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The rise of intensive farming has led to a decrease in the number of farmland birds due to the loss of nesting sites, nests being destroyed by machinery and more frequent nest predation. In cooperation between the Institute of Ecology and Earth Sciences at the University of Tartu and the BirdLife Estonia, 133 Northern lapwing nests were monitored from 2020-2021. The study confirmed that the hatching success of Northern lapwing chicks is influenced by both farming methods and habitat fragmentation.
No artificial fertilisers, pesticides or synthetic plant-protection products are used in organic farming. Soils are kept fertile by rotating crops and using organic fertilisers, such as manure and compost. Such environmentally friendly fields support biodiversity, since the use of nitrogen fertilisers and glyphosate is minimised, landscape features are established and a 2-5 metre grass strip is maintained along field edges.
Organic and environmentally friendly fields create a more diverse landscape for birds, with the forest edges, hedges and drainage ditches bordering such fields serving as suitable feeding areas for farmland birds. They also act as barriers to predators, which can easily predate nests on intensively managed monoculture fields. However, the impact of field elements on nest predation remains unclear. For instance, while a predatory bird may struggle to find a nest in the dense vegetation of an organic field, scent-driven mammals (which outnumber predators on the edges of the landscape) are less affected by poor visibility.
Less than half of the Northern lapwing chicks (43.6%) observed in the study hatched. The main reason for this was nest predation (40.6%), followed by the nests being destroyed by farming activities (12%) and the nests being abandoned (3.8%). The main predators were redfoxes, wild boar and birds in the corvid family. Similar rates of nest loss have been observed in Spain, England and Germany, while in Sweden, 45% of nests have been lost due to farming activities.
The chances of a clutch surviving a 24-hour period were 96.7% on average. With a 28-day incubation period, around 39% of Northern Lapwing clutches make it to hatching. The 24-hour survival of clutches was significantly lower in organic fields than in intensive ones (94% vs 98%), but there was no difference in clutch survival between environmentally friendly and intensive fields.
Although predators raided Northern lapwing nests much more frequently in organic fields, this was significantly reduced where there were drainage ditches. Nest predation by predators was also at its highest in organic fields, but this depended on the nesting density of the Northern lapwing as well: the more lapwing nests there were in an area, the less other birds predated the nests (since lapwings defend their nests together).
As organic fields support landscape biodiversity but also favour nest predators, the question arises as to whether organic fields are an ecological trap for birds. There is no straightforward answer to this question, as many organic fields are located in areas where predators are more abundant than on intensively managed lands. Although clutch survival may be lower in organic fields, it is likely that predation may be offset by the higher abundance of food in such fields, giving Northern lapwing chicks a greater chance of survival in organic fields.
An important factor in making fields more bird-friendly is the vegetation on ditches. The study found that bank vegetation surrounding or running through a field significantly reduces mammal predation and increases hatching success by as much as 14%. This may be due to the habitat preferences of medium-sized predators (foxes, badgers, et al.) – due to the moisture, it is not practical for them to dig burrows there – but also to the availability of sufficient food (there may be more rodents, amphibians, invertebrates and wild birds on a ditch bank, so the predator has no reason to go into the field to hunt).
Today’s fields are large and have few landscape features due to the pressure of intensive farming, and agricultural subsidies are designed to make them attractive to farmers (i.e. easy to manage) and simple to monitor. However, by simplifying matters, it is all too easy to go against ecological principles and overlook species well-being. Promoting environmentally friendly farming requires careful consideration of a range of strategies. To ensure successful bird nesting, drainage should support ditches and bank vegetation, but limiting predator abundance may also be beneficial.
The research paper “Linking farming practices and landscape elements to nest predation of an iconic farmland wader” can be found HERE.
This article is writteb by Marko Mägi. It was originally published on the “Birdwatcher blog”.
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