By Kara Leimberger (PhD Student)

As mentioned in previous posts, one of our research questions involves temporarily removing Heliconia – a plant that provides nectar to many hummingbird species. Before and after removing Heliconia, we will measure which plants the hummingbirds visit and how often they are visiting. Will the hummingbirds miss the Heliconia so much that they leave the study area to search for nectar elsewhere? In this case, we might see less frequent visitation to the remaining flowers in the plot. On the other hand, maybe hummingbirds will stick around but consume more nectar from different plants, especially if the study plot is not connected to other easily accessible patches of forest.

For example, imagine that your typical breakfast consists of eggs, toast, and orange juice. Imagine that you wake up one day, hungry and ready for breakfast, but then realize that you are suddenly out of eggs! Do you then fill up on toast and orange juice? Do you find the stale corn flakes that have been sitting in the pantry for months? Or do you get out of your pajamas and make a trip to the grocery store (or if you’re a hummingbird, another forest patch)?

To measure how hummingbirds respond to Heliconia removal, we are using portable, camouflaged cameras positioned next to nectar-producing flowers. The cameras are programmed to take one picture every second, which means that a single camera running during the day (~12 hours) gives us 43,200 photos! The camera method lets us be very efficient (or lazy?) researchers because we do not have to watch flowers all day, but it sure means we have lots of photos to look at! We hope to use a computer program (MotionMeerkat) to sift through all these data quickly and accurately to find the moments when the flowers have visitors. When we tested cameras here at the research station, flower visitors have included hummingbirds, butterflies, wasps, and curious tourists. Below are some of the hummingbird photos we have gotten so far!

Green Hermit visiting Heliconia ramonensis

Green Hermit evaluating a H. tortuosa (and apparently our camera)

Rufous-tailed hummingbird visiting a domesticated banana plant (which has very abundant and sugary nectar)

This is one of the short-billed more generalized species that we study here in Costa Rica. Despite weighing in at <4 g, this bird can intimidate other hummingbirds nearly three times its size to defend a nectary clump of flowers.

Species of the day: Passiflora vitifolia (passion flower) found in one of our fragmented forest patches today. One of our research questions is how local extinction of Heliconia will indirectly influence other plant species like this one (via pollinator limitation). This is a favorite of hummingbirds because of its high amounts of sugary nectar… but can it keep hummingbirds coming to the patch even after Heliconia is gone?

By Matt Betts

2016 marks our 8th year at Las Cruces Biological Station in the pursuit of hummingbirds, pollination, life, the universe and everything (apologies to Douglas Adams). This year is a milestone as is the first full field season of our work on the importance of ‘hub’ species to pollination networks; over the years we’ve found that a remarkable number of hummingbird species (at least 9) use Heliconia tortuosa as a resource during the dry season. We now also know that tropical forest fragmentation is causing a decline in this plant species (evidence lies in much reduced densities of ‘baby’ heliconias in small forest patches). So what will be the ecological impact of these declines? What happens when you remove a critical ‘hub’ from a network? (e.g., a key ‘friend’ in a social network, a key individual in a terrorist network, a key neuron in the brain, or in our case…a keystone plant from a pollination network).

It turns out very little is known about the properties of pollination networks when species are removed. 

One possibility is that the network collapses; dependent birds depart from locations where heliconia no longer exist and as a result pollination of many other flower species suffers. An alternative is that “re-wiring” occurs; birds just change their foraging habits a bit (e.g., Big Macs versus steak) and keep up their pollination services to remaining plants. So, over the coming 3 years we intend to test these ideas using various experiments and methods that you’ll hear about in more detail as the months roll by.

I should mention that we’ve added several key members to our team: Prof Andy Jones (Oregon State Botany) is working with us on genetics and plant ecology. Kara Leimberger is visiting this season before starting her PhD in my lab in the fall. Jessica Greer (OSU graduate) has worked with us for three years as an integral part of our citizen science project and pollen identification effort but until now had not seen our study site (or the tropics for that matter). Finally, Luis Arias, a PhD student from University of Toronto under the supervision of Prof. Helene Wagner is here to work on H. tortuosa demography and seed dispersal.

Kara Leimberger, Jessica Greer and Luis Arias (left to right) – the new additions to the OSU Hummingbird Research Project.