the social creation of distinctive places. What is it, then, to engage with storied places, with swifts’ meaningful neighbourhoods, buildings, and holes? What does it mean to care in this case? I conclude by coming back to the expression “watching [the city] with swifts’ eyes”. Of course, it is impossible for us to fully grasp the experiential world of other animal subjects. The expression “with swifts’ eyes” does not imply putting or imagining oneself in the birds’ place. It rather signals a practice of attentiveness and imagination that experiments with a proximity to the bird, by paying attention to what matters or could matter to them in the shared environment. How does this attentiveness take shape along with the transformation of buildings? Which tensions or contradictions emerge in their wake?

Perhaps the most striking occurrences that call attention are swifts’ “screaming parties”, during which they pursue each other over their territory. While first hearing these screams and then recognizing them, these parties draw swift lovers to notice the birds’ particular neighbourhoods and nesting places. Without such opportunities, it is rare to notice one of them entering a hole. Swifts’ sounds are thus crucial to further scrutinize small crevices in walls and eaves, both for the members of a colony and for their human enthusiasts. From there, Martine’s attention enlarges through an accumulation of local observations. Not only swifts’ stubborn fidelity to their nesting sites leads her to return each spring to these same places, anticipating the joy of finding migrators again, but she also learns from other connoisseurs what the architectural preferences of these birds may be, and becomes more aware of them. In this way, specific historical artefacts, like putlog holes or historic towers, compel attention and hold aesthetic appeal. They call to reactivate these otherwise forgotten inheritances with which the birds have woven their world for centuries, despite the prevalence of human-centred aesthetics in architecture. Swift caretakers are also drawn into their world when refining nest-box technologies to craft better scenarios for them. These boxes demand a surplus of attentiveness, like when using playbacks of swifts’ calls in the hope of attracting them. Yet, they can easily be turned into compensation instruments that justify destruction.

In addition, the practice of engaging with swifts’ storying of places implies the sparking and stretching of imagination. The expression “watching [the city] with swifts’ eyes” signals how that practice of attention involves imagination, like when spotting old towers and starting to see the promise of circling parades and their aesthetic pleasures. I pinpoint this imaginative work, too, when Martine suggests their “fictional presence”. This consists of conveying importance to interlocutors previously ignorant of swifts, by mimicking the birds’ movement during a meeting, showing objects, or through oral descriptions in situ; when Martine mimics the swifts’ calls in a way that plays into their quest for sociability; or when sharing anecdotes or videos on her blog. The attentiveness in the care for swifts is intimately bound up with these acts of imagination.

These ways of paying attention and of stretching the imagination belong to a form of care through which swifts and humans come to be with each other, in meaningful ways, through material interfaces of buildings such as holes, eaves, nest boxes, house blocks, putlog holes, or certain kinds of towers. Rather than a co-becoming through bodily co-presence and touch, the relating through which these species constitute each other is mediated by those specific architectural interfaces. As these buildings and their material invitations have long attracted swifts in human-made cities, today they appeal to human caregivers and their abilities to respond to swifts’ storied places through their ears, eyes, mimicry, imagination, and reshaping of the built environment. In this way, these buildings lure both swifts and humans to cross each other’s worlds. It is through such attentive and imaginative practices that material interventions with a fuller appreciation of swifts’ meaningful worlds emerge, and will most likely spread.

Acknowledgements

I am deeply grateful to Martine Wauters; this article could not have been researched if she had not generously welcomed me into her impressive practice dedicated to swifts’ fate. Thank you as well to Mélanie Tamm for sharing with me her knowledge about putlog holes, and to Alain Boeckx and Steyn Van Assche for sharing theirs about the Cokerie du Marly wasteland. For allowing me to publish their pictures, thank you to Luca de Carli, Elizabeth Thornburn, Mark Pearse, Brigitte De Boeck, Jean-Claude Hardy, Nick Winship, and again to Martine Wauters. For their insightful comments on earlier versions of this manuscript, I thank the two anonymous reviewers, as well as Wakana Suzuki, Filippo Bertoni, Jeannette Pols, Thibault De Meyer, and the members of the SEED lab (Socio-Économie, Environnement et Développement) at the Université de Liège. Thank you to Stephen Creek who assisted with editing. The research for this article would not have been possible without unemployment benefits in Belgium.