What traits drive response of birds to tropical land-use change?

Could fruit eating species such as the black-mandibled Toucan be disproportionately affected by land-use change?
Could fruit eating species like the black-mandibled Toucan be disproportionately affected by land-use change? (Photo credit to Ettore Bacocchi on flickr)

Everyone pretty much knows about the crisis of biodiversity loss facing the tropics.

In case you missed it tropical forests are being rapidly cleared, which human population increases and along with consumption. All this has lead to large losses of biodiversity in the tropics.

So far, so boring.

However, up until recently we didn’t have much of an idea how the characteristics of species in the tropics influenced their response to land-use change.

‘Why would we want to know that?’ – I hear you ask. Well if you’ve seen my blog before you will know that traits are  a good way of linking biodiversity change to changes in ecosystem function and services. This is the first step to working out the consequences of the massive changes in biodiversity we have seen over the last century. Simply put – we need to know this stuff.

Given what I think, it was great to find out at the recent BES 2012 annual meeting in Birmingham about a paper looking at how bird species with different traits respond to land-use change in the tropics.

Tim Newbold, a postdoc at the World Conservation Monitoring Centre in Cambridge, and colleagues compiled an impressive dataset of  >4500 records of >1300 bird species from 23 studies of  land-use change in the tropics. They then used data on habitat preferences, migratory status, diet, generation length and body size to determine how differences in these traits related to birds’ response to land-use change.

They found that long-lived, non-migratory, primarily frugiverous or insectivorous forest specialists were likely to be less abundant and less likely to occur in intensively used habitats.

Probabilities of presence and abundance relative to primary forest based on dietary preferences of tropical bird species
Probabilities of presence and abundance relative to primary forest based on dietary preferences of tropical bird species

Of these characteristics diet preference is perhaps the most easy to link to changes in ecosystem function and services.

The loss of insect eating species may impact the control of pest species with potentially negative consequences for tropical agriculture. However, this assumption depends heavily on pest species abundances not reducing in line with bird declines. It is also entirely possible that if pest species also reduce in abundance forest loss will lead to little change in crop damage.

The reduction in fruit eating bird species may have consequences for forest regeneration and maintainance of plant diversity. Many secondary forests that are isolated from primary forest have been shown to lack large seeded tree species. Any reduction in the abundance of fruit eating birds suggests another barrier preventing the recovery of plant species communities in secondary forests.

I really liked this paper. It shows the value of large datasets for making generalisations and the results are potentially important for investigating change in ecosystem function and services in tropical forest ecosystems. The good news is it looks like there is a lot more of this type of work on the way with the PREDICTS project aiming to do take a similar approach to many questions related to land-use change. I’m excited to see what they come up with next, provided they don’t scoop me in the process…

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