{"id":37665,"date":"2025-02-11T00:01:34","date_gmt":"2025-02-11T05:01:34","guid":{"rendered":"https:\/\/beyondpesticides.org\/dailynewsblog\/?p=37665"},"modified":"2025-02-10T16:35:48","modified_gmt":"2025-02-10T21:35:48","slug":"study-finds-increased-offspring-mortality-in-pesticide-laden-birds-nests","status":"publish","type":"post","link":"https:\/\/beyondpesticides.org\/dailynewsblog\/2025\/02\/study-finds-increased-offspring-mortality-in-pesticide-laden-birds-nests\/","title":{"rendered":"Study Finds Increased Offspring Mortality in Pesticide-Laden Bird\u2019s Nests"},"content":{"rendered":"

(Beyond Pesticides<\/em>, February 11, 2025) In a Science of The Total Environment<\/em><\/a> study, scientists test over 100 blue tit (Cyanistes caeruleus<\/em>) and great tit (Parus major<\/em>) birds\u2019 nests for pesticide residues in comparison with the number of dead offspring and unhatched eggs within the nest. Fur-lined nests, from animals treated with ectoparasitic chemicals<\/a>, expose birds to compounds that can impact reproductive success. The authors found fipronil<\/a>, a phenyl pyrazole insecticide, in all nests, with the majority also containing the neonicotinoid insecticide imidacloprid<\/a> and synthetic pyrethroid insecticide permethrin<\/a>. The data shows higher insecticide levels are linked to increased offspring mortality and threaten biodiversity<\/a>.<\/p>\n

This study highlights an important exposure route that is overlooked. \u201cAlthough not all bird species use fur for nest building, a substantial number do, especially cavity-nesting species,\u201d the researchers share. \u201cPrevious research<\/a> found that 74% of studied woodland bird species in central Europe incorporated fur into their nests.\u201d Many bird species in the U.S. also line their nests with fur, such as black-capped chickadees, tufted titmice, and chipping sparrows.<\/p>\n

While there is a wide body of science<\/a> showing reproductive effects from pesticides, the researchers highlight the study\u2019s novel design, saying, \u201cTo the best of our knowledge, no previous studies have been performed to detect and quantify veterinary ectoparasitic drugs in the fur used for nest-building and explored the potential associated effects in these bird species.\u201d They continue, writing, \u201cThe environmental impact of insecticides used as ectoparasitic treatments for companion animals is not well understood, since they are not subject to detailed environmental risk assessment.\u201d<\/p>\n

Many veterinary treatments include active ingredients that are banned from agricultural use in the European Union but are still prevalent in the U.S. in both residential pest management and agriculture, increasing the risk of exposure for nontarget organisms such as birds. As the authors state: \u201cFarm livestock and companion animals such as dogs and cats are routinely treated with chemicals such as pyrethroids (e.g., permethrin and cypermethrin<\/a>) and avermectin insecticides (e.g., ivermectin). Other products, including neonicotinoid insecticides like imidacloprid (banned as a plant protection product in the EU in 2018<\/a>) and the phenylpyrazole insecticide fipronil (banned for agricultural use<\/a> in 2013), continue to be widely used for veterinary ectoparasitic treatments for pets.\u201d<\/p>\n

\u201cThese chemicals are frequently applied topically, sometimes monthly, in the form of shampoos, spot-on treatments, sprays, or impregnated collars,\u201d they continue. \u201cAn estimated 80% of dogs and 82% of cats<\/a> are treated against fleas using an insecticide at least once per year.\u201d These include products such as Frontline\u00ae, with the main active ingredient fipronil, and Advocate\u00ae, which contains imidacloprid. (See additional resources related to pets and pesticides here<\/a>, here<\/a>, here<\/a>, here<\/a>, and here<\/a>, as well as previous coverage on Seresto\u00ae pet collars here<\/a>.)<\/p>\n

Since residues from these chemicals can persist on an animal\u2019s fur for extended periods of time, this allows toxic compounds to be dispersed into the environment and come into contact with wildlife<\/a>. Certain species of birds, in particular, are exposed to these insecticides as they collect animal fur to provide an inner lining to their nests, which impacts the adults, eggs, and nestlings.<\/p>\n

Within the study, which analyzes 103 nests collected from September to October 2020 across the United Kingdon, the authors detected 17 out of the 20 insecticides in the screening. The number of insecticides per nest ranges from two to eleven, leaving no nests pesticide-free. \u201cFipronil, imidacloprid, and permethrin were detected in 100%, 89.1%, and 89.1% of samples, respectively,\u201d the researchers report.<\/p>\n

The three active substances found in the highest concentrations include the neonicotinoid dinotefuran<\/a>, synthetic pyrethroids permethrin, and cypermethrin. \u201cOverall, a higher number of either dead offspring or unhatched eggs was found in nests containing a higher number of insecticides, higher total concentration of insecticides or a higher concentration of fipronil, imidacloprid or permethrin, suggesting that contact exposure of eggs to insecticides in nest lining may lead to mortality and lower reproductive success,\u201d the authors conclude.<\/p>\n

They continue, \u201c[T]he number and total concentration of insecticides found in nests, along with the concentrations of fipronil, imidacloprid, and permethrin when considered separately, predicted a higher number of unhatched eggs and\/or dead offspring for both bird species together or great tits alone.\u201d The researchers suspect the heightened effects seen in great tits is due to the amount of hair and fur within their nests as compared to the blue tits. Blue tit nests tend to be constructed with more bark and feathers, highlighting behavior-dependent exposure variations between bird species.<\/p>\n

The authors also note that the effects seen in this study may not represent the full impact of pesticide exposure from residues within the nests, saying: \u201cBlue tit and great tit adults tend to clean up the nests of any unhatched egg or dead chicks before the end of the breeding season when nests where collected. Thus, we likely underestimate the actual number of unhatched eggs and dead chicks of the studied nests.\u201d<\/p>\n

The effects on global bird populations<\/a> from pesticides has been studied since the 1960\u2019s when Rachel Carson brought attention to the matter through her book Silent Spring<\/em><\/a>. Research continues to note impacts on nontarget organisms<\/a> from beneficial insects that provide ecosystems services<\/a> to all wildlife that is necessary in preserving biodiversity<\/a>.<\/p>\n

This study \u201cadds to an already long list of evidence for negative environmental effects from pesticides, in particular fipronil and imidacloprid,\u201d the researchers say. Additional studies find:<\/p>\n