Back in November 2013, during my research and teaching trip to Brazil, I discussed an amazing garden that we visited in which the owner had set up around a dozen hummingbird feeders that were attracting hundreds of individual birds from over 20 species. As I mentioned, one of the owner’s concerns was that by feeding the birds he might be negatively affecting the reproduction of hummingbird-pollinated plants in the surrounding forest. I thought it unlikely but there have been very few tests of this idea, and none in that part of South America.
After I left, a Master’s student called Jesper Sonne, based at the Center for Macroecology and Climate in Copenhagen, worked with my Brazilian and Danish colleagues on collecting data to address this question. Between us we analysed and wrote up the results, and have recently published the paper in the Journal of Ornithology under the title “Spatial effects of artificial feeders on hummingbird abundance, floral visitation and pollen deposition“.
The abstract is below and if anyone wants a PDF, please drop me a line. But the take home message is that although these feeders have a significant local effect on hummingbird abundance, there’s no evidence that they affect plant reproduction in the vicinity. It’s nice when predictions prove correct….
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Abstract
Providing hummingbirds with artificial feeders containing sugar solution is common practice throughout the Americas. Although feeders can affect hummingbird foraging behavior and abundance, it is poorly understood how far this effect may extend. Moreover, it remains debated whether nectar-feeders have a negative impact on hummingbird-pollinated plants by reducing flower visitation rates and pollen transfer close to the feeders. Here, we investigated the effects of distance to nectar-feeders on a local hummingbird assemblage and the pollination of Psychotria nuda (Rubiaceae), a hummingbird-pollinated plant endemic to the Brazilian Atlantic Rainforest. At increasing distance (0–1000 m) from a feeding-station, where hummingbirds have been fed continuously for the past 13 years, we quantified hummingbird abundance, and rates of flower visitation and pollen deposition on P. nuda. We found that hummingbird abundance was unrelated to distance from the feeders beyond ca. 75 m, but increased steeply closer to the feeders; the only exception was the small hummingbird Phaethornis ruber, which remained absent from the feeders. Plants of P. nuda within ca.125 m from the feeders received increasingly more visits, coinciding with the higher hummingbird abundance, whereas visitation rate beyond 125 m showed no distance-related trend. Despite this, pollen deposition was not associated with distance from the feeders. Our findings illustrate that artificial nectar-feeders may locally increase hummingbird abundance, and possibly affect species composition and pollination redundancy, without necessarily having a disruptive effect on pollination services and plants’ reproductive fitness. This may apply not only to hummingbirds, but also to other animal pollinators.
Prof. Jeff Ollerton - ecological scientist and author 
Not exactly on topic – but I’ve wondered whether I should be stocking a set of bird feeders year round, or only from late fall trough to early spring? The lack of feeding in nicer months resting on the thought that the birds should fend for themselves when conditions are not onerous. This is a periurban landscape with a fair level of habitat at close hand.
The advice of the RSPB is that feeding all year round is recommended, but you need to be careful about what it is you feed – see: http://www.rspb.org.uk/makeahomeforwildlife/advice/helpingbirds/feeding/whentofeed.aspx
This work is interesting as possibility of increased local abundance of Hummingbirds can increase with Artificial nectar feeders , and increase species composition.Promoting and conserving urban biodiversity and its sustainable use will benefit- if this approach and finding works with other species.
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Nice to see a study addressing such an interesting topic and relevant topic, and to learn there were no obvious negative impacts on pollination. I always notice how many bees are attracted to these hummingbird feeders as well. Wonder how their numbers or abundance are affected if at all?
Good question which, as far as I know, has not been addressed.
Awesome blog
nice information
Jeff, great blog… lots of good discussion points. However, consider that the final impact of feeders is context dependent. It is not the same to use feeders in urban environments than in forest reserves, public or private, or reserves in lowland forests vs highland forests, where climatic conditions are more demanding-.
Feeders cause a lot of mortality to other pollinators, such as wasps and bees (they drown in the feeder solution). They attract other animals as well (in the tropics, bats, coatis, raccoons, to name a few). Usually, places that use feeders use them for a long time without looking at potential consequences.
The absence of evidence is not the evidence of absence. Thus, more research is needed before we could conclude that feeders are either neutral or beneficial to pollinators. Their effects are context-dependent. All the best, GA
Hola Gerardo – thanks for the comment. Yes, I completely agree, there are lots of factors that need to be considered here and more work needs to be done, there are too few studies of how these feeders affect local ecology. And, yes, context is everything!
Dear Jeff, have you or anyone studied the effect of sugar made nectar on the health of urban hummingbirds? I´m trying to find a convincing answer on whether it is benefical or disadvantageous to place hummingbird feeders in big cities vs planting flowers. Thanks!
Hi Alejandro – I think it’s a really interesting question but I don’t know of any studies, sorry. It would be worth you sending out a request on Twitter. If you tag me I will retweet it. Jeff
Can you send me the complete pdf please?
Sure, it’s on its way to you now.
I remember getting a hummingbird feeder as a kid, and though I used it for a while, I eventually stopped because I worried that I was preventing the hummingbirds from pollinating flowers. I randomly thought about this again many years later and found this article. Nice to have some research to address some of my earlier concerns, and now I feel more comfortable putting out the feeder again (in the spring) after many years. Thanks!
Thanks Joel – yes, I think that on balance the benefits of having the feeders outweigh any potential harm. I include the story of this garden and our research in my new book: https://pelagicpublishing.com/products/pollinators-and-pollination-ollerton-9781784272289