Grup d'Anellament de Calldetenes-Osona

Since 1984, one of the most important activity of the GACO is the construction, placement and control of nest boxes.

The first nest boxes were from ICONA and these where subjected by a hole in the top. However, there were some problems. In rainy days, some water leaked inside the wood house and also with strong winds the box could booted, leaving only the roof hooked.

From the beginning, an interesing characteristic from our nest boxes, was that these were holded by the wall, and not from the roof. Later, the protector was installed. Through the years, different models have been evolved since the actual standard (Nest box GACO 2000).

Over time we have done some studies, such as "Les caixes NOSE"¹ and "El control de llana"². Thanks to the knowledge in that activity, we have customised the nest boxes for different species (shapes, sizes and hole diameter).

As a outreech tool, we have done some nest box workshops, where the participants not only could build nest boxes, but also bird feeders.

So far today, GACO has built and placed more than 14.500 nest boxes.

1. NOSE nest boxes
2. The wool control