Damage caused by crows and rooks on seedlings: how to combat them effectively?

Corvids, especially crows and rooks, are responsible for a lot of damage to agricultural crops. Corn and sunflower seedlings are regularly affected. And the economic losses amount to several million euros each year.

Although various control methods have been developed to combat these birds, their effectiveness varies. In addition, certain agricultural practices can also help limit the damage. 

We offer you an overview of the effectiveness of solutions for combating corvids.

What are the problematic corvid species?

Corvids pose significant problems to agricultural crops, particularly due to their omnivorous diet and opportunistic behavior. 

Let’s first discover the main species concerned:

• Rook : This bird is one of the main pests. It is recognizable by its black plumage which contrasts with its grayish white beak which is bare at the base. It lives in colonies. Rooks find their food in cultivated land, in particular by digging the ground for seeds, berries, or even invertebrates such as insects and earthworms.
• Black Crow : Another problematic species. The black crow is sedentary and territorial, living in pairs. Entirely black, including the beak, it is omnivorous and feeds opportunistically. Its main food sources are seeds, fruits, as well as small vertebrates such as lizards or chicks.
• Jackdaw : Smaller than its congeners, the jackdaw lives in colonies, often on the outskirts of towns and villages. Although its impact is generally less in rural areas, it can cause damage to crops located near urban areas.
• Common Raven : Imposing in size, the common raven is distinguished by its strength and ability to easily dig up seeds or damage young shoots. Although it is less common than other corvids, it can also have an impact.

These species, due to their group behavior and varied diet, cause much damage to agricultural crops. Their presence is usually exacerbated in areas close to their natural refuges, where they find both shelter and food.

What damage do these corvids cause?

Corn and sunflower are particularly vulnerable during their early growth phases. Corvid attacks are concentrated between sowing and the 4-5 leaf stage for corn, when young plants measure between 10 and 15 cm. For sunflower, the critical period extends to the 4-leaf stage. 

During this phase, corvids can consume a large part of the seeds, or even destroy the young shoots.

Vineyards are not spared either, with frequent damage to grape berries, which can be pecked en masse by these birds  .

The mass effect is also one of the most problematic characteristics of corvids: moving in large groups, they can ravage a plot of land in a very short time.

Which areas are most at risk?

Areas located near natural refuges such as woods, large trees or parks are particularly at risk. Similarly, isolated plots or those where human presence is less, such as large plots or those far from homes, attract these birds more.

Areas where corn or sunflower cultivation is not widespread are also more exposed, as these crops become points of attraction for corvids, thus amplifying the pressure on the few farms present. These various factors combined make corvids a real scourge for farmers, which requires the implementation of appropriate control strategies to protect crops.

What are the methods of combating crows and rooks?

Controlling crows and ravens is a major challenge because of their high intelligence and adaptability. These birds are able to recognize traps, evade scare devices, and quickly learn to get around obstacles set up to deter them. 

Various methods exist, but their effectiveness varies.

Trapping: a method of control

Trapping is one of the most widely used techniques to control black crow and rook populations. The traps, known as crow traps, use live birds as decoys to attract their fellow crows. This method requires rigorous monitoring, with daily visits to verify captures and an annual review of the results. Although effective in locally reducing the corvid population, trapping is not a definitive solution, as it must be renewed regularly to maintain its effectiveness.

Scaring: a temporary solution

Scaring, whether by sound or visual means, is another method commonly used to try to deter corvids. 

The detonations produced by scare cannons are among the most widespread sound techniques. However, this method causes significant noise pollution, often a source of conflict with neighbors, especially in inhabited areas. In addition, corvids quickly become accustomed to these noises, which reduces the effectiveness of the method over time.

Visual techniques, such as the use of kites, helium-filled balloons, or colored plastic ribbons, also offer limited protection. These devices disturb corvids for only a few days, after which the birds adapt and ignore these distractions. Scaring, while effective in the short term, temporarily displaces the problem without solving it in a lasting way.

It should also be noted that certain methods, such as scarecrows or hanging dead crows, have proven ineffective.

Favor natural predators

An alternative approach is to encourage the presence of natural predators of corvids, such as birds of prey. Installing perches for species such as the kestrel, the buzzard or the sparrowhawk helps to regulate corvid populations in a more ecological way. These predators put pressure on pest bird populations. This method, although taking time to show significant results, offers a sustainable solution by promoting biodiversity and restoring the natural balance of agricultural ecosystems.

What are the agricultural techniques to limit the damage?

In addition to control methods, agricultural practices can reduce the vulnerability of crops to corvids: 

• Opt for deep sowing : sowing at a depth of about 4 cm reduces the risk of corvids digging up the seeds. This technique protects the seeds by making them less accessible to birds looking to feed.
• Rolling the plots : after sowing, it is advisable to roll the plots to bury the seeds well in the soil. This limits their visibility and thus reduces the attractiveness of the plot for corvids.
• Avoid cloddy soils : When sowing, it is best to avoid soils with too many clods or a high presence of crop residues. These conditions make it easier for corvids to find food.
• Stagger your sowing in relation to neighbouring plots : sow on different dates from your neighbours to reduce the pressure exerted by corvids. This allows the birds to be dispersed over several plots and limits the impact on a single crop.
• Wait several days between tillage and sowing : To reduce the attractiveness of the plot, it is advisable to leave an interval of several days between preparatory tillage and sowing. This gives the corvids time to lose interest in the plot before the seeds are planted.
• Take into account the particularities of organic farming : in organic farming, where sowing can be carried out later, crops become more vulnerable to attacks by corvids. It is therefore essential to combine this practice with other protective measures to minimise risks.

Another destructive bird to discover: the pigeon