Birds are known to use a variety of tactics to defend their eggs and young. Harsh sounding alarm calls are often given when small birds encounter a predator and, if necessary, they will also mob intruders. Although such maneuvers are not likely to injure unwelcome visitors, they will make it unprofitable for a predator to continue looking for prey, especially when their neighbors are alerted to an intruder’s presence.

   Early detection and having help mobbing a predator are two reasons why birds that nest on open, sandy beaches breed in groups. The more eyes watching for danger the better. Also, when surrounded by other nesting birds the chances that your chicks will be attacked are diminished.

   Perhaps because there is safety in numbers, it is common for breeding colonies to contain more than one species as is the case in Florida. In mixed-species colonies of Black Skimmers and Least Terns, it is near impossible for Great Blue Herons or humans to approach undetected. A heron that lands near a colony is quickly greeted with an intense aerial bombardment by most of the resident adults.

   While adults are mobbing the intruder, flightless chicks scramble to huddle under clumps of grass while others crouch in depressions in the sand to reduce their profile. After a threat is repelled and the adults return to the colony, the chicks must scramble again to find their parents. Although adult skimmers don't cannibalized each others offspring, has some gulls are known to do, they will deliver a sharp peck to chicks that have strayed into areas that they don't belong. Such punishment is capable of causing permanent injuries.

   Mobbing, unfortunately, cannot deter all predators such as a fox or human. In such circumstances, a parent must modify its defensive tactics. For example, when walking away from a breeding colony, I came upon a skimmer flopping on the ground as if it was having trouble getting airborne. Apparently, I came too close to one of its chicks hiding in the grass. When I focused my attention on the adult, the wayward chick ran back into the colony.

   For most ground nesting birds, feigning injury is usually a last ditch effort to divert a predator’s attention away from a nest or concealed offspring. Obliviously, a parent's first priority is not giving away the location of its nest. In other words, when a predator is in the vicinity avoid visiting the nest; and second, when the coast is clear still approach one’s nest with extreme caution. These are two rules strictly followed Black-necked Stilts and for good reasons.

   Terrestrial predators are not likely to spot a stilt’s simple cup nest made of sticks and reeds. Also, the mottled, dark green to brown eggs are superbly camouflaged; so much so, that an untended nest is more difficult to spot than a nest with an adult sitting on eggs … reason enough not to return to one’s nest when a predator is nearby.

   Since female birds typically spend more time incubating eggs than males, females are often dull-colored compared to a males. Not so for Black-necked Stilts. Both males and females incubate the eggs and both exhibit highly conspicuous black-and-white feathers.

   Along with their eye-catching appearance, stilts go out of their away to attract attention. Black-necked Stilts, in particular, are quick to respond to potential threats. Their first line of defense is to fly over the intruder while giving alarm calls. If the incessant noise does drive away the threat, both sexes resort to diving bombing. And, if a predator continues to approach, one of the parent’s will land and start frantically flapping its wings as it hops away from the nest.

   If the concern parent manages to get the intruder’s attention, it will periodically stop its frantic movements and crouch low in the grass as if settling on a batch of eggs, a behavior called false-brooding. What it does next, however, depends upon the predator’s actions. If the intruder approaches the stilt, the bird moves further a field before again crouching. This hide-and-seek routine continues until the predator is out of sight of the nest or catches on to the ruse.

   When all the dancing and screaming fails to achieve the desired results, Black-necked Stilts shift into overdrive and start vigorously flapping their wings while jumping up and down and running in circles. A simple glance of the predator towards the nest is all that it takes to start feigning an injury. A full-on broken-wing display, however, isn’t performed until the intruder approaches within 20 meters of the stilt’s nest.

   Because of a stilt’s small size, physical assault could cause more harm to the defender than to a predator. Fortunately, evolution has provided birds with a suite of behaviors to deceive their enemies. Still, being able to perform all of the tricks in one’s arsenal doesn’t guarantee success. What’s necessary is employment of the right tactic that matches the intentions of an intruder. Assuming that birds are capable of thinking through all of their options, we are left with the question: how would a parent know what to do and when?

   Given that similar defensive behaviors are exhibited by most ground nesting birds, it is likely that most antipredator displays are genetically encoded. Still, many birds appear to creatively combine instinct and learning. Not only do they learn to vary how they response to different types of predators and circumstances, birds can respond rapidly and appropriately as if they are explicitly aware of what they are doing.

   When stilts are incubating, for example, they readily mob crows and gulls, predators known to relish eggs, but after their young have hatched stilts respond more vigorously to Great Blue Herons, a predator that preys on small vertebrates including birds. Though all stilts exhibit similar behaviors when threaten, no two birds react the same or with the same intensity.

   Although herons are not a threat to young Killdeer raised in the Badlands Nat. Park, South Dakota, parents still have to contend with a variety of threats such as birds of prey, coyote, fox, and bison. Each type of predator, understandably, demands a different response. When a bison approaches a killdeer’s nest, for example, broken-wing displays are rarely performed. Instead, they lunge at the animal’s face in an attempt to startle the buffalo into changing its course. When confronted with a large herbivore that consumes only grass, the real danger is having one’s nest trampled.

   In contrast, while walking along a dirt road within the park a killdeer landed in front of me and slowly walked away as if giving a personal tour of the surrounding Prairie Dog Town. Like stilts, it stopped periodically to crouch as if settling on a batch of eggs. When I turned and left the road, the Killdeer again flew in front of me, but this time it walked back towards the road. Presumably, my off-road detour would lead me closer to killdeer’s real, hidden nest.

   As I continued walking, the bird’s calls and displays increased in frequency and intensity until it eventually flatten itself on the ground and pathetically flapped its wings and spread open its tail, an act that exposed a rufus-colored patch on its lower back. This time, its dramatic performance got my attention and I turned back wince I came with the killdeer leading the way.

   I encountered a second killdeer in the parking lot of Freezout Lake Wildlife refuge in Montana. At the time, the bird didn’t bother to run in front of me, but immediately performed an impressive broken-wing display at my feet. Again, I must have inadvertently strayed close to a nest or a crouching chick hidden among the gravel. I looked for quite awhile but failed to find either. Since the appearance of a killdeer’s chicks are so well camouflaged, I wonder if they also lack a distinctive smell that could attract mammalian predators. Video