A large nest of Polybia liliacea. This is one you probably do not want to disturb!
Compared to my time in French Guiana, I found that travel by river offers a much greater volume of observations than walking in the forest. When I was in French Guiana travelling trails on foot, I was lucky to encounter one example of a particular habitat in a day, but on the boat I could see the same type of habitat many times over. Needless to say, this was a great natural history lesson in the making.
One of the particular habitats we saw a lot of was the meanders of the river, where the river loops and bends around long curves. These bends form spontaneously via the action of vortices along curves in the river, and on the inside of each curve there is high deposition of silt (on the outside is a high level of erosion). This is the process by which oxbow lakes are formed. The result is that the inside curve is an area that was formerly river-scoured, but now has abundant new soil. Within these areas are a sparser forest, dominated by a few fast-growing tree species such as Cecropia and Triplaris (called “Long John” in Guiana). These are habitats that harbor a beautiful example of tropical symbiosis.
Yellow-rumped Caciques (Cacicus cela) bathing together in the early evening. These are highly social birds with colonial nesting.
One of the first things that I noticed about these meander forests is that they more often than not contained a large colony of nesting Icterid birds, either Green Oropendolas, or Red-rumped or Yellow-rumped Caciques, with the latter being the most common. All of these birds are known to preferentially nest in association with large, aggressive wasp species, such as Polybia rejecta and Polybia liliacea. This is thought to benefit the birds in two ways. Number one is that the wasps can help dissuade nest predators, such as monkeys. Number two is that populations of predaceous wasps may reduce the parasite burden (particularly parasitic Philornis flies) that the nestlings endure.
A colony of Cacicus cela nesting in association with Polybia liliacea. We also saw them with Polybia rejecta and Epipona spp. wasps.
In turn, the wasps nest in these particular trees for a reason. They nest in trees that are occupied by Azteca ants, a type of dolichoderine ant that basically owns the tree, with large carton nests containing perhaps millions of moderately small workers and hundreds of queens. The wasps nest here because the Azteca repel one of the wasps’ worst enemies: army ants. Although army ants (Eciton burchellii and Eciton hamatum) vastly outweigh the Azteca individually, the Azteca, by virtue of their overwhelming numbers, can keep army ant columns from advancing quickly up the tree (Servigne 2003). As army ants are all about blitzkrieg, and quickly stripping an area of profitable prey (Kaspari et al. 2011), they have learned to avoid the Azteca trees, which would take a protracted guerilla campaign to overcome. It has been recently shown that the wasps in turn benefit the ants, helping to repel some of their predators, such as woodpeckers (Le Guen et al. 2015)!
Nesting association between Azteca (left), Polybia (centre) and Cacicus (upper right).
In examining again and again the morphology and placement of the nests in these associations, I was struck by a thought: perhaps the birds are also a net benefit to the wasps and the ants as well! I know from my research how formidable Red-throated Caracaras are in destroying wasp nests….What if these large numbers of nesting caciques help protect the wasps from the caracaras? It is not so outlandish a hypothesis, as the large nesting aggregations of caciques have been shown to mob bird nest predators such as monkeys and Black Caracaras and drive them away (Robinson 1985). Perhaps the Red-throated Caracaras may be driven away as well by large numbers of defensive caciques.
Could wasps derive protection from Red-throated Caracaras from cacique or oropendola colonies?
I was amazed by the numbers of large wasp nests we encountered at these sites, in stark contrast to the relatively low numbers I encounter in normal forests. It is not just the presence of ants which is keeping these nests safe, as Azteca occur in large numbers all over the forests. I think something else is going on here to help protect these wasp nests, and I bet it is the birds. Anyway, I would love to go and study this sometime, but this story just reinforces to me the inspiration that I only get by going to the field.
The Black Caracara, a known predator of cacique nests, is sometimes mobbed and driven away by Yellow-rumped Caciques.
SERVIGNE, P. 2003. L’association entre la fourmi Azteca chartifex Forel (Formicidae, Dolichoderinae) et la guepe Polybia rejecta (Fab.) (Vespidae, Polistinae) en Guyane Française. Universite Paris-Nord.
This is another account of a bird preying on wasp nests, one that was completely unexpected. This involved the Black-throated Antshrike, Frederickena viridis. Black-throated Antshrikes are members of the Thamnophilidae, or antbirds, a largely Neotropical family known for being associates of army ants. Basically, these birds “attend” army ant raids and parasitize the ant colony by quickly grabbing the insects, lizards and arachnids that flee the approaching ant swarm.
Eciton burchellii army ants. These impressive swarm raiding ants kick up quite a lot of prey from the leaf litter, which antshrikes are only too happy to steal.
During fieldwork in 2010, we caught a male Black-throated Antshrike is doing its own dirty work, striking wasp nests, causing the wasps to abscond, and feeding on the brood. Here is the video (edited for time, as the whole attack sequence lasted 42 min):
A: Polybia scrobalis B: Polybia bistriata
The two wasp species in question were Polybia scrobalis and Polybia bistriata, which we had placed in a video arena for our experiments documenting Red-throated Caracara feeding behaviour. In some ways, you could say that the antshrike was parasitizing us! This was all recorded as intended by our automated video system, which reacts to motion in the video stream and records the action with a 5-s pre-recording buffer. On that morning, my field assistant Tanya Jones and I were just getting up and having breakfast when this antshrike was attacking. By the time we were done breakfast, the antshrike was too!
A few things to note: Unlike their behaviour with the Red-throated Caracaras, this Polybia scrobalis colony fought back. At 0:30, 1:22 and 1:45 in the video, you can see wasps attacking the antshrike, and in the second two instances, the antshrike plucking off the wasps.
Wasp on antshrike at ~30s
Wasp on antshrike at 1:22
Wasp on antshrike at 1:45
For comparison, here is an attack on the same wasp species by Red-throated Caracaras:
So why do the wasps attack the antshrike and not the caracaras? Can these wasps can evaluate the threat posed to the colony and adjust their defence/retreat appropriately? Maybe the wasps somehow evaluate the odds of successfully driving away a predator and abscond if nest defence is likely to be hopeless. After all, the workers which are killed in nest defence are still a loss. Continued defence piles up the losses, and if defeat is inevitable, it is better to retreat with your worker force intact.
Alternatively, it could be that the colony the caracaras attacked was worse off in some way, and more likely to abscond, but the possibility remains that wasp defensive behaviour against vertebrates is plastic. There is definitely room for some exciting research here.
Considering the White Woodpecker, the Black-throated Antshrike, and the Red-throated Caracara (among others) it seems that more and more vertebrate predators are being found that prey on wasp nests. In these cases, it appears that the birds are minimizing the risk of stinging by inducing the absconding response of their swarm-founding prey before moving in close to feed on the larvae.
While I was a little upset that these nests fell to the antshrike rather than giving me more data on caracara predation, getting a paper out of it and learning something new was well worth it.
Melanerpes candidus approaching the nest of social paper wasps. Photo by Miguel Rangel Jr. used under terms of a CC-BY-SA licence.
In the latest issue of Revista Brasileira de Ornithologia, I found a paper on a topic near and dear to my heart: birds preying on wasp nests. In this case, it is an account of the White Woodpecker, Melanerpes candidus preying on the nests of Polybia paulista. In this paper, Ivan Sazima describes the predation tactics used by this woodpecker when attacking a large, well-defended nest. Ivan conducted this research at Parque Ecológico Prof. Hermógenes de Freitas Leitão, in the state of São Paulo, Brazil.
Like the Red-throated Caracaras I studied, the White Woodpecker appears to exploit the absconding response of these swarm-founding wasps in order to secure its meal of wasp brood. Rather than inflicting rapid, catastrophic damage, however, the woodpecker takes its time, approaching the nest gradually and tapping the branch to which the nest is attached. During this approach, some of the wasps come out to sting, and if this gets too fierce, the woodpecker will retreat. Sazima attempted this tactic himself with a similar nest of P. paulista, and got stung severely for his efforts. Sazima suspects that the continuous nature of the woodpecker’s disturbance is what is required to induce the wasps to abandon their nest. Also, the agility of the birds at evading attacking wasps also means they can keep this harassment up longer than an unprotected human.
This paper is a valuable contribution to the study of wasp and bird behaviour, as it highlights that certain anti-predator strategies of social wasps (stinging, alarm recruitment) can be defeated by exploiting the evacuation swarming (absconding) behaviour of these wasps. Bearing this in mind, it is no wonder that so many species of swarm founding wasps have cryptic nests to escape the detection of diurnal vertebrate predators.
I especially love one of the concluding sentences:
The foraging behaviour of the White Woodpecker reported herein results from so-called anecdotic, natural history oriented observations, often disregarded by theory-trained biologists. Nevertheless, this kind of observation draws attention to phenomena that later may prove more widespread or commoner that previously thought.
I could not agree more. Please head over to read the paper yourself, as the photos of the behaviour are great, and the text well worth the read.
Here are a series of images I shot during the course of a summer day in Vancouver. All are hymenopterans, which, in addition to being tasty, are of course the best insects out there.
A nest I uncovered of Myrmica specioides, a recent introduction on the West Coast.
A big Megachilid.
Myrmica rubra against the sky (bribed with a bit of honey).
I have always wanted to get a shot of one of these chrysidid beauties. I believe it is Pseudomalus auratus.
A gorgeous Philanthus beewolf, showing just how much they really do love flowers.
A queen and workers of Myrmica rubra, the European Fire Ant.
Myrmica rubra tending aphids, a few of which appear to be mummies.
Ammophila wasps at sunset, shot with the 300 mm lens.
In addition to the bundles of sleeping bees I found at Iona Beach on Saturday, I also encountered some Ammophila wasps. Their name means “Sand Lover” and they are major predators of caterpillars in sandy habitats. They sting their prey precisely to paralyze it, then bury them in dungeons under the sand for their larvae to eat. The wasps I was shooting were resting on various vegetation, especially stiffer dead flowerheads. The rain made for some beautiful texture and reflections.
Most sleeping Hymenoptera I find seem to have a preference for dead vegetation. Perhaps this is less attractive to other animals and makes for a disturbance-free night? In addition, the dead twigs and flowers are often stiffer and don’t blow around as much.
In sleeping mode, these wasps grasp tightly with their mandibles. If you disturb them, they quickly re-grasp the substrate rather than waking and moving.
Here is one on a living plant. I like the way the droplets highlight the smooth abdomen.
It can be a wet business sleeping in the rain. I suppose while they are sleeping they must shut down their grooming responses.
Here is another Sphecid, not Ammophila, but perhaps Isodontia?
Tomorrow I will thrill you with some more sleeping hymenopterans…I have saved the best of them for last!
Photo copyright Phillipe Gaucher, 2008. The fruit sitting near the chick is from the tree itself.
Determining the diet of birds is difficult undertaking. Because predation is so difficult to observe in the field, a relatively unbiased way to gather data on food habits is to place a camera in the nest to record the types of food brought to chicks. In my literature search on Red-throated Caracaras, I had come upon several references of gut content examination from shot specimens [1], as well as some field observations by J.M. Thiollay [2] and Whittaker [3], but little in the way of quantifiable data on the diet of caracaras. Because my research project was on the adaptations of a specialist predator of social wasps, we needed to first determine whether Ibycter americanus was in fact a specialist!
There are lots of delicious wasps in the jungle, like these Apoica albimacula, but are the caracaras eating them?
In 2008, my field assistant Onour Moeri and I were extremely fortunate to discover a nest of Red-throated Caracaras not far from the Inselberg Camp of the Nouragues Station in Central French Guiana. They appeared to be nesting in a large bromeliad, 45 m up a Chrysophyllum lucentifoliumtree. These big trees in the Sapotaceae produce a large hard fruit, that despite its copius latex, is a favourite food of spider monkeys (Ateles paniscus).
There were certainly lots of spiders coming to the tree every few days, raining down discarded fruits from high above. We evacuated the area as soon as they reached the tree, as the hard, heavy fruits were travelling very quickly when they hit the ground!
This find was a great breakthrough for us, as we now had a reliable focal point to find the birds and observe their behavior. We were extremely excited, because this was only the third nest ever observed by scientists, and as such was an amazing opportunity to gather data on the habits of the birds. We spent the first few weeks on the ground below the nest tree, watching with binoculars as adult birds arrived with food. We observed them bringing wasp nests and fruit, arriving roughly every half hour. This was not the most fun thing to do, as sitting still in the jungle looking up all day is actually kind of difficult, especially when it rains. The data we were getting was spotty and probably quite biased…Not good!
The nest bromeliad!
We also found another nest in 2009, in another bromeliad 40 m up a different tree. We have good reason to suspect it was made by the very same group. I am not showing any footage of this, due to its low quality! We got good data from it however.
Luckily, going above and beyond the call of duty, Philippe Gaucher (the technical director at Nouragues, and a good friend) was kind enough to track down some video recording equipment in Cayenne and bring it back for us to set up a nest camera. On Feb 2 he climbed the nest tree to install it. The nest contained a single caracara chick, which we later sexed as a female, via a genetic analysis from a plucked feather. The still pictures Philippe took up there were the very first (that I know of) ever taken of a Red-throated Caracara chick. Evidently, these caracaras had not constructed the nest at all, but rather had torn the bromeliad leaves to make a platform to lay an egg on. Like many insects and frogs, the Red-throated Caracaras are bromeliad breeders!
The photos also showed evidence of predation on both wasps and millipedes! We were extremely excited to have this equipment installed, and that very night we started getting video from the nest.
Philippe climbing the nest tree to install the camera.
Each evening, I would go down to the nest after dark (there were a lot of tarantulas I became quite familiar with) and lug the DVR and usually the 20 kg battery back up the hill. Then every morning before dawn, I would take the recharged battery down and replace the DVR for that day’s recordings. The setup involved a large plastic box, to shield the DVR from rain, plus a tarp to do more of the same thing. With the DVR running in the box, there was little danger of water damage (it was the rainy season), but to leave it there at night without power was out of the question. Unpowered electronic devices (that are not making heat) often succumb to the near 100% humidity of the rainforest.
The DVR in place under the tree. The tarp protects from falling fruit and rain, and the DVR stayed cosy in the Tupperware!
The camera in place over the bromeliad, about 1 m above the nest. Photo by Philippe Gaucher.
After a couple days of recording, we quickly discovered that the “waterproof” camera was less than watertight; our lens had fogged up with internal condensation. A whole day of wasted recording! Phillipe had flown back to Cayenne, so there was nothing for it but to go up the tree myself and fix the camera. I had trained in tree climbing back when I was an environmental activist, so I knew what to do, but still, this was a 45 m straight climb up to a spiky bromeliad, with possibly murderous birds protecting their nest.
The climb was exciting, though relatively uneventful, and I retrieved the camera and dried it out. Then, after jamming a silica gel dessicant pack into the housing, I carefully wrapped every threaded connection with Teflon tape. With the camera returned to the nest, we continued filming.
A Polybia nest brought via an overhead branch.
In total, we managed to get about 100 hours of recording done over 10 days. During that time, we recorded 186 items being brought to the chick, most of which were the nests of social wasps, but also fruits, millipedes and a single snail. Back in the lab, I watched these hours of footage, timing the arrivals and departures, the types of prey, and other aspects of the footage. I organized all of this in a database, which is the best way of storing large amounts of data and retrieving it in a format for analyses.
The chick receives a delivery of an Angiopolybia or Pseudopolybia nest. Notice how packed the brood comb is with larvae and pupae.
Breakdown of the diet over 2 years. Most of the items (and definitely most of the biomass) were the brood-filled nests of social wasps.
A large spirostreptid millipede is brought to the chick.
The large spirostreptid millipedes were brought intact, and were decapitated by the adults, after which they generally tried to feed bits to the chick. Usually, the chick ate very little or perhaps none of this material. These large millipedes are well-defended with a lot of noxious benzoquinones, which are toxic, irritating and carcinogenic compounds. My suspicion is that these are in some way related to chemical defense against ectoparasites, as some birds as well as capuchin monkeys are reported to anoint themselves with the millipedes’ secretions [4].
Onour with a millipede on a stick!
The nasty, nasty secretion from these docile animals. It burns the skin, and seems to stain it purple. Oh yeah, and then your skin smells of millipedes.
Though we had no birds marked, on a few occasions we saw more than two adults bringing prey to the chick, confirming Thiollay [2] and Whittaker’s [3] observations of cooperative breeding . In 2009 we captured and colour-banded four adults and were able to determine that as many as 6 and most likely 7 birds bringing prey to a single chick [5]! This is highly unusual in raptors, and another reason I love these caracaras so much. What kind of remarkable social system is this? Which individuals get to breed? Are all the helpers young from previous years (delayed dispersal) or are there joiners from other groups? We still do not know the answers to these questions, but I hope to find out in the future.
Two adults deliver fruit, while a third remains in the nest with the chick.
Watching the videorecordings of nesting behaviour has been one of the highlights of my career so far. Seeing this drama unfold for the very first time was so exciting; no one had observed this species ever before, and my job was to describe it to the world. What a treat! And to watch closely at all the magical moments in a young bird’s life was just priceless. Check out this caracara chick observing an insect flying overhead. The interest she shows in this event is so cool to see, and you get the notion that she is learning lessons every waking moment that will help her out when she is out foraging for herself.
This young caracara is a truly professional entomologist!
By March 17, we had no more time left in the field, and no one to continue the camera work. We had to take down the setup and get packed up to return to Canada. When I went up the tree to retrieve the camera, it was bittersweet, as we had succeeded in getting great data from our first field season, but our lovely caracara chick would grow up and fledge without us being there to see it. In just a few weeks of observation, she had already stolen our hearts.
Of course, I brought my camera up to take a farewell portrait.
Farewell, little caracara chick! Best of luck, and thanks for all the data! By the way, what is that on your beak?
Wasps are a big part of outdoor life this time of year in Coastal BC. It seems we have more than our fair share of scavenging workers pestering us at barbecues and picnics. The long dry summer was ideal for nest success and thus we have a large population approaching the end of their colony cycles. But which insects are responsible? It turns out only three of the common wasps we see are much of a nuisance outdoors, and all belong to the genus Vespula. Below are some short summaries of what they look like and what the differences are.
GenusVespula: ground or structure nesting, large colony sizes, often scavenge in late season at outdoor cooking or dining areas. They differ from a related genus Dolichovespula by having the mandible closer to the eye than the latter.
Nest entrance typical of Vespula wasps. They will also nest in cavities and structures
Western Yellowjacket: Vespula pensylvanica: native species, builds nests underground, has a “complete yellow eye ring” (see photo)
Common Yellowjacket: Vespula alascensis: somewhat smaller than the Western, this species has an interrupted yellow band behind the eye. This individual is gathering paper fibre for nest-building.
German Yellowjacket (Vespula germanica): This also does not have a complete band around the eye, but it does not have the interruption in the yellow band behind the eye. Often black spots are visible on the abdomen.
Dolochovespula: We have two common species in BC, the Common Aerial Yellowjacket, Dolichovespula arenaria and the Bald-faced Hornet Dolichovespula maculata. Unlike the Vespula, these hang their nests from branches and projections, and so they are often visible. They do not scavenge, except for sugar sources (you may see them on fruits or flowers).
Bald-faced Hornet nectaring.
This is a nest of Bald-faced Hornets. Aerial yellowjacket nests are similar, hanging from branches or obstructions.
Common aerial yellowjackets on their nest. The upper one is the queen, the lower one a worker.
“Paper wasps” subfamily Polistinae
Two genera are found in BC; Polistes and Mischocyttarus. They are superficially similar, but Mischocyttarus has an elongate “petiole” joining the abdomen to the thorax. Their nests are open, meaning they are without an envelope, and are often found under overhangs. They are not very aggressive.
The European Paper Wasp: Polistes dominula. This species is overall yellow and black, with yellow or orange antennae.
Polistes aurifer. This species is larger, darker, and much less common than it used to be, perhaps due to competition from Polistes dominula.
Mishchocyttarus flavitarsus. This odd paper wasp is a member of a genus that is mostly found in the tropical and subtropical parts of the Americas. This is one that makes it as far as Canada.
Summary: There is quite a diversity of social wasps in BC, many of which will not be found in cities at all. They are important players in ecosysyems, as predators, scavengers, and possibly pollinators. Avoiding conflict with them is easy, provided they don’t nest near your entrances or walkways, as stinging typically occurs during nest defense. If you wear long sleeved white or light coloured clothing with close fitting cuffs, the chance of an accidental sting are minimized. Some stings can be life-threatening to some people, so if you work with groups of people, familiarize yourself with the symptoms and treatment of anaphylaxis, and always have an Epipen and phone ready.
Nest destruction should be contemplated if the nest is going to bring people or pets very close to the nest entrance, as the number of stings from a defensive colony at close range can be severe. Over-the counter wasp killers work well for simple to access nests, but more difficult to reach nests inside structures may require the pros.
I simply leave nests be if they are out of the way and not likely to pose a threat.
If you find a nest and would like to help us out in the lab, we would love to collect some or all of the wasps! You can emal Sebastian Ibarra at [email protected] or call us at the lab at 778-782-5939.
Sebastian collecting Western Yellowjackets by the water.
Social wasps have many dramatic and painful ways of saying” don’t mess with us”, but some animals just don’t take the hint. Red throated Caracaras are one of these foolish/awesome creatures. If you are in Victoria BC this Wednesday, come out to my talk for the Victoria Natural History Society’s Birder’s night to find out more about loud birds messing with painful wasps. 7:30 pm, March 27, Fraser Building room 159.
Official blurb:
Like the Old World Honey Buzzards, the Red-throated Caracara is a specialist predator of social wasps. Because social wasps are well defended with stings and are avoided by many birds, we were interested in determining how caracaras deal with the defensive wasps. Using video traps to observe caracara predation on social wasps we found that they use several behavioural strategies to avoid wasp defences. Separate work using nest cameras found that up to 7 adult birds were involved in the feeding of a single chick, possibly making the species one of the most social of the Falconidae. Join Sean McCann as he talks about his 5 years of research in the South American rainforest on the unique foraging biology of this species. We meet at 7:30pm in room 159 of the Fraser building. Everyone is welcome. Bring a friend and a coffee mug.
