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Our Mission
SPEA is an Environmental not-for-profit organization whose mission is to support research and conservation of wild birds and their habitats, by promoting sustainable development for the benefit of future generations.
Home  > Study and conservation > Birds Census > Common bird census

Common bird census
The Common Bird Census (Portuguese acronym: CAC) is a long term monitoring programme of common breeding birds and their habitats, in Portugal. It was launched by SPEA in 2004 in continental Portugal and Madeira and later in 2007 in the Azores.

As an example, the Common Bird Index is used as an indicator in the National Strategy for Sustainable Development and the Farmland Common Bird Index is used as an indicator in the Rural Development Programme. In conjunction with data from similar programmes in other countries, our data is producing indicators that measure progress towards objectives set by the Convention on Biological Diversity and European Union to stop biodiversity decline.

  • The project's importance
Since environmental policies affect land management and use, the creation of a Common Bird Index, per habitat (farmland, forest, etc.), in Portugal, is an important tool to measure, over time, the sustainability of decisions and policies taken. The Common Bird Index (Portuguese acronym: IAC), provided by the CAC, is already included as a biodiversity indicator in the National Strategy for Sustainable Development 2005-2015, a first but important step. Also, the Farmland Common Bird Index (Portuguese acronym: IACZA) as been included in the National Strategic Plan for Rural Development 2007-2013. Because of this recognition, the IAC and IACZA indicators are already being used by other official entities in Portugal, namely the Portuguese Environmental Agency, National Institute of Statistics and Ministry of Agriculture, Rural Development and Fisheries.

The Common Bird Census is also of international importance and has been integrated into the Pan-European Common Bird Monitoring Scheme (PECBMS), headed by Birdlife International and the European Bird Census Council (EBCC). This means that the CAC data obtained in Portugal is also contributing annually to the European Union's wild birds indicator.
- Learn more about the PECBMS
You can download the latest PECBMS brochure (see “Documents”, below).

  • Goals
This project's main goals are:
- To obtain information about population variations for a number of breeding bird species in Portugal and calculate annually their respective specific indexes, which show variations in abundance from the initial year;
- Create and propagate the Common Bird Index, including most species, as well as its annual updates;
- Calculate composite indexes that group species associated with the main habitats in Portugal, namely farmland and forest;
- Make an annual contribution to the Pan-European Common Bird Monitoring Scheme (PECBMS), of data on population tendencies of Portuguese species;
- Promote birds and habitats conservation by directly involving a large number of volunteers in crucial bird monitoring projects.

  • How to participate
The Common Bird Census is based on volunteer field work. Each observer is responsible for one or two 10x10 km UTM squares, where he or she must conduct annual bird census, in order to obtain a continuous monitoring of birds and their habitats.

There are five Regional Coordinators, each one responsible for overseeing work in a particular region:
- Northern Region (districts of Viana do Castelo, Braga, Oporto, Aveiro, Coimbra, Vila Real, Bragança, Viseu and Guarda) – Julieta Costa (
- Central Region (districts of Leiria, Lisbon, Santarém, Castelo Branco and Portalegre) – António Rosa (
- Southern Region (districts of Setúbal, Évora, Beja and Faro) – Guillaume Rethoré (
- Madeira – Cátia Silva ( or
- Azores – Hugo Sampaio (
- General support - Rui Machado (

If you have some birdwatching experience and, even more importantly, if you are motivated to participate, join us! Your contribution is essential!
If you are interested in participating in the Common Bird Census please contact the Regional Coordinator for the area where you intend to do the field work.

  • Brief methodology description
In the first year that a square unit is monitored, before any actual census, there should be an initial visit with the sole purpose of scouting the area and selecting 20 listening spots, distributed throughout the different habitats and at least 1 km apart from each other. The habitat at each of these listening spots is recorded (in relative detail), during this first visit.
Each square unit should be visited twice per year for bird census. The first one should take place in April and the second in May (in the Azores the season takes place 15 days later), making sure each visit is at least 30 days apart.
The census last for 5 minutes at each of the sequential 20 spots and must be done in a single day between dawn and the following 4 hours (should be finished by 11am in the first visit and 10.30am in the second visit).
Each year, the census should be carried out in the same spots and in the established sequence, recording any changes in the habitats.
  • CAC at the VI SPEA's Ornithology Conference
The Common Bird Census was represented (by its coordinating team) at the VI SPEA's Ornithology Conference and VI Iberian Ornithology Conference, in Elvas – Portugal, December 2009. An oral communication was presented in plenary session, titled “Censo de Aves Comuns e a criação de um indicador de biodiversidade em Portugal” (Common Bird Census and the creation of a Portuguese biodiversity indicator), which divulged the Common Bird Index and the CAC's main results up to 2008. A workshop was also prepared consisting of an open session, involving collaborators and anyone interested in the CAC, where the project's progression since 2004 was discussed and the new method of submitting observations online, through the portal PortugalAves, was demonstrated. Both presentations can be downloaded at this page (see “Documents”, below).

  • Reports and other documents
1Presentation on the Creation of a Common Bird Index in Portugal (VI SPEA's Ornithology Conference)
2) Presentation Evaluating 6 years of the CAC project (VI SPEA's Ornithology Conference)
3) Azores Common Bird Census Report (2007-2008)
4) Brochure “The State of Europe's Common Birds 2008” (PECBMS)
5) Poster presented at the 17th EBCC International Conference, 2007 (A4 version)
6) 2004 and 2005 Common Bird Census Reports

  • Coordinating Team
This project is currently managed by the following people:

National Coordinator
- Joaquim Teodósio (SPEA's Terrestrial Programme's Manager)

Support and supervision of the Coordinating Team
- Domingos Leitão (SPEA's Executive Director)

Data management and analysis
- Pedro Rodrigues (SPEA)

Regional Coordinators
- Mainland Portugal: Julieta Costa, António Rosa, Guillaume Rethoré
- Cátia Silva (Madeira)
- Rúben Coelho (Azores)
- Support: Rui Machado

  • Sponsorship

Photos: Pisco-de-peito-ruivo © Ray Kennedy (; Pintassilgo © Faísca; Poupa © Faísca; Melro © Faísca.

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