Jerdon states that swallow-plovers live exclusively on insects which they catch on the wing. I doubt whether this assertion is correct. These birds certainly feed largely on flying insects, but as they spend the major part of their time on the sand, over which they run swiftly, I think that creeping things constitute a not inconsiderable portion of their diet.
Their nesting habits are similar to those of terns and plovers; that is to say, the eggs are placed on the sand or bare ground without any semblance of a nest.
I make a point every year, if possible, of spending a morning on a river at the beginning of the hot weather looking for the nests of terns and other birds which lay on churs and sandbanks. Almost every Indian river is plentifully studded with islets which render its navigation difficult, but afford most convenient nesting sites for many species of birds. The sandy islets whereon eggs are laid are nearly always those of which some portion is sufficiently high to escape being flooded when the river rises in consequence of the melting of the snow on the higher peaks of the Himalayas. The selected islands are almost invariably sufficiently far from the river bank to prevent jackals and other predaceous creatures wading across to them. If terns or plovers fail to take such precautions, the chances are that their eggs will come to grief.
This year (1912), on the 15th April, I went out on the Gogra at Fyzabad, and found over thirty nests of swallow-plovers on one islet, on which I also saw two eggs of the black-bellied tern (Sterna melanogaster).
Immediately I set foot on the island the terns and small pratincoles commenced making an uproar, which, of course, amounted to an assurance that they had eggs on the island. One portion of it was well sprinkled with stunted vegetation, and thither I at once repaired, to the great disgust of the swallow-plovers, who flew about excitedly, uttering their lapwing-like cry—titeri, titeri. A search of less than a minute served to reveal a couple of eggs placed on the bare ground between two small plants that were growing out of the sand. As I stooped down to examine these eggs I looked round and saw a very curious and pretty sight. Swallow-plovers were surrounding me. They were nearly all on the ground and striking strange attitudes. Some were lying on the sand as though they had been wounded and fallen to the ground; others were floundering on the ground as if in pain; some were fluttering along with one wing stretched out limply, looking as though it were broken; while others appeared to have both wings injured. I did not count the birds, but at least twenty of them were seemingly injured. I had often seen one bird or a pair behave thus, but never a whole flock.
All the plover family have this injury-feigning instinct, but in none is it so well developed as in the pratincoles.
“The strange antics,” writes Hume, “played by these little birds, at least those of them that had young or hard-set eggs, whenever we approached their treasures were very remarkable; flying past one, they would come fluttering down on to the sand a few paces in front of one, and there gasp and flutter as if mortally wounded, hobbling on with draggled wings and limping legs as one approached them, and altogether simulating entirely helpless and completely crippled birds. No one unacquainted with the habits of this class of birds could have believed, to see them flapping along on the sands on their stomachs, every now and then falling head over heels and lying quite still for an instant, as if altogether exhausted, that this was all a piece of consummate acting intended to divert our attention from their nests.”
Hume here voices the popular opinion that birds, when they behave as though they are injured, are deliberately pretending to be wounded with the object of diverting the attention of an intruder from their eggs or young. I hold this view to be utterly and entirely wrong. Consider the long chain of reasoning that a bird has to make before behaving as swallow-plovers are supposed to do. In the first place the birds must know or believe that the intruder has come with the object of taking their eggs or young ones. They must know or believe that the said intruder would like to capture them in preference to their eggs or young. They must further have discovered that a bird with a leg or a wing broken is easier to capture than one that is sound in limb. They must also know how a bird with a broken wing or leg behaves when endeavouring to escape from a foe. Knowing and believing all these things, the swallow-plover must reason thus within itself: “If I pretend that I am injured the intruder will try to catch me and thus be drawn away from my eggs or young. I will, therefore, proceed to act the wounded bird to the best of my ability.”
I do not for a moment believe that the average swallow-plover has half this knowledge and power of reasoning. Its behaviour can be accounted for in a far more probable manner. We all know that instinct teaches birds to fly away from all birds or beasts of prey or large strange moving objects; but instinct teaches them to guard their eggs. Now, when a human being approaches the eggs of a pratincole, these two instincts come into violent opposition, and the bird’s mental equilibrium is much disturbed; the result is that the bird undergoes all manner of strange contortions. We look at these and say, “What a clever little bird! How well it is acting!” The contortions of the swallow-plover undoubtedly do tend to attract the attention of predaceous creatures, and are probably useful to the species when there are young, for these are able to slip away while the attention of the attacker is momentarily diverted by the parent birds. Hence such behaviour must tend to be perpetuated by natural selection. That it is in no sense an intelligent act is obvious from the fact that such behaviour occurs when there are eggs, and so can do no good; moreover, the parents will go on behaving in this manner even after the intruder has taken the eggs and put them in his pocket!
Textbooks tell us that Glareola lactea lays from two to four eggs. I have never found more than two in a clutch, and think that Hume made a mistake when he said “from two to four,” and as plagiarism is very rife among writers on ornithology, other ornithologists have copied his statements without acknowledgment, and, of course, reproduced his mistake!