Canada’s Birds Have Been Shrinking Since the 1970s as Insect Populations Plunged by Over 60%, Study Finds
Long-term research links the collapse of flying insect populations to smaller body size and lower breeding success in tree swallows, underscoring the growing impact of biodiversity loss and climate change.
A new long-term scientific study has found that Canada’s birds are becoming smaller and producing fewer offspring as flying insect populations have declined by more than 60% since the late 1970s. Researchers say the findings provide compelling evidence that insect loss is reshaping bird populations and disrupting ecosystems.
The study focused on tree swallows, insect-eating birds that breed around the Long Point Bird Observatory in Ontario. By analyzing decades of ecological data, scientists discovered that the dramatic reduction in flying insects has left the birds with less food, resulting in smaller adult body size and reduced reproductive success.
Researchers estimate that flying insect abundance at the observatory has fallen by more than 60% over the past four decades. Tree swallows, which feed almost exclusively on aerial insects, have proven to be highly sensitive indicators of these environmental changes because their survival and breeding are closely tied to insect availability.
The research also suggests that biodiversity loss and climate change are acting together to intensify the decline. Changes in seasonal weather patterns are altering the timing of insect emergence, while shrinking insect populations reduce food supplies during the critical breeding season. Scientists warn that this mismatch leaves adult birds struggling to raise healthy chicks.
The authors point to the rapid expansion of neonicotinoid pesticides during the 1990s as one likely contributor to the collapse of insect populations, alongside habitat degradation and climate-related environmental changes. While the study does not identify a single cause, it highlights the cumulative effects of multiple human-driven pressures on ecosystems.
The findings mirror broader conservation trends across Canada. According to the State of Canada’s Birds assessments, aerial insectivores—including swallows, swifts and nightjars—have experienced some of the steepest declines of any bird group, with populations falling by nearly 59% since 1970. Scientists say the new research helps explain why these species continue to struggle.
Experts warn that the decline of insects has consequences extending far beyond birds. Insects are essential pollinators, decomposers and a vital food source for countless animals. Their disappearance threatens entire food webs, agricultural productivity and ecosystem resilience, making insect conservation increasingly important for biodiversity and human well-being.
Researchers say the study offers hope because many of the drivers of insect decline—including pesticide use, habitat loss and landscape management—can be addressed through targeted conservation policies. Protecting native habitats, restoring wetlands and reducing harmful chemical use could help rebuild insect populations and, in turn, improve the long-term prospects for Canada’s declining bird species.
