Photo of a bird exclusion cage placed from February to June on an oilseed rape field, and photo of a western yellow wagtail

Birds and insects regulation

The role of birds in the regulation of insects in arable crops

In arable crops, birds often occupy the highest position in the food chain, feeding on pests (phytophagous insects that attack crops) and their intermediate predators, mainly insects and other arthropods (such as spiders), that feed on these pests. The effects of bird predation on insect pest populations are difficult to estimate without a complete description of prey-predator communities and their complex interactions.

We sampled bird and arthropod communities in 30 oilseed rape fields in spring 2019 and 2020, in France. To assess the effect of birds on arthropods, we used exclusion cages, preventing flying vertebrates (birds and bats) from accessing 30 m² plots in the field, in order to be able to measure the "predator" effect of the latter compared to plots not equipped with cages (see photo). We were then able to determine the direct and indirect influences of birds on arthropod predators and phytophagous insect populations in arable crops.

We found no evidence of bird predation on all intermediate predators (Carabidae and other predators) or on phytophagous insects. We observed that the more abundant the insects of the family Carabidae (carabid beetles) were, the fewer the insect pests, but this type of relationship was not observed for the other groups of predators, suggesting the key role of carabid beetles in regulating phytophagous insects. We analysed the effect of agricultural practices on these multitrophic interactions, showing that the pesticide treatment frequency indicator had adverse effects only on the abundance of Carabidae (and no effect on other predators nor on phytophagous insects), while tillage frequency did not affect the communities studied.

The network of agricultural fields that supports this work continues to be observed: oilseed rape and faba bean pests and their natural enemies are measured by local stakeholders as well as INRAE, through several ongoing or future theses.

Reference: Serée Lola, Antoine Gardarin, Olivier Crouzet, Aude Barbottin, Muriel Valantin-Morison, and François Chiron. 2021. "Exploring Multitrophic Interactions in Oilseed Rape Fields Reveals the Prevailing Role of Carabidae". Ecology and Evolution 11 (21): 15377 88.

Modification date : 05 July 2023 | Publication date : 03 January 2022 | Redactor : OR