1. Urbanization and habitat loss: The expansion of urban areas has resulted in the loss of natural habitats, including parks, gardens, and green spaces, which are essential for sparrows. As cities expand, sparrows face a decrease in nesting and foraging sites.
2. Changes in agricultural practices: The intensification of agriculture, including the increased use of pesticides, herbicides, and fertilizers, has negatively impacted sparrow populations. These chemicals can reduce food availability and directly harm sparrows and their food sources.
3. Competition with other bird species: House sparrows often compete for resources, such as food and nesting sites, with other bird species, such as starlings and pigeons. In urban areas, these competing species may have an advantage, leading to a decline in sparrow populations.
4. Climate change: Changes in climate, including fluctuations in temperature and precipitation patterns, can affect the availability of food and nesting sites for sparrows. Extreme weather events can also directly impact sparrow populations.
5. Disease: House sparrows are susceptible to various diseases, including avian malaria and salmonellosis. These diseases can spread rapidly through sparrow populations, leading to significant declines.
6. Lack of nesting sites: The availability of suitable nesting sites, such as cavities in trees or buildings, is crucial for sparrow reproduction. The loss of nesting sites due to urbanization, renovation of older buildings, or changes in construction practices can contribute to sparrow decline.