Bird-friendly viticulture

If you are into wine, the Matorral of central Chile is viticulture heaven. This Mediterranean biome has very warm and dry summers and moderate, rainy winters – ideal conditions for grapes. The Matorral’s natural vegetation is a diverse sclerophyll forest composed of trees and shrubs with hard, short and often spikey leaves. Many of these trees and shrubs are endemic – found in the matorral and nowhere else, as are some of the animals that depend on the vegetation for sustenance, making this region a “biodiversity hotspot”.  Humans enjoy its benign climate as well, which is why most of Chile’s population and largest cities occupy this bioregion.  

Mattoral ecosystem dominates central Chile. Credit: A. Muñoz-Sáez

Unfortunately, the demands of humans for wine and domiciles can come into conflict with the Matorral’s biological diversity.  Much of the natural vegetation has already been cleared and most is privately owned, so there is little potential for setting up large preserves.  As a long-time bird enthusiast, Andrés Muñoz-Sáez wondered whether even small pockets of natural vegetation could help maintain the biologically diverse bird community in the region.  So he and his colleagues conducted a series of systematic surveys to see whether the presence of remnant natural vegetation in the immediate area, or the presence of a continuous forest nearby, increased bird diversity within a vineyard.

A vineyard in central Chile shrouded by fog and surrounded by a sclerophyll forest. Credit: A. Muñoz-Sáez

The researchers conducted 6 auditory and visual surveys for birds in 2014 at 20 vineyards that differed in the amount of surrounding natural vegetation.  They repeated this process early and late in the 2015 breeding season, for a total of 360 surveys. There were three types of surveys: (1) Within the vineyard with no natural vegetation remnants within 250 meters, (2) within remnants within the vineyard, and (3) within native vegetation adjacent to the vineyard.  The mean size of a remnant was 0.17 hectares. All told, the researchers recorded 5068 birds belonging to 48 species.

A burrowing owl keeps watch while perched on a vineyard fencepost. Credit: A. Muñoz-Sáez

Both species richness (left graph below) and overall bird abundance (right graph below) were lowest in the vineyards without remnants nearby, and highest in remnants and in the surrounding matorral. Richness and abundance were very similar in remnants compared to the surrounding matorral. 

Species richness (mean number of species – left graph) and mean number of birds (right graph) per survey conducted in surrounding matorral (M), remnants within a vineyard (R) and in vineyard with no nearby remnants (V). Error bars are 1 standard error. Horizontal bars with *s above bars indicate statistical differences between treatments. * = P < 0.05. *** = P < 0.001.

From the standpoint of species composition (which species were present), bird communities in vineyards with remnants were more like those found in surrounding matorral than like those in vineyards without remnants. Perhaps most important from the standpoint of conserving biological diversity, the mean number of endemic bird species was greatest in matorral (3.02 endemic birds per survey), intermediate within remnants (1.11) and negligible within the vineyard without remnants nearby (0.03).

Muñoz-Sáez and his colleagues advocate retaining remnant native vegetation within vineyards to provide local habitat for native birds.  Their surveys indicated that insectivorous birds were more than six times as likely in remnants than in vineyards far removed from remnants.  From the standpoint of providing ecosystem services to humans, insectivorous birds can benefit vineyard production by removing unwanted insect pests. Given that many remnants are in less productive areas such as steep slopes, or along streams, the costs of maintaining and not developing these remnants are relatively minor, while the benefits to the viticulturist and the ecosystem can be substantial.

note: the paper that describes this research is from the journal Conservation Biology. The reference is Muñoz‐Sáez, A., Kitzes, J. and Merenlender, A.M., 2021. Bird‐friendly wine country through diversified vineyards. Conservation Biology35(1), pp.274-284. Thanks to the Society for Conservation Biology for allowing me to use figures from the paper. Copyright © 2021 by the Society for Conservation Biology. All rights reserved.

Subsidized Shorelines: where pelagic meets benthic

Chris Harrod met his wife, Christina Dorador, while both were working at the Max Planck Institute for Limnology in Germany.   Subsequently Dorador began a postdoctoral position in her native Chile, and Harrod went for a visit over Christmas, 2007. He was impressed by the beautiful rocky inshore habitat that was dominated by kelp forests and many species of invertebrates and fish.

Macroalgal forest

Rocky shoreline near Tocopilla, Chile. Credit: Chris Harrod.

As a fisheries biologist, Harrod soon immersed himself in the inshore kelp forest-dominated ocean, and was stunned by the sheer volume of stuff floating around. The water was green rather than blue, and filled with decaying phytoplankton and zooplankton. Where did all this stuff come from? Harrod knew that off the Peruvian and north Chilean coasts, prevailing winds move surface waters away from the shoreline, inducing upwelling of deeper nutrient-rich waters to the surface. This nutrient flux is the basis of a huge anchoveta fishery, which feeds humans, fish, marine invertebrates and marine mammals. He wondered whether the mass of floating debris in the inshore habitat might originate from offshore waters brought in from upwelling, and if the debris actually fueled some of the larger fish and molluscs that dominate inshore kelp forests. The prevailing opinion was that the energy for these fish and molluscs originated from the inshore photosynthetic kelp, rather than from photosynthetic phytoplankton further offshore that get their nutrients from upwelling.


Two bilagay, Cheilodactylus variegatus, swim among green algae in a debris-laden inshore habitat off the coast of Chile. Credit: Chris Harrod.

While you can ask a fish or mollusc what they had for dinner, it is very difficult to get them to respond. Fortunately, ecologists can use stable isotope ratios – the ratio of a rare (and nonradioactive) isotope of an element to its standard common isotope – to help get the answers they need. Harrod collaborated with several researchers in this study, including his Master’s student, Felipe Docmac, who collected and analyzed much of the data and was the first author of the paper. Docmac and his colleagues used the ratio of heavy and light isotopes of carbon (C) and nitrogen (N) to calculate d13C (the ratio of 13C to 12C) and d15N (the ratio of 15N to 14N) to infer where inshore fish were getting their energy.

The basic question was whether the nutrients supporting the food web were primarily from pelagic or benthic sources. In this case, the pelagic source refers to phytoplankton from the offshore areas of upwelling, while the benthic source refers to kelp and green algae that grow on the bottom (benthos) of the inshore habitat. Docmac and his colleagues collected invertebrates and large fish from five different sites along the north Chilean Coast, and calculated 13C and 15N values from tissue samples. Invertebrates were divided into two groups: filter-feeders were represented by mussels, which fed on suspended materials (such as the prolific floating debris), while benthic grazers were gastropods (snails) that fed on benthic kelp and green algae.


Five collection sites along the northern coast of Chile.

I’m going to skip the precise details of how stable isotope analysis actually works; I’ll provide enough information so you can understand the findings. There are two important facts to keep in mind. First an animal’s stable isotope ratio is influenced by the stable isotope ratio of its food source. So an animal feeding on prey with high d13C and d15N will itself have higher stable isotope ratios than will an animal feeding on prey with lower d13C and d15N. Second, the stable isotope ratio increases as we go up the food chain in a predictable manner, because the lighter isotopes of carbon and nitrogen tend to be more readily excreted than are the heavier isotopes.

We are now ready to look at the data. First, notice that while there is some variation from location to location, the (Pelagic) mussels tend to have consistently lower d13C values than do the (Benthic) gastropods (X-axis of graph), but fairly equivalent d15N values (Y-axis of graph). The benthivorous fish have, as we would expect from animals higher up the food chain, much higher d15N values than either of the invertebrates. But here is the key. The benthivorous fish have a much lower d13C value than do the benthic invertebrates (gastropods). If gastropods (and presumably other grazers) were in the benthivorous fish food chain, then we would expect the fish to have a higher d13C value than do the benthic gastropods. The researchers thus conclude that these fish are deriving most of their energy from the pelagic debris that is washing in from ocean currents.


d13C (X-axis) and d15N (Y-axis) stable isotope values in benthivorous fish (black circles).  Bars emanating from each point indicate 95% confidence intervals (CI). Numbers inside symbols indicate the site of origin for each sample (see map above), Also shown are values for filter-feeding mussels (red up-pointing triangles) and grazing gastropods (blue down-pointing triangles). Gray lines indicated predicted values of diets that were based solely (100%) on pelagic or benthic sources.

The researchers were stunned by these findings. Going into the study, Harrod did not know what he would find, but would not have been surprised by a 15% contribution from pelagic sources, or maybe even 30%. But he was blown away that the data indicated estimates of greater than 90% pelagic contribution at most of the sites. Ecologists have long known that one ecosystem may subsidize a second ecosystem with resources. For example, salmon carcasses can provide nutrient subsidies to trees near riverways, or even deeper into the forest after being transported by bears. But the extent of the subsidy in this study is unprecedented. Docmac and his colleagues urge researchers to explore exactly how the pelagic materials get into the food web, and to see whether such subsidies are common near other upwelling zones worldwide so that coastal resources can be managed more effectively.

note: the paper that describes this research is from the journal Ecology. The reference is Docmac, Felipe, Miguel Araya, Ivan A. Hinojosa, Cristina Dorador, and Chris Harrod. 2017. Habitat coupling writ large: pelagic‐derived materials fuel benthivorous macroalgal reef fishes in an upwelling zone. Ecology doi:10.1002/ecy.1936. It was published online on Aug. 2, 2017, and should appear in print very soon. Thanks to the Ecological Society of America for allowing me to use figures from the paper. Copyright © 2017 by the Ecological Society of America. All rights reserved.