Raptors provide an important ecosystem service by scavenging carcasses in agricultural landscapes

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.

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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

A failed experiment: earwigs as pests and predators in fruit orchards

Field ecology experiments are fickle. Even with best laid plans in place, they can fail…Nature doesn’t follow sampling protocols.

When this happens, should you publish the results? Most people would say no, and I would generally agree. Failed experiments are different to negative results. The latter are important additions to the scientific literature, but the former have very limited use. The results of failed experiments will have limited value, depending on why the experiment failed and how many data points were left intact. But they can have some use as ‘what not to do’ baselines for other researchers. Continue reading

Artificial pollinators are cool, but not the solution

Agreed, bees and other insect pollinators are under threat globally from multiple human pressures. If pollinators disappear completely from an ecosystem, their loss will affect the structure of those ecosystems and the natural foods and fibres we use from the ecosystem. So, finding solutions to the problem of pollinator decline are imperative.

This is why the robo bees story sounds like such a seductive idea. Imagine creating tiny drones with hairs on them that can be programmed to do a bee’s job? Wow! We are off the hook. Continue reading

Sustainable Agriculture: Best of 2016 & the wooden spoon

All good things come to an end. 2016 was a year just like any other; some dreadful things happened and some wonderful things happened, depending on who you talk to.

For people interested in sustainable agriculture, it was a pretty exciting year. But in keeping with the annual theme of misinformation, there were also plenty of fails. Here are some of the highlights for me: Continue reading

Tarzan on Ecosystem Services

They are singing the legend of Tarzan…They speak of his power over the animals of the jungle. Because his spirit came from them. He understood them. And learned to be as one with them.

 

Last week I watched The Legend of Tarzan (2016) because I was trapped on a plane for 4 hours. It really wasn’t that bad, despite the scathing reviews it has received. All the outraged critics must have had very high expectations. It’s just a bit of Hollywood fun that is very enjoyable if you don’t take it all too seriously. And there are some nice historically-accurate details to counteract the fantastical story.

As the credits rolled, it struck me that it also provides some good examples of ecosystem services. Continue reading

Unlikely plant-pollinator relationships

When we think about planting for pollinators, the first plants we reach for are often ones with obvious flowers, usually bright and showy, perhaps with an attractive scent, and lots of pollen and nectar. Most of these will be insect-pollinated plants, which is why they are so attractive to pollinator insects – they have co-evolved with pollinators to reap the reproductive benefits of insect visitation.

But pollinators also use plenty of other plants that we wouldn’t think of as being ‘pollinator plants’, particularly plants that are pollinated by wind, like conifers and grasses. Some grasses are pollinated by bees. And some bees feed on fungi. These interactions have been observed by scientists and naturalists for centuries, but are often forgotten when we talk about pollinator conservation.

This is one of the key challenges with the ecosystem services concept. Trying to justify conservation of pollinator insects because they provide us with benefits, i.e. fruits and seeds from plants they pollinate, is not always useful. Partly because this approach overlooks the fact that pollinators also need lots of other resources to survive, some of which we may not benefit from. And separating ‘insect-pollinated crops’ (e.g. almonds, stonefruit, berries) from ‘wind-pollinated crops’ (e.g. wheat, rice, corn) when we talk about managing farms for pollinator conservation, ignores the fact that some pollinators will regularly visit wind-pollinated crops to collect pollen for food.

I’m currently writing a review of records of pollinator species visiting plant species that we traditionally assume to be wind-pollinated, after noticing some of these interactions at field sites and in my own garden (stay tuned!). I didn’t find any records of some of these plant-pollinator interactions in my literature review, so I’m recording them here. One-off ecological observations are rarely accepted by academic journals, because they are not considered scientific studies. But, in conjunction with other knowledge, they can provide important information for future research hypotheses.

Continue reading

Cost-benefit trade-offs of bird activity in apple orchards

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