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 PÃ©ter EstÃ³k 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].

EstÃ³k 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, EstÃ³k 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.

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 EstÃ³k 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 EstÃ³k 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.

EstÃ³k, P., ZsebÅk, 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., JÄdrzejewska, B., JÄdrzejewski, W. & Wajrak, A. 2005. Factors affecting carcass use by a guild of scavengers in European temperate woodland. Canadian Journal of Zoology 83, 1590-1601.