Things have been rather quiet here at Ibycter lately, with less in the way of Weekend Expedition posts and no Cheapskate Tuesday posts for a while. The reason for this is that Catherine and I are getting ready to make a trip to Honduras to do a preliminary conservation study on Red-throated Caracaras.
If you remember from back in June, the Honduran Conservation Coalition found and monitored a nest site in the Olancho Department, and they believe there is still a sizable population of caracaras nearby. I have wanted to work on Red-throated Caracara conservation biology for a long time, as no formal study has been done on the conservation of these birds in Central America. They are in steep decline across the region, and have disappeared from Mexico and Guatemala.
I was invited by Mark Bonta to come and do some research on these birds, and so, because I had funding from the National Birds of Prey Trust to do conservation research, I informed them of a change in venue to the heart of the region where caracaras are declining. We have since secured some more funds from the Zoo Conservation Outreach Group, as well as a private donor, and so we will be going to implement the start of the project.
This project will see us engaging the local volunteers and researchers to help us determine home range sizes and habitat occupancy of caracaras in the forests near Gualaco. We will do radio tracking of birds from various caracara groups in the area, and will hopefully be able to get a preliminary estimate of home range size. We will also do call-playback surveys of the forests in order to determine the numbers of groups occupying the area. A third objective is to make further documentation of nesting behavior and food habits of the caracaras, as this is relatively unknown for the region.
Anyway, we ship off Monday, and will arrive in Tegucigalpa on Tuesday. After that we will be guided around the region and introduced to the stakeholders and collaborators. This is my very first field research conducted outside the bounds of a research camp, so making sure that everything is in order is a bit stressful.
We hope, however to continue to blog both here, at Catherine’s SpiderBytes blog and also at the ESC blog about all the cool stuff we encounter and the process of doing exploratory field research.
If you happen to be in Vancouver this coming Sunday, please consider dropping by for my talk at UBC’s Beaty Biodiversity Museum.
The talk is at 1 pm at the Museum’s lecture hall. The talk is geared to a general audience, and will be filled with cool videos from our recent paper, as well as other unpublished stuff about territoriality and social behaviour.
Here is the blurb:
Red-throated Caracaras are way cool because…They are the wasp-murdering superheroes of the rainforest! Not many animals like to attack and eat social wasps because the stings of these insects are usually an effective defense. The Red-throated Caracara manages to overcome this defense daily, bringing 9 to 15 wasp nests per day to its chicks, and somehow avoiding a painful death from wasp stings. Sean McCann, PhD student at Simon Fraser University and his team investigated the nesting, territorial, and wasp predation behaviour of these wasp specialists over five years to get a better picture of the fascinating life history of these amazing birds.
Red-throated Caracaras are specialist predators of the brood of social paper wasps, as our previous research confirmed. The big question we wanted to answer was: how do they manage to attack and subdue the workers of these well-defended wasp nests? A previous study by Jean-Marc Thiollay suggested that Red-throated Caracaras may possess a chemical repellent that keeps the wasps from approaching and attacking them, but this hypothesis was never tested.
We sought to shed more light on this by sampling chemicals from the birds and by observing the predation behavior firsthand.
To do this, we set up a “feeding station” to record the caracaras attacking wasps. We lured the caracaras near to the video arena by playing recordings of their vocalizations from an amplifier near the site. The birds would come to investigate the source of the calls, and once they saw the wasp nests we had set out there, the caracaras went in for the kill, and we captured the behaviour on video.
This is the video arena we set up in the forest behind the camp. Maintaining the condition of the “waterproof” video cables and connectors was very difficult in the rainy season!
These are the five species of paper wasps we managed to get the caracaras to attack.
The caracaras did not seem to have significant problems with the smaller wasp species Polybia bistriata, Polybia scrobalis or Polybia affinis. None of these seemed to attack the caracaras at all. But check out the following video of an attack on a larger Polybia jurinei nest:
The caracaras knocked two of these nests to the ground, and later flew down to retrieve them. In another attack on a nest of Polybia jurinei, the caracaras repeatedly slammed into the nest, and eventually the wasps abandoned their defense. These situations where the wasps abandon their nest represent a behaviour known as absconding. The swarm-founding wasps, with sufficient nest disturbance, can fly off en masse to quickly found a new nest elsewhere. They lose that batch of brood, but save the workers from an ultimately futile defense of the nest.
My suspicion is that larger nests than these would put up much more of a fight. Unfortunately, we never got to record attacks on some of the truly huge nests that can occur in the tropics. We did record the aftermath of one such attack on Polybia dimidiata:
The video data do tell us that the type of chemical defense envisioned by Thiollay does not seem to be how the caracaras avoid wasp stings, but we did look for potential chemical repellents anyway.
Sampling from a caracara face using solvent-soaked cotton swabs. We also sampled the feathers and feet, using both methanol and hexane.
We anticipated that any potential chemical repellents would be detectable by the antennae of sympatric wasps, so we brought nests of Polybia bistriata back to the lab to test the caracara extract for compounds perceptible to wasps using coupled gas chromatography/electroantennography (GC/EAD)
As you can see from this example GC/EAD recording, Polybia bistriata antennae respond to several components of the caracara foot extract (the top trace shows the chemicals, the bottom shows the antenna’s response). Compound A is sulcatone, while the compounds labelled B are iridodial isomers, and compound C is a boring old fatty acid (which is found on most animals). Iridodial and sulcatone are repellent compounds, but best known from dolichoderine ants, such as Azteca.
We suspected that the caracaras may have picked up these compounds from Azteca ants. To follow up, we sampled Azteca chartifex near the field station at Saut Pararé and compared their pygidial gland secretions with the caracara foot extracts using GC/MS.
At the top is the GC/MS trace of the Azteca sample, at the bottom is the trace from the caracara feet. Notice the shared ketones and the iridodial isomers. We found these ant-type compounds only on the feet, suggesting that the caracaras are attacked by Azteca while perching.
And this is why we suspect caracaras come into contact with Azteca! Polybia rejecta nests in close association with Azteca, which protect the wasp nests from army ants. It could well be that the caracaras are attacked by Azteca while preying on these wasps. It is also possible that the caracaras are just incidentally attacked while perching on Azteca-infested trees. Photo provided by Pablo Servigne.
In summary, the caracaras do not have much difficulty with smaller species such as P. bistriata; just tearing into the nest is sufficient to cause these wasps to abscond. With larger species, the caracaras have to use more persuasive tactics, such as knocking the nest to the ground or striking it repeatedly. While it does not seem the caracaras have chemical repellents, the discovery of the ant-derived defensive chemicals highlights the surprisingly intricate connections between organisms in the rainforest.
I just came by this footage via twitter this morning, and it looks like it was put out by the Fundación Rapaces de Costa Rica, and was shot by Chris Jimenez. It shows some absolutely gorgeous footage of a caracara chick, so evidently they found a nest! Be sure I will try to track down more information about this footage and the story behind it! In the meantime, enjoy, as the chick footage is very lovely!
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?
Photos from the Honduran Conservation Coalition website.
I received an email last night from Mark Bonta, a researcher with the Honduran Conservation Coalition, alerting me to some big news from Honduras! A nest of the Red-throated Caracara was found by Isidro Zuniga, a researcher with the coalition in the pine forests of Olancho province. This is a sparsely-populated region of dense forests and rugged mountains which is filled with a multitude of fascinating plants, animals and habitats. You can read the press release from this morning here.
This is big news for raptor biology in general, as it is only the fifth Ibycter americanus nest found by researchers in the world, and the very first from Central America! Not only that, but on a personal note, it means that there are actually other researchers taking up study of my very favourite bird. The Red-throated Caracara was only recently re-discovered in Honduras, by Narish and Jenner in 2004*, also from Olancho. This could mean that there is a stable population of this species in these pine forests, and gives some hope for its continued persistence. For too long this species been neglected by science, despite its fascinating biology, and the fact that it has been nearly extirpated from much of Central America. Now, with sightings in Nicaragua, and this recent discovery in Honduras, I think there is cause for hope for research into the conservation issues for these birds.
In fact, in the press release, the Honduran Conservation Coalition, in partnership with the Peregrine Fund and others state that this is the start of a concerted research effort. The preliminary information is a but a teaser of things to come, and when these data become available they will add greatly to the known biology of the species.
So far, we know that Mr. Zuniga spent six weeks observing the nest, recording prey deliveries and nestling care. The nest was in a pine tree, although from the video it is unclear whether the nest is constructed by the birds or is just a platform on a broken tree (the two nests we have found in French Guiana used a bromeliad as a nesting platform, with no nest material brought by the adults). Only a single chick was being reared, which accords well with our findings in French Guiana.
The nests we found in French Guiana were in large epiphytic bromeliads, which are in short supply in the pine forests of Olancho. What could they be nesting on?
There is also some video of the nest, with footage of adults and the young bird.
I am really excited by these findings, and I eagerly look forward to learning more. How many adults brought prey? What was the nest made of? What kinds of wasps were they preying on? What types of fruits, if any would they find in the pine forests?
All these questions will no doubt be answered in time, and as always, I will be eager to learn more about this awesome bird!
*Narish AJ., Jenner T (2004) Notes on the Red-throated Caracara, Ibycter americanus in Honduras. Cotinga 22: 100.
Remember those photos of the Red-throated Caracaras in Nicaragua from last week? Here is the video of one of the birds, making alarm calls and holding a piece of a Polybia brood comb. This video comes from Pablo Elizondo, director of the Costa Rica Bird Observatories, who was with Mandred Bienert when they encountered the birds. I strongly suspect this bird is engaged in brood care, as the tail feathers are extremely worn, as if it is spending considerable time in a nest.
For all those interested, please come out to my talk today at the Science Rendezvous event at SFU today: 12:10 PM in AQ3005 at the Burnaby Campus. I will be discussing the foraging adaptations of this remarkable specialist predator of social wasps, with many exciting videos and pictures.
This photo of of a Red-throated Caracara was taken by Manfred Bienert on April 18 near the village of Bijagua, which is just adjacent to of the Reserva Biológica Indio Maíz and close to the Costa Rican border. It shows one individual of a group of six perched high in a tree with a piece of wasp nest (Polybia spp.).
This photo is important documentation of the continued presence of Ibycter americanus in Nicaragua, where they are considered extremely rare, having declined across most of Central America over the past several decades.
Despite the status of the Red-throated Caracara across much of this region, there are no formal conservation plans for these birds as they are not in danger of going globally extinct. In this way, the statistics used by the International Union for Conservation of Nature (IUCN) can be misleading on a regional scale, as when a species is labelled “Least Concern” it misses out the fact that the bird may be disappearing in many countries.
Another caracara in the same group. Photo by Manfred-Bienert
In Mexico, Red-throated Caracaras have been considered extirpated for some time, although it was previously present in Oaxaca, Chiapas [1], and Veracruz [2]. They are listed as critically endangered in the Republic of Costa Rica [3], and “probably extirpated” in Guatemala [4,5]. In Honduras, the species has only recently been rediscovered after being largely extirpated since 1955 [6]. In Panama, they are considered vulnerable.
Factors responsible for these declines have not been identified, although habitat destruction is probably involved. Illegal shooting of birds could also be a factor, as they are likely to have a very slow rate of reproduction and a highly developed cooperative breeding system (we documented a group of 6-7 adults caring for a single chick) [7].
I am glad to see that these impressive wasp-loving birds have not completely disappeared from Nicaragua, and am grateful for people like Manfred Bienert for documenting the wonderful birds of the region.
References
1. Iñigo-Elías E (2000) Caracara comecacao (Daptrius americanus). In: Ceballos G, Márquez-Valdelamar L, editors. Las aves de México en peligro de extinción. Instituto de Ecología, UNAM–CONABIO–Fondo de Cultura Económica. pp. 126–127.
2. Lowery GH, Dalquest WW (1951) Birds from the State of Veracruz, Mexico. University of Kansas Publications, Museum of Natural History. Lawrence, Kansas: University of Kansas Publications. p. 556.
3. AOCR (Comité Científico de la Asociación Ornitológico de Costa Rica) (2005) Lista de Especies de Aves con Poblaciones Reducidas y en Peligro de Extincion para Costa Rica: 1–2.
5. Dickerman RW (2007) Birds of the Southern Pacific Lowlands of Guatemala With a Review of Icterus gularis.
6. Narish AJ., Jenner T (2004) Notes on the Red-throated Caracara, Ibycter americanus in Honduras. Cotinga 22: 100.
7. McCann S, Moeri O, Jones T, Donnell SO, Gries G, et al. (2010) Nesting and Nest-Provisioning of the Red-throated Caracara (Ibycter americanus) in Central French Guiana. Journal of Raptor Research 44: 236–240. Available: http://dx.doi.org/10.3356/JRR-09-75.1.
Red-throated Caracaras (Ibycter americanus) are impressive birds that are brightly coloured, extremely loud, and travel around the forest in gangs. They seem to act as if they own the forest, and alarm call vigorously whenever they see you or any other potential threat. I have seen them chase away Harpy Eagles (as have others!), as well as Toucans.
Sounds like a badass bird! If you do a Google Scholar search for “Red-throated Caracaras and Predation“, you might find some surprising things. In the primatological literature, they are listed in several papers (1-2) as being predators of Saguinus mystax, the Moustached Tamarin, a small monkey. This is quite odd, as to my knowledge there is only a single account of Ibycter americanus taking vertebrate prey: Anolis and Ameiva lizards found in the stomach of a single bird shot in Mexico (3).
Certainly, other caracara species, such as the similar, but more distantly related Black Caracara (Daptrius ater) do prey on vertebrates. The Black Caracara has been reliably reported preying on fish (4) and juvenile caciques (5).
Saguinus mystax. From Wikimedia Commons, User:Postdlf
But the Red-throated Caracara is a different species, with different habits, and is not well-known to take vertebrate prey.
So where does this idea come from?
All the references that I could find about predation on tamarins by Red-throated Caracaras come from a thesis (6) by a researcher named Maria Marleni Ramirez entitled “Feeding Ecology and Demography of the MoustachedTamarin Saguinus mystax in Northeastern Peru”, published in 1989 at the City University of New York. The exact passage about this predation incident appears on page 87 (Daptrius americanus is a former name for the Red-throated Caracara that is no longer used):
“Raptors flying overhead invariably elicited strong alarm responses from the tamarins. Moustached tamarins gave several alarm calls per day that were apparently directed towards birds, thus suggesting that they may be important predators of tamarins. The tamarins’ reaction to attacks by raptors was very strong, as indicated by the loudness and duration of the calls. Daptrius americanus was observed to attack and barely miss a juvenile S. mystax. The moustached tamarins reacted by giving very loud screeches at the same time the Daptrius was diving towards the juvenile.”
Now to be fair, I have been attacked by Red-throated Caracaras (see video), but I never have inferred from this that these birds were trying to prey on me (Although one did strike my ear while I was climbing their nest tree). Or perhaps I didn’t take it personally!
The following video was taken by Tanya Jones in 2009, and shows a group of Red-throated Caracaras diving at me as I climbed their nest tree. I am located right behind the bromeliad; part of my foot is visible below.
And that is the danger of inferring predation by witnessing one antagonistic encounter between two species, with no video records or stomach contents. Because in my book, predation involves killing and eating the prey, and this was not observed here. In fact, my research, as well as one other study, show that the predominant food items consist of wasp larvae and fruits (7,8), with not a single vertebrate among them. I would not say that Dr. Ramirez’ observation constitutes predation.
’cause doesn’t this look better than a monkey?
What I interpret this situation to have been is a mobbing attack on monkeys by caracaras defending a nest site, or merely defending their territory from occasional nest predators. I have seen caracaras chasing Toucans in a similar fashion. I have no doubt that the caracaras could kill, and possibly eat a tamarin (They have an average mass of around 500 g, or roughly the size of a small caracara), but surely some stomach contents would have showed up to indicate such an event. Other than the account of lizards in the one shot in Veracruz, I can find no such records.
Thus I think that it is definitely premature to list the caracara as one of the “known predators of Saguinus mystax”. Instead, I would probably put the two species in a long list of “animals in the jungle that don’t like each other very much” and leave it at that.
There is still much we do not know about this charismatic bird, or indeed about the trophic relations of rainforest animals in general, but hasty generalizations from a single observation are unlikely to improve matters.
Ramirez, M.M., 1989. Feeding ecology and demography of the Moustached Tamarin (Sanguinus mystax) in Northeastern Peru. PhD Thesis. City University of New York. pp. 87-88 (email me for a copy of the relevant pages)
