Zoo Atlanta will close early on Sat., May 25 for Brew at the Zoo. Gates will close at 1:30 p.m. and grounds will close at 3 p.m. 

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Avian weaponry

Down in the Lower Zoo lives a fascinating little bird, the masked lapwing (Vanellus miles). These Australia natives are members of the family Charadriidae, a group that includes plovers and other shorebirds. The long, slender legs of these birds make them look like they’re wearing stilts, an adaptation to wading in shallow water looking for prey. Watch as they run nimbly from place to place, almost as if tiptoeing. The other thing you’ll notice upon first observing these birds is the ornate yellow face mask extending from the corner of the eye up to the forehead and down to the base of the beak. Whereas decorative features in birds are often made from feathers, the mask in this species is actually made from a thick fold of skin, a feature that develops as chicks age to adults.

One thing you may not spot on first glance is that these birds have a secret weapon: wing spurs. The spurs are located on the carpus (wrist) and are kept tucked into the feathers when not in flight. The spur comes from a bony process on one of the metacarpal bones. This process is often beneath the skin in many bird species, but in lapwings the bone sits externally and is covered in a hard layer of keratin (the same stuff found in your fingernails). What is this feature for, you might ask? These spurs are used like tiny clubs! Lapwings will beat their wings with spurs out to fend off predators, guard their nests, and compete with other members of the same species during the breeding season. In the closely-related gray-headed lapwing (Vanellus cinereus), spur length has been shown to be sexually dimorphic (different between the sexes) and longer in males, and thus useful in distinguishing males from females (Wakisaka, 2006).

Is it unusual for birds to have this kind of armament? As it turns out, not really. Similar weaponry can be found in other members of the plover family, waterfowl, and the pigeon family, among others. Some have sharp, knifelike spurs used for cutting, while others have modifications like clubs used for bludgeoning. Different parts of the wing may have been modified into weapons, ranging from the radius, the radial carpal bone, to the metacarpal bone (as in lapwings). For a full discussion on this topic, see Rand, 1954. Screamers are particularly famous for their armaments, having not one but TWO sets of spurs, both originating from the metacarpal bone. In our own collection, I’ve noticed that our Victoria crowned pigeons can pack a serious wallop when beating their wings. Maybe that’s because the extensor process of the metacarpal bone has been modified into an enlarged, club-like projection (Worthy, 2001).

So, back to the lapwings. It’s certainly worth keeping in mind that these deceptively innocent birds have hidden weapons when we need to handle them for transport, medical procedures, etc. for our own safety. But it’s also worth knowing that these structures can become injured. Recently, one of our females accidentally broke off a piece of her spur and had to receive topical medications (don’t worry, she’s fine now). So, next time you’re at the Zoo, see if you can spot the hidden weapons on our lapwings, and keep in mind that these innocent and cute-looking birds might not be quite as defenseless as they seem!

References:

Rand, A. L. 1954. On the spurs on birds’ wings. The Wilson Bulletin 66, 127-134.

Wakisaka H. et al., 2006. Molecular sexing and sexual difference in carpal spur length of the Gray-headed Lapwing Vanellus cinereus (Charadriidae). Ornithol Sci 5, 133–137.

Worthy, T. H. 2001. A giant flightless pigeon gen. et sp. nov. and a new species of Ducula (Aves: Columbidae), from Quaternary deposits in Fiji. Journal of The Royal Society of New Zealand 31, 763-794.

Kelsey Kriesch, Bird Team

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