40 HAWAIIAN BIRDS. 



Heterorhynchus wilsoni Rothschild. Akiapolaau. 



In the akiapolaau we have another of the interesting and ex- 

 traordinary bird forms with which Nature has favored the Ha- 

 waiian Islands, there being a distinctive species for each island. 

 In external form this bird resembles the akialoa, though more 

 compactly and robustly built than that bird, but the yellow belly 

 and the short, blunt mandible, in contrast with the long, delicate 

 maxilla, serve at once to distinguish the two apart. The differ- 

 ences of form, and especially the different bills, indicate a corres- 

 ponding difference in habits, of which, indeed, these differences 

 are the direct result. 



The akiapolaau frequents the same deep forests as the akialoa, 

 though by no means wholly unknown in more open woods, and 

 like that species it passes over the large limbs and trunks of trees 

 with great rapidity, all the while peering to the right and left for 

 the hidden haunts of its insect food. It has the same habit of 

 probing into the leafy crowns of the ieie vine and into the thick 

 mosses and lichens. But the short, blunt mandible of the akia- 

 polaau has conferred new powers upon it which the other bird 

 does not possess. By means of it, when the maxilla is agape, it 

 can flake off lichens and even pound off small knobs and excres- 

 cences under which it suspects larvae to be concealed. Again, 

 fixing itself firmly to a limb by its stout claws, it will seize a small 

 excrescence between the mandibles and tug away at it till it 

 wrenches it off, when it probes the cavity beneath for larvae with 

 its upper mandible. The skull is unusually thick, and the muscles 

 of the neck and the maxilla are remarkably developed so as to 

 permit this double function of the bill as a hammer and as a 

 wrench. To some extent then the akiapolaau has progressed 

 towards the structure and the functions of a woodpecker, though 

 in the main it is very different from any of the members of that 

 tribe, not a single representative of which has found its way to 

 the islands. 



It may be added in passing that no family of birds is more 

 needed in the islands than the woodpeckers. Dead timber is very 

 abundant in the forests and, as Hawaiian insects lead hidden lives 



