Research shows that swallows eating insects near farms are being exposed to pesticides through their food. A 2026 study of 389 swallows in Canada found that 30% of Barn Swallows and 25% of Tree Swallows had neonicotinoid pesticides in their blood, with thiamethoxam being the most common. According to Gram Research analysis, insects living in wetlands near cropland are picking up these pesticides from agricultural runoff, and when birds eat those contaminated insects, they accumulate the toxins in their bodies.
According to Gram Research analysis, scientists studied swallows in Canada and found something troubling: the birds eating insects from farmland are getting exposed to pesticides called neonicotinoids. Researchers looked at what two types of swallows were eating and tested their blood for pesticide residues. They discovered that about 30% of Barn Swallows and 25% of Tree Swallows had pesticide traces in their bodies. The problem is that insects living in wetlands near farms are picking up these pesticides from agricultural runoff, and when swallows eat those insects, they get poisoned too. This research suggests that protecting wetlands from farm chemicals could help save these bird populations, which have been declining for decades.
Key Statistics
A 2026 research article analyzing 389 blood samples from swallows in Saskatchewan, Canada found that 30% of Barn Swallows and 25% of Tree Swallows contained detectable neonicotinoid pesticide residues, with thiamethoxam being the most prevalent pesticide detected.
According to a 2026 study of 309 fecal samples from swallows in agricultural Canada, both Barn Swallows and Tree Swallows consumed insects dominated by flies and related species (74-84% of diet), with emergent aquatic insects serving as vectors for pesticide contamination.
A 2026 analysis of 389 swallow blood samples found that adult birds had higher pesticide detection frequencies and concentrations than nestlings, suggesting pesticide accumulation increases with age and foraging experience in contaminated agricultural landscapes.
Research examining 389 swallow blood samples in 2026 showed that thiamethoxam concentrations were significantly associated with higher crop cover and greater consumption of emergent aquatic insect families, indicating wetlands are primary pathways for pesticide exposure.
The Quick Take
- What they studied: Whether swallows eating insects near farms are getting exposed to pesticides, and which insects are carrying the most pesticide contamination.
- Who participated: Two species of swallows (Barn Swallows and Tree Swallows) in Saskatchewan, Canada. Researchers analyzed 309 fecal samples (poop) and 389 blood plasma samples from adult birds and nestlings.
- Key finding: About 30% of Barn Swallows and 25% of Tree Swallows had detectable pesticide residues in their blood, with thiamethoxam being the most common pesticide found. Birds eating more insects from wetlands had higher pesticide levels.
- What it means for you: If you care about bird conservation or live near agricultural areas, this shows that farm pesticides are harming birds through their food chain. Protecting wetlands from agricultural runoff could help restore declining bird populations. However, this is one regional study and may not apply everywhere.
The Research Details
Researchers collected samples from two swallow species in Saskatchewan, Canada, an agricultural region. They examined what the birds ate by analyzing their droppings using DNA technology (metabarcoding), which identifies insect species from tiny genetic traces. They also took blood samples from 389 birds and tested them for seven different neonicotinoid pesticides—a class of insecticides widely used on crops.
The team compared pesticide levels between adult birds and baby birds, and looked at how local farming practices (crop coverage and wetland presence) affected both diet and pesticide exposure. This approach allowed them to trace the connection between agricultural intensity, insect contamination, and bird exposure.
By studying two swallow species with different foraging habits, the researchers could see whether pesticide exposure patterns varied based on where and how birds hunted. This comparison strengthened their ability to understand the relationship between farming practices and bird contamination.
This research design is important because it connects three things that are usually studied separately: what birds eat, where they eat it, and what toxins they’re exposed to. By doing all three simultaneously, researchers could prove that pesticides are actually reaching birds through their food, not just theoretically. This real-world evidence is stronger than lab studies alone.
The study used modern DNA technology to identify insects accurately, which is more reliable than visual identification. Testing 389 blood samples provides solid statistical power. The research was published in Environmental Research, a peer-reviewed journal. However, the study was limited to one region in Canada during one time period, so results may not apply everywhere. The sample sizes for some pesticides were small, which could affect precision.
What the Results Show
Both swallow species ate similar types of insects, with flies and related insects (Diptera) making up 74-84% of their diet. This shows that swallows are specialized hunters targeting specific insect groups. When researchers tested blood samples, they found pesticide residues in about one-quarter to one-third of the birds—a surprisingly high detection rate.
Thiamethoxam, a neonicotinoid pesticide commonly used on crops, was the most frequently detected pesticide and also appeared in the highest concentrations. Adult swallows had more pesticide detections and higher concentrations than nestlings, suggesting that older birds accumulate more pesticide exposure over time as they forage more widely.
The connection between farming and pesticide exposure became clear when researchers analyzed the data by location. Birds in areas with more crop coverage had higher thiamethoxam levels. More importantly, birds that ate more insects from wetlands (emergent aquatic insects) had higher pesticide concentrations, suggesting that wetland insects were the primary source of pesticide contamination. This indicates that agricultural pesticides are running off into wetlands and contaminating the insects that live there.
Barn Swallows and Tree Swallows showed different dietary preferences based on their local environment. Barn Swallow diet was more influenced by nearby wetland coverage, while Tree Swallow diet was more affected by crop coverage. This suggests the two species forage in different habitats, yet both ended up with similar pesticide exposure levels. The fact that both species showed comparable contamination despite different foraging patterns indicates that pesticide contamination is widespread in the agricultural landscape.
This research adds concrete evidence to a long-standing concern: aerial insectivores (birds that catch insects in flight) have declined dramatically in North America since the 1980s. Previous research suggested that agricultural intensification was responsible, but this study provides direct proof that pesticides are reaching these birds through their food. The findings align with other research showing that neonicotinoid pesticides harm insect populations and contaminate non-target species.
The study was conducted only in Saskatchewan, Canada, during a specific time period, so results may not apply to other regions or years. Researchers tested for seven specific neonicotinoids but didn’t test for other pesticides that might also be present. The study doesn’t prove that pesticide exposure is causing bird population declines—it only shows that exposure is happening. Sample sizes for some individual pesticides were small, which could affect the precision of those findings. The research is correlational, meaning it shows relationships but doesn’t definitively prove cause-and-effect.
The Bottom Line
High confidence: Protect and restore wetlands in agricultural areas to maintain clean insect populations for birds. Moderate confidence: Reduce neonicotinoid pesticide use in areas near wetlands and bird habitats. Low confidence: Specific pesticide alternatives are better, as this study doesn’t compare different pesticides. These recommendations apply most directly to agricultural regions similar to Saskatchewan.
Farmers and agricultural policymakers should care because this shows their practices are affecting wildlife. Birdwatchers and conservationists should care because it explains part of why swallow populations are declining. Homeowners near agricultural areas should care because it shows how farm chemicals spread beyond farm boundaries. People concerned about pesticide use in general should care because it demonstrates unintended consequences of agricultural chemicals.
Protecting wetlands would likely take 2-5 years to show measurable improvements in bird pesticide exposure, as it takes time for contamination to clear and insect populations to recover. Population-level improvements in bird numbers could take 10+ years to become apparent, as birds need multiple years of clean food sources to rebuild populations.
Frequently Asked Questions
Are birds dying from pesticides in farmland?
This study found pesticides in 25-30% of swallows but didn’t measure whether exposure causes death. However, pesticide exposure can weaken birds and reduce reproduction. The widespread presence of pesticides in birds’ blood suggests it’s a significant health stressor contributing to population declines.
How do pesticides get into bird food?
Pesticides sprayed on crops run off into nearby wetlands during rain or irrigation. Insects living in these wetlands absorb the pesticides. When swallows catch and eat these contaminated insects, the pesticides accumulate in their bodies. This is called bioaccumulation.
Can I protect birds from pesticides in my area?
Yes. Avoid using neonicotinoid pesticides on your property. Plant native plants to support insect populations. Create or protect wetlands and water sources. Support agricultural policies that reduce pesticide use near wildlife habitats. These actions help maintain clean insect populations for birds.
Does this study apply to all birds or just swallows?
This study specifically examined two swallow species in Canada. Other insect-eating birds likely face similar pesticide exposure, but this study doesn’t prove it. The findings probably apply to other aerial insectivores in agricultural regions, but may differ in non-agricultural areas.
Why are swallows declining if they’re still eating insects?
Pesticides reduce insect populations overall, so swallows have less food available. Pesticide exposure also weakens birds’ health and reproduction. This study shows pesticides harm birds both by reducing their food supply and by directly poisoning them when they eat contaminated insects.
Want to Apply This Research?
- Track weekly bird sightings in your area (species, location, time of day) and correlate with local weather and agricultural activity. Note pesticide application dates if known. Over months, patterns may emerge showing how farming practices affect bird presence.
- If you live near farmland, create a pesticide-free zone by planting native plants that attract insects and birds, and avoid using neonicotinoid pesticides on your property. Log your actions in the app to track how local bird activity changes.
- Set up a monthly bird count in the same location at the same time. Use the app to track species diversity and abundance. Compare your data across seasons and years to see if bird populations are stable, increasing, or declining in your area. Share data with citizen science projects like eBird.
This research describes pesticide exposure in swallows and suggests potential health impacts, but does not establish definitive cause-and-effect relationships between pesticide exposure and bird population declines. The study was conducted in one region (Saskatchewan, Canada) and may not apply to all geographic areas or bird species. This information is for educational purposes and should not replace professional ornithological or agricultural advice. If you have concerns about pesticide use affecting local wildlife, consult with local wildlife agencies, environmental scientists, or agricultural extension services. Always follow label instructions when using any pesticides, and consider consulting professionals before making changes to pest management practices.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.