Philosophical Transactions of the Royal Society Special issue on brood parasitism is now out

Together with Steven Portugal (Royal Holloway University of London), Ros Gloag (University of Sydney), and Claire Spottiswoode (University of Cape Town / University of Cambridge), we now have a special issue on brood parasitism published in Philosophical Transactions of the Royal Society B.

Our goal was to bring together (i) research that was using new approaches to answer long-standing questions or challenge assumptions (hyperlinks lead to example papers from the issue), and to (ii) include studies on brood parasites from across the animal kingdom. Although widespread in animals from insects, fish, and birds, papers on brood parasitism rarely cite each other across these taxonomic boundaries, as we show in our Introduction article (also find a pdf here). We then included (iii) reviews and opinion articles that presented new ideas and ways of thinking about brood parasitism. In this way, we hoped that the special issue would be like reciprocal co-evolution: new approaches sparking new ideas, that should generate further novel advances.

It was an interesting journey from conception of the issue idea through to final publication, with many of the deadlines coming over the Christmas “break”. But, it was an excellent way to catch up with some of the exciting advances and ideas, and some new examples of brood parasitism that I was less familiar with. Cuckoo fungus!

Our first "informed bird" has fledged!

At the end of November, Victoria Franks passed her viva with examiners Joah Madden (Exeter) and Bill Sutherland (Cambridge). We’re very proud of our first “fledgling”! Here Vix describes her main findings:

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My PhD at the University of Cambridge (supervised by Rose Thorogood, and John Ewen from ZSL) investigated how early-life social experiences affect foraging behaviour in naïve juvenile songbirds. I addressed this topic in wild hihi (Notiomystis cincta), a threatened New Zealand passerine - juveniles form groups after fledging which could be important for their learning and survival, but conservation efforts focus on moving individuals (not groups) to seed new populations.

The very talented Vix Franks, adding the finishing touches to her PhD thesis

I first explored how juveniles learn about food in comparison to adults, what social experiences they encounter early in life, and how these experiences influence their foraging decisions. My results showed that fledgling hihi learned about novel foraging opportunities (i.e. feeding stations) from their parents (available from BioRxiv), but did not learn as efficiently as more experienced adults when they were independent (see the published results). However, juvenile hihi formed ‘gangs’ during early independence which might provide new sources of social information from peers and other adults (BioRxiv). My experiments showed that social information from the gang allowed juvenile hihi to update their foraging behaviour, rather than maintaining behaviours learned earlier with parents (BioRxiv). As a consequence, group members conformed to the collective behaviour of peers in the same time and place as themselves, even when they moved among gangs (BioRxiv). Together my findings demonstrate that juvenile social experiences have implications for learning and can help young animals overcome the challenges of naïvety during early life.

How does this knowledge affect conservation management? A major tool for hihi is to seed new populations with reintroductions of juveniles, but these translocations of individuals disrupt both the physical and social environment. My results suggested that there is potential for downstream consequences on foraging and survival. During a planned translocation, I used social network analysis to explore whether juveniles maintained group associations once reintroduced, and considered the impacts of removal of group members on the birds left behind at the source site. While group identities largely remained intact for birds that were not moved, juveniles moved to a new site formed new social bonds. Most importantly in terms of their conservation, individuals that lost more associates were less likely to survive the first few months post-release (BioRxiv). Our plan is to explore this relationship further and investigate whether we can mitigate this cost of social disruption for improved conservation outcomes.

The Great Hihi Sperm Race is on!

One of our main study species is the Hihi, a threatened passerine bird from New Zealand.  

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Hihi are extremely conservation reliant. They need supplementary feeding, nest boxes and other forms of intensive management at most sites and this makes them an expensive bird to protect.  Yet they are a "canary" of New Zealand forest health - hihi need healthy complex forests to survive, and research by our group (led by Caitlin Andrews) is showing that healthy forests also need hihi (via pollination of threatened plants).  Hihi have complex social relationships and we are also demonstrating that the social environment of hihi is an intricate part of their ability to find new food sources (led by Victoria Franks).  Meanwhile, breeding success is critical for hihi populations, but research has shown that many males are "firing blanks", leaving eggs infertile.

To help raise money for on-the-ground conservation, a collaborator from the New Zealand Hihi Recovery Group (Dr Helen Taylor, University of Otago, New Zealand) has therefore set up The Great Hihi Sperm Race.  Visit www.hihispermrace.co.nz, click on your favourite male, and place a (bet)donation.  Meanwhile, Helen and her team will be analysing hihi sperm samples with the help of a mobile sperm lab, a microscope and a video camera to find which male's sperm swims the fastest! 

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Hihi sperm x400 Image Credit Helen Taylor

It’s a light-hearted way of raising awareness and much needed conservation funding for a beautiful yellow and black bird that was widespread throughout the North Island until humans arrived, bringing mammals such as rats, destroying hihi habitats, and reducing numbers down to just one population by the 1880s.

Hihi numbers are higher now, thanks to conservation efforts, but there are still only seven populations in the whole country. It’s not known how many individuals there are, and the future of the sugar-loving bird is still threatened thanks to its reliance on complex mature forest habitats, few of which exist in New Zealand at this point.

Please help us raise money and better protect hihi for the future - Betting is open until midnight on Sunday 22nd April NZ time.

Gentleman hihi, start your...er...engines!

For more information, contact: Helen Taylor, Department of Anatomy, University of Otago, New Zealand.

Older and wiser? What we now know about age & learning in hihi

Young animals face many challenges when they become independent from their parents. One problem is they need to find food, but have little experience to help them. Even human teenagers can struggle when there’s no one else around to do the shopping, and for wild animals, making the best foraging decisions is even more crucial for their survival. Victoria Franks is investigating how juvenile birds overcome this challenge during her PhD.

Foraging in young hihi is particularly important to think about. While we provide 6 of the 7 hihi populations with supplementary sugar water for conservation management, not much is known about how they learn to find food. Understanding if juveniles are poorer trial-and-error learners could help inform how we provide food, or explain why young hihi seem to be more social than adults (perhaps they need to use a “wisdom of the crowd” strategy). In her recent paper published in Behavioural Processes, Victoria set out to ask: how do hihi learn about food sources, and do adults and juveniles learn differently?

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A male hihi trying out the feeder task. He figures out that white marks the correct hole and receives a sugar water reward. Photo credit: Victoria Franks.

Over a couple of weeks in May 2015, Victoria gave hihi at Zealandia Eco-Sanctuary (Wellington, New Zealand) a small feeding challenge. When they entered their normal feeding station, they now encountered a feeder with three access holes, but only one contained food. This hole was marked white, while the other two holes were marked black: we predicted that hihi would learn through trial and error which hole provided food. After a few days Victoria changed the position of the food hole with the white marker and recorded which holes hihi now tried. This meant we could detect how many mistakes adults and juveniles made: did they follow the white marker (the “right” hole), or did they go back to the old location (now a “wrong” hole)?

Finally, Victoria changed the task again, but now switched the marker of the food hole from white to black. Now white no longer marked food, and it was fascinating to watch the birds figure out what they needed to do after each switch.

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The feeder task was presented in three different ways - letters denote the holes with capitals indicating which provided food. In Stages 1 & 2 the white circle marked a food reward, but the location changed, whereas in Stage 3 the location remained the same but the colour changed. The figure is taken from the paper.  

We found juveniles continued visiting more non-food holes than adults, although both age groups did learn about which hole meant food. Adults seemed to pay better attention to both colour and location to help them find food, whereas juveniles used location only. This meant adults generally re-located the food more quickly than juveniles. Ultimately, juveniles had to spend longer in the feeder station to get the same amount of food as adults.

What strategies could juveniles use to help them avoid the risk of wasting time and energy when foraging? Victoria's next step is to determine if being social helps: perhaps they can use the experience of others to help their own learning. This “social learning” can help animals avoid mistakes they make when learning alone, but it also comes with its own downsides if everyone copies a wrong decision. Time will tell if young hihi have a solution…

Thank you to everyone at Zealandia who helped us with this study. If you’d like to read more, the paper is freely available.

Franks, V. R., & Thorogood, R. (2017). Older and wiser? Age differences in foraging and learning by an endangered passerine. Behavioural processes.

Two papers in one week: how birds learn (and why it matters!)

Week 51 turned out to be a big week for our group: two papers out to finish the year! 

The first paper from Victoria Franks' PhD was accepted by Behavioural Processes: "Older and wiser? Age differences in foraging and learning by an endangered passerine." This was the culmination of hard work in the field and behind a computer, to understand what and how hihi juveniles learn.  The study forms an important part of Vix's thesis because it reminds us that adults and juveniles do not necessarily learn about food in the same way - and it dispels any rumours that hihi can't learn! 

A male hihi learns to associate the while circle with a food reward. From Franks & Thorogood Behavioural Processes 2017.

Secondly, we had a big paper come out from our work on the co-evolutionary consequences of  social interactions among predators in Nature Ecology & Evolution: "Social transmission of avoidance among predators facilitates the spread of novel prey".  This was the experiment that started our core research project, but it needed some nice modelling by Hanna Kokko to finish it off.  There's more in a "Behind the Paper" blog post on Nature Ecology & Evolution Community, and Science News produced a fantastic video about it:

Finally, Liisa Hamalainen and her assistant Marianne Teichmann have now finished a gruelling set of experiments in Konnevesi continuing this research project.  The take home message: Blue tits never do what you expect them to! 

Work with us! 4 yr PhD and 3 yr Postdoc opportunities available.

We are recruiting for a 4-year PhD position, and a 3-year Postdoc to be based at the University of Helsinki, Finland.  Both positions will be part of a project investigating the role of the social environment in facilitating the evolution of host defences against brood parasites.  We will conduct field work in Finland to manipulate personal and social information, and use genomic approaches to investigate responses to parasitism and range expansion.    

Interested? Apply! For more information and application details: Phd position,  Postdoc.

Moominsummer Madness

Summer is short in Finland, but in the first year since the group moved to Helsinki we made the most of it.  Sadly, it's now getting darker and time to say good bye to our great interns that joined us: Marie Froehly (Université de Strasbourg, FR) and Feli Pamatat (University of Bielefeld, DE). 

Marie helped out Vix and Caitlin with a heroic effort of video-watching, spending two weeks in Cambridge and two more in Helsinki.  During the recent translocation, we filmed hihi in the aviaries to gain a greater understanding of social interactions and individual variation in foraging during captivity.  Marie watched many hours of videos to collect the data and began making headway into the analysis - picking up R skills along the way. 

Feli started the summer with three weeks in Oulu, Finland, conducting an experiment with Robert Thomson (University of Cape Town, SA) and Jere Tolvanen (University of Oulu) to investigate defences of alternative cuckoo hosts. She then finished this up with two months in Helsinki to watch provisioning videos and to learn how to analyse growth data.  Feli finished up her visit by giving an entertaining presentation about avoiding a ticking (cuckoo egg) time bomb.

Please contact us if you'd like to join as an intern in the future.

Informed Birds at Behaviour 2017

Behaviour is a great conference - it encompasses the full breadth of Tinbergen's Four Questions. This means that we can learn new things about mechanisms from people with a stronger background in animal psychology, and mix with new developments in our understanding of the evolutionary function of animal behaviour.  

All of our Informed Birds presented this year at Behaviour 2017.  If you missed us, here's a summary:

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Victoria Franks - do hihi juveniles conform TO Local foraging traditions?

1. Young naïve animals can learn socially about food, but we don’t know who they pay attention to: for example, parents or peers?
2. My study species is the hihi, a passerine. Young hihi spend two weeks with parents after fledging, so could learn about food from them.
3. Young hihi also form groups once independent from parents, so could learn about food when socialising with peers.
4. I asked: do juveniles learn from parents, do they keep this behaviour once independent or do they change how they forage with peers?
5. First, at nests hihi parents and fledglings learned about a two-option feeder (food/no-food), one-option feeder (food), or stayed naïve.
6. Fledglings only used feeders if their parents did, and copied their parents’ learned preference for the food option.
7. When juveniles left parents and formed two groups, I used two-option feeders (food/food) to test if nest experiences affected foraging.
8. Hihi didn’t keep their parents’ preference, but those from nests with feeders did use group feeders earlier than naïve peers.
9. To begin there was no bias in option use. As time went by one was used more, but this was the opposite option in the two groups!
10. If hihi moved groups, they changed their behaviour to the new groups’ preferred option, especially when it was being used by more hihi.
11. To sum up: young animals can learn about food with parents, but once independent they change foraging behaviour to match local peers.

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Liisa Hämäläinen - if predators feel toxic, do they pay more attention to social information about food?

1. To avoid aposematic prey, predators need to learn to associate their signal with unpalatability – how do they gather this information?
2. Predators can sample prey themselves or use social information from others.
3. Social information use can lower the cost of prey warning colouration because fewer prey need to be killed to educate predators.
4. Questions: 1) Does a predator's toxin load affect information use? 2) How do educated predators use social information?
5. Wild great tits shown social information using video playback in temporary captivity, then birds forage in ‘novel world’ that contains 2 types of artificial prey: 1) palatable and cryptic, 2) unpalatable and conspicuous.
6. We manipulated birds’ toxin load (high/low) before providing social information of unpalatable prey (info/control).
7. Birds that received social information saw a demonstrator eating unpalatable prey and showing a clear disgust response; controls saw prey only.
8. We predicted birds with an increased toxin load should be more likely to use social information and attack fewer unpalatable prey.
9. But, toxin load did not affect foraging choices; regardless of toxin load, socially educated birds attacked fewer unpalatable prey.
10. Next we investigated if birds reversed their learned avoidance faster after receiving social information of same prey being palatable.
11. In nature educated predators could get conflicting social information if they observed another individual consuming a Bayesian mimic.
12. We predicted that educated birds would attack more previously unpalatable prey after seeing a demonstrator eating it happily.
13. We found that individuals were reluctant to reverse their learned aversion, regardless of social information.
14. Summary: birds use social information about prey defences regardless of their toxin load and are reluctant to switch learned preferences.
15. Social information use by predators can reduce predation on novel aposematic prey but is unlikely to affect mimic-model dynamics.

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Caitlin Andrews - how do dietary specialisations change in a novel environment? 

Click here to see a close-up of Caitlin's poster

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Rose Thorogood - Social transmission helps explain the evolution of warning coloration 

1. Many animals learn to avoid food by observing bad experiences of others, but what does this mean for prey?
2. With Johanna Mappes, we asked (1)Does social information reduce the cost of conspicuousness?
3. Use video playback to manipulate social information before wild great tits must forage in a "novel world" for tasty, but cryptic, or conspicuous but unpalatable food.
4. Social information from another predator's disgust reduces predation risk for the unpalatable prey.
5. Next, Hanna Kokko used model to address: Can this effect facilitate the evolution of aposematism?
6. Social transmission means fewer prey must be killed for predator population to learn, effect is even stronger if predators and prey can move.
7. Now we ask, What are the consequences of social transmission across prey communities? (see Liisa's talk above).
8. And, how can this work across a predator-prey community? (with Hannah Rowland).
9. Blue tits are ecologically similar to great tits, but don't use social information as much.
10. Pay attention to video playback, and make quicker decisions, although the decision itself is not different from random (Hämäläinen et al. PeerJ 2017).
11. What's next? testing social transmission of avoidance in the wild using network-based diffusion.

Can video playback provide social information for foraging blue tits? Yes, but do they use it?

Two weeks ago marked a big moment for the Informed Birds research group - my first PhD paper (and Rose’s first paper as a PhD supervisor!) was published:

‘Can video playback provide social information for foraging blue tits?’

L. Hämäläinen, H.M. Rowland, J. Mappes, R. Thorogood. PeerJ 5, e3062 (2017).

I conducted this experiment last winter at the Sub-Department of Animal Behaviour in Cambridge using 25 blue tits from Madingley Woods (all birds were returned to the woods after 4 days). My aim was to investigate how blue tits use social information about food palatability, and I studied this using video playback of a foraging demonstrator.

A blue tit (Cyanistes caeruleus) watching video playback (L. Hämäläinen)

Video playback should be a good tool for studying information use – all birds can receive a “standard” amount of information – but video playback had not been used with blue tits before. Therefore, we first tested if blue tits would pay attention to birds on a screen.

We found that blue tits clearly paid attention to the demonstrator bird: they hopped on their perch more when a bird was on the screen versus when there was only a feeding cup. We also found that birds behaved differently, depending on what the demonstrator was eating – observers paid more attention if the demonstrator ate a bitter-tasting mealworm! We don’t know if this was because the demonstrator was more active when eating a bitter prey item (like many birds, blue tits wipe their beaks and shake their heads vigorously), or because this aversive response provided more “useful” information for observers.

Hm, which cup? Social information about cup colour and potential food items did not lead to copying, but birds did make decisions faster. (L. Hämäläinen)

The second part of my experiment tested if a demonstrator’s behaviour affected the observer’s food choices. The idea was that blue tits that observe another find and eat a bitter worm should avoid foraging from the same coloured cup – in other words, observers should associate cupc colour with the risk of finding unpalatable prey. On the other hand, watching a demonstrator find a palatable worm should result in observers foraging from the same coloured cup.

Contrary to our prediction, we found that the observers did not seem to use social information in their foraging decisions. Instead, from a choice of two cups 50% of birds chose the same cup as the demonstrator (regardless of its contents). This suggested that the blue tits’ foraging choices were completely random, but we decided to look at the results more closely to try and understand why.

In fact, watching a demonstrator did affect their foraging! Birds that matched our predictions (i.e. avoided the cup after a demonstrator found an unpalatable worm, or chose the same cup after witnessing a demonstrator find a palatable worm) made their cup-choice much more quickly than individuals who did not.  This suggests that birds that appeared to choose at random may actually have been influenced by social information – but we’re not (yet) able to explain how this happened. Any ideas?

In summary, our results suggest that video playback can provide social cues to blue tits and it therefore provides a promising method for studying social learning in parid tits. However, we still do not know how these cues are later used in decision-making and this will be the challenge for the next chapters of my PhD!

Hihi translocation in progress

In 2005, we reached a milestone with hihi on Tiritiri Matangi Island with the first translocation of birds to seed a new population (Zealandia, in Wellington).  Thirteen years (and many translocations) later, Vix and Caitlin are now experiencing their first hihi translocation.  

The translocation in 2005 was also an experiment: the hihi recovery group tried something new - most of the birds moved were juveniles.  Tiri was producing lots of young each year, but it was suspected that there were not many opportunities for them to recruit to the breeding population.

Since the first Tiri translocation, we've been looking more closely at juvenile behaviour.  First, Kate Richardson's research with hihi moved to Maungatautari suggested that dispersal and choice of breeding location might be influenced by broad-scale familiarity among birds. Now, Vix's PhD research is showing us that juvenile hihi spend lots of time together, and some individuals have stronger social bonds than others.  How will translocation alter these bonds? Will moving "friends" together make it easier for them to adapt to their new location after translocation? How will they respond to the changes in resources? And, what happens to the birds left behind on Tiritiri?  This translocation to Rotokare - the first to investigate the role of social behaviour in this context - should give us some answers.  But, given what we know about hihi already, it's sure to also throw up lots of surprises!  Stay tuned...

How to prep an aviary for #hihitranslocation. Should start catching birds in morning! @docgovtnz @ZSLScience @DOCTSAmbassador pic.twitter.com/fWq4Uyssvo

— Dr John Ewen (@hihinews) 26 March 2017

Happy hihi settling and tucking in to their "cafeterias" on the #hihitranslocation. They're spoiled for choice! @hihinews @informedbirds pic.twitter.com/IYcKG1ncj9

— Vix Franks (@VixFranks) 28 March 2017