Auburn University professors comment on the decline of the bird population

Auburn University School of Forestry and Wildlife Sciences faculty members Dr. Chris Lepczyk, professor of wildlife biology and conservation, and Dr. Graeme Lockaby, associate dean for research, comment on the effect of the declining bird population in North America and how to protect birds.

Recent news stories, such as “Where have the wild birds gone? 3 billion fewer than 1970,” have documented the decline of birds, which provide a number of key ecosystem services to humans that we depend upon. These include pollination, nutrient cycling, consuming insects, dispersing seeds, scavenging and many other aspects.

Dr. Christopher Lepczyk, professor of wildlife biology and conservation:

What is the main threat to bird populations?

Plain and simple, it is people. The specific reasons include loss of habitat (this is the main reason, but a lot of factors cause loss of habitat); increased mortality due to collisions with windows, buildings and communication towers; increased predation by house cats; increased light and sound pollution; climate change; use of synthetic fertilizers, herbicides and pesticides in agriculture; and loss of overwintering habitat and stopover habitat for migratory birds. One of the main problems is there are a great number of factors that are all acting in concert to negatively affect bird populations. The simplest story is that people have removed a large amount of habitat that birds use, and continue to do so, and engage in activities and practices that are detrimental to birds, wildlife and the ecosystem in general.

What can homeowners and landowners do to protect birds?

The Smithsonian Migratory Bird Center and the 3 Billion Birds organization recommend these good tips.

• Make windows safer, day and night

• Keep cats indoors

• Reduce lawn, plant natives

• Avoid pesticides

• Drink Bird Friendly coffee

• Protect the planet from plastics

• Watch birds, share what you see

More details about these tips can be found on Smithsonian National Zoo website.

How does deforestation affect bird populations?

Many of the birds in North America that have been declining inhabit forest ecosystems. While the eastern half of the U.S. has undergone afforestation over the past century (due to farmland abandonment and other land-use changes), the amount of large intact forest remaining has decreased. Forests in the U.S. have increasingly been fragmented (made into smaller forests in terms of actual size or function) due to an increase in roads and road density; the number of houses built in forests and forest understories; the expansion of farmland and people into forested areas; changes in the amount, size and intensity of forest fires and other disturbances (e.g., insect outbreaks); and the movement from multispecies forests to plantation agriculture forests that may not be composed of native species. In other words, deforestation results not just from trees being cut down to make way for people, but the loss of native forest systems and the systematic reduction in forest size.

Alternatively, can an area have too many birds and what would be the effect?

Certainly, we can have locations that have too many birds. But this is generally due to either people or some factor in the environment causing a large increase. For instance, many urban areas and cities have large numbers of pigeons (rock doves) that people find annoying (they defecate on lots of buildings, for instance). However, the total amount of pigeons in urban areas is still less than the amount of birds that likely would have existed in that same location without a city. We can have too many birds also in situations where we improve the habitat, such as through providing food, water or shelter. A case in point is Canada geese, which have large numbers in urban areas that have large amounts of open water in the winter and food. Essentially people have made urban habitats desirable for geese and they no longer migrate and instead have large populations in areas where people live and work. As a result geese often cause human-wildlife conflict due to increased amount of pollution from defecation and harassment. But I would overall say that we don't have lots of situations where there are too many birds.

Dr. Graeme Lockaby, associate dean for research:

What effect does a loss of birds have on mosquito-borne diseases?

Much depends on the particular disease and mosquito vectors in question. Some diseases such as Zika are probably minimally affected since the Ae. aegypti and Ae. albopictus mosquitoes may breed in open containers near yards and urban areas where avian biodiversity tends to be low. 

Most research on this question has pertained to West Nile virus which has a more complicated relationship with birds. Certain types of birds known as corvids can serve as an active reservoir of West Nile and thereby help spread the disease. So, if the bird loss involved corvid populations, their loss would reduce the incidence of West Nile. However, if other types of birds declined, the chances of a Culex species mosquito encountering a corvid would be increased which, in turn, would promote West Nile incidence.