Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

Raptor vs raptor


Photo by John Sykes, provided by Jon McGowan, used with permission.

Here's something you don't see everyday: a female Northern (or Eurasian) sparrowhawk Accipiter nisus and male Common kestrel Falco tinnunculus, photographed together after (it seems) the hawk grabbed the kestrel as a potential prey item. The photo was taken by John Sykes in the Wick Fields area near Christchurch, Dorset, UK, and has been featured by Jon McGowan at The Natural Stuff. Whatever was going on, both birds flew off unharmed. Female sparrowhawks (larger than males) frequently prey on relatively large birds, including pigeons and magpies, and they're not afraid to take on birds similar in size to themselves. When subduing such large prey, they grip and squeeze it with the talons, but they also start to dismember it (yes, while it's still alive) with the bill (Fowler et al. 2009). In this case, it's possible that the sparrowhawk made a mistake, and grabbed the kestrel thinking that it was a more easily dispatched potential prey item.

Photo © 2011 Rick Remington. Be sure to check out the whole sequence.

Or perhaps this was a bold, or experienced, sparrowhawk who thought, or even knew, that she could take on a kestrel and win. After all, remember that intraguild predation - predators killing predators - is common and ubiquitous across the natural world. There are many, many cases on record of raptors killing and eating members of other raptor species. Sparrowhawks are already documented kestrel predators, as are peregrines, goshawks, buzzards and hen harriers. Peregrines F. peregrinus have been observed killing short-toed eagles, sparrowhawks and other raptor species (Hammond & Pearson 1993). This article is not about owls, and I'm going off at a slight tangent here, but I just have to mention the incredible series of photos, taken by Rick Remington in Chicago, where a peregrine repeatedly swooped at a grounded, and clearly terrified, Snowy owl Bubo scandiacus. Some of the poses adopted by the owl were so remarkable that they've fooled people into thinking that they were looking at a person in an owl costume. You can see all the photos for yourself here.

Oh, and - one more thing. Unless you're a bird phylogeny nerd, you're probably imagining that the two species shown above are fairly close relatives. Several recent molecular studies indicate that falcons are not, in fact, close to other raptors (hawks, eagles, Old World vultures, New World vultures and secretarybirds). Rather, they belong in a clade with parrots and passerines (Ericson et al. 2006, Hackett et al. 2008, Suh et al. 2011), now called Eufalconimorphae. The morphological similarity present between falcons and the members of the hawk-eagle-vulture-secretarybird clade (now best termed Accipitriformes) is thus (presumably!) a striking case of convergence*, but it helps explain some of the otherwise weird features exhibited by falcons and not seen in those other raptors. Within Eufalconimorphae, parrots and passerines form Psittacopasserae.

* The possibility does exist that a 'raptor-like ecomorph' was primitive for the clade that includes Eufalconimorphae and kin, and Accipitriformes and kin.

Neornithine bird phylogeny recovered by Suh et al. (2011). (Falcons + (parrots + passerines)) = Eufalconimorphae.

Seriemas seem to be close relatives of Eufalconimorphae (Ericson et al. 2006, Hackett et al. 2008, Suh et al. 2011). You might like to think what this means for phorusrhacids.

Oh, and can everybody please stop using the word 'raptor' as a popular term for deinonychosaur, or dromaeosaurid? Admittedly, this rarely causes confusion, but it looks dumb and naive given that THE WORD RAPTOR IS ALREADY IN USE FOR ANOTHER GROUP OF ANIMALS. It would be like deciding to call sauropods 'elephants' or something.

Anyway, we're here because I wanted to show you the photo that you've just seen at the very top of the article; it's pretty exceptional and I hope you're pleased to see it. For previous Tet Zoo articles on raptors, see...

And for articles on owls, see...

Refs - -

Ericson, P., Anderson, C., Britton, T., Elzanowski, A., Johansson, U., Kallersjo, M., Ohlson, J., Parsons, T., Zuccon, D., & Mayr, G. (2006). Diversification of Neoaves: integration of molecular sequence data and fossils Biology Letters, 2 (4), 543-547 DOI: 10.1098/rsbl.2006.0523

Fowler, D. W., Freedman, E. A. & Scannella, J. B. 2009. Predatory functional morphology in raptors: interdigital variation in talon size is related to prey restraint and immobilisation technique. PLoS ONE 4(11): e7999. doi:10.1371/journal.pone.0007999

Hackett, S. J., Kimball, R. T., Reddy, S., Bowie, R. C. K., Braun, E. L., Braun, M. J., Cjojnowski, J. L., Cox, W. A., Han, K.-L., Harshman, J., Huddleston, C. J., Marks, B., Miglia, K. J., Moore, W. S., Sheldon, F. H., Steadman, D. W., Witt, C. C. & Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320, 1763-1768.

Hammond, N. & Pearson, B. 1993. Birds of Prey. Hamlyn, London.

Suh, A., Paus, M., Kiefmann, M., Churakov, G., Franke, F. A., Brosius, J., Kriegs, J. O. & Schmitz, J. 2011. Mesozoic retroposons reveal parrots as the closest living relatives of passerine birds. Nature Communications Aug 23;2:443. doi: 10.1038/ncomms1448.

The views expressed are those of the author and are not necessarily those of Scientific American.

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