Tag Archives: Hummingbirds

Hummingbirds have a sense of smell: so why do we keep saying that they don’t?

P1110560

One of the general features associated with specialised hummingbird-pollinated flowers in the New World is that they often have no scent perceptible to the human nose.  This is then interpreted as evidence that hummingbirds have no sense of smell, which strikes me as circular reasoning at best.  This “fact” is then frequently repeated in text books and on the web, for example at the Bird Watcher’s Digest site, at The Spruce site, and at the World of Hummingbirds.

However I know of only two research papers that have tested whether or not hummingbirds can smell, both of them short notes; and in both cases they found that the hummingbirds they tested could associate scents with food in artificial flowers.  Those studies (with links to the originals) are:

Goldsmith, K.M. & Goldsmith, T.H. (1982) Sense of smell in the black-chinned hummingbird. Condor 84: 237-238

Heringer, H. et al. (n.d. – c. 2006?) Estudo da capacidade olfatória em três representantes da subfamília Trochilinae: Eupetomena macroura (Gould, 1853), Thalurania furcata eriphile (Lesson, 1832) e Amazilia lactea (Lesson, 1832).  Unpublished manuscript – possibly a student project (?)

It surprises me that this has been so little studied, given how much research has otherwise been done on hummingbirds.  Have I missed any other studies?  Clearly vision is more important for hummingbirds when locating food, but that’s not the same as stating that hummingbirds have no sense of smell.  Seems to be one of those myths that won’t go away, of which there are many in pollination biology.

Comments welcomed, as always.

 

Advertisements

Leave a comment

Filed under Biodiversity, Birds, Pollination

The influence of floral traits on specialization and modularity of plant–pollinator networks in a biodiversity hotspot in the Peruvian Andes – Watts et al. (2016)

Watts et al Figure 1

The second paper from the PhD thesis of my former student Dr Stella Watts has just been published in Annals of Botanyhere’s a link to the journal’s website.  It summarises the major findings from her field work on plant-pollinator interactions in the high Andes of Peru:

Watts, S., Dormann, C.F., Martín González, A.M. & Ollerton, J. (2016) The influence of floral traits on specialization and modularity of plant–pollinator networks in a biodiversity hotspot in the Peruvian Andes.  Annals of Botany doi: 10.1093/aob/mcw114

This paper represents a major piece of research, including extensive field data collection over multiple sites in a challenging environment at altitude; state-of-the-art data analysis; and then summarising all of this into a single, digestible paper, with some great figures.  I’m very proud to have been part of it!

Here’s the abstract; please email me or Stella if you’d like a copy of the full PDF:

Background and Aims:  Modularity is a ubiquitous and important structural property of ecological networks which describes the relative strengths of sets of interacting species and gives insights into the dynamics of ecological communities. However, this has rarely been studied in species-rich, tropical plant–pollinator networks. Working in a biodiversity hotspot in the Peruvian Andes we assessed the structure of quantitative plant–pollinator networks in nine valleys, quantifying modularity among networks, defining the topological roles of species and the influence of floral traits on specialization.

Methods: A total of 90 transects were surveyed for plants and pollinators at different altitudes and across different life zones. Quantitative modularity (QuanBiMo) was used to detect modularity and six indices were used to quantify specialization.

Key Results:  All networks were highly structured, moderately specialized and significantly modular regardless of size. The strongest hubs were Baccharis plants, Apis mellifera, Bombus funebris and Diptera spp., which were the most ubiquitous and abundant species with the longest phenologies. Species strength showed a strong association with the modular structure of plant–pollinator networks. Hubs and connectors were the most centralized participants in the networks and were ranked highest (high generalization) when quantifying specialization with most indices. However, complementary specialization d’ quantified hubs and connectors as moderately specialized. Specialization and topological roles of species were remarkably constant across some sites, but highly variable in others. Networks were dominated by ecologically and functionally generalist plant species with open access flowers which are closely related taxonomically with similar morphology and rewards. Plants associated with hummingbirds had the highest level of complementary specialization and exclusivity in modules (functional specialists) and the longest corollas.

Conclusions: We have demonstrated that the topology of networks in this tropical montane environment was non-random and highly organized. Our findings underline that specialization indices convey different concepts of specialization and hence quantify different aspects, and that measuring specialization requires careful consideration of what defines a specialist.

2 Comments

Filed under Bees, Biodiversity, Birds, Honey bees, Mutualism, Pollination, University of Northampton, Wasps

The integration of alien plants in mutualistic plant–hummingbird networks – a new study by Maruyama et al. (2016)

The collaborations with researchers in Brazil and Denmark in which I’ve been involved in recent years, focused particularly on hummingbirds and networks of plant pollinator interactions, have been very productive, most recently seen in a study of the effects of hummingbird feeders on diversity and abundance of the birds.

This collaboration continues with a new study that has just been published in the journal Diversity and Distributions which deals with the way in which non-native plant species are exploited by assemblages of hummingbirds in the New World.  Here’s the abstract:

 

Aim:  To investigate the role of alien plants in mutualistic plant–hummingbird networks, assessing the importance of species traits, floral abundance and insularity on alien plant integration.

Location: Mainland and insular Americas.

Methods: We used species-level network indices to assess the role of alien plants in 21 quantitative plant–hummingbird networks where alien plants occur. We then evaluated whether plant traits, including previous adaptations to bird pollination, and insularity predict these network roles. Additionally, for a subset of networks for which floral abundance data were available, we tested whether this relates to network roles. Finally, we tested the association between hummingbird traits and the probability of interaction with alien plants across the networks.

Results: Within the 21 networks, we identified 32 alien plant species and 352 native plant species. On average, alien plant species attracted more hummingbird species (i.e. aliens had a higher degree) and had a higher proportion of interactions across their hummingbird visitors than native plants (i.e. aliens had a higher species strength). At the same time, an average alien plant was visited more exclusively by certain hummingbird species (i.e. had a higher level of complementary specialization). Large alien plants and those occurring on islands had more evenly distributed interactions, thereby acting as connectors. Other evaluated plant traits and floral abundance were unimportant predictors of network roles. Short-billed hummingbirds had higher probability of including alien plants in their interactions than long-billed species.

Main conclusions: Once incorporated into plant-hummingbird networks, alien plants appear strongly integrated and, thus, may have a large influence on network dynamics. Plant traits and floral abundance were generally poor predictors of how well alien species are integrated. Short-billed hummingbirds, often characterized as functionally generalized pollinators, facilitate the integration of alien plants. Our results show that plant–hummingbird networks are open for invasion.

 

The full reference is: Maruyama, P.K. et al. (2016) The integration of alien plants in mutualistic plant–hummingbird networks across the Americas: the importance of species traits and insularity.  Diversity and Distributions (in press).

Happy to send a PDF to anyone who would like one.

1 Comment

Filed under Biodiversity, Biogeography, Birds, Brazil, Pollination

How do artificial nectar feeders affect hummingbird abundance and pollination of nearby plants? A new study in the Journal of Ornithology

Hummingbirds on feeds in Brazil

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….

———————-

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.

Hummingbirds on feeds in Brazil 2

8 Comments

Filed under Biodiversity, Birds, Brazil, Gardens, Pollination