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Which by its shape offers less air resistance.


An order of small birds characterised by morphological and physiological adaptations to unique lifestyles. This order, which comprises 478 species, is the second most diverse order in the Class Aves, being surpassed only by the Passeriformes. The Apodiformes are divided into the families Apodidae (swifts), Hemiprocnidae (treeswifts) and Trochilidae (hummingbirds). Of the 3 families of Apodiformes, only the swifts are represented in the Portuguese avifauna.

Average life expectancy

Average number of years that individuals of a given species live.


Divided into two branches or arms. With two tips.


Counting the individuals in a population.​

Citizen science

Involvement of citizens in scientific research activities, to which they actively contribute, in most cases by sending data that serve as a support for different studies.


A group of living beings that live together or use a certain place simultaneously for resting, feeding or breeding.​

Conservation status

A concept indicating the degree of preservation and abundance of populations of a species in nature and how likely it is that these living beings will become extinct in the near future. The factors taken into account include: population size and trend, reproductive success rate, survival rate, known threats, etc.

Convergent Evolution

Evolutionary phenomenon that occurs when similar selective pressures originate similar adaptations in different taxonomic groups. Structures such as bat and bird wings, despite being evolutionarily unrelated, perform the same function (flight).


Protruding moulding on the façade of a building, which serves as the upper finish and protection from rain.


Deficiency of water and mineral salts in the body to the point that vital functions cannot be carried out.


Word that identifies a group of people (inhabitants, residents, natives) in relation to a particular place.


The variety and quantity of food items that individuals of a given species consume.


Place where several animals gather to spend the night.


Edge of a roof. Row of tiles forming the lowest part of the roof.


The biological capacity for localisation and orientation through the emission of sound waves and the analysis of the resulting echo.

Ecological niche

Set of conditions and resources necessary for the establishment of a species in an ecosystem and its relationship with it. These include the habitat, the role the species plays (producer, consumer, decomposer, etc.), the species' ability to adapt to limiting factors (temperature, humidity, pH, etc.), the species' reproductive needs (nesting sites); etc. ​

Ecosystem services

The set of goods and services derived from ecosystems that are fundamental for maintaining well-being and future economic and social development. Ecosystem services are classified into four categories: provisioning (water, timber, food...); regulating (air purification, CO2 storage, pest regulation...); cultural (recreational and tourist activities...) and supporting (soil fertilization, photosynthesis, nutrient cycling...). Swallows and swifts by controlling insect populations provide a valuable regulating service.


Surface of land with an accentuated slope.​


Which is natural and exclusive to a specific region.


Period or region where a migratory bird spends the summer.


Each of the exterior sides of a building.


Taxonomic category between Species and Family. A group of species that descend from a common ancestor, thus sharing evolutionary characteristics.​


A strategy observed in various groups of animals, which group together in more or less structured populations, either permanent or temporary, with the aim of protecting the individuals that are part of the group.


A drop in body temperature to the point where vital functions are no longer viable.


The process by which birds keep their eggs at a temperature suitable for the development of the embryo within the egg, from laying until hatching.


Animal that feeds on insects, worms, and other invertebrates.


Having no vertebrae or inner skeleton. A group of animals that includes insects, spiders, crustaceans, and many others.


The number of eggs birds lay before they hatch. Many species may lay more than one clutch in the same year or breeding season.


Carl Nilsson Linnæus was a Swedish botanist, zoologist and physician, responsible for popularising and disseminating binomial nomenclature and scientific classification, and is thus considered the "father of modern taxonomy".

Migratory movements

Voluntary and intentional phenomena with a periodic nature with the aim of finding suitable conditions (food availability, nesting sites, suitable meteorological conditions, etc.).


Act of minimizing or reducing damage or negative effects.


Animals that maintain a single partner indefinitely.


Taxonomic category between Family and Class. A group of families that descend from a common ancestor, thus sharing evolutionary characteristics.


A zoogeographical region north of the  Tropic of Cancer. It includes the northern part of the Old World (Europe, North Africa, the Arabian Peninsula and part of Asia).


Order of passerines (small and medium-sized birds). This order, which comprises 6640 species, is the most diverse of the Class Aves, representing 60% of the total number of species. Of the 144 families of Passeriformes, 32 are represented in the Portuguese avifauna.​


The study of periodic biological phenomena or processes (e.g. flowering, fruiting, migration) in their relation to climate and environmental conditions.

Population fluctuations

Variations in the number of individuals in the colony.


Animal that feeds on other living beings.


Animals that serve as a source of food for other animals.


Outer feathers of a bird's wing. Bird wings are made up of flight feathers (primaries, secondaries and tertiaries) and their coverts.


Examine thoroughly and methodically.

Recruitment rate

Percentage of new breeding individuals in the colony between consecutive years.



One that does not migrate, spending the breeding season and the winter in the same area.



Birds’ tail feathers. They control the direction and speed of flight.



Triangular appendix covering the caudal vertebrae of birds, where the tail feathers are inserted.​

Sampling unit

Unit in which the quantitative and qualitative characteristics of a population are observed and measured. In this particular case, it will be the building or group of buildings where the colony under study is located.


Scientific ringing

Technique of capture and individual marking of birds using metal rings with exclusive alphanumeric codes.


Inner feathers of a bird's wing. Bird wings are composed of flight feathers (primaries, secondaries and tertiaries) and their coverts.

Sexual dimorphism

Set of characteristics that allow the distinction between male and female.​


A totally or partially open building covered with a roof.


Empty space between two structures.

Specific restrictive

All scientific names are composed of two words (binomial nomenclature). The first identifies the genus. The second - specific restrictive - identifies the species within the genus. The use of the specific restrictive alone has no meaning and must always be accompanied by the genus name.


The abbreviation "spp." (plural) indicates "multiple species." This abbreviation is used to refer to multiple species within a genus.


Taxonomic category below the Species. Populations of a given species that inhabit different regions of the species' range and show variation among themselves (e.g. genetically, behaviourally and morphologically). These variations are not sufficiently distinct to confer species status on each of the populations.​

Survival rate

Percentages of individuals alive between consecutive years.​

Taxonomic authority

Entity that regulates the identification, naming and classification of living beings. Different authorities have different classifications for certain organisms. There are four main authorities: IOC, eBird/Clements, Howard and Moore, HBW and Birdlife International.​

Taxonomic classification

System used to organise living beings by means of pre-established criteria. Taxonomy is the area of biology responsible for identifying, naming and classifying living things. The basic classification of living things is: Kingdom, Phylum, Class, Order, Family, Genus, Species and Subspecies.


A state of reduced physiological activity in an animal, usually marked by reduced body temperature and metabolic rate. This allows animals to survive periods of reduced food availability.

Tracheobronchial syrinx

The syrinx is the organ responsible for the production and emission of sounds. In passerines, the syrinx is located at the lower end of the trachea and in the upper parts of the bronchi.

Throat patch

Part of the face corresponding to the front of the lower jaw.


Species whose morphological characteristics are fixed as a standard for the genus to which it belongs.


Distance between the ends of a bird's wings when fully spread.​


Period or region where a migratory bird spends the winter.

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