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Arquitectura e Biodiversidade. Construção de edifícios amigos das andorinhas e dos andorinhões. Biodiversidade em contexto urbano.


Nowadays it is essential to understand that our cities are ecosystems and that the more complex they are, the safer and healthier they will be for humans. If some of the species that share the urban space with us may cause some harm, others provide us with invaluable services. And to be able to enjoy these services we only need to provide them with shelter. Among them, insectivorous species are those whose presence brings us the most obvious benefits. It is to animals such as swallows and swifts, frogs, geckos and bats that we owe the fact that our cities are not infested with mosquitoes. It is therefore urgent to promote biodiversity in an urban context, especially by protecting the most sensitive species or those that provide us the most important ecosystem services, so that they can be established in parks, gardens and even in buildings.

The modernisation of architecture and construction techniques and materials has proven to be one of the main factors threatening swallows and swifts. Although urbanisation represents a threat to biodiversity, proper urban planning can be a strong tool for the preservation and enhancement of biodiversity. When designing a building, solutions can be devised to provide safe nesting places for birds, without the droppings that sometimes accumulate under nests causing any inconvenience.


Swallows nest outside buildings by "gluing" their clay nests under the cornices or protected spans. Unlike the majority of other birds that try to hide their nests, swallows, as they take advantage of the protection that the vertical wall offers, not only make their nests clearly visible, but they are also unconcerned about the dirt they cause. When the little swallows hatch from their eggs, dirt soon begins to accumulate under the nests, which easily denounces the presence of the birds and can become a nuisance for those using the building. 

The solution for promoting nesting swallows in a building, which results in peaceful coexistence with these birds, is to design buildings that have façades with the following characteristics:

  • north or east facing

  • over 4 metres in height

  • rough wall cladding

  • cornices protecting nests from rain and not placed over windows, balconies or resting or passing places

  • do not confront obstacles close to the nest height, such as tall trees or other buildings


With a façade that meets the previous requirements and stands on a gardened site, we close a cycle and allow the swallows to transform the insects on which they feed  into fertilizer for the plants that grow there. The placement of a few artificial nests facilitates and accelerates the occupation of the site by swallows seeking to nest in colonies.


Swifts use small sheltered and difficult to access openings inside buildings, which resemble those that exist on the cliffs where their ancestors used to breed. Thus, they prefer old buildings where they find these conditions, such as stone constructions or traditional tiled roofs. Unlike swallows, their nests are barely noticeable and rarely leave any trace of their presence.

In modern buildings, the cracks between components are almost non-existent and therefore, with rare exceptions, do not offer conditions for these birds to nest. In order for a new construction to house a colony of swifts, it is necessary to think about solutions still at the design stage, and fortunately there are specific products on the market to accommodate these birds.


Opening roof tiles - internal roof structures are where most urban swifts nest. The construction of new, insulated roofs and the restoration of old roofs limits the access to possible breeding sites. The incorporation of some tiles with adequately sized openings (28mm x 65mm) allows swifts to enter the roof, but not pigeons or other inconvenient birds.


Nest box bricks - one of the most practical solutions to swallow friendly buildings is the installation of bricks which already have their nests incorporated. Embedded in the building, preferably on north or east facing façades, they offer ideal security and insulation conditions for these birds, and are a commonly used solution in other countries.

Nests built into the building - the best solution for enhancing the presence of swifts in our cities is to create structures in buildings dedicated to them. A flock of swifts flying in and out of a structure on the top of a building could be a symbol of the relationship between cities and biodiversity. There are a number of solutions for this, which always include creating small openings (+/-16 dm3) accessible through cracks (28mm x 65mm) in a north or east facing façade.


The demolition and restoration of buildings or façades lead to the destruction of many swallows and swifts colonies. With the cleaning and painting of façades the nests of swallows are destroyed, which with some difficulty and much persistence will try to rebuild them in the following spring. The restoration of roofs and stone constructions, on the other hand, in a more drastic way, permanently seals the cracks that the swifts use to access their nesting places. This phenomenon is recurrent and has special impact because the optimal period for construction and restoration works coincides with the birds' breeding period. Furthermore, the colonies are not recorded, there is no information about their presence and there is no training on how to proceed when a colony is found in a building to be restored. As a result, many colonies are destroyed and often nests with eggs or even small birds inside are destroyed.


It is important to remember that it is forbidden to destroy nests, namely those of swallows and swifts, even if empty and during the breeding and non-breeding season. Therefore, in the case of a building intervention where we notice that there are nests, the solution is to request an authorisation from the ICNF, which tries as far as possible to minimize the impact that the work may have on bird conservation, issuing the necessary licenses and accreditations.

The most conscious measures include:

• try to ensure that the construction schedule does not coincide with the birds breeding season

• ensure that swifts' access to their nesting sites is not fenced off

• install nest boxes in a nearby location as a mitigation measure

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