Reserva Ecológica Costanera Sur

Sitio realizado por aficionados a la observación de aves desde 10 de enero 2006

Nesting - Wren-like Rushbird

Order: Passeriformes (Suboscines) - Family: Furnaridae

The Wren-like Rushbird is a resident passerine at Costanera Sur. Its unmistakable call gives it away, though it is not easy to find and follow. Its voice resembles a starting scooter followed by a quick and sustained clicking sound sometimes interrupted by a long buzz.

Junquero/Wren-like RushbirdPhoto August 2009 © Silvia Vitale Associated with the aquatic environment this bird lives in rush beds growing in shallow waters. It moves around quickly and restlessly in search for food or material for nest building. It rushes from one place to another madly. Its brownish colour and its small size also contribute to losing sight of it easily. Characteristic position: perching on different stalks with open legs and swinging to keep balance when it is windy.

The nest is big compared to that of other birds of the same size. It is almost 30 cm and is built at half meter above water. It is almost rounded with an entrance. Both adults build the nest. They weave the nest attached to rushes (Juncus) using the stalks as a warp. These stalks are easily leaned by the wind. So, the nest must be very flexible to bear the strain it is subject to. Ii is most protected in the middle of the clump. They use plant fibers or vegetal material collected from the surroundings. Once the nest is finished they put feathers on the base.

The nest is supported by columns, formed with stalks tied together. The Rushbird circles around the stalks winding the fibers and hooking the ends in the weave. Some are neatly covered with threads, others more roughly grouped. As they progress upwards in the cone they interweave other stalks as part of the structure. They render the weave more compact by adding long fibers and small bits of material to stuff open spaces. These bits are fixed "screwing" with the bill. All the work is done from the inside to the outside of the nest. They are very meticulous. Before leaving for more new material, they always check for loose ends to be corrected or adjusted. In the video this little bird can be seen pulling a fiber to tighten it.

Junquero/Wren-like Rushbird31-10-2009 © Roberto Ares Junquero/Wren-like Rushbird1-11-2009 © Roberto Ares
The left photo was taken when the nest was already under construction. There is a lower structure with the shape of an inverted cone connected with a roof by means of a column. One day later they have reached the height of the cup and begin to close the nest. The sign shows a weaving resource: to wind the fibers into a triangle.

They work very diligently. It is an incessant coming and going. They do not work at the same time on the nest. One comes in, the other goes out. Each one weaves the materials gathered nearby. Sometimes they leave the nest to have a break or feed. On one occasion the nest was left unattended and some curious male Chestnut-capped Blackbirds, which also breed nearby, came closer to investigate.

Junquero/Wren-like Rushbird4-11-2009 © Roberto Ares Junquero/Wren-like Rushbird4-11-2009 © Roberto Ares
Left photo: Nest is ready. The sign shows one of the columns, where the cone lies on. The entrance is rather inconspicuous. Right photo: Bringing a feather to cushion the inside. The other adult is already in the nest. From now on they are seen hopping around singly. By December there was no more signs of movement in the nest. Unluckily the clutch failed.

The time which lasts the construction of the nest (almost a week judging by the film) are days of mutual stimulation exhibited by displays. This species does not present sexual dimorphism, which prevents the differentiation of activities by sex. Nevertheless, some repeated patterns of behaviour let guess who was who.

Junquero/Wren-like Rushbird Junquero/Wren-like Rushbird
Captured displays: The male stimulating the female pecking at her back (Out of the nest). The female stimulating the male exposing her cloaca. The male holds passive (In or very near the nest). Most of the times when there was a clicking in the nest or near it it was ellicited by the female. When the male showed up she exposed her cloaca. She might be urging the male to finish the nest.

2009 © Roberto Ares

Video November 2009 © Roberto Ares