The extreme heat of recent days and the anticipated heat this summer, combined with scarce rainfall during the bird breeding period, threatens the reproductive success of many bird populations. Various species rely on mud to build their nests, forming structures similar to small planes or swallows. As development and rehabilitation projects increasingly disturb these crucial materials, the destruction of nests, even when abandoned, becomes a legal offense with hefty penalties.
“Every swallow or sycamore nest is built from tiny mud pieces carried in the beaks of dedicated parents. The birds collect a small amount of mud, chew it to homogenize it, remove any impurities, and carefully press it into the nest under construction,” explains a specialist from the Spanish Society of Ornithology (SEO/BirdLife).
5,000 flights for a slot
The mud-carrying capacity in a single beakful is limited. A fully constructed nest of a Common House Martin may require around 2,500 mouthfuls of mud, or the equivalent amount. The pair makes more than 5,000 trips between the mud source and the nest, dedicating roughly two weeks to complete the work.
The nest is maintained and repaired by the occupying pair, who tend to reuse it across years.
The NGO warns that if hundreds of nests of these species are destroyed each year, the shortage of mud to rebuild nests will worsen the situation and complicate their breeding cycles.
what does the law say
Destruction of both nestlings and empty nests of protected birds is treated as a serious offense under national and European law, carrying penalties that can be severe.
Law 42/2007 on natural heritage and biodiversity states: “It is forbidden to deliberately kill, harm, disturb or capture wild animals, by any method, at any stage of their life cycle. This prohibits detention and capture alive, destruction, damage, collection and retention of nests, offspring or eggs, even if the last is empty, as well as possession, transportation, trade and sale of living or dead specimens or their remains, including foreign trade.”
Thus, property owners and tenants are not allowed to remove nests of protected birds such as swallows or terns, especially during the breeding season. These birds begin laying eggs and rearing chicks before embarking on a long migratory journey back to Africa.
The importance of swallows, terns, and other insectivorous birds lies in their daily consumption of large numbers of insects, which helps reduce agricultural pests. Without this natural pest control, crop damage could rise significantly. These birds play a vital role in crop protection and food security.
Anyone witnessing nest destruction can file a complaint with the Civil Guard’s Nature Conservation Service (Seprona).
HOW TO HELP BIRDS COPE WITH THE TEMPERATURE
Like humans, birds experience physiological stress from heat. To help them, provide accessible water sources for drinking and bathing. A simple dish on windowsills, patios, or gardens can offer a much-needed respite.
Addressing mud shortages is also important. Create muddy areas near nesting sites so birds can gather the material they need while minimizing energy spent on transport.
Water is a scarce resource, and while urban water points exist, access for birds can be limited.
Urban planning should consider biodiversity. Public spaces designed with nature in mind can be more wildlife-friendly and help mitigate climate-related heat stresses. City trees, for example, can reduce heat islands by several degrees, benefiting both wildlife and residents.
In this context, nature-based solutions have proven to be effective and cost-efficient for cooling cities and supporting biodiversity in hot periods. The goal is to create urban environments that sustain wildlife while improving human well-being.
Endnotes on conservation emphasize that urban planners and communities can play a crucial role by integrating habitat features, water sources, and mud-rich areas into city landscapes to sustain insectivorous birds through heat waves and droughts.