Nectar-feeding Rufous-backed Robins in western Mexico

In earlier posts I highlighted two instances of nectar-feeding by birds in western Mexico, that of Tropical Parulas (Setophaga pitiayumi) and Streak-backed Orioles (Icterus pustulatus) on Spondias purpurea and various species of hummingbirds taking nectar from wild cotton (Gossypium aridum).

Recently, I had the opportunity to observe additional bird species collecting nectar from the African Tuliptree (Spathodea campanulata), a common ornamental species in the region. The bird species collecting nectar from this tree included Orchard Orioles (Icterus spurius),


…Hooded Orioles (Icterus cucullatus),



…and Yellow-winged Caciques (Cassiculus melanicterus).


All of the above species are well-documented nectar collectors.1

The final bird I saw collecting nectar — the Rufous-backed Robin or Thrush (Turdus rufopalliatus) — was a considerably bigger surprise.

While many of the True Thrushes, including Rufous-backed Robins, consume significant amounts of fruit, I could only find one record of them consuming nectar.  An unpublished source indicates that Asian species, the Grey-sided Thrush (Turdus feae), collects nectar from the flowers of the legume Acrocarpus fraxinifolius.2

So why would birds that eat sugar-rich fruit rarely if ever take the opportunity to collect similarly sugar-rich nectars?  Apparently, the answer to this question lies in the kinds of sugars found in fruit and nectar.3

The sugars in fruit are almost always glucose and fructose.  These sugars are simple and directly absorbed in the intestines of frugivores without need of further processing. Conversely, most floral nectars have sucrose as their predominant sugar.  Sucrose is a disaccharide formed from glucose and fructose and cannot be absorbed by the intestines until it is broken down into glucose and fructose by the enzyme sucrase.

Rufous-backed Robins in specific1 and, True Thrushes in general3, lack measurable quantities of sucrase. Therefore, they can’t digest sucrose-rich solutions. Some bird species lacking sucrase may suffer something called osmotic diarrhea when fed sucrose-rich solutions.  Not surprisingly, they tend to avoid consuming such solutions.

There are, however, some plants that produce floral nectars where glucose and fructose are the predominant sugars.3  Such plants are more common in the Old World than in the New.  This may be the result of a more equitable sharing of the avian nectar-feeding niche in the Old World between passerine species that can and can’t digest sucrose.  In the New World, sucrose-digesting hummingbirds dominate this niche possibly reducing the selection for plants that produce floral nectars rich in glucose and fructose rather than sucrose.

This then may explain why I was able to observe Rufous-backed Robins feeding on nectar.  The tree they were collecting nectar from, the African Tuliptree, is one of those Old World species whose nectar contains glucose and fructose instead of sucrose.4

As always, one question answered leads to others.  Is this a relatively new behavior for Rufous-backed Robins or have we managed not to see them collecting nectar from other native plant species whose nectars contain glucose and fructose instead of sucrose?  Also, the calyces of the African Tuliptree produce large quantities of water which are necessary for floral development and which then spills over into the opening flowers.  In the relatively xeric environment along this part of the west coast of Mexico, has this unusual feature played any role in the origin and maintenance of nectar feeding in this thrush?

References and Sources

1Martinez, del Rio, Carlos. (1990).  Dietary, phylogenetic, and ecological correlates of intestinal sucrase and maltase activity in birds.  Physiological Zoology 63(5): 987 – 1011.

2P. D. Round (in litt. 1998).

3Lotz, Chris N. and Jorge E. Schondube. (2006).  Sugar preferences in nectar- and fruit-eating birds: behavioral patterns and physiological causes. Biotropica 38(1): 1 – 13.

4Rangaiah, K., S. Purnachandra Rao, and A. J. Solomon Raju.  (2004). Bird-pollination and fruiting phenology in Spathodea campanulata Beauv. (Bignoniaceae). Beitrage Zur Biologie Der Pflanzen 73: 395 – 408.

The Petroglyphs of La Pintada, Jalisco, Mexico

In April of 2015 I visited the small pueblo of La Pintada not far from Tomatlán in Jalisco, Mexico.  My objective was to see ancient artwork in the form of the impressive petroglyphs found there. After finally finding La Pintada and then driving around in the pueblo for a while, I finally found them.

As the third of the three maps below shows, the petroglyphs aren’t far from the road.  The problem is that there’s an irrigation canal between the road and the petroglyphs.  I’m not a long jumper and I didn’t feel like wading, so I looked for another way to reach the petroglyphs for a closer look.

On the other side of the canal I rode into the pueblo where a woman asked if I was looking for something.  When I said I was trying to find a way to get to the piedras pintadas, she told me to wait for just a second.  She then went and fetched a fellow who would serve as my guide.

When my guide and I got to the rocks, it gave me a better look at what was visible from the road and I also got to see some things not visible from the road.

As can be seen, most of the petroglyphs were spirals and concentric circles.  As can also be seen, there was also a large rectangular figure carved on vertical surface.   For me, there was nothing recognizable inside this rectangle and my guide speculated that maybe it had served as a map at one time.

Anyway, these are just the more prominent and easily accessible petroglyphs.  A systematic survey of the area revealed a total of 97 petroglyph rocks.1

Next, my guide led me to another area where he speculated that the former inhabitants ground food and at least occasionally visited after dark.

The shallow depressions are found throughout the Americas and are quite typical of those used for grinding maize and other things. While my guide suggested that the smaller diameter holes may have supported torches, I wonder instead if they might have been used for pounding hard seeds, for instance, as a step in the process for making pinole.

So who was responsible for making the petroglyphs and when did they make them?

Sometimes with petroglyphs there is relatively clear evidence of who the artists were.  Good examples can be found not far from La Pintada. La Pintada lies in the Río Tomatlán River Valley.  Within this valley, scientists have located 747 boulders with rock art. With one exception — the unique and fascinating pictographs of La Peña Pintada2 — all are petroglyphs.1

Almost all surface artifacts in close proximity to these 747 boulders can be traced to the Nauhuapa phase of occupation* (A.D. 1300 to 1525 and even into the colonial period).1,3  In a few cases, boulders with petroglyphs were even part of these people’s houses. All of this suggests that these same people were the artists.

There are a few instances, however, where surface artifacts in proximity to rock art are predominantly from the Aztatlán phase of occupation which began around 1215 A.D.1,3  In these cases, the Aztatlán may have been the artists.

Until recently, the situation at La Pintada has been less clear.1 A nearby excavation found pottery sherds traceable to three prehispanic phases of occupation in the area: the Capacha, the La Pintada (named after the location), and the Aztatlán. By far the most abundant sherds were from the La Pintada with Capacha and Aztatlan sherds being much less common.

Before I talk about which is most likely responsible for the petroglyphs, I think it’s worth taking a moment to reflect a little on who these people were.

The Capacha Culture (1500 to 800 B.C.) was found along the Pacific coast from Sinaloa to Colima although elements can also be seen in the Rio Balsas Depression of Guerrero.4 These people intensively exploited marine resources but also farmed maize. Their pottery was very distinctive with what appear to be links to northwest South America (click here for a video in Spanish).

The affinities of the people of the La Pintada phase (400 B.C. to A.D. 300)1 to the greater cultures of the time are unclear.  They were contemporaries of the  “shaft-and-chamber tomb” culture that occupied a semicircular band through the highlands of Jalisco whose ends broadened upon reaching the coasts of Colima and Nayarit.4  Their external ties, though, seem to be strongest to the Autlán-Tuxcacuesco area in the mountains of southwest Jalisco.   At La Pintada, intensive craft production along with the presence of exotic shells and minerals suggests that trade was important for these people.  It is estimated that around 1000 people lived at La Pintada at that time.

The Aztatlán Culture (A.D.200 to 900 in its initial phases with its greatest development and expansion from A.D. 850/900 to 1350)5 ranged from Tomatlán, Jalisco northward to Sinaloa and occupied the river valleys of the coast. Here they practiced extensive floodplain agriculture.4  They grew and exported various tropical plant products like cacao and cotton and also specialized in various crafts. During their tenure, they became a significant part of the trade route for items from the American Southwest like turquoise that previously had moved along the eastern slope of the Sierra Madre Occidental.

So which of these cultures is most likely responsible for the art at La Pintada? To see what the current thinking is, I emailed Dr. Joseph B. Mountjoy, the archaeologist who has done most of the archaeological research in the Río Tomatlán River Valley and who also done work at various other sites in western Mexico.  In his reply, he pointed out that nobody so far has been able to definitively link the Capacha Culture to rock art.  Also, while there is Aztatlán pottery sherds at La Pintada, they are so few in number that he doubts that the Aztatlán had much of a presence at the location.  This argues against them being the artists.

Conversely, in his own recent work at two locations not far from Puerto Vallarta, Dr. Mountjoy has found petroglyphs in association with contemporaries of the La Pintada phase of occupation.  This suggests that the inhabitants of La Pintada at this time could very well be responsible for the artwork. If so, the La Pintada petroglyphs could be at or around 2,000 years old.

Visiting La Pintada

There is nothing like a visitor’s center at La Pintada.  You will need to park in the pueblo and ask around for a guide.  Be sure to pay your guide.  I think I paid around 200 pesos for the services of mine.

*Phase of occupation refers to the time that a particular culture occupied the Tomatlán River Valley.

References and Sources

1Mountjoy, Joseph. 1987. Antiquity, Interpretation, and Stylistic Evolution of Petroglyphs in West Mexico. American Antiquity 52 (1):161-174.

2Mountjoy, J.B. 1982. An interpretation of the pictographs at La Peña Pintada, Jalisco, Mexico. American Antiquity 47 (1): 119-126.

3Mountjoy, J.B. personal communication, 17 November 2018.

4Beekman, C.S. 2010. Recent research in western Mexican archaeology. Journal of Archaeological Research 18: 41-109.

5Aztatlán, Periodo Clásico. 2017. Retrieved 18 November 2018 from

Mountjoy, Jospeh. 1987. Proyecto Tomatlán de salvamento arqueológico: el arte rupestre. Colección Científica, Arqueología, no. 163, INAH, Mexico.

Chamela-Cuixmala Plant List (Traditional Dicotyledonae) with Photographs

In August of 2017 I began to photograph and identify flowering plants at Cuixmala and the Fundación Ecológica de Cuixmala.  To help with identification, I relied heavily on two area plant lists to narrow down the possibilities. Both of these were produced by the preeminent plant taxonomist for the Chamela-Cuixmala area, Dr. Emily J. Lott.

Initially I used her list found at the Estacion Chamela website ( but later used the more recent and extensive one she published in 2002 in the book Historia Natural de Chamela (HNC).  Nevertheless, in the course of identifying what the HNC list suggested would be about 10% of the species present in the area, I had already found 4 species “new” to the area (Funastrum bilobum, Hibiscus colimensis, Nama jamaicensis, and Solanum angustifolium).

Also, while doing the identifications, it was apparent that there had been numerous taxonomic changes. Many of these were the result of revolutionizing molecular phylogenies published since 2002.

Consequently, I decided to update Lott’s HNC list, at least for the “traditional dichots”.

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Lambs and Wolves, Alcoholic Flux, Animals and Alcohol, Not Everything in the Garden was Rosy, and a Warning from Eubulus

In June of 2015, below the ostentatious facade of Casa Cuixmala and amidst the property’s exotic cast of zebras and impalas, my daughter and I were privileged to witness something truly elegant and special on an otherwise obscure liana (Paullinia fuscescens) growing along one of the trails:


Neoponera ants and the vast majority of paper wasp species are powerful insect predators.[1],[2]  Such seemingly placid interactions between them and their potential prey might initially bring to mind the idyllic scene foretold by the Old Testament prophet Isiah :

The wolf and the lamb shall graze together; the lion shall eat straw like the ox…

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A Crab Spider and its Wasp

Doing a morning walk in Cuixmala on the trail along the Pistia-filled lake near Carretera 200 (across from the fundación), I came across something “floating” in the air in front of me.  Usually this is a caterpillar hanging by one of its silken threads.  As can be seen in these photos, that wasn’t the case here:

Crab spiders (Family Thomisidae) are incredible in taking on larger and seemingly dangerous prey like this paper wasp (Polistes dorsalis) without the assistance of a web.  Instead, they hang out motionlessly and frequently camouflaged at flowers or on leaves with fallen flowers.  Here, they pounce on their prey and hold them with their first two pairs of legs while biting and injecting venom.  Crab spiders are not dangerous to humans but you have to think that their venom is pretty powerful.

What happened here?  While paper wasps don’t collect pollen to feed their offspring, they do occasionally visit flowers to feed on their nectar.  They also search plants for caterpillars and other insects that they feed their offspring.  For whatever reason, this one got too close to a crab spider.

While crab spiders don’t build webs, they still make and use silk.  Normally eating their prey where they catch them, this one shot a line of silk out and left its perch with the wasp in its chelicerae (jaws).  We can’t know exactly why it did this but perhaps a large ant or some other dangerous animal or potential predator got too close.

While the crab spider in the photos is holding the paper wasp by the base of its head, this doesn’t mean that’s where it delivered its deadly bite.  Crab spiders prefer to feed from the head where they inject digestive enzymes and then suck up the slurry.  What they suck up from the head must be very good.  One study of crab spiders feeding on fruit flies showed that they always started at the head and then switched to the abdomen to complete their meal.  If, however, a new fly appeared while a crab spider was feeding from the head of a captured fly, the spider would prefer trying to catch another fly rather than finish its meal at the other end of the captured one.

Anyway, shortly after the last picture the crab spider fell to the ground with its paper wasp where I presume it finished its meal.


Pollard, S.D. Oecologia (1989) 81: 392.