Suppose you’re interested in the anatomy and biology of ground hornbills. Now suppose that you get the chance to make physical contact with one of these awesome birds. Here, at last, is the opportunity to get bitten!! Surely you’ve always wanted to know what it feels like when a ground hornbill bites you. No? Ok, maybe it’s just me. Anyway, the opportunity to get bitten by a ground hornbill presented itself to me a few weeks ago, so who was I to miss out?
As I can now confirm from personal experience, it turns out that ground hornbills don’t bite hard enough to hurt. My impression is that the bird just wasn’t able to exert enough force to, say, crush a large beetle or snail shell, let alone break the bones of a vertebrate prey animal. But, then, that isn’t what these birds do anyway: they grab things with their bill tips, squeeze them, and shake them and/or beat them against objects or surfaces before they go limp enough to be thrown to the throat and swallowed (Burton 1984, Baussart & Bels 2010).
I find this interesting because a criticism that’s been levelled (informally) at the ‘terrestrial stalker’ models as goes azhdarchid pterosaurs (Witton & Naish 2008) is that they lack evidence for a strong bite (and that strong bite, so it’s been inferred, is required, so it’s been suggested, for the terrestrial stalking hypothesis to work). Well, so far as I can tell, ground hornbills – the best extant analogues for azhdarchids, according to Witton & Naish (2008) – don’t really have a strong bite either. Incidentally, one more thought on that Witton & Naish (2008) while I’m here. The metrics associated with the paper show that it’s been viewed more than 16600 times, and the pdf itself has been downloaded more than 1700 times [graph below, generated by PLoS ONE metrics, shows steady and apparently continuous increase in viewings of our article. Interesting]. The following occurred to me recently: does this mean that it can perhaps be regarded as the most-read pterosaur article of all time? I don’t know, but it’s certainly possible. Anyway…
This is, of course, all just a bit of fun (and it all started out as an excuse to use the photos you see here): it doesn’t really tell us anything about the bite strength of ground hornbills, or about the strengths and limitations of hornbill jaws or skulls in general. After all, we don’t know that the bird was biting especially hard (it might, for all we know, have been being gentle with me), and we don’t know how much pressure needs to be exerted on my fingers before that amount of pressure is actually “a lot” (whatever that is). And maybe human fingers (or my fingers in particular) are poor at gauging pressure – I certainly seem to be poor at gauging everything else. So, maybe the bite of that hornbill was, actually, really strong.
Want to compare my idiosyncratic and potentially grossly inaccurate whimsical musings with some hard science? Well, tough. So far as I can tell, there’s no empirical published work of any sort on hornbill bite strength. Indeed, there’s little on birds in general: a couple of studies have been published on finches (van der Meij 2004, van der Meij & Bout 2004, 2006) and Degrange et al. (2010) recently reported data from seriemas and eagles, and published an estimate for the large phorusrhacid Andalgalornis [one of their figures is shown here: see their paper for the full story]. Robust-billed finches like the Hawfinch Coccothraustes coccothraustes bite at somewhere between 310 and 700 N (this was previously discussed in the article Coccothraustes: most bizarre of finches), seriemas and eagles bite at about 50 N, and the suggested bite force for Andalgalornis is 133 N. This is low for a predator of its size (c. 40 kg): mammals with that sort of bite force include otters, jaguarundis and grey foxes. But, then, I wouldn’t much like to be bitten hard by an otter or jaguarundi. British wildlife TV presenter Terry Nutkins lost two of his fingers to a pet otter he once kept.
I’ve now been bitten (sometimes by design, sometimes not) by a reasonable variety of birds, the majority of which are of course too small and too weak-jawed to hurt the human they’re biting. Owl bites don’t hurt (as discussed recently, their power is in their feet), but I’m not sure about falcons, hawks or eagles (please do say if you have direct experience). But even really big birds – waterfowl and ratites, for example – have weak bites for their size: ratites in particular have flimsy skulls and small jaw muscles, and power-biting just isn’t something that you need to do when you make a living from picking at shoots and seeds and grabbing insects. Swans and geese (I’ve now been bitten by many) can’t really hurt by biting alone, but some of them have a nasty habit of ‘chattering’ their jaws on your fingers. I don’t know why. A Chinese swan-goose Anser cygnoides did this to me and broke through the skin, causing tiny, pin-prick like marks in my skin thanks to the serrated edges on its rhamphothecae [the adjacent photos show Mute swan Cygnus olor, Greater rhea Rhea americana, Greylag Anser anser, and my hand].
It’s a different ballgame when we start thinking about parrots, and let’s just say that I don’t much want to get bitten by one. A cockatoo did once bite right through my jacket purely for its own entertainment, and a Kea Nestor notabilis bit through my camera strap because I was stupid enough to let it. Then again, having a scar caused by parrot bite might be pretty cool. A lot of people who do hands-on work with animals have neat wounds: I always like that scene in Jaws where Hooper and Quint are comparing their healed shark injuries. Well, that’s just like real life.
For previous articles on bird feeding behaviour, biting and such, see…
- Coccothraustes: most bizarre of finches
- Terrestrial stalking azhdarchids, the paper
- At the 56th SVPCA – hello Dublin! (discusses feeding behaviour in waterbirds)
- B. rex!
- When tapirs don’t attack, and when Meller’s duck does
- Condors and vultures: their postures, their ‘bald heads’ and their sheer ecological importance
Refs – -
Baussart, S. & Bels, V. 2010. Tropical hornbills (Aceros cassidix, Aceros undulatus, and Buceros hydrocorax) use ballistic transport to feed with their large beaks. Journal of Experimental Zoology Part A: Ecological Genetics and Physiology 313A, 72-83.
Burton, P. J. K. 1984. Anatomy and evolution of the feeding apparatus in the avian orders Coraciiformes and Piciformes. Bulletin of the British Museum of Natural History (Zoology) 47, 331-443.
Degrange, F. J., Tambussi, C. P., Moreno, K., Witmer, L. M. & Wroe, S. 2010. Mechanical analysis of feeding behavior in the extinct “terror bird” Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE 5 (8): e11856. doi:10.1371/journal.pone.0011856
van der Meij, M. A. 2004. A tough nut to crack: adaptations to seed cracking in finches. Unpublished thesis, Leiden University.
van der Meij, M., & Bout, R. G. (2004). Scaling of jaw muscle size and maximal bite force in finches Journal of Experimental Biology, 207 (16), 2745-2753 DOI: 10.1242/jeb.01091
- . & Bout, R. G. 2006. Seed husking time and maximal bite forces in finches. The Journal of Experimental Biology 209, 3329-3335.