drone photo, done pic, aerial view, Tij observatory

Tij observatory is a eco-paradise for bird watchers

| 21 : 00 – 09 December 2019 |

Tij observatory, bird watching, observatory, egg shaped structure, timber construction

Tij observatory design by RO&AD Architecten and RAU Architecten resembles an oversized egg in a nest in Netherlands.

Intended for birdwatchers observing the sandwich terns off the coast near Scheelhoek island, the observatory takes its form of a tern’s egg. This special viewing place was opened in April 2019 as part of the Haringvliet Dream Fund.

egg shaped structure, timber construction, birs observatory, bird watching by lake

Photo – © Katja Effting


landscape photography, walk in woods, walkway in woods, observatory, thatched roof

Photo – © Katja Effting

The ‘eco-egg’ was built across a dam-alike hydro constructions called ‘sluices’. These opening assisted to improve water quality and biodiversity while stimulating fish migration. The salt-resistant structure nestled in the surrounding nature reserve will develop while a healthier ecosystem in the upcoming years.

Photo – © Katja Effting

The bird hide situated in Scheelhoek, a nature reserve near Stellendam, consists of a timber framework. The design is such that it can be assembled and dismantled completely on site. Its base is made of Accoya, while it’s upper part is made from pinewood. The outer covering is a thatched roof of local weed.

salt water lake, bird watching by lake, Tij observatory, egg shaped structure, bird watching nest

Photo – © Katja Effting

From the Architects –

Tij  (name explanation: This is a Dutch word joke. ‘TIJ’ means ‘tide’ which refers to the returning tides in the Haringvliet, but quickly pronounced it also means ‘the egg’) Tij is the biggest and most striking of a series of objects designed to celebrate the opening of the Haringvliet sluices in November 2018.


Photo – © Katja Effting

The sluices were opened in order to improve water quality and biodiversity, while also stimulating fish migration from the North Sea to the river delta system of Maas and Rhine in the Netherlands. This will create a new, salt-resistant and salt-loving natural environment. The biodiversity in surrounding nature reserves will increase and a more robust, healthier ecosystem will develop in coming years.

drone view, view of a fishing lake, drone photography, observatory


To let people experience and explore these changes, a series of bird observatories have been designed in the Haringvliet area. Tij is an egg-shaped bird hide situated in Scheelhoek, a nature reserve close to Haringvliet sluice near Stellendam, Netherlands. The reserve consists of large reed beds on the inside of the coastal defenses and some flat sand islands outside. These islands are breeding and feeding grounds for several species of birds like the common tern, spoonbill, and the icon of this area, the sandwich tern.

view of sea, Tij obervatory, drone photo of sea, Scheelhoek, nature reserve, Netherlands

Photo – © Merijn Koelink

To prevent the birds from being disturbed, the last section of the path is actually a tunnel. It’s made of re-used mooring posts and second-hand azobe planks which were once used in the brick industry. The tunnel is covered in sand to provide habitat for terns or waders.

aerial view of a nature reserve, Tij observatory, drone photography, Scheelhoek nature reserve

Photo – © Merijn Koelink

The outside of the tunnel provides artificial nesting holes for sand martins. The end point of the walking route is the egg-shaped bird hide from where you can view hatching terns and all the other species that live in and around the water.

Photo – © Katja Effting

Design of Tij observatory –

The egg itself is modelled on a sandwich tern egg, and sits on a nest of sand, much like a tern would have done it herself. The nest of the egg consists of vertical ‘feathers’ of chestnut poles, reeds and small sand dunes.

sketch, design, timber structure, timber frame, egg shaped structure


The egg itself is parametrically designed to achieve a good ratio between form, structural integrity, size of the timber, and size of the openings. The structure has been constructed as a File-to-Factory Zollinger to provide relatively big spans with small timber parts.

Photo – © Katja Effting

The lower part of the egg, which floods a few times a year, is made of Accoya. The upper part, which stays dry all year, is made of pine. The upper part is thatched with local reed, harvested from the inside of the sea defences.

interior view of Tij observatory, timber construction, timber framework, egg shaped framework

Photo – © Katja Effting

The thatched roof stops just above the highest possible water line. The floor inside the egg is a hybrid wood (CLT – Cross laminated timber)- concrete floor which acts as a structural stabiliser and from where there is a beautiful view of the surrounding islands, the Haringvliet sluices and the water.

thatched roof, wooden platform, interior view of a observatory, timber frame, parametric design

Photo – © Katja Effting

Tij is thatched with local reed and has a timber structure which has been completely File-to-Factory produced in 402 parts and has been assembled at the site. It can be completely dissembled. Through its re-usability, its modularity, its materials and its contribution to the nature environment, it is almost completely circular and sustainable.

timber construction, site work, Tij observatory

Photo – © Katja Effting

Reflecting the transitory nature of all things, it must also be noted that Bird-EI is also temporary and will be taken apart at some point in future. At that time, it may be reused or recycled without detrimental effects to nature or man.In this way, we have created an (eco)system where man and nature can come closer together and be a part of each other’s world.

Photo – © Katja Effting

Project details –

Project name – Tij observatory

ArchitectRO&AD Architecten, Bergen op Zoom – RAU Architecten

Project location – Stellendam, Netherland

Project type – Bird hide, bird observatory, Leisure, Hotel

Design team – Ad Kil, Ro Koster, Martin van Overveld, Athina Andreadou, Loyse Rebord, Rodrigo Altamirano + Thomas Rau, Michel Tombal, Jochem Alferink

Completion year – 10/2018 – 03/2019

Commissioner – Vogelbescherming & Natuurmonumenten

Contractor – Van Hese Infra, Middelburg

Photography – © Katja Effting | Drone photographs – © Merijn Koelink

Landscape designH+N+S Landschaps Architectuur, Amersfoort

Main structural engineer – BreedID, Den Haag | Structural engineer woodAalto University Finland

Wood engineeringGeometria, Finland | Thatched roof – Elg Rietdekkers, Schoonebeek

Leave a Reply