This post is from my PhD student Rebecca Peisley, who I co-supervised with Gary Luck. Rebecca submitted her thesis earlier this year. Find the paper here: The role of avian scavengers in the breakdown of carcasses in pastoral landscapes. Also read Rebecca’s previous post on her other PhD work in apple orchards here.
Animal carcasses such as deceased livestock, road-kill or culled animals are a fact of life in agricultural landscapes, and can encourage increased and unwanted visits from wild dogs and foxes and also contribute to the spread of disease. Scavenging birds in these landscapes can remove carcasses, and therefore provide an important ecosystem service for farmers.
Perhaps the most well-known examples of carcass removal services in agricultural landscapes, which are worth millions of dollars each year, are those provided by vultures in Europe, Asia and Africa. The removal of carcasses by vultures near human settlements can reduce the number and visitation rates of rabid dogs that would otherwise be attracted to the carcasses, and in so doing, reduce the spread of rabies to the human population.
Unfortunately, vulture populations have suffered severe declines in recent years, and do not occur worldwide. However, other bird groups such as raptors and corvids are also common scavengers and a diverse assemblage of these occur in Australia. Like vultures, the scavenging behaviour of raptors and corvids has the potential to reduce the prevalence of unwanted pests such as red foxes and wild dogs in the landscape, and also reduce the spread of diseases such as blowfly strike. However, the benefits of carcass removal in agroecosystems in Australia are not widely recognised and have not yet been quantified. Continue reading →
This is a guest post from my PhD student Rebecca Peisley, who I am co-supervising with Prof Gary Luck. Rebecca will submit her thesis early next year. She has been working on a really cool project looking at the costs and benefits of bird activity in apple orchards, vineyards and cattle grazing systems across south-eastern Australia; this blog is about her work in apple orchards.
Birds are commonly found in agroecosystems around the world and their foraging activities within crops can result in positive or negative outcomes for producers. For example, birds can help increase saleable yields by preying on insect pests that damage fruit, or removing leftover fruit after harvest, which helps prevent disease and assists in nutrient cycling. However, birds can also contribute to production losses by eating and damaging fruit before harvest, or preying on beneficial insect pollinators.
We cannot then assume that birds are simply ‘good’ or ‘bad’: the same species can in fact be ‘both’. But in our literature review, we showed that most studies of birds in agroecosystems have just considered either costs or benefits separately, which limits our understanding of how birds influence crop yields over spatial and temporal contexts.
In order then to gauge an overall outcome of bird activity, we look at both their beneficial and detrimental activities together in the same crop system and consider the trade-offs that exist between them. For example, the beneficial activity of insectivorous birds preying on pest insects in an apple orchard and reducing insect damage to fruit is traded off against the detrimental activity of the same birds preying on beneficial pollinators resulting in reduced fruit-set. Continue reading →
It’s hard to keep wild animals out of farms. Birds, mammals and insects all affect crop yields, in positive ways (such as flies pollinating flowers) and negative ones (such as when birds damage fruit).
Agricultural research and management programs often deal with these interactions by focusing on simplistic “good” and “bad” labels: aphids are annoying pests, for example, whereas bees are little angels.
Read the rest of our piece at The Conversation.
And see the papers behind the article here:
Saunders ME, Peisley RK, Rader R, Luck GW (2016) Pollinators, pests, and predators: Recognizing ecological trade-offs in agroecosystems. AMBIO 45:4-14.
Peisley RK, Saunders ME, Luck GW (2015) A systematic review of the benefits and costs of bird and insect activity in agroecosystems. Springer Science Reviews 3:113-125.