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Focus: evolution of the avifauna

In 2012-2013, pursuant to the Birds directive, an estimate of the numbers and trends concerning bird populations was carried out by the 3 Regions. It was ascertained that 107 bird species nested in the Brussels Region over the period 2000-2012 (including 11 non-indigenous species), or almost 60% of the total nesting species in Belgium. The available data make it possible to highlight a stabilising or growth of Brussels populations for 50% of species, and a regression for 20% of them. However, since 2000, 5 new species of nesting birds have established themselves, whereas 6 have become extinct locally.
The annual monitoring of common birds has made it possible to highlight a trend for the period 1992-2013 for 42 species. Among these, 11 species have seen their numbers increase (including 2 exotic species), 16 are stable, and 15 are in decline. The common birds whose decline is the most pronounced are migratory birds.

Birds are a useful indicator for the status of biodiversity. Their particularly high dispersal capacity makes it possible to react quickly to changes which occur in the environment. Furthermore, birds are present in most natural habitats and are represented at practically every level of the food chain, even the highest levels (insectivores, predators). They can also be easily observed.

The monitoring of the Brussels avifauna is based on various mechanisms: the creation of atlases which itemise the distribution and abundance of nesting birds (every 10-20 years), monitoring campaigns of common avifauna or groups of targeted species, specific scientific studies, etc. This monitoring is essentially carried out by Aves, the ornithological division of the Natagora non-profit organisation, at the request of Brussels Environment.

Nesting birds

The last atlas of nesting birds in the Brussels Region, covering the period 2000-2004, made it possible to survey 103 species (including 11 non-indigenous, and 7 which had died out locally or were on the brink of extinction during the drafting of the atlas), which equates to approximately half of the nesting species in Belgium. Of these species, only 16 could be considered as abundant. These are essentially opportunistic species capable of adapting to the urban environment  (certain passerines, wood pigeons, crows, etc.), while species which were more ecologically demanding were usually rare.

The analysis of historical data covering the Brussels Region enabled the authors of the atlas to highlight profound changes, both in terms of nesting densities and the composition of species:

  • the average number of species per km2 is in decline, falling from 36.1 in 1989-1991 to 33.7 in 2000-2004;
  • 14 species have recently disappeared or practically disappeared at the regional level and more broadly at the Brabant regional level;
  • a dozen or so species restricted to open or semi-open environments (fields, wasteland, etc.) disappeared between 1944 and 2004;
  • the number of species of non-indigenous nesting birds has increased sharply and the populations of some exotic species is increasing exponentially (parakeets).

These negative trends have been somewhat delayed by the resurgence or emergence of remarkable nesting birds (Northern goshawks, middle spotted woodpeckers, peregrine falcons) as well as by the increase of several indigenous species which benefit from more favourable or frequent biotopes (in particular in parks and gardens), more suitable natural environment management measures, and protective measures. In this respect, we can observe the progression of populations of housemartins which has been recorded since 2003 - after a drastic decline - and which is probably linked to several campaigns encouraging the mounting of nesting boxes which were conducted in several Brussels municipalities. In 2013, regional numbers of housemartins were almost 300 couples whereas there were only 33 couples in 2002.

In 2013, pursuant to the Birds directive which imposed a monitoring obligation in particular, an estimate of the numbers and trends concerning nesting species was carried out by the 3 Regions. It was ascertained that 107 bird species nested in the Brussels Region over the period 2000-2012 (including 11 non-indigenous species), or almost 60% of the total nesting species in Belgium. The available data make it possible to highlight a stabilising or growth of Brussels populations for 50% of species, and a regression for 20% of them. However, since 2000, 5 new species of nesting birds have established themselves, whereas 6 have become extinct locally.

Annual monitoring of common birds

The annual monitoring of common birds has been organised since 1992. This is done using the "listening points" method, which consists of itemising, in the spring, all of the birds seen or heard during a 15-minute period at a fixed observation site. This method, which especially suits species whose territorial manifestation occurs through birdsong, makes it possible to monitor around one third of the Brussels avifauna. The network of listening points currently includes 114 stations which are representative of the green spaces in Brussels but also of densely built-up environments.

For the period 1992-2013, a trend has been highlighted for 42 of the 103 nesting species (species seen or heard with a sufficient frequency, or the majority of species prevalent in the Brussels Region). Of these:

  • 11 species (26%) have seen their numbers increase, including, by a significant margin, the western jackdaw, the common buzzard, and the rock dove, as well as 2 exotic species (the rose-ringed parakeet and Alexandrine parakeet);
  • 16 species (38%) are stable;
  • 15 species (36%) are in decline, including, by a significant margin, the house sparrow, the common whitethroat, the willow warbler and the starling.

The monitoring suggests there has been a slowdown in the progression of populations of rose-ringed parakeets for several years.

Long-term evolving trends for 42 nesting species (1992-2013)
Source: NATAGORA – AVES, 2013

The following charts highlight the evolution of particular bird groups:

Evolving trends of the common avifauna in the Brussels Region: specific indices pertaining to particular groups (1992-2013)
Source: WEISERBS A. 2013


The common birds whose decline is the most pronounced are migratory birds (warblers, chiffchaffs, common swifts, etc.). The loss and degradation of their habitats in overwintering sites as well as the decrease in local resources (insectivore species) are two hypotheses put forward to explain this trend. A moderate downward trend has also been observed for small garden passerines. A favourable evolution overall - equating to an increase or stabilising of populations - has however been observed for corvids (jackdaws, crows, jays and magpies), indigenous cavernicolous species (the group made up of the nuthatch, the green woodpecker, the great spotted woodpecker, the blue tit, great tit and marsh tit, and the short-toed treecreeper), as well as for species "related to buildings and structures" (the rock dove, the black redstart, etc.).

Status of Natura 2000 birds

Pursuant to the conservation measures imposed for Natura 2000 sites, a monitoring campaign of some animal species and natural habitats is carried out, including for 7 species of birds found in the Brussels Region and which feature in annex I of the Birds directive (this details the species which are considered to be particularly endangered; around 70 of these nest, overwinter, or pass through Belgium).

Of these species, 4 nest in the Sonian forest (the European honey buzzard, the middle spotted woodpecker, the black woodpecker and the kingfisher) and have stable populations. The stabilising, even progression, of these species at the regional level imply that their biotopes are safeguarded (vast clearings, diversified forests including oaks and pines, the maintaining of old or dead trees and cavity trees, wetlands with steep and unobstructed banks, countryside rich in hedgerows and meadows, etc.).  The other species listed in Annex I which are present in the Brussels Region are the Great Egret (overwintering of 2 to 5 birds per year since 1996), the European Nightjar (occasional observations) as well as the Peregrine Falcon (first nesting in 2002, 12 territorial couples in 2014 of 7 have nested).
 

Date de mise à jour: 08/12/2017
Documents: 

Factsheets

n°2. Oiseaux (.pdf, in French and Dutch only)

n°3. Les passereaux en forêt de Soignes  (.pdf, in French and Dutch only)

n°4. Les oiseaux exotiques  (.pdf, in French and Dutch only)

n°14. Biodiversité : monitoring des espèces (.pdf, in French and Dutch only) 

Study(ies) and report(s) (In French and/or Dutch only)

Plans et programmes