Problematic coexistence – sharing our buildings with birds

Most species that nest on buildings used to nest exclusively or at least mainly in cliffs. With the emergence in ancient times of the first large buildings such as the Acropolis, Roman amphitheatres and aqueducts, new opportunities opened up for cliff nesters and other birds of human settlements. Barn Swallows were considered widespread in Ancient Greece and Italy. As settlements developed, cliff-nesting birds from eastern Europe, the Mediterranean and western Asia established themselves in central Europe. Large parts of central Europe were covered in forest and offered few nesting sites for these species – with the exception of some tree-nesting jackdaws and swifts. In present-day Switzerland, some species are largely or even completely dependent on buildings for nesting: Common, Pallid and Alpine Swift, Barn Swallow, Northern House Martin, House Sparrow and Italian Sparrow. In the case of species like White Wagtail, Black Redstart, Spotted Flycatcher and Eurasian Jackdaw, a part of the population uses buildings for nesting. Goosander, Peregrine Falcon, Yellow-legged Gull and Eurasian Crag Martin are increasingly found to breed in buildings.

Colonisation of buildings: the trend continues

We do not know which species was the first to nest on buildings, or when this happened and where. The House Sparrow is assumed to have become a constant companion of humans in central Europe ever since the emergence of agriculture in early history. The pigeon towers of the Middle East and nesting towers for swifts in Italy show that humans have encouraged the colonisation of settlements by cavity breeders for centuries or even millennia. Humans quickly learned that birds could be attracted and used for culinary purposes.

The earliest documented colonisation of buildings in Switzerland relates to the Alpine Swift colonies in the minster and the Christoffel Tower in Bern in 1768/1769; historical records note that the chicks were considered a «delightful meal». The expansion of the Alpine Swift in Switzerland seems to have been quite slow, however. It was not until the demolition of the Christoffel Tower and construction work on the minster around 1890 prevented the birds from occupying their nests that a wave of expansion was triggered. Subsequently, the first broods were found in Lucerne in 1892, in Zurich in 1911 and in Schaffhausen in 1922. The colonisation of buildings by the Alpine Swift has progressed since the early 20th century leading to the gradual occupation of about 70 towns.

Crag Martins have been known to nest on buildings in the Canton of Valais since 1919, but such nests were an exception until 1970 and were still considered rare as late as 1982. They have become much more common since about 1994. The Swiss population of the Crag Martin has grown by about 60 % since 2003. In Alpine valleys, pairs nesting in cliffs as well as those using buildings appear to be increasing. Buildings are probably used in an opportunistic manner as «artificial cliffs», mostly in proximity to existing breeding sites. The Crag Martin is increasingly colonising the Central Plateau, where it nests on high-rises as well as in cliffs and on bridges. On the whole, however, new colonies outside of the Alpine range remain a marginal phenomenon.

Other species did not attempt to nest on buildings in Switzerland until the 1990s, such as Peregrine Falcon in 1991 and Yellow-legged Gull in 1994.

Modern building design is a problem

Architectural styles and building materials differ widely between regions. Houses with stone-slab roofs like they are common in Ticino or Engadine GR provide numerous nesting sites for Common Swifts. In central Switzerland, on the other hand, building structure is much less favourable, and offers few opportunities for Northern House Martins to build their nests. Also, the open barn design that has become popular in recent years is much less suitable for the Barn Swallow.

Alpine Swifts have the advantage of mostly nesting in colonies on prominent buildings and enjoying a certain popularity among the public. As a result, the impact of building renovations on Alpine Swifts is often recognised early on. In most cases, solutions can be found to protect and maintain the colony. The nest sites of the Common Swift in our towns and villages, on the other hand, are more numerous and spread out. Preserving them when buildings are renovated or creating enough new sites is an ongoing task. Some municipalities have introduced swift inventories to keep track of nesting sites.

As a consequence of our modern «flawless» building design, few new nest holes are created for Common Swifts and other birds that nest on buildings. Due to high aesthetic standards, the use of certain construction materials, and potential problems with insulation, it can be difficult to create spaces for nesting birds.

Urbanisation and low acceptance put birds under pressure

The heightened construction activity throughout the country creates further difficulties for birds: as urban density grows, foraging sites for Common Kestrel, Eurasian Jackdaw, Common Redstart, Spotted Flycatcher, House Sparrow and others disappear. In urban habitats, food is scarce, often too low in protein, or has to be transported over long distances. As a result, the breeding success of Eurasian Jackdaws in urban areas is poor. House Sparrow populations are also declining in many central European cities. Because most paths and forecourts are paved, the Northern House Martin has trouble finding sufficient nesting material. The use of large glass surfaces increases the risk of fatal collisions for many species.

In many areas, birds that rely on buildings for nesting face difficult conditions – not least due to a lack of acceptance from humans. The fact that these species’ broods are protected by the federal act on hunting and for the protection of wild mammals and birds is too often overlooked.