Patronat de Turisme de la Diputació de TarragonaDiputació de Tarragona
Terres de l'Ebre 
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros fotografia
© Ferran Almendros foto natura
© Ferran Almendros fotografia
© Ferran Almendros fotografia

RietVell

Birds and farming

When we are enjoying bird watching, we know that there is something more to it than just identifying birds and observing their habits, how they feed, hunt, fish, how they swim or dive, how they take off or land, how they glide or move their wings, whether they are alone or in large flocks, how they sleep on one or two legs, or fight for a particular corner on the far end of a tree trunk, or defend their chicks or conquer a partner, how they patiently incubate their eggs or tirelessly rear their chicks. More than just their beauty and behaviour, there is also an ecological relationship with their environment.

We should know that birds just like other animal, vegetable and microscopic organism, have a relationship based on energy and materials with their physical, chemical, water, land and air environments. This is especially interesting in ecosystems in wet areas, and even more so in an environment which has been radically transformed and humanized such as an agricultural one. In these systems, birds play an essential role in things which concern us so much, like producing food for human consumption, environmental health and landscape maintenance. It is like when we go to the cinema or theatre; more than the aesthetics of costumes and conversations, we are interested in understanding the role of the characters, the plot and the meaning of the piece in question.

The ecological role with a socio-economic influence concerns all species not only birds. For example, garden insects, pollinators and other non-pests are essential for tomato plants to produce tomatoes and for lemon trees to produce lemons. Without bees, bumble bees, hoverflies or butterflies, flowering plants would not interchange pollen and wouldn’t bear fruit, and without ladybirds, earwigs and other predators, greenflies would ravage the leaves and stalks of our young nurtured plants. We need them for food.

It has been years now since the beneficial influence of bats was discovered in the rice fields on the Ebro Delta; yet another non-ornithological presence on the agricultural scene in wetland areas. Right in the middle of rice farming, when in sufficient number, these small bats gulp down moths which evolve from rice borer larvae Chilo suppressalis. The effect is impressive as they convert the worst agricultural plague into the best fertilizer for plants which is bat guano, saving money on pesticides and chemical fertilizers and avoiding pollution of the air and water. It is enough just to have one refuge for these animals per hectare and above all give them time to settle in. This is a similar role to that of frogs when they were in plenty, as they are also fond of moths, or to what fish do by eating mosquito larvae when in open water. In a balanced system, everything which is in abundance is taken advantage of and there is no plague whatsoever.

However, we want to discover the role of birds, and it is nothing new to emphasize the beneficial effect of insectivorous birds on agriculture. In 1868, a group of farmers, who were alarmed by the capturing of insectivorous birds by the plumage industry which had become highly developed because of Victorian fashions, asked the Austro-Hungarian Emperor, Franz Joseph 1, to sign an international treaty to protect birds which were beneficial to agriculture. In 1902 an International Agreement for the Protection of Birds Useful to Agriculture was signed in Paris. This agreement established the prohibition of capturing certain species of birds and obligations referring to the protection of their nest and eggs. One of the precursors of Catalan ornithology from the nineteenth century, Emili Tarré, who had already published informative work titled "Els aucells més útils a l’agricultura de Catalunya (1902)" - “The most useful birds for agriculture in Catalonia (1902)", describes, one by one, the species of birds and their beneficial behaviour for the land. A public awareness which should always keep doing.

Between 1958 and 1959 Chinese ornithologists demonstrated that 25% of what sparrows ate was grain, while 75% was plague insects, and this was to stop the large scale extermination of these birds ordered by Mao Tse-Tung after declaring them enemies of the revolution because of their consumption of rice grain. The massacre of sparrows populations in China left rice fields to the mercy of plagues of locusts, causing an agricultural catastrophe with millions of deaths due to starvation, which forced the Chinese to import new sparrows from the neighbouring Soviet Union.

At our Delta, this insectivorous ecological task is shared by house sparrows and tree sparrows, along with a large number of summer insectivores such as reed warblers, great reed warblers, swallows and the Eurasian penduline tit, as well as all the granivores which capture insects to feed their chicks. For this reason at Riet Vell Reserve, Clot Ornithological Reserve and Comandanta Forest we position more than 150 boxes for tree sparrows and house sparrows in need of natural holes to nest, as at the Delta there are very few trees.

For forty years, red swamp crawfish have been a bothersome problem for rice fields as, by custom, they dig up the edges of fields producing water leakage, making it difficult to manage water levels which can build up causing bridges to collapse. At the moment these crawfish are the staple diet of Audouin’s gull, herons the glossy ibis and a wide variety of other species at the Delta which take advantage of them, visibly lessening their population. Birds also keep an eye on them. In fact, this is a great example of how biodiversity helps to integrate and control exotic invasive species. Now, it is the turn of the apple snail.

The apple snail, the most dangerous exotic species for rice fields at this moment, seems to have many natural enemies, such as the carp, the mallard, the eel and rat, however now there seems to be one which is multiplying all over the delta, and is able to devour even the biggest examples of apple snail. The glossy ibis, which have always eaten gastropods on a regular basis, are now a real immune system against this plague in fields which are still not infected, as they search fields on both sides of the delta, inch by inch for all the small organisms their beaks can reach. We wish them luck. We need them.

There are birds which are not beneficial to rice fields, like the purple swamphen which can cause an important loss to fields near their nesting areas in reed beds and ponds, although during the winter they leave the fields clear from club rush roots. In other places such as Japan or Doñana, the roots of this weed are eliminated by wild geese, a migratory animal which rummages around in the sediment to get energy from the tiger nuts found there. In those areas rice fields do not suffer from this weed. However, here, very few geese migrate.

To our surprise, about birds and farming, this year, whilst we were planting rice there were some reeds floating alongside sheaves, and we saw how whiskered terns nesting in Riet Vell Lake took the reeds one by one to build their floating ephemeral nests. The colony of whiskered terns this year has reproduced successfully, and so has that of the common tern and the seagull at the lake, swallows at the observatory and Eurasian tree sparrows and kestrels in box nests. The relationship between birds and farming is fantastic and activity is balanced, and never ceases to surprise the attentive observer.

Events 2015 SEO/BirdLife RIET VELL RESERVE

Event Date Reason Contents
Festival of Natural and Cultural Diversity  15 August (Saturday) Festival with international volunteers and local traditions. Presentation of activities, volunteers’ cultures, traditions at the Delta and nature at the reserve, games, ringing, introduction to the rice fields etc...
International Birdwatching Day 3-4 October DMBirds


Variety of activities at Riet Vell and El Clot,  with ringing, games, participation in harvesting “rice 000”, etc...
Fang (mud) Festival  Sunday 15 November SEO/Catalonia Social Festival Variety of activities, mud moving, ringing, building, paella, “arrozvolución 000”, themed talks.
The lapwing party Sunday 6 December Activity for bank holiday weekend Birds which are winter visitors, with games at observatories, ringing etc... (or mud festival activities if delayed from November due to weather)
Sponsoring owls at Riet Vell Christmas 2015 Sunday 20 December Ringing and Sponsoring This activity could be brought forward or delayed depending on birth dates or development of chicks.
International day of wetlands Friday 29  - Sunday 31  January   Talks and different activities.