A study, published in the journal Science, discovered that bird population in North America has declined by almost 3 billion in the last 48 years.
Study results revealed that bird population in North America has fallen by 2.9 billion since 1970, which represents an approximately 29% decline in the total population of birds over that time period.
The study stated ""Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of individuals that can result in compositional and functional changes of ecosystems." Peter Marra, senior author of the study and director of the Georgetown Environment Initiative at Georgetown University, pointed out that "You only need to fly across the country to see that we've drastically changed the face of the earth."
To calculate how much change actually happens in the bird populations, researchers conducted an analysis of range-wide population estimates of 529 species of birds and included biomass estimates from weather radar networks to track birds during their biannual migrations across the continent.
They discovered that the birds found in grasslands such as sparrows, warblers, blackbirds and finches were hit by the decline the most. Their populations went down by a whopping 53% in the past five decades. Results also showed that almost three-quarters of all grassland species are experiencing population decline because grasslands are more prone to habitat loss and exposure to toxic pesticides from nearby farmlands.
Pesticides causes harm to birds in various ways, including the contamination of seeds that they eat. which leads to the loss of weight that makes it difficult for them to migrate. Pesticides also cut down the insect population, which is the primary source of prey for birds.
Another cause of death among birds is window collisions. Approximately 600 million birds annually are killed by these collisions. Every year, cats also hunt down as many as 600 million birds.
