Tetrapod Zoology

If you’re a long-time reader of Tet Zoo you’ll be familiar with the remarkable fact that Greater noctules Nyctalus lasiopterus predate on nocturnally migrating passerine birds (this was discussed in a ver 1 article that I’ll update and recycle for ver 2 at some stage). Various predatory microbats around the world predate on small birds, but it was a bit of a surprise to learn that this behaviour occurred in western Europe. Of course, bats don’t have it all their own way: it’s well known that bats are heavily predated upon by raptors and owls. As revealed today by Péter Estók and colleagues in Biology Letters, however, it now seems that hibernating pipistrelle bats have another predator to worry about: the Great tit Parus major. Say what? For those non-Eurasians who may not be familiar with this species, it’s a very widespread and distinctive tit (or titmouse, if you must), easily identifiable thanks to its black head, striking white cheeks and black belly stripe. With a total length of 14 cm and a mass of 13-21 g, it’s one of the largest tits [adjacent photo from wikipedia].

Estók et al. (2009) observed 18 predation events on pipistrelles by tits that occurred over two winters in one Hungarian cave, and they even managed to film the behaviour. The tits’ behaviour was not opportunistic: they specifically searched for hibernating bats, using both auditory and visual cues, and then pulled them out of their roosting cavities and pecked them to death [see gory photo below]. Because bat-hunting has been going on at the cave for more than ten years, Estók et al. (2009) speculate that cultural transmission has occurred (that is, that the birds have learnt this special habit from other individuals). However, when other foods were offered in the same cave, the tits went for that instead and ignored the bats, so it’s possible that bats are a last option when little else is available.

i-2a7c9d3481a86ede69b7ab8248f1b0fc-pipistrelle_killed_by_tit_9-9-2009.jpg

While this is the first study that establishes the Great tit as a part-time bat predator, this is (as usual) not really a ‘new’ discovery. As Estók et al. (2009) note, bats that appear to have been killed by Great tits have been discovered at or around caves before (in Poland and Sweden). Given the remarkable opportunism of this flexible species we should expect it to take advantage of new food sources.

Murderous tendencies!

Though mostly feeding on insects and seeds (in the winter, 90% of the northern European Great tit diet consists of plant material*), the Great tit is fairly powerful and formidable for its size, and can use its bill to break into hazelnuts and acorns. It’s also an accomplished raider of caches created by other passerines (in particular those of the smaller Marsh tit Poecile palustris and Coal tit Periparus ater**; unlike these species, the Great tit does not [in general] hoard food), and it’s even been reported to use tools (conifer needles) to winkle insect larvae out of bark (Gosler 1993). It’s also a part-time scavenger, it’s habit of picking at the bones of hoofed mammals being well known (e.g., Selva et al. 2005). There are even historical records where the birds were seen feeding on the bodies of executed people.

* As is the case with so many ‘European’ birds, the species has a huge range that encompasses much of Asia as well as northern Africa. It inhabits tropical woodland and forest as well as the habitats of the cool north.

** You’ll note that I’m using the new taxonomy for tits. Parus of tradition warrants splitting up (due to deep genetic divergences and a lot of disparity) and is also paraphyletic, given the discovery that Pseudopodoces is deeply nested within it.

Rather less well known is that the Great tit sometimes uses its relatively large size and powerful bill to kill smaller passerines, and indeed Barnes (1975) noted that “A topic of some interest to earlier writers was the alleged murderous tendency of great tits” (p. 112). Barnes described two or three cases where Pied flycatchers Ficedula hypoleuca were “found dead with smashed skulls in nest-boxes taken over by great tits” (p. 112), and also referred to occasions when Great tits had attacked and killed birds that were caught in traps, nets or cages. Caris (1958) reported a case in which an English Great tit was seen flying away with a dead Goldcrest Regulus regulus (one of Europe’s smallest passerines: it may weigh just 5g); it had been killed by a peck to the back of the head, and had had its eyes pecked out and skull mangled. Even better, Howard Saunders (1899) wrote that “The Great Titmouse will attack small and weakly birds, splitting their skulls with its powerful beak in order to get at their brains; and it has even been known to serve a Bat in this manner”. A bat… reported killed by a Great tit in 1899? The behaviour has, therefore, been in the literature for a long time, but being ‘in the literature’ is not the same as ‘has been studied and properly documented’. So, hats off to Estók et al. (2009), this is still pretty amazing stuff [adjacent still from the BBC News site].

One last thing: Ed Yong is a faster worker than I am, and has also produced an article on the same subject. Aww, nuts.. that’s why I should avoid writing about new discoveries.

For other articles on tits and bats see…

Refs – -

Barnes, J. A. G. 1975. The Titmice of the British Isles. David & Charles, Newton Abbot.

Caris, J. L. 1958. Great tit killing and carrying goldcrest. British Birds 51, 355.

Estók, P., Zsebők, S. & Siemers, B. M. 2009. Great tits search for, capture, kill and eat hibernating bats. Biology Letters doi: 10.1098/rsbl.2009.0611

Gosler, A. G. 1993. The Great Tit. Hamlyn, London.

Saunders, H. 1899. An Illustrated Manual of British Birds. Gurney & Jackson, London.

Selva, N., Jędrzejewska, B., Jędrzejewski, W. & Wajrak, A. 2005. Factors affecting carcass use by a guild of scavengers in European temperate woodland. Canadian Journal of Zoology 83, 1590-1601.

Comments

#1 Craig York
September 9, 2009

Brain-eating Tits!? Clearly, the Zombie Tit invasion has
begun.

Interesting and entertaining as always.
#2 NoAstronomer
September 9, 2009

Darn, Craig beat me to it.

BRAAAINSS!
#3 Jerzy
September 9, 2009

A friend bird ringer also saw Great Tits eating brains out of mist-netted Long-tailed Tits.

That is why Tits find it so natural to come to suet feeders. Must associate it with dead people.
#4 lkr
September 9, 2009

Great tits be warned! David Pearce has you on the list for deprogramming, or else. After the lions…
#5 Neil
September 9, 2009

Predatory great tits! I had to check the date on that one! I’ll never look at one the same way again…
#6 Bluey Armstrong
September 9, 2009

I recall a story about Great Tits learning to steal the cream from the milk bottles that had just been introduced to England. They would peck through the aluminum caps. The interesting thing was the speed with which this behaviour spread throughout the Tit population. Does anyone have more details?
#7 Darren Naish
September 9, 2009

Bluey (comment 6): it’s Blue tits, not Great tits, that learnt to exploit milk bottles. They were first reported doing it in about 1921: it rapidly spread (via cultural transmission) and peaked during the 1960s but now seems to have died out, I presume due to the decline of both the milk delivery business and the use of full-fat milk. If you want to know more google ‘blue tit milk bottle’ or such.
#8 John Harshman
September 9, 2009

With a total length of 14 cm and a mass of 13-21 g, it’s one of the largest tits.

Bonus trivia question: what actually is the largest tit? (Hint: a quite close relative of the great tit, though you wouldn’t think so to look at it.)

Must…resist…cheap…tit joke.
#9 John Harshman
September 9, 2009

Sorry. Must remember to read the whole article before posting in future, as you have already supplied the answer.
#10 Darren Naish
September 9, 2009

Yeah, but people should feel free to guess anyway
#11 Raptor Lewis
September 9, 2009

Dr. Naish,

First of all, I must be honest with you *snort*, that the Title made me for some reason think was a post about humans and not a raptor. Haha! Sorry.

The fact that bats are predated for their brains, does seem odd, yet disgusting. If they are going for the nutritional tissues and organs, why not head for the liver? I’m told that the liver is the most nutritional organ in the animalian body. Instead, they’re eating the brains after cracking open the brain case and leaving the carcass to decay! I don’t know about you, but that is the wierdest predator behavior I’ve ever seen. o_O Most predators would attempt to eat the whole thing in a matter of days if it’s a large carcass and just the whole thing if it’s a carcass the size of the bat. I am officially caught off gaurd :/

Thanks for posting!
#12 jck
September 9, 2009

Great Zombie Tits! Epithet du jour.
#13 Jerzy
September 9, 2009

What was with this brain-eating cryptid in Heuvelmans famous book?

Maybe it was a tit, too?
#14 Nathan Myers
September 9, 2009

A new T-shirt design is badly needed.
#15 Darren Naish
September 9, 2009

T-shirt: bring it on. Someone badly needs to do a range of Tet Zoo t-shirts. I’ll provide the art and so on.
#16 Erin
September 9, 2009

Oh this is so going in the New York Times feed. Traffic mongering, what? Not me…
#17 William Miller
September 9, 2009

>>Parus of tradition is paraphyletic, given the discovery >>that Pseudopodoces is deeply nested within it, and >>encompasses a lot of disparity anyway.

Now what causes this to be split into several genera, rather than lumping Pseudopodoces into Parus? If genera don’t represent “real” entities, wouldn’t it be best to do the smallest changes (=fewest binomials changed) necessary to obtain monophyly?

Is it simply the tradition within tetrapod (and maybe vertebrate in general, I don’t know) taxonomy to keep genera small? Surely there’s more disparity in the plant genus Euphorbia than in the entire Paridae…
#18 J.Harshman
September 9, 2009

Actually, the split into several genera substantially predates the Pseudopodoces thing. The impetus was the unexpectedly deep genetic divergence within traditional Parus. I don’t know how it compares to Euphorbia, but it’s greater than within most passerine genera. Though it’s true that keeping Pseudopodoces requires even further splitting of Parus sensu strictu. Just don’t blame it for Poecile, etc.

Gill, F. B., Slikas, B., & Sheldon, F. H. (2005). Phylogeny of titmice (Paridae): II. Species relationships based on sequences of the mitochondrial cytochrome-b gene. Auk 122: 121-143.
#19 Bec
September 10, 2009

I’d buy a Tet Zoo t-shirt.
#20 Allen Hazen
September 10, 2009

A propos of “cultural” transmission of milk-botle-predation, is there a readily accessible source for cultural tradition in small passerines? My department at the University of Melbourne (Australia) moved some years ago to a building with large windows hinged at the top, so opening at the bottom. The first few years, “swallows” (sorry, don’t know actual species) that blundered into the building would fly repeatedly at the glass in an effort to get out, but after a few years I noticed that they were nonchalantly flying to hte window sill, giving a last look around, and jumping out at the bottom of the window: I took this to be an instance of “cultural” change among “sparrows.”
#21 Raymond
September 10, 2009

-Raptor Lewis

Great Tits are overwhelmingly herbivorous; nevetherless
you question is quite fascinating! It may be that Great
tits are using a combination of territorial behavior and
hunger to deal with hibernating bats.

This is interesting in many other ways, it is likely
that passerine and anserine birds and Vesperoid bats will
inherit the Earth.

-Yes, I will buy a Tet Zoo T-shirt….
#22 David Marjanović
September 10, 2009

Is it simply the tradition within tetrapod (and maybe vertebrate in general, I don’t know) taxonomy to keep genera small?

It’s even more restricted: Varanus has up to 70 or so species, Anolis around 400, and the frog genus Eleutherodactylus probably runs in the hundreds, too.

sensu strictu

Sensu stricto.
#23 Dave H
September 10, 2009

“The fact that bats are predated for their brains, does seem odd, yet disgusting. If they are going for the nutritional tissues and organs, why not head for the liver? I’m told that the liver is the most nutritional organ in the animalian body. Instead, they’re eating the brains after cracking open the brain case and leaving the carcass to decay! I don’t know about you, but that is the wierdest predator behavior I’ve ever seen. o_O Most predators would attempt to eat the whole thing in a matter of days if it’s a large carcass and just the whole thing if it’s a carcass the size of the bat. I am officially caught off gaurd :/”

My guess would be that a bird with a short, straight, sharply-pointed bill finds it easier to peck a hole through a rigid-walled container (ie. a bat skull) to reach the contents than to mash its way through skin, connective tissue and muscle to get at the liver. A hooked, raptor-like beak must be better for tearing a hole through flesh. Perhaps if tits continue down this route they’ll evolve one in the future.
#24 Craig York
September 10, 2009

Jerzy-

That sounds like the Nandi Bear-”An African Proteus” as
Heuvelmans termed it, as it seemed to vary greatly in its
description. ( Other than its eating habits. )

Its odd to see ‘cultural’ attached to animal behavior,
especially as the only other instance of brain-eating
I can think of comes from New Guinea…
#25 Dartian
September 10, 2009

Strange that so many readers of a zoology blog are surprised about the brain eating; it’s actually not that uncommon behaviour among predators. My cat quite often ate only the heads of the small rodents it had caught. And in the wild, predators as diverse as weasels, monkeys, and owls may sometimes eat only the head/brain of their prey.
#26 JS Lopes
September 10, 2009

After all this, Batman and Robin should be renamed Batman and Titmouse…
#27 Raymond Minton
September 10, 2009

Some interesting new information, Darren (though for a minute there I thought you may have radically changed your website’s format!)
#28 Jerzy
September 10, 2009

Nandi Bear! Right!

Nandi Bear was a tit, probably Rufous-bellied Tit. This explains why it was not discovered before: people just overlooked little birds or considered them too small to kill sheep. Tits probably gang up in flocks, many tits for one sheep. Strange, but there is a precedent – New Zealand Kea parrot.

And now, thanks to Tet Zoo, another mystery is solved!

(sorry – you provoked it with New Year postcard posted in September and showing a marsupial mole. Now you need at least one more bird-related post, or I will blow up your brain – without pecking!).
#29 Zach Miller
September 10, 2009

Great tits, huh? So why is there a picture of a nuthatch when it should be one of your Page 3 girls? *snicker*
#30 Dartian
September 11, 2009

Ah, at last I’ve been able to read the actual paper itself! Didn’t really want to comment on it before that.

Darren:

While this is the first study that establishes the Great tit as a part-time bat predator, this is (as usual) not really a ‘new’ discovery.

Indeed it isn’t, as Estók et al. point out in the paper. For example, Radzicki et al. (1999) reported evidence of apparent predation on hibernating bats by not only great tits but also by blue tits Cyanistes (a.k.a. Parus) caeruleus. What’s truly novel about Estók et al.’s study is that it’s apparently the first time that the act of predation itself has been properly recorded.

As Estók et al. (2009) note, pipistrelles that appear to have been killed by Great tits have been discovered at or around caves before (in Poland and Sweden)

Actually, in the Polish cases the victims weren’t pipistrelles. Radzicki et al. (1999) found three individual bats of the following species: barbastelle Barbastella barbastellus, brown long-eared bat Plecotus auritus, and Natterer’s bat Myotis nattereri. The barbastelle was dead, while the other two were very badly injured but still alive. All three had wounds on their backs (where hibernating bats have a deposit of brown adipose tissue), and the barbastelle had also had its brain partly eaten. The tits certainly do seem to have a modus operandi.

PS. The bat-eating habits of parids, and the reference to the Radzicki et al. (1999) paper, have been mentioned before here on Tet Zoo.
#31 Christopher Taylor
September 11, 2009

after a few years I noticed that they were nonchalantly flying to hte window sill, giving a last look around, and jumping out at the bottom of the window

House sparrows (Passer domesticus) around the central bus station in Hamilton, New Zealand, have learnt to fly across the light detectors for the automatic doors so that the doors will open and the sparrows can get inside the terminus and forage for dropped food around the cafe. I forget exactly when, but there was a write-up on it in Notornis a couple of years back.
#32 Allen Hazen
September 11, 2009

Christopher Taylor–
“sparrows … have learnt to fly across the light detectors for the automatic doors so that the doors will open and the sparrows can get inside … and forage for dropped food”
—->That sounds disturbingly like “tool use”! Corvids are Passerines, aren’t they? If we get a few more stories about sparrows to go with all the amazing videos of New Caledonian crows, we may begin to suspect the whole order of intelligence!
#33 David Marjanović
September 11, 2009

Corvids are Passerines, aren’t they?

Yep.

we may begin to suspect the whole order of intelligence!

TV sez crocodiles learn from the behavior of their victims.

I think the real question is what a bloated brain like ours is really good for.
#34 Christopher Taylor
September 11, 2009

That sounds disturbingly like “tool use”!

Bringing up the question of how exactly one defines “tool use”, I suppose. After all, there’s no need to assume that the sparrows actually directly connect the doors opening to the little black widget in the corner, as opposed to associating the doors opening with their flying in a particular spot in the air. But is one of these necessarily more complex an association than the other – and to what extent, considering the end result is the same, is the difference really significant?
#35 Nathan Myers
September 11, 2009

Wasn’t it the purpose of the brain, once, to cool the blood?

The only things we haven’t seen non-human brains do are grammar and accurate throwing.
#36 David Marjanović
September 12, 2009

Wasn’t it the purpose of the brain, once, to cool the blood?

Yep, under Aristotle. Doesn’t work well with physics, though; indeed, there are animals with special adaptations (big nasal cavities with a good blood supply) to cool the brain…

Hasn’t some grammar been seen in macaques?
#37 Dartian
September 15, 2009

Hmm. John’s question in comment #8 is still unanswered:

Bonus trivia question: what actually is the largest tit?

According to Harrap & Quinn’s Tits, Nuthatches and Treecreepers (1996), the sultan tit Melanochlora sultanea has a body length of 20.5 cm and a weight of 34-49 g. And according to Madge & Burn’s Crows and Jays (1994)*, Pseudopodoces humilis has a body length of 19 cm and a weight of 42-48 g.

* Written when Pseudopodoces was still thought to be a corvid.

So, while it’s a close call, it seems that the sultan tit may reach a larger maximum size and is thus – still – the largest tit.

How many bonus points was that?
#38 John Harshman
September 15, 2009

I will admit to not having thought about Melanochlora (which does indeed seem to be a tit, though the support isn’t great) when I asked the question. But I’m going to make several attempts to save face if nothing else.

1. Questioning relevance. A one gram difference at the right extreme of a distribution about which we know little, and from two separate sources at that, isn’t a good guide to relative size. And hey, what about the huge difference in the left extreme, and presumably the mean?

2. Dueling sources. Del Hoyo et al., Handbook of the Birds of the World, Volume 12: Picathartes to Tits and Chickadees (2007) repeats your figures for Melanochlora, but gives Pseudopodoces as 42.5-48.5. OK, still a little short, but now only half a gram.

3. Moving goalposts. I meant to say “What’s the smallest tit within the genus formerly known as Parus?” Melanochlora is not ambiguously within traditional Parus.

By the way, that big difference in weight variance intrigues me. My first thought is that Melanochlora must have a bimodal size distribution, i.e. major sexual size dimorphism. But I haven’t found any information on this.
#39 Dartian
September 16, 2009

John:

that big difference in weight variance intrigues me

Actually, the relative difference in weight variance seems to be slightly smaller in the sultan tit (34-49 g) than in the great tit (13-21 g)*.

* As given by Darren in the main post.

There is, of course, always the possibility that such variation in size hints at some undetected taxonomical variation. The sultan tit definitely seems to be relatively understudied, and I wouldn’t be surprised if further research elevated its various disjunct populations/’subspecies’ to full species status. As for the great tit… well, it is sometimes called the ‘best studied bird species in the world’. That seems like cruel taunting when you consider the confusing mess that is the taxonomy of the Parus major superspecies. See, for example,

Eck, S. & Martens, J. 2006. Systematic notes on Asian birds. 49. A preliminary review of the Aegithalidae, Remizidae and Paridae. Zoologische Mededelingen Leiden 80, 1-63.
#40 John Harshman
September 16, 2009

OK, now I’m going to fall back to

4. Small variance in Pseudopodoces suggests a small sample size that doesn’t capture the population size variation well, and that there are unsampled individuals larger than any damn Sultan Tit.

So there. And yes, Melanochlora has several quite well-marked “subspecies” across a wide geographic range. I don’t know anything about their potential promotion to species, or any size differences among them, or (still) anything about the extent of size dimorphism within the species or any of its subspecies. Hey, there’s a research project for some enterprising ornithologist.
#41 Dawid Mazurek
January 10, 2010

Great tits are just great… if you know what I mean